Liberty4Ever's Laser Build Log
Re: Liberty4Ever's Laser Build Log
by Liberty4Ever » Tue Oct 02, 2012 5:04 am
Documenting The Design:
I'm trying hard to make this build log useful to the reader, but I do find that I often design best when I think about something, then write about it. Explaining it formalizes and crystalizes my thoughts, so it's helpful to me as well. Hopefully, some people are interested in a stream of consciousness peek into the design process, although it's been more like Fear And Loathing In Las Laser.
I've been in the early design stages so far, so I've been talking about what I'm doing and why. That'll change soon, as the build log focuses more on building. I absolutely will be posting pictures and information useful to builders. I don't have 3D parametric design software, so I won't be publishing any nice 3D renderings, assembly drawings, or any of the other nice documentation I've seen on some of the BuildLog.net posts. It's a shame, because I could greatly benefit from 3D CAD software to help me visualize the extruded aluminum framework as I design it. I do, however, plan on drawing some sketches by hand, and I may CAD some 2D drawings to take the place of assembly drawings. At the very least, I'll take pictures that I can annotate in lieu of an assembly drawing. That'll be good for guys, who aren't much on reading and just want to "make it look like this".
More Frame Design Musings:
Designing the frame should be fairly simple, as most of the complexity is the XY stage that's already done for me. Once the frame is built, if someone wanted to duplicate it, that should be very easy from the info I'll provide. Similarly, it should be easy to do the parametric modifications manually if anyone would prefer to stretch or shrink my X or Y dimensions to fit their needs.
I originally imagined the frame for my laser as fairly complicated, but I'm now leaning toward a simpler design. 40mm X 40mm exterior aluminum extrusions with maybe 20mm X 40mm interior braces, creating a structure that's little more than a sturdy frame to attach the laser bed, places for the electronics and pumps and blowers inside, a lid on top, and a laser tube box on the back, possibly incorporating the cooling system. In fact, I think I'll put the laser power supply in the rear mounted laser box as well, with the laser tube on top and everything else underneath. The coolant radiator would have a strong blast of forced air cooling out the bottom on one side, and there would be a filtered air input vent on the bottom on the other side, and the air moving through the laser box would also carry away the cooling air that's forced out of the laser power supply by its internal fan. The signals to the laser box would be 120 VAC for the laser power supply, 24VDC for the cooling fans, a 24VDC signal from the coolant flow switch, a 24VDC signal from the coolant low float switch, and the laser enable signal. I'll probably route all of the signals to a 10 pin Amp Mate-N-Lok connector, so I have a few extra pins for anything I might want to add later. When you make it up as you go, it's good to have spare wires, extra pins, etc. I think I'll make the laser box removable to make it easier to transport the laser by draining the coolant, unplugging the electrical connector, and unbolting the laser box from the back, with the rest of the laser now 8" to 10" narrower so it'll go through doors more easily. Conceptually, I like the idea of an integrated laser tube and cooling system, including the pump, reservoir, radiator and cooling fans.
I was planning on a pair of doors on the front of the laser enclosure, but I doubt I'll need access that often. I'll probably just install removable body panels on all sides. The exhaust ductwork will require the most thought. After using a laser for years with mediocre exhaust, I have some strong feelings about the exhaust system.
More Musings On Laser Bed Size:
The 3' X 5' XY table that I bought is too big for my needs, and the 2' X 2' version I'm planning on chopping down seems like a luxurious size compared to the 1' X 2' laser I've been using, but part of me is still lobbying for a 2' X 4' bed. The incremental cost is negligible, and I already bought the table. It's a shame to waste it.
If I made it 2' X slightly under 5', I could avoid chopping the X axis, and the laser should still fit through a standard interior door, and the laser tube could fit completely behind the bed with no overhang on the right side. It'd take up some precious shop space providing capacity I'd almost never use, and I'd be lifting a much larger and heavier lid. The lid weight and bulk doesn't sound like much, but I run a fair amount of single piece production. Imagine lifting a large lid every minute or so, for hours on end. I could put air springs on the lid to assist the lift and hold the lid open. Or, I could put a solenoid valve on the air pump and have the air supply manually (or automatically!) switch between air assist at the laser nozzle and a pair of air cylinders that opened and closed the lid. 
I do think Bart's Laser 2.x is very clever in the way it uses MakerSlide for rail and structural components. If it had a true 1' X 2' bed, that's what I'd be building. Those few inches made a big difference to me. I probably should have scaled up the Laser 2.X like many others are doing, but I got in a hurry, and I didn't want to be dependent on so many custom machined parts that might not be available in time to fit my impatient schedule, and I didn't want to take the time to make them myself. I'm trying to fast track this project for a change. It's amazing how a few inches of workspace can make or break a project. I liked the Quantum ORD Bot 3D printer design, but I built the Hadron with the larger 12" X 12" build area, and I think the larger Hadron is by far the more popular of the two designs, even though that Quantum ORD Bot is awfully cute. I'd have definitely jumped on a Laser 2.x if it cut 12" X 24" material, and a kit was available. Once I was back in design mode, it seemed easier for me to cheat with a pre-designed professional grade XY stage and design the rest of the relatively easy stuff myself rather than modify the Laser 2.x and try to source the MakerSlide, V-wheels, and the various mounting plates.
Scheduling Parts Orders & Delivery:
My air assist pump is in town. I should have it tomorrow. The 58 pounds worth of XY table and complete optics path is in state and will be here the day after tomorrow. I'll document the build with ample pictures. 58 pounds?!? That must be a helluva strong XY table!
The laser tube and power supply is in China and there is a lengthy shipping delay, so I'll probably cave in to my relentless and unjustified project optimism and order the tube and power supply soon so it'll be here as the rest of the hardware build comes together. Come to think of it, it takes a week or so for Misumi to ship, so that'll put a delay in my build process. I'm stuck with that delay. I can't pre-order the frame that isn't designed yet, and I don't want to try to design the frame until I have the XY frame and all of the major parts so I can decide where the cross braces go to mount the various parts, and I can decide where the exhaust baffles go. I guess I'll work on the LinuxCNC control of the XY table and the laser while I'm waiting a week for the frame parts from Misumi. But the good news is, once it arrives, that extruded aluminum frame goes together quickly.
I'm trying hard to make this build log useful to the reader, but I do find that I often design best when I think about something, then write about it. Explaining it formalizes and crystalizes my thoughts, so it's helpful to me as well. Hopefully, some people are interested in a stream of consciousness peek into the design process, although it's been more like Fear And Loathing In Las Laser.
I've been in the early design stages so far, so I've been talking about what I'm doing and why. That'll change soon, as the build log focuses more on building. I absolutely will be posting pictures and information useful to builders. I don't have 3D parametric design software, so I won't be publishing any nice 3D renderings, assembly drawings, or any of the other nice documentation I've seen on some of the BuildLog.net posts. It's a shame, because I could greatly benefit from 3D CAD software to help me visualize the extruded aluminum framework as I design it. I do, however, plan on drawing some sketches by hand, and I may CAD some 2D drawings to take the place of assembly drawings. At the very least, I'll take pictures that I can annotate in lieu of an assembly drawing. That'll be good for guys, who aren't much on reading and just want to "make it look like this".
More Frame Design Musings:
Designing the frame should be fairly simple, as most of the complexity is the XY stage that's already done for me. Once the frame is built, if someone wanted to duplicate it, that should be very easy from the info I'll provide. Similarly, it should be easy to do the parametric modifications manually if anyone would prefer to stretch or shrink my X or Y dimensions to fit their needs.
I originally imagined the frame for my laser as fairly complicated, but I'm now leaning toward a simpler design. 40mm X 40mm exterior aluminum extrusions with maybe 20mm X 40mm interior braces, creating a structure that's little more than a sturdy frame to attach the laser bed, places for the electronics and pumps and blowers inside, a lid on top, and a laser tube box on the back, possibly incorporating the cooling system. In fact, I think I'll put the laser power supply in the rear mounted laser box as well, with the laser tube on top and everything else underneath. The coolant radiator would have a strong blast of forced air cooling out the bottom on one side, and there would be a filtered air input vent on the bottom on the other side, and the air moving through the laser box would also carry away the cooling air that's forced out of the laser power supply by its internal fan. The signals to the laser box would be 120 VAC for the laser power supply, 24VDC for the cooling fans, a 24VDC signal from the coolant flow switch, a 24VDC signal from the coolant low float switch, and the laser enable signal. I'll probably route all of the signals to a 10 pin Amp Mate-N-Lok connector, so I have a few extra pins for anything I might want to add later. When you make it up as you go, it's good to have spare wires, extra pins, etc. I think I'll make the laser box removable to make it easier to transport the laser by draining the coolant, unplugging the electrical connector, and unbolting the laser box from the back, with the rest of the laser now 8" to 10" narrower so it'll go through doors more easily. Conceptually, I like the idea of an integrated laser tube and cooling system, including the pump, reservoir, radiator and cooling fans.
I was planning on a pair of doors on the front of the laser enclosure, but I doubt I'll need access that often. I'll probably just install removable body panels on all sides. The exhaust ductwork will require the most thought. After using a laser for years with mediocre exhaust, I have some strong feelings about the exhaust system.
More Musings On Laser Bed Size:
The 3' X 5' XY table that I bought is too big for my needs, and the 2' X 2' version I'm planning on chopping down seems like a luxurious size compared to the 1' X 2' laser I've been using, but part of me is still lobbying for a 2' X 4' bed. The incremental cost is negligible, and I already bought the table. It's a shame to waste it.
If I made it 2' X slightly under 5', I could avoid chopping the X axis, and the laser should still fit through a standard interior door, and the laser tube could fit completely behind the bed with no overhang on the right side. It'd take up some precious shop space providing capacity I'd almost never use, and I'd be lifting a much larger and heavier lid. The lid weight and bulk doesn't sound like much, but I run a fair amount of single piece production. Imagine lifting a large lid every minute or so, for hours on end. I could put air springs on the lid to assist the lift and hold the lid open. Or, I could put a solenoid valve on the air pump and have the air supply manually (or automatically!) switch between air assist at the laser nozzle and a pair of air cylinders that opened and closed the lid. I do think Bart's Laser 2.x is very clever in the way it uses MakerSlide for rail and structural components. If it had a true 1' X 2' bed, that's what I'd be building. Those few inches made a big difference to me. I probably should have scaled up the Laser 2.X like many others are doing, but I got in a hurry, and I didn't want to be dependent on so many custom machined parts that might not be available in time to fit my impatient schedule, and I didn't want to take the time to make them myself. I'm trying to fast track this project for a change. It's amazing how a few inches of workspace can make or break a project. I liked the Quantum ORD Bot 3D printer design, but I built the Hadron with the larger 12" X 12" build area, and I think the larger Hadron is by far the more popular of the two designs, even though that Quantum ORD Bot is awfully cute. I'd have definitely jumped on a Laser 2.x if it cut 12" X 24" material, and a kit was available. Once I was back in design mode, it seemed easier for me to cheat with a pre-designed professional grade XY stage and design the rest of the relatively easy stuff myself rather than modify the Laser 2.x and try to source the MakerSlide, V-wheels, and the various mounting plates.
Scheduling Parts Orders & Delivery:
My air assist pump is in town. I should have it tomorrow. The 58 pounds worth of XY table and complete optics path is in state and will be here the day after tomorrow. I'll document the build with ample pictures. 58 pounds?!? That must be a helluva strong XY table!
The laser tube and power supply is in China and there is a lengthy shipping delay, so I'll probably cave in to my relentless and unjustified project optimism and order the tube and power supply soon so it'll be here as the rest of the hardware build comes together. Come to think of it, it takes a week or so for Misumi to ship, so that'll put a delay in my build process. I'm stuck with that delay. I can't pre-order the frame that isn't designed yet, and I don't want to try to design the frame until I have the XY frame and all of the major parts so I can decide where the cross braces go to mount the various parts, and I can decide where the exhaust baffles go. I guess I'll work on the LinuxCNC control of the XY table and the laser while I'm waiting a week for the frame parts from Misumi. But the good news is, once it arrives, that extruded aluminum frame goes together quickly.
Apparently, I didn't build that! 
- Liberty4Ever
- Posts: 274
- Joined: Wed May 30, 2012 1:49 am
- Location: Lexington KY
Re: Liberty4Ever's Laser Build Log
by Liberty4Ever » Tue Oct 02, 2012 5:27 pm
First Part For My Laser Build Arrived Today
We're off to a slow start, but the first component of my laser build arrived today. I got the 38 LPM air assist pump from Amazon.com.
http://www.amazon.com/dp/B002JLJC0W/ref=pe_175190_21431760_M3T1_ST1_dp_1
It delivers the amount of air I expected, and I think it'll be just about right for an air assist pump. I wouldn't want to go any smaller. It's not very tolerant of back pressure, so I'll reserve final judgment on its adequacy until it's plumbed and pushing air through the nozzle.
It's a bit noisy, but not quite as bad as I expected. Once it's buried inside the laser, I doubt I'll be able to hear it over the din of the exhaust blower. The rubber feet on the bottom should do a good job of keeping the conducted noise out of the laser framework.
It does have some pulsing, as others have mentioned. I had a four foot long length of 1.5" PVC pipe that was capped on both ends with instant tubing press fittings that I originally built as a deionized water reionizer - don't ask! I was planning on using it as an accumulator to even out the air pulses, but when I went into the basement to get it, I realized that after hanging on to it for about six years, I threw it away in a rare minor basement cleanup effort a month or so ago. No problem. I suspect that running 3/8" tubing and then necking it down to 1/4" tubing for the flexible run through the cable chain will do a decent job of averaging out the pressure pulses.
Speaking of flexible tubing, I'm planning on using ether based tubing from McMaster-Carr. Unlike thin wall silicone tubing, it doesn't pinch easily and restrict the air flow, but it's softer and more flexible at room temperature than typical Tygon tubing, and way more flexible than nylon tubing.
We're off to a slow start, but the first component of my laser build arrived today. I got the 38 LPM air assist pump from Amazon.com.
http://www.amazon.com/dp/B002JLJC0W/ref=pe_175190_21431760_M3T1_ST1_dp_1
It delivers the amount of air I expected, and I think it'll be just about right for an air assist pump. I wouldn't want to go any smaller. It's not very tolerant of back pressure, so I'll reserve final judgment on its adequacy until it's plumbed and pushing air through the nozzle.
It's a bit noisy, but not quite as bad as I expected. Once it's buried inside the laser, I doubt I'll be able to hear it over the din of the exhaust blower. The rubber feet on the bottom should do a good job of keeping the conducted noise out of the laser framework.
It does have some pulsing, as others have mentioned. I had a four foot long length of 1.5" PVC pipe that was capped on both ends with instant tubing press fittings that I originally built as a deionized water reionizer - don't ask! I was planning on using it as an accumulator to even out the air pulses, but when I went into the basement to get it, I realized that after hanging on to it for about six years, I threw it away in a rare minor basement cleanup effort a month or so ago. No problem. I suspect that running 3/8" tubing and then necking it down to 1/4" tubing for the flexible run through the cable chain will do a decent job of averaging out the pressure pulses.
Speaking of flexible tubing, I'm planning on using ether based tubing from McMaster-Carr. Unlike thin wall silicone tubing, it doesn't pinch easily and restrict the air flow, but it's softer and more flexible at room temperature than typical Tygon tubing, and way more flexible than nylon tubing.
Apparently, I didn't build that!
- Liberty4Ever
- Posts: 274
- Joined: Wed May 30, 2012 1:49 am
- Location: Lexington KY
Re: Liberty4Ever's Laser Build Log
by Liberty4Ever » Wed Oct 03, 2012 2:31 am
Ordered The Stepper Motor Power Supply
I just placed an order for the 48VDC 7.3A 350W regulated switching power supply that I'll use for the stepper motors. I paid $35, including shipping.
http://www.ebay.com/itm/270997990406
These power supplies are all made in China, but I purchased one that was stocked in the US so hopefully, it'll be here soon after the XY stage, which is across town and waiting to be delivered tomorrow. The stepper motor drives are on their way and are scheduled for delivery two days later. I've ordered several of these power supplies from China, and they take 1-2+ weeks to arrive, and they almost always arrive with one or both of the metal ears next to the terminal strips bent inward. It's a cosmetic defect and the electronics are fine, but I hate needing to bend the sheet metal back out, and they never look exactly right.
The 7.3 amp rating of the power supply that I ordered was a bit marginal, but I don't ever expect to operate the Z axis when the X or Y axes are operating. The power supply is sized based on my X axis (4 amps) and Y axis (2.8 amps) operating at the same time. Slightly larger 48V @ 8A power supplies were significantly more expensive.
Another good candidate for the stepper motor power supply is the 24V/36V supply that LightObject.com sells for $65. That way, you could have one dual voltage power supply with 36V for the motors and 24V for the control electronics (coolant fans, coolant pump, etc.).
http://www.lightobject.com/Dual-DC-36V-24V-10A-Switching-Power-Supply-Ideal-for-DSP-System-P712.aspx
I didn't get the 24/36 volt supply because I already have a line on a 24/5 volt switching supply, and I'll need 24V for all of the control applications and 5V for some other stuff like the power supply for the digital milliamp meter that displays the laser current.
In theory, the stepper motors can be driven from 24V, but I like the idea of keeping the inevitable noise from the motors off the 24V control power, and even more important, the motors will operate with 24V but they'll probably need a higher voltage to operate at the best speed possible without losing steps. With the lower voltage, the inductance of the motor windings will limit the inrush current and that will limit the number of steps per second. If my 48V power supply isn't here when I'm ready to exercise the XY stage, I'll drive it with 24V, but I'll use the 48V supply for the best speed in the final configuration. The maximum speed is primarily an issue on the X axis flying optics when engraving. The motor controllers I ordered specified a DC power input of 20V to 50V, so I selected 48V. 36V would probably work almost as well.
You don't really need a regulated DC power supply for this stepper motor application. If you have a transformer, bridge rectifier, and a large Coke can sized filter capacitor, you could whip together an unregulated power supply, or you might find one for sale on eBay. Just make sure that the unloaded voltage doesn't spike up higher than the maximum input voltage rating of your stepper motor drivers (50V in my case), and the full load voltage is 36V or higher.
For my CNC lathe retrofit project, I went all out and got a power supply from AnTek. It's been awhile, but I think it had an unregulated 56V supply for the servo motors, as well as an integrated 24V regulated supply for the I/O & control circuits and an integrated 5V regulated supply for the digital electronics. I think I paid about $85. They're very nice CNC power supplies that use toroidal transformers to contain the electrical noise. They also sell the toroidal transformers by themselves if you'd like to make your own unregulated power supply as previously described. My only complaint is that they offer so many different power supplies that it's difficult to find what I want on their website, and their website was slow when I visited it tonight. They need some quick reference tables or an online power supply locator wizard that can locate the right power supply without scanning long lists in a multi-page table format. Maybe they have that, and I missed it tonight.
http://www.antekinc.com
I just placed an order for the 48VDC 7.3A 350W regulated switching power supply that I'll use for the stepper motors. I paid $35, including shipping.
http://www.ebay.com/itm/270997990406
These power supplies are all made in China, but I purchased one that was stocked in the US so hopefully, it'll be here soon after the XY stage, which is across town and waiting to be delivered tomorrow. The stepper motor drives are on their way and are scheduled for delivery two days later. I've ordered several of these power supplies from China, and they take 1-2+ weeks to arrive, and they almost always arrive with one or both of the metal ears next to the terminal strips bent inward. It's a cosmetic defect and the electronics are fine, but I hate needing to bend the sheet metal back out, and they never look exactly right.
The 7.3 amp rating of the power supply that I ordered was a bit marginal, but I don't ever expect to operate the Z axis when the X or Y axes are operating. The power supply is sized based on my X axis (4 amps) and Y axis (2.8 amps) operating at the same time. Slightly larger 48V @ 8A power supplies were significantly more expensive.
Another good candidate for the stepper motor power supply is the 24V/36V supply that LightObject.com sells for $65. That way, you could have one dual voltage power supply with 36V for the motors and 24V for the control electronics (coolant fans, coolant pump, etc.).
http://www.lightobject.com/Dual-DC-36V-24V-10A-Switching-Power-Supply-Ideal-for-DSP-System-P712.aspx
I didn't get the 24/36 volt supply because I already have a line on a 24/5 volt switching supply, and I'll need 24V for all of the control applications and 5V for some other stuff like the power supply for the digital milliamp meter that displays the laser current.
In theory, the stepper motors can be driven from 24V, but I like the idea of keeping the inevitable noise from the motors off the 24V control power, and even more important, the motors will operate with 24V but they'll probably need a higher voltage to operate at the best speed possible without losing steps. With the lower voltage, the inductance of the motor windings will limit the inrush current and that will limit the number of steps per second. If my 48V power supply isn't here when I'm ready to exercise the XY stage, I'll drive it with 24V, but I'll use the 48V supply for the best speed in the final configuration. The maximum speed is primarily an issue on the X axis flying optics when engraving. The motor controllers I ordered specified a DC power input of 20V to 50V, so I selected 48V. 36V would probably work almost as well.
You don't really need a regulated DC power supply for this stepper motor application. If you have a transformer, bridge rectifier, and a large Coke can sized filter capacitor, you could whip together an unregulated power supply, or you might find one for sale on eBay. Just make sure that the unloaded voltage doesn't spike up higher than the maximum input voltage rating of your stepper motor drivers (50V in my case), and the full load voltage is 36V or higher.
For my CNC lathe retrofit project, I went all out and got a power supply from AnTek. It's been awhile, but I think it had an unregulated 56V supply for the servo motors, as well as an integrated 24V regulated supply for the I/O & control circuits and an integrated 5V regulated supply for the digital electronics. I think I paid about $85. They're very nice CNC power supplies that use toroidal transformers to contain the electrical noise. They also sell the toroidal transformers by themselves if you'd like to make your own unregulated power supply as previously described. My only complaint is that they offer so many different power supplies that it's difficult to find what I want on their website, and their website was slow when I visited it tonight. They need some quick reference tables or an online power supply locator wizard that can locate the right power supply without scanning long lists in a multi-page table format. Maybe they have that, and I missed it tonight.
http://www.antekinc.com
Apparently, I didn't build that!
- Liberty4Ever
- Posts: 274
- Joined: Wed May 30, 2012 1:49 am
- Location: Lexington KY
Re: Liberty4Ever's Laser Build Log
by Techgraphix » Wed Oct 03, 2012 4:00 pm
Liberty4Ever wrote: but I don't ever expect to operate the Z axis when the X or Y axes are operating.
Don't forget that steppermotors are powered even is they don't move. Unles you have set the switch that the current will be reduced to half after a second, the total current through steppermotors is constant. It doesn't matter if the are moving or not..
I don't say this powersupply is insufficiant but it is indeed quite marginal..
Kees
- Techgraphix
- Posts: 122
- Joined: Fri Feb 24, 2012 8:37 pm
- Location: Appelscha, NL
Re: Liberty4Ever's Laser Build Log
by Liberty4Ever » Wed Oct 03, 2012 8:23 pm
Current Specification Issues For The Stepper Motor Power Supply, Revisited
I knew that, but wasn't thinking.
Thanks for the reminder about the Z axis stepper motors being powered when not in use. The sad part is, it wasn't long ago that I was reminded of this when we were discussing the ORD Bot Z axis stepper motors. I must be getting Old Timers Disease. I've designed with stepper motors before, but this is apparently a persistent blind spot for me.
The stepper motor drives I ordered have a 50% current mode, presumably when the axis is not in motion.
http://www.lightobject.com/2-Phase-45A-1-axis-Stepping-Motor-Driver-Support-to-Nema-1634-Leetro-replacement-P453.aspx
The maximum current would occur when driving the X and Y axes but not the Z axis. The maximum current would be 2.37A + 3.76A + 1.48A/2 = 6.87 A, which just squeaks in under the 7.3A power supply limit. That assumes the highest current I can select on the stepper drives without exceeding the current ratings of the motors.
I wish I could say that I did due diligence when designing it, instead of lucking out after the fact. It's close enough that there's also the possibility that I won't be so lucky in the real world. If so....
I suspect this won't be the only part that's ordered twice when my brain takes a holiday. Maybe I will get that 36V @ 10A supply from LightObject.com with the integrated 24V @ 2A supply for the control voltage. I can generate the few mA of 5V I need from the 24V supply. It won't be efficient, but it doesn't need to be.
There's absolutely no need for the Z axis stepper motors to be powered at all in this application when the Z axis isn't in motion. There will be four stepper motors, and each is driving a lead screw to raise and lower a relatively light weight bed. There's no way that gravity will be able to back drive the lead screws and lower the bed if the Z axis stepper motors have no current. I'll take a look at the documentation for the stepper motor drives when they arrive in a couple of days. Maybe I'll devise some clever circuit where the UP and DOWN buttons on the front panel not only signal LinuxCNC to jog the Z axis motors, but also disable the X and Y stepper drives at the same time. I want the laser to be intuitive, but I can't imagine any time other than a "showing off" break-in/demo when the X and Y axes would be active when the Z axis is active.
I won't spend a lot of time wiring or configuring LinuxCNC to implement a Z axis interlock. If it's too complex or mucks up the user interface so much that it complicates the operation, I'm sure I'll be making some small CNC machine in the future that can use a 48V @ 7.3A power supply.
The other option is to keep the four lead screws, put timing pulleys on them, connect them all with a common belt, and drive them with a surplus DC gear motor. UP and DOWN could be implemented with a spring return to center DPDT rocker switch on the front panel. LinuxCNC don't need to know nuthin' about the Z axis.
I still like the design simplicity of four stepper motors directly driving four lead screws. I don't want to mess with those belts and pulleys. I'll look into half power on the stepper drives when not in use. If it doesn't work as well as I think, I'll probably get a bigger power supply.
I'm sure this won't be the last of the design mistakes on this project. Hopefully, there won't be any truly serious ($$$) mistakes,
Techgraphix wrote:Don't forget that stepper motors are powered even is they don't move.
I knew that, but wasn't thinking.
Thanks for the reminder about the Z axis stepper motors being powered when not in use. The sad part is, it wasn't long ago that I was reminded of this when we were discussing the ORD Bot Z axis stepper motors. I must be getting Old Timers Disease. I've designed with stepper motors before, but this is apparently a persistent blind spot for me.
The stepper motor drives I ordered have a 50% current mode, presumably when the axis is not in motion.
http://www.lightobject.com/2-Phase-45A-1-axis-Stepping-Motor-Driver-Support-to-Nema-1634-Leetro-replacement-P453.aspx
The maximum current would occur when driving the X and Y axes but not the Z axis. The maximum current would be 2.37A + 3.76A + 1.48A/2 = 6.87 A, which just squeaks in under the 7.3A power supply limit. That assumes the highest current I can select on the stepper drives without exceeding the current ratings of the motors.
I wish I could say that I did due diligence when designing it, instead of lucking out after the fact. It's close enough that there's also the possibility that I won't be so lucky in the real world. If so....
I suspect this won't be the only part that's ordered twice when my brain takes a holiday. Maybe I will get that 36V @ 10A supply from LightObject.com with the integrated 24V @ 2A supply for the control voltage. I can generate the few mA of 5V I need from the 24V supply. It won't be efficient, but it doesn't need to be.
There's absolutely no need for the Z axis stepper motors to be powered at all in this application when the Z axis isn't in motion. There will be four stepper motors, and each is driving a lead screw to raise and lower a relatively light weight bed. There's no way that gravity will be able to back drive the lead screws and lower the bed if the Z axis stepper motors have no current. I'll take a look at the documentation for the stepper motor drives when they arrive in a couple of days. Maybe I'll devise some clever circuit where the UP and DOWN buttons on the front panel not only signal LinuxCNC to jog the Z axis motors, but also disable the X and Y stepper drives at the same time. I want the laser to be intuitive, but I can't imagine any time other than a "showing off" break-in/demo when the X and Y axes would be active when the Z axis is active.
I won't spend a lot of time wiring or configuring LinuxCNC to implement a Z axis interlock. If it's too complex or mucks up the user interface so much that it complicates the operation, I'm sure I'll be making some small CNC machine in the future that can use a 48V @ 7.3A power supply.
The other option is to keep the four lead screws, put timing pulleys on them, connect them all with a common belt, and drive them with a surplus DC gear motor. UP and DOWN could be implemented with a spring return to center DPDT rocker switch on the front panel. LinuxCNC don't need to know nuthin' about the Z axis.
I still like the design simplicity of four stepper motors directly driving four lead screws. I don't want to mess with those belts and pulleys. I'll look into half power on the stepper drives when not in use. If it doesn't work as well as I think, I'll probably get a bigger power supply.
I'm sure this won't be the last of the design mistakes on this project. Hopefully, there won't be any truly serious ($$$) mistakes,
Apparently, I didn't build that!
- Liberty4Ever
- Posts: 274
- Joined: Wed May 30, 2012 1:49 am
- Location: Lexington KY
Re: Liberty4Ever's Laser Build Log
by Liberty4Ever » Thu Oct 04, 2012 4:44 am
Bought The 80W Laser Tube & High Voltage Laser Power Supply - $940 Delivered
Terminator (paraphrased): "I'll take the phased plasma rifle in the 80 watt range."
Gun Store Clerk: "Just what ya see, pal."
http://www.ebay.com/itm/251151358563
I got the RECI brand laser that most sellers say is rated as an 85W or 90W laser tube that's de-rated to run at 80W for a useful life of 8,000 to 10,000 hours. That should be a lifetime for me. Even though I run production on the laser, and I expect to be running more production with new products once I have my own laser, that will probably mean the two days a month I currently lase will increase to 3-4 days a month. Strangely, even though this is generally regarded as a better laser, I didn't pay a price premium over the market price for lesser lasers that generally sold for more money. This was one of the lowest cost options in the 80W laser and power supply class.
Here are some pictures, info provided by the seller, and specs:
The laser tube:
The low voltage end:
The high voltage end:
The high voltage laser power supply:
I have a lot to do before I'm ready for the laser tube and power supply, but I felt compelled to buy it now, because the estimated arrival if I order today is "Between Friday, Oct. 19 and Thursday, Nov. 1". I hope it'll be arriving just as I need it. I'm trying to fast track this project, which is a novel concept for me. I usually dream about projects, and agonize over projects, but don't build very fast anymore. I guess I'm still suffering from project burnout from when I was a young controls engineer, doing all of the engineering and a fair amount of wrenching and wire pulling on very large high-pressure projects with insane schedules. I think my adrenal gland might be worn out. Instead of adrenaline, I now run on caffeine.
Well, I've spent about $2600 in the last week on my front burner git-R-done-quick laser project. I expect to spend another $900 to $1000 in the next month to finish the project. Almost all of the big stuff has now been purchased. The only other big ticket item is the aluminum extrusion, brackets and fasteners for the framework and the body panels. From a work perspective, I believe the most difficult and time consuming part of this project will be repairing the deck on my house, and then enclosing the patio under the deck to make room for the laser and other dirty/stinky manufacturing equipment. This is Build Log, not This Old House, so I'll save you guys that part of the project, but if I disappear for a while, that's probably where I am. I took off my laser eye patch and put on my Bob The Builder hard hat. Either that, or I'm sleeping, which I haven't been doing very much lately.
I still owe you guys a bill of materials spreadsheet, with sources, links, part numbers and cost. I'll get on that, right after I sleep a little bit. I need to draw a schematic, too.
Terminator (paraphrased): "I'll take the phased plasma rifle in the 80 watt range."
Gun Store Clerk: "Just what ya see, pal."
http://www.ebay.com/itm/251151358563
I got the RECI brand laser that most sellers say is rated as an 85W or 90W laser tube that's de-rated to run at 80W for a useful life of 8,000 to 10,000 hours. That should be a lifetime for me. Even though I run production on the laser, and I expect to be running more production with new products once I have my own laser, that will probably mean the two days a month I currently lase will increase to 3-4 days a month. Strangely, even though this is generally regarded as a better laser, I didn't pay a price premium over the market price for lesser lasers that generally sold for more money. This was one of the lowest cost options in the 80W laser and power supply class.
Here are some pictures, info provided by the seller, and specs:
The laser tube:
The low voltage end:
The high voltage end:
The high voltage laser power supply:
For sale is a new RECI brand (top of the line) 80 watt laser tube with matching 80 watt RECI brand power supply. The maximum laser power exceeds the rated 80 watts. When operated at the rated output power (80 watts) then it has a long life of 8000 hours. The reason for the long life is because the operation below the maximum output power will maintain the gases for lasing much longer. The 8000 hour life begins with laser use and lasing the gas.
Notice the laser's high quality and durable holders for the rear mirror and output coupler. See the plastic safety covering that is located on the high voltage end in the photo. This safety covering protects the laser machine user from the high voltage line and accidental discharge. [Liberty4Ever Note: Avoid accidental discharge whenever possible!] The way it works is that the high voltage (red cable) connector will be screwed onto the metal housing. Then, the plastic sheath is slid over-top the wire so that only the insulated part of the cable is exposed.
This laser tube is well designed and has a long life. If you need laser support stands (for this diameter) then notify at end of sale and two will be provided at no additional charge and included in your shipment.
If you need technical support on the installation, it will be provided at no additional cost. (English is our first language and we sell laser machinery for our business.)
LASER SPECIFICATIONS
-----------------------------------
BRAND: RECI
USAGE OUTPUT POWER: 80 WATTS
TUBE DIAMETER: 80 MM
TUBE LENGTH: 1.2 METERS
MAX OPERATING CURRENT: 28 mA
MAX POWER SUPPLY VOLTAGE: 28 KVA
LASER BEAM DIAMETER: 6.9 MM
LASER BEAM QUALITY: TEM00
LASER STABILITY: +-4 %
LASER DIVERGENCE: 2.4 MRAD
The RECI brand 80 watt laser power supply is calibrated and the potentiometer is adjusted down to 28 mA in order to maximize the lifetime of your 80 watt laser tube.
POWER SUPPLY SPECIFICATIONS
-----------------------------------
AC Input Voltage AC 110V
AC frequency 47~440HZ
Maximum Input Power 550 w
Maximum Input Current: 5A
Maximum Output Voltage DC: 40 KV
Maximum Output Current: 32 mA
Efficiency : 94%
Average fault free time: ≥30000h
Response time ≤1ms (from turn on to the output current up to 90%)
Operating Temperature: -10°C~+40°C
Relative Humidity: ≤90%RH
Voltage Thresholds:
---> Input-Output AC1500V 1min. ≤10mA
---> Input-Enclosure AC1500V 1min. ≤10mA
---> Output-Enclosure Connect
Dimensions: 200 mm*160 mm*80 mm(L*W*H)
I have a lot to do before I'm ready for the laser tube and power supply, but I felt compelled to buy it now, because the estimated arrival if I order today is "Between Friday, Oct. 19 and Thursday, Nov. 1". I hope it'll be arriving just as I need it. I'm trying to fast track this project, which is a novel concept for me. I usually dream about projects, and agonize over projects, but don't build very fast anymore. I guess I'm still suffering from project burnout from when I was a young controls engineer, doing all of the engineering and a fair amount of wrenching and wire pulling on very large high-pressure projects with insane schedules. I think my adrenal gland might be worn out.
Instead of adrenaline, I now run on caffeine.Well, I've spent about $2600 in the last week on my front burner git-R-done-quick laser project. I expect to spend another $900 to $1000 in the next month to finish the project. Almost all of the big stuff has now been purchased. The only other big ticket item is the aluminum extrusion, brackets and fasteners for the framework and the body panels. From a work perspective, I believe the most difficult and time consuming part of this project will be repairing the deck on my house, and then enclosing the patio under the deck to make room for the laser and other dirty/stinky manufacturing equipment. This is Build Log, not This Old House, so I'll save you guys that part of the project, but if I disappear for a while, that's probably where I am. I took off my laser eye patch and put on my Bob The Builder hard hat. Either that, or I'm sleeping, which I haven't been doing very much lately.
I still owe you guys a bill of materials spreadsheet, with sources, links, part numbers and cost. I'll get on that, right after I sleep a little bit. I need to draw a schematic, too.
Apparently, I didn't build that!
- Liberty4Ever
- Posts: 274
- Joined: Wed May 30, 2012 1:49 am
- Location: Lexington KY
Re: Liberty4Ever's Laser Build Log
by Liberty4Ever » Fri Oct 05, 2012 1:43 pm
XY Table & Optics Arrived
The XY table that I purchased as a screw-together kit arrived a couple of days ago, along with the laser tube mounts, the 1st and 2nd mirror mounts, the flying head with the 3rd mirror mount and focusing lens mount and air assist enclosure, the lens and mirrors, the 10600 nm laser safe glasses, and a free gift from Marco - a coil of very nice silicone tubing. I've been too busy to post an entry about it. It was all packaged VERY well. I had stayed up all night cutting parts on my friend's laser and got one hour of sleep when the UPS delivery man woke me up with this 14" X 14" X 64" present on my front porch.
It was very well packed, and was festooned with FRAGILE stickers, presumably to guilt any UPS gorillas who might want to topple it end over end into a truck or something.
It took a while to hack through the clear packing tape and the glass fiber reinforced strapping tape, only to find a giant bubble wrapped dog bone inside. Had this been an actual laser... curiosity would have killed the cat.
I spent about 45 minutes unwrapping a mountain of bubble wrap, and I've barely had time to peel back the microfoam wrap on each of the three bundles in the XY stage, but I'm blown away by the apparent quality. The package weighed 58 pounds, and that mountain of bubble wrap that probably cost $40 didn't weigh much. Most of the weight is the XY stage. It's VERY heavy duty. It seems over designed for a 3' X 5' table. I'm planning on cutting it down to a more manageable size for my shop, and it should be ridiculously rigid and precise when chopped down.
I finally found a few minutes to peel back the leathery foam wrapping the cushions these big parts from rubbing against each other. Did I mention the very professional packaging that seems to have completely spared these difficult to ship items from the abuses of cross country ground shipping? The component quality deserves more than crappy cell phone pictures, so I used the good camera. It deserves better than my photographic skills, but I can't do much about that. I should have better pictures with better lighting during the assembly process. I plan on doing that on a large granite surface plate across town, so I didn't want to do too much unwrapping at this early stage. I still have about seven miles to go before assembly, testing, disassembly, chopping down the size, and reassembly.
Here are the Y rails (left and right on my machine), with the Y axis torque rods stored inside for transportation. I expected these torque rods to be hollow tubes for maximum stiffness and minimum mass, for minimum rotational inertia, so the Y axis can accelerate and decelerate quickly, but at first glance they appear to be very beefy precision ground stainless rod. I believe these rods will be inserted into the flexible shaft couplings on the dual shaft Y axis stepper motor on the back section of frame tubing. The timing belt pulleys (shown on the left but above the image for the right torque tube) will be at the back corners of the frame on the left and right side, driving the timing belt that moves the X axis assembly in the Y direction (front and back). Note the Y axis limit switch at the bottom of the image.
Here are the two Y axis rails that will be on the left and right of my laser table. The idler pulleys at the top of the image will be at the front of the table. The X axis assembly will mount to the two trucks shown on the rails. These trucks slide on the rails as smooth as glass. I plan on having a very powerful exhaust system, because I don't want any abrasive gritty particles from the lasing process to linger around and find their way onto any of the rails. These rails seem like overkill for a laser. Lasers usually have spindly looking parts made to be very lightweight, so the low mass can be accelerated quickly. I get the impression that I could swap out the stepper motors for beefy servo motors and mount a 1 HP router on the gantry and have a heck of a nice gantry router.
Here's the end of the aluminum X axis rail with the X axis idler timing belt. Note the beefy bearing mount, the beefy timing belt, and the beefy rail under the bearing mount and idler.
On the other end of the X axis assembly is the X stepper motor, which doesn't look big enough for all of the other beefy parts. I think I'll need to fabricate an L shaped bracket to mount to the bracket shown at the top, so the 2nd mirror can be up and to the left in this image, to redirect that laser beam down the X axis.
Here are the front and back pieces of the frame, with the Y axis stepper motor. The dual shaft stepper motor connects to the Y axis torque rods via the flexible shaft couplings, to drive the X axis assembly to the front and rear.
Here's the center of the X axis assembly, showing the gantry where the flying optics will mount. Finally, something that looks beefy but light enough to whip around at high rates of acceleration. The gantry truck slides effortlessly on the beefy rail.
Here's the obligatory Bag-O-Fasteners. The hex keys are not the cheap variety that's normally included for assembly, but the ball end variety. There's also a tap. I think that's included if I want to mount another pair of limit switches. I probably do. I like limit switches on both ends of each axis whenever possible. I haven't found any instructions yet, but given that this XY table was preassembled and all I need to do is bolt together the subassemblies, it should be fairly obvious where everything goes once I unwrap all of the parts and have them laid out before me.
Here are four brackets, presumably for connecting the four sides of the frame.
These pictures do not do this XY table justice. They portray it in the least favorable light possible, but hopefully some sense of the quality and extreme beefiness shines through.
The XY table that I purchased as a screw-together kit arrived a couple of days ago, along with the laser tube mounts, the 1st and 2nd mirror mounts, the flying head with the 3rd mirror mount and focusing lens mount and air assist enclosure, the lens and mirrors, the 10600 nm laser safe glasses, and a free gift from Marco - a coil of very nice silicone tubing. I've been too busy to post an entry about it. It was all packaged VERY well. I had stayed up all night cutting parts on my friend's laser and got one hour of sleep when the UPS delivery man woke me up with this 14" X 14" X 64" present on my front porch.
It was very well packed, and was festooned with FRAGILE stickers, presumably to guilt any UPS gorillas who might want to topple it end over end into a truck or something.
It took a while to hack through the clear packing tape and the glass fiber reinforced strapping tape, only to find a giant bubble wrapped dog bone inside. Had this been an actual laser... curiosity would have killed the cat.
I spent about 45 minutes unwrapping a mountain of bubble wrap, and I've barely had time to peel back the microfoam wrap on each of the three bundles in the XY stage, but I'm blown away by the apparent quality. The package weighed 58 pounds, and that mountain of bubble wrap that probably cost $40 didn't weigh much. Most of the weight is the XY stage. It's VERY heavy duty. It seems over designed for a 3' X 5' table. I'm planning on cutting it down to a more manageable size for my shop, and it should be ridiculously rigid and precise when chopped down.
I finally found a few minutes to peel back the leathery foam wrapping the cushions these big parts from rubbing against each other. Did I mention the very professional packaging that seems to have completely spared these difficult to ship items from the abuses of cross country ground shipping? The component quality deserves more than crappy cell phone pictures, so I used the good camera. It deserves better than my photographic skills, but I can't do much about that. I should have better pictures with better lighting during the assembly process. I plan on doing that on a large granite surface plate across town, so I didn't want to do too much unwrapping at this early stage. I still have about seven miles to go before assembly, testing, disassembly, chopping down the size, and reassembly.
Here are the Y rails (left and right on my machine), with the Y axis torque rods stored inside for transportation. I expected these torque rods to be hollow tubes for maximum stiffness and minimum mass, for minimum rotational inertia, so the Y axis can accelerate and decelerate quickly, but at first glance they appear to be very beefy precision ground stainless rod. I believe these rods will be inserted into the flexible shaft couplings on the dual shaft Y axis stepper motor on the back section of frame tubing. The timing belt pulleys (shown on the left but above the image for the right torque tube) will be at the back corners of the frame on the left and right side, driving the timing belt that moves the X axis assembly in the Y direction (front and back). Note the Y axis limit switch at the bottom of the image.
Here are the two Y axis rails that will be on the left and right of my laser table. The idler pulleys at the top of the image will be at the front of the table. The X axis assembly will mount to the two trucks shown on the rails. These trucks slide on the rails as smooth as glass. I plan on having a very powerful exhaust system, because I don't want any abrasive gritty particles from the lasing process to linger around and find their way onto any of the rails. These rails seem like overkill for a laser. Lasers usually have spindly looking parts made to be very lightweight, so the low mass can be accelerated quickly. I get the impression that I could swap out the stepper motors for beefy servo motors and mount a 1 HP router on the gantry and have a heck of a nice gantry router.
Here's the end of the aluminum X axis rail with the X axis idler timing belt. Note the beefy bearing mount, the beefy timing belt, and the beefy rail under the bearing mount and idler.
On the other end of the X axis assembly is the X stepper motor, which doesn't look big enough for all of the other beefy parts. I think I'll need to fabricate an L shaped bracket to mount to the bracket shown at the top, so the 2nd mirror can be up and to the left in this image, to redirect that laser beam down the X axis.
Here are the front and back pieces of the frame, with the Y axis stepper motor. The dual shaft stepper motor connects to the Y axis torque rods via the flexible shaft couplings, to drive the X axis assembly to the front and rear.
Here's the center of the X axis assembly, showing the gantry where the flying optics will mount. Finally, something that looks beefy but light enough to whip around at high rates of acceleration. The gantry truck slides effortlessly on the beefy rail.
Here's the obligatory Bag-O-Fasteners. The hex keys are not the cheap variety that's normally included for assembly, but the ball end variety. There's also a tap. I think that's included if I want to mount another pair of limit switches. I probably do. I like limit switches on both ends of each axis whenever possible. I haven't found any instructions yet, but given that this XY table was preassembled and all I need to do is bolt together the subassemblies, it should be fairly obvious where everything goes once I unwrap all of the parts and have them laid out before me.
Here are four brackets, presumably for connecting the four sides of the frame.
These pictures do not do this XY table justice. They portray it in the least favorable light possible, but hopefully some sense of the quality and extreme beefiness shines through.
Apparently, I didn't build that!
- Liberty4Ever
- Posts: 274
- Joined: Wed May 30, 2012 1:49 am
- Location: Lexington KY
Re: Liberty4Ever's Laser Build Log
by Liberty4Ever » Fri Oct 05, 2012 6:08 pm
The Optics Path
Also included in the LightObject.com order that arrived two days ago were the mounts and mirrors and lens for the optics path, and some miscellaneous stuff.
Here's a laser tube mount to precisely but gently locate the 80mm laser tube inside the modular laser box that I'll mount to the back of the laser. It not only mounts the laser, but also has three large plastic screws that will allow the laser to be adjusted to align it parallel to the X axis. I bought two of these. They'd be easy and relatively inexpensive to build, but I'm cheating on this build and buying everything I can instead of building. In fact, when I ordered the laser tube, the eBay ad stated that the seller would supply the laser tube mounts free if I needed them, but I guessed they would probably be low quality mounts that would be difficult to adjust, and I had already ordered these mounts, so I didn't request any. I was already getting a pretty good deal on that laser tube, in my opinion. If I didn't have three other projects and my small business to run (and I wasn't hopelessly behind in every other aspect of my life), I'd be inclined to buy less and build more, but I spent $64 on these two laser tube mounts, punched its ticket, and got on with the project. Some people prefer to have four adjusting screws instead of three, so the adjustments are more XY rather than some funky symmetry-of-three scheme. I don't have a strong preference. Making two of these, I'd have made the four screw version because it'd be easier to fabricate in low volume with orthogonal adjusting screws 90 degrees apart instead of three screws 120 degrees apart.
Here are the 1st and 2nd mirror mounts. On the right side mirror mount, notice the split ring. This is a fine threaded collar that can be tightened in place to secure the mirror. On cheaper mirror mounts, I believe the mirrors are epoxied in place, which can make them a pain to replace. These mirror mounts look very substantial, and the 25mm mirrors are large enough that I shouldn't have any trouble getting the bean on the mirror when I start aligning the optics. The design, the housings, and the adjustment hardware all appear to be of very high quality. I think I'll need to fabricate a couple of simple L-shaped flat plate mounting brackets to properly locate these mirror mounting brackets relative to the mounting brackets provided on the XY table. I can probably cut these adapter plates from polycarbonate using my friend's laser. If not, I'll cut some aluminum or Delrin on my milling machine. If you buy the XLE version of the XY table from LightObject.com instead of the PRO version that I bought, the optics and mounts are included, so you won't be making any adapter plates.
Here are the three 25mm molybdenum mirrors (bottom of the image) and the 20mm ZnSe focus lens (50.8mm focal distance, top of image). You can't really see much in this picture, other than how they're packaged, but I didn't want to remove them from the protective packaging until I was ready to install them. The molybdenum mirrors are much heavier than I expected. In retrospect, I think I made a mistake on the molybdenum mirrors. They're recommended for 80W as a minimum laser power because the molybdenum mirrors are more durable than mirrors with thin reflective surface coatings, but they're less optically efficient. I haven't found any hard specs yet, but they may be 2-3% less efficient. Considering there are three mirrors in the optical path, losing an additional 2% or 3% at every mirror adds up. For example, if I replaced 99% efficient mirrors with 97% efficient mirrors, the power heading into the focusing lens would drop from 80W*.99*.99*.99 = 77.6W to 80W*.97*.97*.97 = 73.0W. I want that other 4.6W! Again, I have no idea if these are reasonable guesses for the mirror reflective efficiency. I need to look into that more. If I find better numbers (anyone have good numbers?), I'll update these comparison calculations to match reality. I think I'd rather have more efficient mirrors than more durable mirrors. On the laser I've been using, the exhaust is very weak, and despite that, the optics almost never need to be cleaned, particularly the 1st and 2nd mirrors. On my laser, I'm planning on having a much better exhaust system to get the smoke out before it can deposit on the optics (or the timing belts, or...), and my laser table will be much larger, so if I do my lasing on the right side of the table, it'll be very far away from the 1st and 2nd mirror on the left side of the table, so I don't see those mirrors having a contamination problem. Even if the mirrors were damaged, the mirror mounts make them very easy to replace, and they're not THAT expensive. I may keep a molybdenum mirror for the 3rd mirror, immediately above the focus lens. I doubt it'll get dirty either, but it's a bit more likely to be in the smoke path than the 1st and 2nd mirrors. I've added three of the high quality silicon mirrors (http://www.lightobject.com/25mm-High-quality-Si-Plated-Reflection-Mirror-P117.aspx) to my LightObjects.com wish list. I'll use them for the 1st and 2nd mirrors, and I'll keep one as a spare mirror, along with the two spare molybdenum mirrors. On this project, I expect a lot of little learn-as-I-go mistakes like this.
Here is the laser head mount, which I would refer to as the flying optics. This is mounted on the gantry that zips left and right along the X axis. At the left of the image is a 45 degree mirror mount for the 3rd mirror. I'll probably put a 25mm molybdenum mirror in here. This mirror reflects the laser beam that's traveling in front of the X axis rail and parallel to it, down onto the 20mm focus lens which will be mounted near the top of the nipple shaped air assist nozzle on the right of the image. The mirror and the lens are retained by tightening a finely threaded collar to clamp the outside. The hole in the bottom of the air assist nozzle is a little smaller than I expected, but plenty large enough for the laser beam. I was glad it was small. I sized my air assist pump a little small, but I think it'll push enough air through the nozzle orifice that it'll be just about impossible for smoke particles to swim upstream against that high velocity air stream to reach the focus lens. The laser I'm using now doesn't need much cleaning and maintenance for the optics, and I cut some nasty sooty materials, and those optics are wide open. I expect the optics on my new laser to be virtually maintenance free. I'll interlock the laser to the air assist so I won't be lasing without the air assist. I suppose some people want to cut tissue paper or similar materials that would be blown around by the air assist and might want to disable the air assist, but I don't expect to do anything like that. Some people have their laser wired to their CNC controller as the spindle, and the air assist as mist or flood cooling so it can be turned on and off. I think I'm going to wire the exhaust and air assist to the main laser power switch. When the laser is on, so is the air assist and exhaust, so there shouldn't be any startup issues where the laser is making smoke before the air assist or exhaust system are adequately spooled up and dispersing and venting the smoke. Maybe I won't get an EPA Energy Star rating for my laser because the 18W air assist pump and the 800W exhaust blower are running all the time, but I may never need to clean any of my optics!
The knurled thumb knob just right of center can be loosened and the lower portion of the laser head mount can be lowered 40mm (about 1.6"). It's very tempting to completely forgo any adjustable Z height for the bed and simply adjust the focus lens stalk up and down to focus the laser on the material to be cut. A simple height gauge could be made to place on top of the material to be cut or engraved, and then lower the nozzle until it touches the height gauge. There is also a nice graduated scale on the stalk (barely visible to the right of the knurled thumb knob) to facilitate relative adjustments if you know the difference in the height of the materials you're cutting or engraving.
I plan on using a press fitting for the air assist fitting that threads into the port on the side of the nozzle. The stalk adjusts straight up and down for height adjustment, so that wouldn't be a problem for a fixed air assist tube if adequate tubing is used to allow for the Z axis adjustment of the stalk, but to access the focus lens inside the stalk, the nozzle must be unscrewed. It's secured my a knurled jam nut above the nozzle. The air assist tubing must be removed to unscrew the nozzle. If you wanted a low profile fitting on the nozzle due to its proximity to the work and the potential to snag and hang, an inline press fitting an inch or two up the air assist tubing might be a better option. Disconnect the tubing stub and unscrew the nozzle with a short piece of attached tubing.
Miscellaneous Stuff You Probably Need
I also bought some laser safety glasses. From similar experiences in the past, this is probably one of those pieces of safety equipment that I'll use very little, but like fire extinguishers and firearms, laser safety glasses are an item that's better to have and not need, than need and not have. I'll probably use them once or twice when testing the laser tube and aligning the optics, possibly in an abundance of caution, but an eye is a terrible thing to waste. When ordering, note that you need to buy the laser safety glasses that are designed to attenuate the frequency of laser light that you'll be using. In this case, I bought the 10,600 nm laser safety glasses that are designed to filter light from a CO2 laser. These weren't cheap. They were $45. They weren't much cheaper on eBay, and some were more expensive. I didn't really trust eBay for this purchase. There's little accountability for items like this, because it's not immediately obvious if they work or not. If they don't work when you need them, they were nothing but a false sense of security. Some disreputable companies think nothing of printing trademarked logos, CE marks or other agency approvals on products that were never tested, have not met the standards, and may not even be designed to be anything more than a "looks like" copy. I didn't want to buy a pair of cheap sunglasses on eBay with a pad printed fake CE mark.
Marco threw in a roll of silicone tubing. I was thinking about using some flexible ether based tubing I've used in the past. I was thinking the silicone tubing might be a bit too flexible and I didn't want it to kink and cut off the flow of coolant, but I need not have been concerned. By now, the laser suppliers have the details pretty well worked out, and this silicone tubing looks perfect for this application. It has an 8mm ID and a 12mm OD. It should simply slip onto the inlet and outlet ports on the laser tube without requiring so much force that the glass retort might be broken. Again, the laser folks have this all figured out by now. I'll keep the tubing runs as short as possible, and design the cooling system with gentle curves in the tubing to maximize flow and minimize the chances of kinking the tubing. I'll probably use plastic barb fittings on the pump outlet, the radiator and the flow switch.
Observations So Far
The XY table and the optics that I received from LightObject.com all look absolutely wonderful. For the past six years, I've been using the heck out of a friend's desktop laser cutter. I think he spent about $12,000 on it, and frankly, the components I've received from LightObject.com make his American manufactured laser look like a 6th grade science project, and not even the winning entry!
I've been super busy lately, essentially adding this laser build to my already insane schedule. Caffeine is your friend! I'm trying to stay up on the posts to this laser build log, because I know myself well enough to know that once I fall behind, I probably won't get caught up again.
It's time to head across town to work on the giant CNC gantry machine with dual 15 HP routers and a 7.5 HP radial saw. I need to get the Z axis moving today so I can get the servo drives ordered for the X and Y axes. When I get home after that, my second order from LightObject.com will be here, and maybe the slightly undersized stepper motor power supply that I ordered.
I hope to start building and testing the XY table for my laser build next week, finally deciding on the size of the XY table I want, getting a few more parts on order, and designing the extruded aluminum frame. I'll try to start the BOM spreadsheet this weekend, which will be a big help in placing the many little miscellaneous parts orders for things like switches and breakers, and I'll try to draw the first rough pass on the schematic, mostly to organize my thoughts and make sure I'm focused on the big picture. It's easy to lose sight of that when focused on distracting details at this point of the project. At best, that results in a wait near the end of the project when a forgotten part is ordered and everything grinds to a halt until it arrives. At worst, there is some disassembly and moving things around to accommodate an omitted but much needed part. Good project management skills and attention to the big picture and all of the details can save time and money and frustration and brain cells. It's better to spend more time thinking and planning, and less time drilling holes, mounting parts, finding mistakes, unmounting parts, drilling new holes....
Also included in the LightObject.com order that arrived two days ago were the mounts and mirrors and lens for the optics path, and some miscellaneous stuff.
Here's a laser tube mount to precisely but gently locate the 80mm laser tube inside the modular laser box that I'll mount to the back of the laser. It not only mounts the laser, but also has three large plastic screws that will allow the laser to be adjusted to align it parallel to the X axis. I bought two of these. They'd be easy and relatively inexpensive to build, but I'm cheating on this build and buying everything I can instead of building. In fact, when I ordered the laser tube, the eBay ad stated that the seller would supply the laser tube mounts free if I needed them, but I guessed they would probably be low quality mounts that would be difficult to adjust, and I had already ordered these mounts, so I didn't request any. I was already getting a pretty good deal on that laser tube, in my opinion. If I didn't have three other projects and my small business to run (and I wasn't hopelessly behind in every other aspect of my life), I'd be inclined to buy less and build more, but I spent $64 on these two laser tube mounts, punched its ticket, and got on with the project. Some people prefer to have four adjusting screws instead of three, so the adjustments are more XY rather than some funky symmetry-of-three scheme. I don't have a strong preference. Making two of these, I'd have made the four screw version because it'd be easier to fabricate in low volume with orthogonal adjusting screws 90 degrees apart instead of three screws 120 degrees apart.
Here are the 1st and 2nd mirror mounts. On the right side mirror mount, notice the split ring. This is a fine threaded collar that can be tightened in place to secure the mirror. On cheaper mirror mounts, I believe the mirrors are epoxied in place, which can make them a pain to replace. These mirror mounts look very substantial, and the 25mm mirrors are large enough that I shouldn't have any trouble getting the bean on the mirror when I start aligning the optics. The design, the housings, and the adjustment hardware all appear to be of very high quality. I think I'll need to fabricate a couple of simple L-shaped flat plate mounting brackets to properly locate these mirror mounting brackets relative to the mounting brackets provided on the XY table. I can probably cut these adapter plates from polycarbonate using my friend's laser. If not, I'll cut some aluminum or Delrin on my milling machine. If you buy the XLE version of the XY table from LightObject.com instead of the PRO version that I bought, the optics and mounts are included, so you won't be making any adapter plates.
Here are the three 25mm molybdenum mirrors (bottom of the image) and the 20mm ZnSe focus lens (50.8mm focal distance, top of image). You can't really see much in this picture, other than how they're packaged, but I didn't want to remove them from the protective packaging until I was ready to install them. The molybdenum mirrors are much heavier than I expected. In retrospect, I think I made a mistake on the molybdenum mirrors. They're recommended for 80W as a minimum laser power because the molybdenum mirrors are more durable than mirrors with thin reflective surface coatings, but they're less optically efficient. I haven't found any hard specs yet, but they may be 2-3% less efficient. Considering there are three mirrors in the optical path, losing an additional 2% or 3% at every mirror adds up. For example, if I replaced 99% efficient mirrors with 97% efficient mirrors, the power heading into the focusing lens would drop from 80W*.99*.99*.99 = 77.6W to 80W*.97*.97*.97 = 73.0W. I want that other 4.6W! Again, I have no idea if these are reasonable guesses for the mirror reflective efficiency. I need to look into that more. If I find better numbers (anyone have good numbers?), I'll update these comparison calculations to match reality. I think I'd rather have more efficient mirrors than more durable mirrors. On the laser I've been using, the exhaust is very weak, and despite that, the optics almost never need to be cleaned, particularly the 1st and 2nd mirrors. On my laser, I'm planning on having a much better exhaust system to get the smoke out before it can deposit on the optics (or the timing belts, or...), and my laser table will be much larger, so if I do my lasing on the right side of the table, it'll be very far away from the 1st and 2nd mirror on the left side of the table, so I don't see those mirrors having a contamination problem. Even if the mirrors were damaged, the mirror mounts make them very easy to replace, and they're not THAT expensive. I may keep a molybdenum mirror for the 3rd mirror, immediately above the focus lens. I doubt it'll get dirty either, but it's a bit more likely to be in the smoke path than the 1st and 2nd mirrors. I've added three of the high quality silicon mirrors (http://www.lightobject.com/25mm-High-quality-Si-Plated-Reflection-Mirror-P117.aspx) to my LightObjects.com wish list. I'll use them for the 1st and 2nd mirrors, and I'll keep one as a spare mirror, along with the two spare molybdenum mirrors. On this project, I expect a lot of little learn-as-I-go mistakes like this.
Here is the laser head mount, which I would refer to as the flying optics. This is mounted on the gantry that zips left and right along the X axis. At the left of the image is a 45 degree mirror mount for the 3rd mirror. I'll probably put a 25mm molybdenum mirror in here. This mirror reflects the laser beam that's traveling in front of the X axis rail and parallel to it, down onto the 20mm focus lens which will be mounted near the top of the nipple shaped air assist nozzle on the right of the image. The mirror and the lens are retained by tightening a finely threaded collar to clamp the outside. The hole in the bottom of the air assist nozzle is a little smaller than I expected, but plenty large enough for the laser beam. I was glad it was small. I sized my air assist pump a little small, but I think it'll push enough air through the nozzle orifice that it'll be just about impossible for smoke particles to swim upstream against that high velocity air stream to reach the focus lens. The laser I'm using now doesn't need much cleaning and maintenance for the optics, and I cut some nasty sooty materials, and those optics are wide open. I expect the optics on my new laser to be virtually maintenance free. I'll interlock the laser to the air assist so I won't be lasing without the air assist. I suppose some people want to cut tissue paper or similar materials that would be blown around by the air assist and might want to disable the air assist, but I don't expect to do anything like that. Some people have their laser wired to their CNC controller as the spindle, and the air assist as mist or flood cooling so it can be turned on and off. I think I'm going to wire the exhaust and air assist to the main laser power switch. When the laser is on, so is the air assist and exhaust, so there shouldn't be any startup issues where the laser is making smoke before the air assist or exhaust system are adequately spooled up and dispersing and venting the smoke. Maybe I won't get an EPA Energy Star rating for my laser because the 18W air assist pump and the 800W exhaust blower are running all the time, but I may never need to clean any of my optics!
The knurled thumb knob just right of center can be loosened and the lower portion of the laser head mount can be lowered 40mm (about 1.6"). It's very tempting to completely forgo any adjustable Z height for the bed and simply adjust the focus lens stalk up and down to focus the laser on the material to be cut. A simple height gauge could be made to place on top of the material to be cut or engraved, and then lower the nozzle until it touches the height gauge. There is also a nice graduated scale on the stalk (barely visible to the right of the knurled thumb knob) to facilitate relative adjustments if you know the difference in the height of the materials you're cutting or engraving.
I plan on using a press fitting for the air assist fitting that threads into the port on the side of the nozzle. The stalk adjusts straight up and down for height adjustment, so that wouldn't be a problem for a fixed air assist tube if adequate tubing is used to allow for the Z axis adjustment of the stalk, but to access the focus lens inside the stalk, the nozzle must be unscrewed. It's secured my a knurled jam nut above the nozzle. The air assist tubing must be removed to unscrew the nozzle. If you wanted a low profile fitting on the nozzle due to its proximity to the work and the potential to snag and hang, an inline press fitting an inch or two up the air assist tubing might be a better option. Disconnect the tubing stub and unscrew the nozzle with a short piece of attached tubing.
Miscellaneous Stuff You Probably Need
I also bought some laser safety glasses. From similar experiences in the past, this is probably one of those pieces of safety equipment that I'll use very little, but like fire extinguishers and firearms, laser safety glasses are an item that's better to have and not need, than need and not have. I'll probably use them once or twice when testing the laser tube and aligning the optics, possibly in an abundance of caution, but an eye is a terrible thing to waste. When ordering, note that you need to buy the laser safety glasses that are designed to attenuate the frequency of laser light that you'll be using. In this case, I bought the 10,600 nm laser safety glasses that are designed to filter light from a CO2 laser. These weren't cheap. They were $45. They weren't much cheaper on eBay, and some were more expensive. I didn't really trust eBay for this purchase. There's little accountability for items like this, because it's not immediately obvious if they work or not. If they don't work when you need them, they were nothing but a false sense of security. Some disreputable companies think nothing of printing trademarked logos, CE marks or other agency approvals on products that were never tested, have not met the standards, and may not even be designed to be anything more than a "looks like" copy. I didn't want to buy a pair of cheap sunglasses on eBay with a pad printed fake CE mark.
Marco threw in a roll of silicone tubing. I was thinking about using some flexible ether based tubing I've used in the past. I was thinking the silicone tubing might be a bit too flexible and I didn't want it to kink and cut off the flow of coolant, but I need not have been concerned. By now, the laser suppliers have the details pretty well worked out, and this silicone tubing looks perfect for this application. It has an 8mm ID and a 12mm OD. It should simply slip onto the inlet and outlet ports on the laser tube without requiring so much force that the glass retort might be broken. Again, the laser folks have this all figured out by now. I'll keep the tubing runs as short as possible, and design the cooling system with gentle curves in the tubing to maximize flow and minimize the chances of kinking the tubing. I'll probably use plastic barb fittings on the pump outlet, the radiator and the flow switch.
Observations So Far
The XY table and the optics that I received from LightObject.com all look absolutely wonderful. For the past six years, I've been using the heck out of a friend's desktop laser cutter. I think he spent about $12,000 on it, and frankly, the components I've received from LightObject.com make his American manufactured laser look like a 6th grade science project, and not even the winning entry!
I've been super busy lately, essentially adding this laser build to my already insane schedule. Caffeine is your friend! I'm trying to stay up on the posts to this laser build log, because I know myself well enough to know that once I fall behind, I probably won't get caught up again.
It's time to head across town to work on the giant CNC gantry machine with dual 15 HP routers and a 7.5 HP radial saw. I need to get the Z axis moving today so I can get the servo drives ordered for the X and Y axes. When I get home after that, my second order from LightObject.com will be here, and maybe the slightly undersized stepper motor power supply that I ordered.
I hope to start building and testing the XY table for my laser build next week, finally deciding on the size of the XY table I want, getting a few more parts on order, and designing the extruded aluminum frame. I'll try to start the BOM spreadsheet this weekend, which will be a big help in placing the many little miscellaneous parts orders for things like switches and breakers, and I'll try to draw the first rough pass on the schematic, mostly to organize my thoughts and make sure I'm focused on the big picture. It's easy to lose sight of that when focused on distracting details at this point of the project. At best, that results in a wait near the end of the project when a forgotten part is ordered and everything grinds to a halt until it arrives. At worst, there is some disassembly and moving things around to accommodate an omitted but much needed part. Good project management skills and attention to the big picture and all of the details can save time and money and frustration and brain cells. It's better to spend more time thinking and planning, and less time drilling holes, mounting parts, finding mistakes, unmounting parts, drilling new holes....
Last edited by Liberty4Ever on Sat Oct 06, 2012 10:03 am, edited 1 time in total.
Apparently, I didn't build that!
- Liberty4Ever
- Posts: 274
- Joined: Wed May 30, 2012 1:49 am
- Location: Lexington KY
Re: Liberty4Ever's Laser Build Log
by Liberty4Ever » Sat Oct 06, 2012 9:02 am
Coolant Temperature Monitoring & Alarm
Maybe my Google Foo is weak, but I was shocked at the lack of panel mounted thermometers with a simple high temperature alarm. I thought this would be a common application and I could take my pick, and find a nice panel mounted digital display for the coolant temperature with an output that could disable the laser if the coolant started to overheat. Instead, I found some cheap battery operated devices intended for monitoring aquariums, some 220VAC only models, and I was surprised that so many of the digital thermometers were Celsius only. I guess they don't call it a Quarter Pounder With Cheese in Europe, because of the metric system. Don't get me wrong. I love the metric system and wish the US had converted when we made the half hearted attempt in the mid 1970s... but we didn't.
With my limited choices, I was almost always forced to buy a dedicated temperature controller with a complex front panel with a lot of push buttons and a confusing display of present value and set point, when I wanted to keep it simple. I'm trying to be an industrial controls guy and buy a solution, but I finally gave up after two hours of looking and bought a cheap digital thermometer. Here's what I bought.
http://www.ebay.com/itm/330795894274
I was a bit reluctant to buy such a cheap digital thermometer, but then I read the following on the eBay ad.
How could I possibly go wrong?
I probably should have bought a similar module with 7-segment LEDs instead of the color graphical LCD. Often, the cheap graphical LCDs will have a limited lifespan. It was only $5.50 including free shipping, so I bought a spare. If they both die, I'll replace it with an LED version.
Being an electrical engineer, my first backup plan to implement the high temperature alarm was building a simple add-on circuit with a quad op amp to monitor the thermometer's NTC thermistor, with voltage follower input buffer, amplifier, hysteresis to avoid triggering on noise around the alarm set point to prevent rapid laser enable and disable cycling, a voltage follower output buffer, and a relay output to shut down the laser. Then I came to my senses and went back into BUY THE SOLUTION mode. Happily, there are many good choices for submersible thermal switches. Here's what I bought:
http://www.ebay.com/itm/360486833885
I'll add a simple relay to disable the laser when the thermal switch opens. I'll have a reverse engraved error indicator on the main panel next to the digital thermometer that is back illuminated by a red LED to display COOLANT OVERHEAT. The bimetallic thermal switch has hysteresis built into the way it works, so it'll probably enable the laser again when the coolant temperature drops 10C or so.
It looks like the submersible thermal switch may have too much hysteresis. In the event that it requires the water temperature to cool down too much before resetting for my application, I decided to buy a backup thermal switch. At these prices, it's cheap insurance to keep my project on track. The backup isn't submersible, so I'd need to machine an aluminum block with a coolant passage and a milled pocket for the bimetallic dome thermal switch.
http://www.ebay.com/itm/170831821863
Much as I generally prefer all of the sensors to be inputs and the controller to make smart choices based on those inputs, in the case of my laser, I have limited inputs to the PC with just the optically isolated parallel port, and for the safety of the any people in the area, I don't want to rely on a properly functioning PC to shut off the laser if the door is open. Similarly, I don't want to rely on the PC to protect the laser by shutting it down if any of the faults indicates the laser cooling system may be compromised. So my plan is to wire all of the fault conditions as series connected relay or switch contacts. If any one of them opens, the laser is disabled, an appropriate error message is illuminated on the front panel, and a single LASER DISABLED signal is sent to the LinuxCNC PC so it knows to stop everything. I'll probably use the laser enable relay logic to enable the stepper motor drivers so all motion and the laser are disabled in hardware at any sign of a problem. It would be wired as an enhanced E-Stop circuit that added DOOR OPEN, COOLANT OVERHEAT, NO COOLANT FLOW, and possibly EXCESSIVE LASER CURRENT. The milliamp meter doesn't have a high current alarm output, so I may get to build that op amp circuit after all... but I'll probably engrave the front panel with the maximum laser current and monitor that manually with no automatic shutdown for that unlikely fault mode. Keep it simple.
One advantage to being in the GZF time zone (where all of the Geek Zombie Freaks live): I can order my cheap eBay electronics from Shenzhen, China at 2:55 AM, and it's marked as shipped at 3:32 AM. Of course, it'll still take two weeks to get here.
Speaking of late night geek zombie freaks, I guess that works both ways. I just got an email notification at 4:07 AM EST that Roy at Panucatt has just shipped my second Azteeg X3 controller for my second Hadron ORD Bot 3D printer. Roy is in California. It's after 1 AM there. I'm having a Bladerunner flashback of Roy Batty in the elevator with J.F. Sebastian, on his way up to see Dr. Tyrell.
"Queen to Bishop 6. Check."
"Got a brainstorm, huh, Sebastian? Milk and cookies kept you awake, huh? Lets discuss this. You better come up, Sebastian."
Maybe my Google Foo is weak, but I was shocked at the lack of panel mounted thermometers with a simple high temperature alarm. I thought this would be a common application and I could take my pick, and find a nice panel mounted digital display for the coolant temperature with an output that could disable the laser if the coolant started to overheat. Instead, I found some cheap battery operated devices intended for monitoring aquariums, some 220VAC only models, and I was surprised that so many of the digital thermometers were Celsius only. I guess they don't call it a Quarter Pounder With Cheese in Europe, because of the metric system. Don't get me wrong. I love the metric system and wish the US had converted when we made the half hearted attempt in the mid 1970s... but we didn't.
With my limited choices, I was almost always forced to buy a dedicated temperature controller with a complex front panel with a lot of push buttons and a confusing display of present value and set point, when I wanted to keep it simple. I'm trying to be an industrial controls guy and buy a solution, but I finally gave up after two hours of looking and bought a cheap digital thermometer. Here's what I bought.
http://www.ebay.com/itm/330795894274
I was a bit reluctant to buy such a cheap digital thermometer, but then I read the following on the eBay ad.
I am sure it the right thing you need now.
Don't hesitate, bid now and never miss it. You will receive a parcel contains as below.
How could I possibly go wrong?
I probably should have bought a similar module with 7-segment LEDs instead of the color graphical LCD. Often, the cheap graphical LCDs will have a limited lifespan. It was only $5.50 including free shipping, so I bought a spare. If they both die, I'll replace it with an LED version.
Being an electrical engineer, my first backup plan to implement the high temperature alarm was building a simple add-on circuit with a quad op amp to monitor the thermometer's NTC thermistor, with voltage follower input buffer, amplifier, hysteresis to avoid triggering on noise around the alarm set point to prevent rapid laser enable and disable cycling, a voltage follower output buffer, and a relay output to shut down the laser. Then I came to my senses and went back into BUY THE SOLUTION mode. Happily, there are many good choices for submersible thermal switches. Here's what I bought:
http://www.ebay.com/itm/360486833885
I'll add a simple relay to disable the laser when the thermal switch opens. I'll have a reverse engraved error indicator on the main panel next to the digital thermometer that is back illuminated by a red LED to display COOLANT OVERHEAT. The bimetallic thermal switch has hysteresis built into the way it works, so it'll probably enable the laser again when the coolant temperature drops 10C or so.
It looks like the submersible thermal switch may have too much hysteresis. In the event that it requires the water temperature to cool down too much before resetting for my application, I decided to buy a backup thermal switch. At these prices, it's cheap insurance to keep my project on track. The backup isn't submersible, so I'd need to machine an aluminum block with a coolant passage and a milled pocket for the bimetallic dome thermal switch.
http://www.ebay.com/itm/170831821863
Much as I generally prefer all of the sensors to be inputs and the controller to make smart choices based on those inputs, in the case of my laser, I have limited inputs to the PC with just the optically isolated parallel port, and for the safety of the any people in the area, I don't want to rely on a properly functioning PC to shut off the laser if the door is open. Similarly, I don't want to rely on the PC to protect the laser by shutting it down if any of the faults indicates the laser cooling system may be compromised. So my plan is to wire all of the fault conditions as series connected relay or switch contacts. If any one of them opens, the laser is disabled, an appropriate error message is illuminated on the front panel, and a single LASER DISABLED signal is sent to the LinuxCNC PC so it knows to stop everything. I'll probably use the laser enable relay logic to enable the stepper motor drivers so all motion and the laser are disabled in hardware at any sign of a problem. It would be wired as an enhanced E-Stop circuit that added DOOR OPEN, COOLANT OVERHEAT, NO COOLANT FLOW, and possibly EXCESSIVE LASER CURRENT. The milliamp meter doesn't have a high current alarm output, so I may get to build that op amp circuit after all... but I'll probably engrave the front panel with the maximum laser current and monitor that manually with no automatic shutdown for that unlikely fault mode. Keep it simple.
One advantage to being in the GZF time zone (where all of the Geek Zombie Freaks live): I can order my cheap eBay electronics from Shenzhen, China at 2:55 AM, and it's marked as shipped at 3:32 AM. Of course, it'll still take two weeks to get here.
Speaking of late night geek zombie freaks, I guess that works both ways. I just got an email notification at 4:07 AM EST that Roy at Panucatt has just shipped my second Azteeg X3 controller for my second Hadron ORD Bot 3D printer. Roy is in California. It's after 1 AM there. I'm having a Bladerunner flashback of Roy Batty in the elevator with J.F. Sebastian, on his way up to see Dr. Tyrell.
"Queen to Bishop 6. Check."
"Got a brainstorm, huh, Sebastian? Milk and cookies kept you awake, huh? Lets discuss this. You better come up, Sebastian."
Apparently, I didn't build that!
- Liberty4Ever
- Posts: 274
- Joined: Wed May 30, 2012 1:49 am
- Location: Lexington KY
Re: Liberty4Ever's Laser Build Log
by canadianavenger » Sat Oct 06, 2012 11:13 am
Liberty4Ever wrote:I probably should have bought a similar module with 7-segment LEDs instead of the color graphical LCD. Often, the cheap graphical LCDs will have a limited lifespan. It was only $5.50 including free shipping, so I bought a spare. If they both die, I'll replace it with an LED version.
That's not a color graphical LCD. It's a mono segment LCD with a colored graphical inlay. You can see the meter segments faintly in the picture under the red part. So you have a fixed number if digits and fixed resolution of where the meter shows its position.
- canadianavenger
- Posts: 153
- Joined: Wed Nov 30, 2011 3:24 am
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