The recent Epilog Laser Challenge at Instructables.com got me thinking about building a low cost CNC laser. The engraver they had as the prize had a list price of about $8,000. The income tax on that would be quite a lot. I thought a larger more powerful machine could easily be built for less than the amount you would have to pay for the tax. The Epilog Zing 16 is 30W with an area of 16" x 20". Try to beat that for less than $1,000. I understand that a huge part of what you get from Epilog is software, safety, support and a guarantee, so it is not a really fair challenge.
I want to approach this in a very serialized manner to prevent wasting excess money or time. The design should be very scalable to more powerful lasers. I will start with the lowest power laser as a proof of concept. I have built several successful CNC routers from scratch so I feel confident on the mechanics. The laser issues will all be new. There is a lot of mystery on the Chinese parts. I will try to fill in all I can along the way.
I give up. The weather wins. I am moving my contraption inside. I don't have much space in my electronics work area, but I'll make do. The first thing I need to do is plumb the exhaust outside. I'll set this up before I move it so I don't have to work around it.
Please...no comments from you southern hemisphere weasles. I know...you just got back from the beach..blah,blah, blah
I have my laser in the garage which is normally unheated. When it is this cold, I hate to fire up the the heater. My controller is ready to test. It works really well on my eletronics bench and on the scope, but I can't test it. It will probably be several days before I get a chance. The graphic above is today...and that is warm for this week.!
My house just is not big enough to bring the laser in.
I had a few setbacks trying to get the controller installed. I got the it installed and tried to do some tests with it, but the Lantronix WiPort Ethernet board would not connect. It is a pretty old board and had seen a lot of abuse, so I guess it finally died. I switched it out with an RS232 to TTL adapter I have. That worked fine. The controller was working again. It took a little time to redo the PC program to use RS232 over Ethernet.
The next test reveled a few other problems. My test setup uses a Xlylotex 3 axis stepper controller, but my laser has a home brew controller that has opto isolators sized for 5 volts. The XMOS 3.3v was not able to drive it enough. The XMOS can only drive a a few milliamps anyway, so I was worried I may have blown some of the I/O pins. When I got back to my workbench the system was acting very strangely. One motor would spin both ways, the other would only run in reverse and nothing would happen if I tried to run both motors at the same time. I spend a lot of time trying to debug the issue thinking it was blown output pins. It turned out the one motor's direction wired got switched with a ground wire. I fixed that and everything is back to normal. I have another of my stepper controller boards that I jumpered out the optos. Hopefully it will run on 3.3V. I think it will because it is now quite similar to the Xylotex board.
Moving the setup between electronics workbench and the where the laser is takes some time, so each each iteration is a real time consumer. I will not be able to test it again until at least tomorrow.
I added some jog buttons to the interface and added a progress bar. I will probably add some more controls for the Z axis too.
The whole project is ready for some testing on the laser. That will probably happen after Xmas....XMOS after XMAS ho ho ho. I expect a few problems and to learn a few things. I'll post anything that happens.
I did a little cleanup on the PC side software for the engraving controller. Right now it is just good enough to test with. It needs a lot of clean-up and error checking.
The image is streamed from the program to the controller. It sends the image data one row at a time. While it is engraving one row, the next row is being sent. As always, click on the image for a larger view.
I made a little progress on the XMOS engraver controller. The motion and the power control are pretty much done.
Below is a picture of my test setup. The XMOS XK-1 development board is the little green square in the lower right corner. It has a JTAG programmer hanging off the right side of it. The red PCB above that is a Lantronix WiPort development board. That is only used as a simple way to get serial data to the board while I am testing. It is a Ethernet to serial system. It is actually quite handy not to have to deal with USB drivers at this stage. The PCB with the heatsinks is a very old Xylotex 3 axis control board to power the steppers.
If you think this is ugly, you should see the controller program on the PC. The buttons and text boxes are just scattered randomly about as I needed them.
The video shows an engraving simulation running. I have the engraving parameters slowed down because they were just a blur on the video. The Y step over is also exaggerated to make it easier to see. There is an LED on the XMOS board representing the laser power. The it is running an image that is a slow gradient, so it can show up on the video. It is hard to see on the video but it is slowing ramping up and down in intensity.
The XMOS pins run at 3.3V. They are 5V tolerant. The PWM at the laser will require 5V so I need to run that through a transistor or something to get it up to 5V.
I received some new 0.080" pitch belts and pulleys from Stock Drive. I wanted to increase my steps per inch. I directly drive my belt from the steppers. The current belt is 0.200" pitch. That size limits the steps per inch to about 800. Mine is actually 667 right now. I wanted at least a 1000. A 20 tooth pulley gets me exactly 1000 steps per inch. The belt looks almost as strong as the 0.200" belt, but it is a lot more flexible around the pulley. I bought 20ft of open ended belt. I plan to join the belt where it meets the laser head. I plan on gluing a small piece of belt to a plate with the grooves pointing out. This will act as a clamp to hold the belt. The grooves will prevent the belt from slipping.
I received a request on the forum for a block diagram. The closest thing I have is my system schematic. I posted it ways back in the buildlog, but I updated it to show how it is currently setup. I have been working on the engraving controller, so I really dumbed it down for a while. The pot often comes off to test the PWM.
The engraving controller is moving along. I switched to using an XMOS chip. The PIC was working, but I realized, eventually I would probably run into a performance limit with an 8-bit 40MHz micro. The XMOS circuit is controlling the motors perfectly. The PWM power control is working. I am now working on the PC side software which will stream the image to controller. I will create a web page dedicated to the effort when I have it cleaned up a little.
I was playing around with some motion control algorithms and tried one out on a PIC microcontroller. I didn't see much on the Internet on this so I posted a version here. It is dumbed down to the very basics so it should be easy to follow. This should be adaptable to other micros
The laser power supply remains "charged-up" for quite a while after the power is disconnected. The power supply contains a large amount of capacitance so it can still power the laser for a few seconds after the power is disconnected. This is a laser and high voltage danger. I don't know how long it takes to self discharge, but it could be quite a while. Keep this in mind when working with it. I would give it several minutes before touching any wires or the tube.
The bottom line is even disconnected from power, these puppies can still kill you. Take your time....be safe.
I received a few requests to start a forum. So here it is. This is my first attempt at running phpBB, so please be kind with the comments and suggestions. If you have any trouble. It is kind of embarrassing having a forum with no posts, so if there is not much activity after a few weeks I will pull the plug.
Another laser builder
Fertito over at Fertito Custom Designs is working on a laser cutter. We have been trading a lot of email lately. He is just getting his 25W laser tube turned on. He plans to cut materials to make kites for kite surfing, snow kiting and paragliding. He has already made several plotters and plans to convert one to a laser cutter. Check out his web site. It is in French, but you can get inspired by his work. He programs his own controllers and software.
There have been a few questions lately on how to setup the power supply. I probably rushed through it before. He is a move comprehensive explanation. Click on the image for a larger view.
The power is supplied to the power supply via the black terminal block on the upper left side. It has four terminals, but only three of them are labeled. The top one should be connected to earth ground. This is the center center terminal on a three prong plug. I also connected the chassis to earth ground just in case there is a malfunction. This way the case will always be safe to touch. The next two down are for AC power. They are interchangeable. I hooked neutral to the upper AC terminal and line to the lower one. Be sure you are supplying the correct voltage. It should be labeled 110V or 220v somewhere on the case. The lowest terminal is the negative return for the laser tube. One my tube it was the terminal at the output end of the tube.
The green terminal block on the right side is the control interface. The top terminal has +5V on it. If you are using a potentiometer to control the power, this can be use on one side as shown in the schematic below. The IN terminal controls the power. This can be the wiper of the pot or your PWM input. The manual for the power supply suggest 20-50kHz, but slower PWMs seem to work if you are OK with slow response. The next down is ground. This gives you a reference to ground that can be used on the pot and should be connected to your controller board so they are tied together.
The next terminal is labeled WP. This stands for water pump. It has nothing to do with the pump. It is actually an interlock circuit. It must be tied to ground for the power supply to turn on. It is intended to be hooked up to a switch that will open if the cooling fails. I also ran it through an emergency off switch. Many times Mach3 or EMC2 has messed up and left the laser on at the wrong time. It is nice to have a quick way to turn off the laser quickly. I also always power up the system with the emergency off switch open.
The last two terminals are the enable pins. You can use either or both of these to turn on the power supply. Connecting the L pin to ground will turn it on or connecting the H pin to 5V will turn it on. I use the L pin through a manual switch and use the H pin for software control.
If there are any further questions please let me know
I have been trading email with Henry at Full Spectrum Engineering. They have some nice laser kits. It sounds like you get the price of a Chinese laser with the support and electronics of a US supplier. Check out their controller and keep an eye on the site.... there may be some great new stuff for us home builders coming. Tell Henry you heard about them here.
I have made a lot of good contacts via this build log. Many people are building their own machines. I finally convinced one to start a build log. This is Greg's build log at LECCOMPUTING. He has made a lot of progress. I am jealous of his table lift design. Go with his method over mine. Good job Greg!
I can donate web space to anyone one else who wants to start a build log.
Low Res Images engraved in wood, marble and slate.
I haven't been making too many entries lately. I am still frustrated with engraving. The best I can do right now is from my G-Code converter program (see above). That works OK on basic images. I have been working on a "stand-alone" controller board for true grayscale engraving. I have most of the pieces of the puzzle working on the bench and o'scope. I need to get them on the machine then cleaned up.
I have been working on some electronics lately for this project and some other things. I have most of the power supply control circuit tested. I may go for a PCB soon. I added the top and front panels to the enclosure. I still need to add the door.
I worked on getting my image to g-code program engraver program working with EMC2. It actually worked better than Mach3. I will doe a complete write on getting it to work, but the short answer is this. I used M64P0 and M65P1 to control the beam. It works similar to M10 M11 in Mach3.
Here are the results on wood and glass. They are monochrome, but the best I have made yet. I don't think there is any good way of doing true gray scale with the software available to the home builder. I think it is going to take a custom built FPGA controller. I order a development kit. Right now I am happy to be able to spell FPGA. It may take me a while.
I got some of the parts I was waiting for. I got it controlling the power. It reads Mach3 PWM and sets the digital pot which is hooked to the laser power supply. I switch to using a PIC microcontroller. I started a dedicated page to track it's progress in one place.
I wrote a little program to allow simple raster engraving of an image. It imports an image then outputs G-Code of lines to create that image. Right now it only works with one gray level. Anything 50% gray (or color equivalent) or darker gets etched. It is currently hard coded for my M11P1 method of turning on the laser. I may add some sort of configurable post processor to allow other types of control. It needs a bit of test before I turn it loose. The program was written in the free version of VB.NET 2008. I will release the program and source after I test it a while. It is rather simple and only took me about 1.5 hrs to write.
Below is a screen shot of the program and the Mach3 toolpath window.
There is some construction going on in my garage, where I keep the laser, so I have not had good access to it lately. I decided to build a power supply interface PCB. I have a page dedicated to the project. I want to put everything you ever need on a single board. I would appreciate feedback on the features and design.
The challenge with g-code control via Mach3 is turning the laser on and off. Using the spindle features does not do a good job. Even if you set all the configurable delays to zero there is still a short delay before movement starts. This makes a spot at the start of the cut. The better method appears to be the M10Px/M11Px method. This is pretty well described by "twehr" at the Mach3 support Forum on this thread. M11Px turns on the output x and M10Px turns it off. It also appears to wait for movement before it actually does it's action, so just manually entering M11P1 will not do anything until a G01 or G01 comes along to actually move somewhere.
I setup Output #1 to control my pin #8. Therefore M11P1 would turn on pin 8. I hooked that to my power supply. It worked perfectly. I ran to code the the thread mentioned above and it worked.
Creating a post processor.
That is all well and good if you want to type in a lot of G-Code. To do any real work you need a post processor for your CAM software. Coming from a woodworking background, my software of choice is VectricAspire. That is a high end 3D package, but they have a full range of software including the bargain priced Cut 2D which would work well for laser cutting. They all appear to share the same post processor files. They have a nice guide to the post processor file format here.
I started out by renaming the Mach3 Arcs Inch post processor file to "_BJD_laser_inch.pp" I preceded it with the underscore so it sorts to the top of their massive list of files". I started by removing all references to Z moves in the G01 and G1 moves. I use the Z for my table height which I don't want moving while running. I also removed all M03 (Spindle On) and M05(spindle off) items. I then added a PLUNGE_MOVE section to do the M11P1 (laser on) and a RETRACT_MOVE section to do the M10P1 (laser off). In the footer section I added a rapid move to X0.0300 Y0.0000 right before the move to 0,0. This insures there will be some movement after the last "cut" even if the last "cut" ended at 0,0. The post processor file I created is here.
In the Aspire program I created a new tool to use for the laser. I used the End Mill template and created a 'End Mill Laser" tool. The diameter, etc really do not matter. The only thing special I did was gave it a huge 10" cut depth. I wanted to make sure the software always did a single pass for "depth". I gave it a 0.005 diameter just so it would show up on previews.
I tested it with some text and....It Works. Here is the G-Code for reference. You can paste the code into my commenter if you want to know what it does line by line.
I tried the Koolance flow sensor on my cooling circuit. It is made for a higher flow, but I thought it might work for my circuit. It has a switch that opens and closes at a frequency proportional to flow. It appears to always be closed at zero flow. It added virtually no back pressure to the flow. If you blow in one end the thing spins like crazy for at least 30 seconds.
I tapped into my cooling circuit at a convenient spot by cutting the input line. Note to self: Next time turn the pump off before cutting the line. Ideally it would go on the output line to be sure flow actually went through the tube, but this was just a basic test. As a simple audible test of switch frequency, I put a piezo speaker on the switch. I shot a poor quality video of the test, so you can hear the sound. My video editor shows the audio wave form, so it was real easy to count the beeps per second. At full flow, the frequency was about 7.5Hz. I think this is fine. I can easily design a circuit to monitor this flow and generate an alarm when adequate flow is not present.
I am not having much success with the Mah3 Engraving Trigger for Laser or Impact Plugin. The description of the plugin is "Imports Photo and outputs DigTrigger at variable number of 5us pulses to trigger laser to grayscale output of image during X motor output". That is about the extent of the documentation, but the source code is available.
Basically it is supposed to import an image and set a bunch of trigger points. As far as I can tell, the trigger points are based on the steps along the X axis. It uses a series of 5us or optional 40us pulses to get a grayscale image. You use the "Digital Trig" (First selection on the Output Signals tab of the Ports and Pins setup) on the enable of your power supply. I set that up as pin 8. If you toggle the Active Low option while in the Output Signals tab, you can test the connection. That worked fine.
I loaded an image and started scanning. The tube was barely turning on. Only a faint glow could occasionally be seen. The head was moving correctly and an extremely faint image was emerging. The image did look like the picture, but way, way too faint. I had the power level turned all the way up using my manual potentiometer. I tried both ways on the 40us Trigger option. I tried making custom images for the test like all black, all white and all 50% gray.
I hooked my setup to my oscilloscope and captured the output of the digital trigger. I was running on a large 50% gray GIF. The pulses are running at a very low duty cycle. The period appears to be relative to the step rate. This a typical scope trigger constant 50% gray.
My image did look like the picture, so there must be some modulation of the pulses, but at 50% gray I would like 50% of the current power level (50% duty cycle. Here is the image I tried to engrave. You can kind of see a face. It needs some work.
The single web page was getting a little bandwidth heavy. I never expected it to get this big. I changed this page to include only the most recent entries, with the most recent first (blog style). I also split off some of the topics to their own pages.
Let me know what you think (firstname.lastname@example.org) There are a few unfinished links to things under construction.
I am now offering free web space to anyone who wants to create a buildlog. Contact me for info.
I had a friend make an assist air nozzle today. He made it on a CNC lathe out of aluminum. I put a 1/8-NPT tapped hole in the side and attached a 1/4" diameter barbed fitting. The nozzle will do two things for me. The first is it will keep smoke from getting to, and destroying the lens. It will also blow the smoke away from the beam allowing it to get full power to the work piece. The nozzle fits over the lens retaining ring and attaches via a couple of clamping screws. I will need to figure out how to route the hose. I think I will run it through the cable guide for the Y axis. Then I need to figure out the best way to deal with the moving X axis. Here is the drawing
I bought this little thing to try to measure flow. I will need to make a circuit to convert the frequency to a go/no go signal for the power supply. It sends out a frequency proportional to flow. It has little blue LEDS inside that can be controlled. Maybe I will figure out a way to use that as a visual cue Solid blue is good, blinking is bad? It was only $16. I will probably use a PIC chip to time the frequency and set the output. I can put a pot on there to adjust the set point. I bought it from Koolance. It will be here on Friday. My flow is pretty slow compared to this is used to, but I'll give it a try.
Cooling. I started the day by getting some anti freeze. I work in an unheated garage and it is going to get cold soon. I used Propylene Glycol. I heard other people use this and it appeared to work fine for me. It has a greenish tint to it so it makes it easy to see the water circuit and air pockets.
Beam divergence. I wanted to know the beam divergence so I setup a target about 10.5" away from the end of the tube. I measured a spot size of about 9.5 mm diameter. I plugged the numbers into my calculator page and got a 1.4mrad divergence. I think my max distance on my machine will be about 1.2meters so the max. beam at the lens will be about 6.6mm (0.26in).
Mirror Alignment. I first made large scale adjustment by looking down the mirrors with my eye. After that, I worked from the tube to the lens, one at a time. I placed a very thin sheet of hobby plywood (1/32" thk.) in front of the mirror and fired a low power beam. I adjusted the mirror until marked the plywood dead center. I then moved to the next mirror until I got to the lens. It took about 45 minutes.
Lens. I did not know which way was up on the lens. I searched around the Internet for information on collimator lenses. I did not find much. The best picture is on Wikipedia. It appears that the more rounded side aims towards the laser. If anyone knows more about this please tell. Anyway, the lens pretty much looks the same on both side. I tried shining a red laser through and appeared to get better results one. So I decided to try it that way and it worked. For all I know it works either way. Note: ZnSE is not safe to handle...use gloves.
Focusing: My lens is a 55mm focal length. So where exactly is that measured form? Front, back middle? With the lens inside the holder it is difficult to tell anyway. I decided to just adjust until I got the thinnest line. When I got pretty close, I backed off about 1/8". The then used Mach3 to draw a 4" line while moving the table up 1/4". This cause a line to go from thick to thin and back to thick. Both thick and thin were of course still very thin, but you could see the thinnest point of the line. I then interpolated to the correct focal length. I can now use a reference point to set my work. 2.88" from the top of the plate with the lens holder to the top of my work. Easy to measure with my caliper. I may make a simple gauge block.
Smoke: I cut a lot of lines and circles in wood. Boy does it make smoke. The exhaust fan does pretty good, but I need to hook up the air assist soon. PS: The unfocused beam makes awesome smoke rings when it burns those little 5mm dots ;-)
Mounting. This tube is shorter than the others I have seen, but the diameter is the same and my clamps work fine. I had to move them together more than before. The nylon adjustment screws hold it firmly with very little pressure.
Cooling: I hooked up the tube to the water supply. The first tube had a bigger water fittings, so the tubing I bought did not fit real tight. I decided to get some better tubing. The only tubing I could find at Menards that would fit was latex tubing. This worked out pretty well.The tube basically has three cooling circuits. There is the main circuit that cools the beam. Then there are separate circuits to cool the mirrors/apertures at the ends. The tube I got from LightObject had tubing between the circuits. The new tube does not. I cut small pieces of the latex tubing and installed them. I then ran the rest of the tubing to the back of my enclosure. I bought 2.5 gallons of distilled water and filled the bucket. I measured the flow. It is only running about 25 GPH. I'll have to see if that is enough by measuring the temp rise. There were some air pockets in the cooling circuit, due to the orientation of the tube. I had to rotate the tube to get the fitting on the tube to get the air to go out. I wanted to leave the output tube in the bucket above the waterline as an audible flow indicator, but I think I will leave it below air can never back flow in when the pump is off.
Power Supply: The power supply came with a red positive lead. I added a blue/black 16 AWG lead for the tube return circuit. The return lead hooks to the output end of the tube and the positive lead hooks up to the mirror end. Hooking the power supply leads to the tube is tricky. They should not be soldered or the tube/wire interface might be compromised and the gas will leak. I laid the lead against the tube electrode and wrapped very small gauge wire around them to secure/tie it on.
A made a temporary manual control panel. It has a 5K pot for power level control and two buttons wired in parallel to enable the power supply. One is a momentary push button and the other is a push on/push off style. I grounded the water pump safety circuit. It is hooked up per below.
First Test: I dialed the pot down as far as it would go and pushed the button. I got nothing. I turn the pot to about 5% and tried it again. It worked. I pushed the button about as fast as I could. The video makes it look slower, but that might be the camera or video compression. The smoke was instantaneous. The tube and power supply are silent, but there was a little pop sound from the wood block as it got hit. I think the hit was fast enough that the mark on the wood should represent the beam diameter. It measures about 5.1 mm. The mark is at least .03 deep. I was actually quite shocked at the power.
The tube made it from Shanghai to me in 3 days. I detailed the unboxing here.
Waiting for a tube.
I ordered a tube from LightObject way back in early August. The tube arrived about two weeks later broken, totally smashed actually. LightObject was a bit slow to react to the problem, but did send a second tube. That tube arrived a few weeks after the first also broken. This one only had a water fitting broken off. I don't think the gas envelope was broken, but I'll never know. Both were very poorly packaged. Due to several factors, I lost all confidence in LightObject and requested my money back. After about a week, I got a complete refund. Overall not a pleasant experience, but at least I did not loose any money. The guy there said that it was the fourth broken tube they had in a month (2@40W & 2@80W).
Anyway, I ordered a new tube from love-happyshopping from eBay. The order was placed 9/27/09. I have received a few robot emails, but no confirmation of shipping yet. They do have a very good eBay rating though.
This build this has been a two steps forward, one step back type project. Today was definitely a two steps forward kind of day. I put a lot of parts together. I got most of the Z table together. I am missing one sprocket to hook it to the motor, but you can manually move it.
The four corner threaded shaft assemblies were put together and installed. Leveling was pretty easy. If you lift a corner of the table you can spin the lift nut. This allows easy adjustment to within about 0.015, which should be plenty good for the z-axis. I eye-balled it until it was close then measured the distance relative to the Y support beams. I tweaked each nut until all measured the same.
I also added an air filter for the general flushing air. It is simply a $2 furnace filter. You can see it through the holes in the bottom of the enclosure.
...Proceeding more with final assembly. I got the missing sprocket for the table lift. It works pretty well. It is a little noisy, but does the job. The long spans between sprockets causes the chain to droop a little and that creates noise on the sprockets. I may replace with a long belt some day. I mounted the DIN rail terminal blocks and wired them to the exhaust blower, power supply and power outlets. I installed the gantry. I added a cable carrier to mind the moving cables from the gantry. This is a short piece from KabelSchlep (love the name). I had it left over from my first router. I ran some cooling hoses. I had to make two small adjustments. One of the cooling fittings pointed straight at the Y motor, so I moved it. The plate that holds the cable carrier to the gantry was bumping into one of the table riser top bearing mounts when the gantry was at the front, so I trimmed the bearing block.
I made some mounts for the laser tube out of some HDPE cutting board. These will hold the tube in place and allow fine adjustments. I have it shown with stainless steel screws, but I will get some nylon screws that will not scratch the tube. I have one shown on a small piece of extrusion to show how it mounts. The drawing is here.
I completed the rear panel. It is made from 3/8 baltic birch. I put some spare varnish on it so it won't stain easily. I used a separate piece as an interface panel. I thought I might need to modify it some day, so it will be easy to swap out. I cut it from 1/16" FR4 (G10). I have 3/8 barb fittings for the water in and out. I used a quick release air fitting for the assist air. I decided to keep the air pump outside the enclosure because it vibrates a little and that might degrade a fine engraving. There is a Qualtek p/n 763-00/001 power entry module for the input power. It has an integral switch and fuses. There is a power outlet for the air and water pumps. Each socket is a separate circuit, so they can be controlled independently. There is also the 25 pin D connector for the parallel port of the computer. I installed a big exhaust fan I got as a free sample a while back.
Table Lift Parts
I made all of the table lift parts. They are made from 3/8" plywood. I used some 9mm skate bearings and some 5/16" threaded rod. There is a gear for #25 chain that will drive the lift mechanism The white piece is made from some poly cutting board. It has a tee nut pressed into it. It is designed to fit into the back of the table. It is designed to float a little so I don't have to worry about perfect alignment of all the lift screws and the table. The shape prevents rotation.
I worked on the table. This is the platform the moves up and down with the work piece on it. I made it by laminating some 1/2" plywood with some 1/16" 6061-T6 aluminum. Hopefully the aluminum will dissipate the heat from the laser when it cuts through the part. I will have some aluminum honey comb on top so the beam will be a little spread out by the time it hits it.
I laminated it using contact cement and then cut it out with my router. I also put a few screws around the lift points for extra support. I cut some of the plywood away to lighten it. It is very stiff though.
I had some leftover DIN rail terminal blocks (Altech CTS2.5UN), so I will use them for the AC distribution. They are cheap and easy to use. They are connect by a buss bar across the centers. They are rated for plenty of current and can use a 12-24 AWG wire. The color coding is nice. I will try to get matching wire colors.
I am waiting for parts again, so I thought I would start looking into the power control via Mach3 and eventually EMC2. I started this page on the topic.
I am getting ready to wire up some parts, so I needed a decent schematic. I created this one. It should fairly represent how I will start using the system for testing. I am going to use a controller board I designed a couple years ago. It is basically a motherboard for 3 stepper daughter boards and a spindle relay card. It is opto isolated and has 5 inputs. I will probably make a custom board for this project after I get a feel for how I will use it.
The stepper board is based on the Allegro A3977 chip. It is the same chip that the Xylotex board uses. Here is the schematic for the board. It is a very simple part to use. The only issue for the hobbyist is that it is surface mount.
Installed Floor and Back
I installed the floor and the back. I ran out of T-Nuts, so I was only able to add a few screws per piece.
Floor and Back
I am going to start mounting more parts inside, so I need to put the floor and back on. I made them out of 3/8 baltic birch plywood. I cut most of it on my router, so I did not fully dimension the part, but it is to scale if you need to take dims of it. I had to clear several frame pieces and brackets. Since I used the router, I could get fancy here, but not needed. Enclosure Skins Drawing
I got the power supply today. It is a lot smaller than I thought it would be. The picture below is from the light object web-site. Mine actually came with a perforated cover. I am missing the black negative return wire. I have have a topic on there forum to get the fix for that. It has two terminal blocks. One is for the control and is of the removable plug in style. The over is for larger gauge wire and has screw terminals. The power supply has WWW.INMYDY.COM on it, but I could find nothing on the web for it. I also made a drawing for the dimensions.
I was having trouble finding a decent price on a PC style water cooling system. It was going to cost well over $100. I decided to try a pond pump. They should be designed for continuous use. They are also sump style pumps so they are cooled by the water. I bought a 258 GPH pump at Harbor Freight for $19.95. I am also going to skip the radiator for a while and just use a large reservoir. A got a $5 gallon paint bucket at Home Depot. I ultimately want a fully self contained cooling system, but this will work for a while. If I can find a cheap radiator like a transmission cooler, heater core or even something off a discarded mini fridge I will use that. I have a digital temperature controller that I will use to monitor the water temp. It has an alarm output that could be used. I will probably put a brass fitting in the cooling line just after the output from the laser tube where I will put the thermocouple.
The mirror assemblies came as a kit. There were no instructions, but they were pretty straight forward to assemble. I put the two big pieces together then pushed the springs through the counter sunk holes. The springs are a tight fit so they tend to stay in place while you are working. The retainer wires are sort of glued together. They actually look like 7/16 pin nails for a pneumatic nailer. I separated them with an Exacto knife. Be careful or they will launch across the room. I installed a pin on one side then used the Exactor blade to lift the other side while sliding the pin in. I created a detailed drawing of the assembly so you can get the dimensions.
I got the whole frame together and test both motors together. See the video below. The first part is in engrave mode. The second is in cut mode. This was run via Mach3 with the engraver plugin. My next step is to install the mirrors. The speed are what I expect a normal run would be. The motors can go many times faster.
I have been waiting for some more material and some metric hardware to finish the frame. I did wire up all of the photo-interrupters. I bend one of the ground leads over to the other one and soldered it. I put a 100Ohm resistor in-line on the +5V (red) wire. Then soldered the black wire to ground and the white wire to the collector.
Well the Ponoko laser cut parts finally arrived. They have a seven step process that they track on your designs. They "started" and "checked" the design the first day. It was then stuck on "material paid for" for 7 days. Then all the rest of the steps cleared at once. I don't know if this is typical. Anyway, since I cut my own parts I really did not need them anymore, so I was not real excited about opening the package, but I was real impressed with the quality. The parts look great. The kerf is almost invisible. It measured to be about 0.006". A dimension that was designed for 2.75" came in at 2.742". I thought that was pretty impressive. They sent the pieces still in the material. They backed it with a sheet of self adhesive masking that kept the parts held in place. I also liked the fact that you get the remaining material. I can use that in the future. The edge quality is near perfect. I was wondering about edge squareness which is often criticized. I stood a part on end on a setup table and it looked near perfect.
This makes me very excited about completing the build and cutting my own parts.
I got the gantry mounted on the frame. I worked fine, but I determined that I did not need the v-rail and wheels on the far end (away from the driven end). It was just adding resistance and did not appear to be making it any more ridged. I changed it to just use some small bearings acting as wheels to roll on the top of the extrusion. It tried it and it worked better. It should save about $40 too. Below is a CAD view of it.
I received the photo interrupters from Digikey. I tried them out using the schematic shown in the 7/20/09 post. They worked fine, but my homemade CNC controller card uses opto-isolators, so a change is required. See the snippet from my schematic.
5V_PC and GND_PC come from the PC and 5V and GND are from the controller side. This way any problems on the controller side cannot damage the PC parallel port. U10 is the opto isolator. When it does not see light from the LED in U10 R21 pulls the X_LIMIT circuit up to 5V_PC. When it sees light from the LED in U10 it switches to GND_PC through the transistor in U10. To light the LED in U10 it needs a connector to ground on J3-6. The photo-interrupter will provide this.
R1 limits the current through the LED per the data sheet. While there is nothing blocking the light, the transistor in U2 switches the line to ground, which is what we wanted. This should be a very easy circuit and cable to make for each interrupter.
I made a little breadboard to test it an check the speed. The opto is white and a little hard to (near bottom).
I hooked it up to a scope to measure its speed. As you can see the the response time is about 1.6ms. It is dependant on how fast and well you block the light. At full speed that relates to about 0.05". This should be fine. My blocker is 0.50".
I built the center section of the frame today. I installed the v-rails using the same technique I used with the gantry. I then bolted together the rest of the parts. I only built enough to make it strong and set the correct span for the to get the gantry installed.
I got most of the gantry built today. I made a the idler pulley for the end of the belt out of a machine bushing epoxied to a bearing. I found the bushing at Menard's for $.39 and it fit perfectly.
I put it all together with the motor and belt. I fired up a new configuration of Mach3 and tuned the motor. I could easily get past 2500ipm, but I wanted to stay with the 25000Hz kernel speed so I limited it to 2000. The acceleration was set to 300. The steps per inch is 666.67. I ran it for about 30 minutes without problems and the motor stayed cool. I think I can downsize the motor. See the video of it in action.
I got tired of waiting for Ponoko so I cut the parts from 6mm polycarbonate on my router. I used a 0.0626 end mill I got from PreciseBits.com. I cut at 25 ipm and 0.062 pass depth. It took about 15 minutes to cut everything.
I started putting what I am calling the "laser car" together. It is the thing that supports the final mirror and lens. The hole in the v-wheel is 0.187 dia. A #10-32 screw is about 0.001 bigger. I sanded some #10-32x1.0" long socket head screws. I chucked them in a drill press and sanded for a few seconds. I put a split lock washer on first, then the v-wheel, then a hex nut as a spacer, then through the plastic and a flat washer, lock washer and hex nut on the other side.
I mounted the car onto the gantry extrusion. The v-wheel one the back side is mounted in a slot. I tightened it slightly, then used a #4-40 screw to push it tight against the v-rail. I then tightened it firmly. It slides with very little friction and has no play.
..Back from family vacation
Still waiting for the Ponoko parts. It does not look like they have done anything for 4 days. I am not impressed so far.
I started looking into the limit/home switches. I think I will use some IR photo interrupters. They look just about as easy to use as micro-switches. They seem to be pretty popular with the higher end home built CNC systems. This one from Panasonic looks good. I think the package will mount easily on the extrusions. The price is only $1.33 in low quantities at Digikey. The data sheet is here.
Hooking into the logic circuits looks very straight forward. When the IR from the LED hits the phototransistor Sig. out goes to Vcc. When the beam is blocked it is pulled to ground through RL. This should be a good failsafe design because any break in the cable going to the photo interrupter would be sensed as reaching the limit and stop the motion.
Here is how it will probably be implemented. I might be able to run the wires inside the t-nut slots of the extrusions. The little interrupter plate will be glued into a slot in the moving plate above. I have it shown in black. It might be fun to make it in clear poly because that is opaque to IR and might spark stupid questions.
I decided to have some parts laser cut at Ponoko. I normally would have routed it, but I won a $50 credit from Instructables.Com., so I thought I would try that. I put all of the parts on a single drawing in Pro/E. I then exported to DXF. I imported into Vectric Aspire do do the nesting. I set the material size to the Ponoko P2 size of 15.1 x 15.1. I joined all of the open vectors. Then I selected all parts I used the following parameters: 0.01 tool dia., 0.08 clearance, 0.06 boarder gap, 90deg rotation and allowed mirroring. It easily fit 2 sets of parts in the area. I exported back as DXF format.
Next I imported into CorelDRAW 10. I changed the lines to blue and set the lines to hairline width. I then exported to .SVG format and sent to Ponoko.
The cost at Ponoko is based on the material and laser run time. I chose 6mm black acrylic with was $15.44. The single set run cost was $32.11 and the 2 set run cost was $59.21. These files could have been optimized to make a single line cut two parts, but I did not bother with that.
I received the Misumi extrusions today. They look great. That is a lot of material for the price. I bought the M3 t-nuts by mistake. I should have bought the M5 versions. They will work for testing and I will swap them out later, after I make sure I don't need anything else from Misumi.
I got some mirrors, mirror mounts and a lens mount from LightObjects. Below are how they were received. Apparently the springs are mounted with little tiny strips of metal. That little out of focus thing next to the springs is four of the strips stuck together. The lens/mirror mount looks OK. I am surprised how small the hole is where the beam enters. I will make detailed drawings of both of these parts soon.
I started work on the gantry. I drilled the v-groove rail. This is available pre-drilled, but I had the cheap undrilled stuff from McMaster-Carr. I used the standard drilling pattern though. I also drilled the gantry extrusion. I taped the drilled v-groove rails in the proper location on the gantry extrusion and used my transfer punches to locate the holes. I then drilled them for a #6-32 tapped hole. I used such small screws to insure that the rails would contact the edge of the extrusion and not get hung up on a screw shaft.
I worked on the table lift mechanism. It consists of four 5/16-18 threaded rods with bearings at the top and bottom. The bottom mount to the floor and the top mounts to the bottom of the Y axis extrusions. Each has a #25 chain sprocket on the bottom under the table. A mount and idler/tensioner completed the assembly. The table has threaded inserts in the corners. See the lift table PDF.
I worked on the support frame assembly. This is all out of 20mm Misumi frame extrusions. I plan on skinning the whole thing in plywood. With some sort of hinged access to the table. Frame Assembly PDF
I changed the timing pulley from 15 to 12 tooth to increase torque a little. I am worried about the direct drive having enough power. I also changed the idler from a timing pulley to a bearing with a large washers. I thought this would be a much easier to implement and cheaper. See the latest gantry and xy assembly PDF.
There is some good info going on this thread at CncZone about building your own 55W laser. It sounds like fun to build one. I may do that after trying a Chinese one. Check out this PDF.
I did some more work on the Y axis. I don't have enough info on the lens holder and mirror assemblies to start fabricating any parts yet. Click it for a bigger view or view the PDF.
The water pumps sold by the Chinese deals all seem to be wiper fluid pumps that are probably not rated for continuous use. I have seen various versions rated for 3lL/min, 7L/min and 15L/min. I thought I would use a PC cooling pump because they are rated for continuous use (80,000hr MTBF). This one from Thermaltake is rated a 500L/hr (8.3 L/min). A local Micro Center store has some cheap radiators.
Air pumps: I plan to add an air assist in front of the mirror. This is a nozzle the is put in front of the lens. It performs to functions. The first is keeping smoke and debris away from the lens. This reduces the amount of cleaning required. If stuff gets on the lens then it the beam will heat it and permanently damaging the lens. The second is it improves the cutting by clearing out the cut. I plan to use an aquarium pump like the one shown below. I have no idea how much air I need. This one is an ActiveAqua 60W, 70L/min version. They are all over eBay.
The basic design of the gantry is shown below. There is a link to a PDF here. It is still pretty crude, but it is what I have so far. It is missing a lot of hardware and misc. items The BOM table on the drawing shows a rough estimate of the price of everything so far. The lengths were used to order the parts from Misumi. I'll add a column for the sources and source part numbers soon. The laser lens/mirror holder is just my best guess at what that part looks like.
I decided to use the HFSF5-2040 profile for the gantry. It has a small radius on the corners and one side is flat so it should work with the v track. It costs about $3.00 per foot.
I ordered some material from Misumi and a mirror, mirror holder and lens holder from LightObject. I will see how they perform with this little order before I order the tube and power supply. I paid using PayPal so I feel pretty safe about the transaction. I can't go very far with the design unless I get decent measurements off these parts.