Liberty4Ever's Laser Build Log

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Liberty4Ever's Laser Build Log

Postby Liberty4Ever » Tue Aug 28, 2012 5:53 am

This may be the most premature build log in the history of BuildLog.net. I'm committed to building a laser, and I've spent many hours reading and researching, and starting the online shopping process, but I haven't bought anything yet, much less built anything. I'm hopefully finishing up a big CNC retrofit project now for a friend's business. I should post a build log about THAT! After that project, I have my own 10X24 Clausing lathe to convert to CNC, and I have one mostly built Hadron ORD Bot to finish and one box-o-parts Hadron kit to assemble. As soon as I retire a couple of these projects, I'll start buying laser parts, but I'm in the laser design mode now.

I like the Laser 2.X design a lot, but I need a slightly larger build area. I frequently cut 12" X 24" sheets of foam, and the slightly smaller working area put a big crimp in my style. Once I started looking into expanding it a little, even with the build logs of others who have built enlarged Laser 2.x projects, it looked like I might be better served by purchasing a 16" X 24" XY laser platform. Yeah, I know... cheating.

http://www.lightobject.com/Pro-400600-X-Y-Stages-for-DIY-CO2-Laser-P707.aspx

Instead of building a desktop laser, I'd like to build a freestanding laser, with the electronics and plumbing contained in an extruded aluminum framework with solid laser-proof panels. I might even be able to integrate the large Harbor Fright exhaust blower inside as well, but I'd like a lot of water stored in there so I can use the thermal mass to keep the laser cool for a few hours without a chiller or forced convection radiator, although using the side panels as integrated radiators might be a neat idea. A quick back-of-the-envelope calculation seems to indicate that an hour of lasing would increase the temperature of 35 liters of water by 10 degrees C, but I need to double check that 10 second calculation. It does seem that I should be able to use the laser for an hour or two at a time without a cooling system if I have a reasonably large reservoir. Keep It Simple Stupid is good.

Now for my question:

I'd like to use a 60W laser tube.

http://www.lightobject.com/60W-CO2-Sealed-Laser-Tube-P70.aspx

The laser tube is 1.2 m long, which will be over four feet long when installed. I'm trying to minimize the footprint to as close to the usable working area as possible. Is there any technical reason why the laser tube needs to be mounted horizontally? I'd like to mount it at the back of the laser, preferably diagonally inside the frame, from bottom right to the top left corner. I'd pump cooling water in the bottom and out the top, and I'd need a funky angle on the first mirror to get the beam heading in the Y direction.

It seems like a lot of people would want to mount a laser tube vertically or diagonally, but I was unable to find the answer to my question. The fact that I've never seen anything but horizontal laser tubes seems to suggest that there is a good reason they're mounted this way. Hopefully it's not such an obvious reason that I look like an idiot for asking.

Barring a vertical diagonal mounting, I guess I'd try mounting the laser tube horizontally, just below the table, along the diagonal of the somewhat enlarged XY plane.
Apparently, I didn't build that! :-)
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Diagonal Tube

Postby kbob » Tue Aug 28, 2012 4:17 pm

Interesting question. The first thing that comes to my mind is that you'll need a much better support for a diagonal laser. The 2.x mounting doesn' require much clamping force to hold the laser tube in place. If the tube is diagonal, you'll need a mount that allows very precise positioning and holds the tube strongly enough that it won't slide down. The moving gantry and carriage will make the whole chassis vibrate to some degree, so you'll need to plan for that, too.

It's not an insoluble problem, but it will require some thought. Unless you're really space constrained, it's probably easier to make the chassis big enough to hold a horizontal tube.

As for mounting the laser diagonally under the table, that would require a fourth mirror, unless you're thinking of a different geometry than I'm thinking of.
Bob
"If you didn't code it, it will never own you." (-:
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Re: Liberty4Ever's Laser Build Log

Postby Liberty4Ever » Tue Aug 28, 2012 5:07 pm

Thank you for the excellent reply kbob.

I had considered the relative difficulty of clamping a 2.5" diameter 48" long glass tube full of water. It's going to be heavy and the outer surface is slick, yet it's glass, and even with the thick walls, it's not going to tolerate much clamping force. And the outside is bristling with fragile glass fittings for coolant water, a high voltage electrical connection, the laser optical output....

My small shop is a study in maximal utilization of vertical space. I don't have much room and I really do want a design with a minimum footprint. I should move so I could have more shop space, but that's a much more intractable problem. :o

The good news is, aluminum extrusion is very flexible and offers many mounting options, and this is hopefully a semi-permanent laser tube installation. The laser tube has an estimated life of 2000 hours and I expect to make intermittent use of it. If it makes it to 1000 hours, that would probably be a lifetime for me... and yes, I can easily justify the cost of the laser, even with such low usage.

How does this sound? I fabricate four clamps for the laser tube, of a similar design to what is typically used. They're essentially split rings, and the top and bottom clamp together to secure the laser tube. I mount the four bottoms to a rigid 40X80 mm aluminum extrusion. I clean the outside of the laser tube with isopropyl alcohol to remove any oils and coat the insides of the four clamps with RTV silicone. Clamp the laser tube and allow the silicone adhesive to cure while the laser tube is horizontal. Then, I can mount the laser tube assembly at an angle and the silicone adhesive will prevent the tube from slipping while the aluminum extrusion adds strength and rigidity.

I'm assuming that it's sufficient to prevent the tube from slipping in the clamps, and support it on a rigid mounting that will avoid any mechanical stress on the glass tube. It doesn't seem that anything inside the tube would care about one g in any direction, or vibration with an angled gravitational field.

Is anyone seeing any problem with this, before I commit to such a design?
Apparently, I didn't build that! :-)
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Re: Liberty4Ever's Laser Build Log

Postby TLHarrell » Tue Aug 28, 2012 6:27 pm

Any particular reason to bump up to a 60w tube with the issue of such an extremely long package? Why not use a 40w? Or, consider mounting the 4' long tube vertically in the rear leg of the machine? Place the first mirror right at the tube, so the plane of the beam paths is around +50". The table surface would be below that, at a workable standing height.
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Re: Liberty4Ever's Laser Build Log

Postby Enraged » Tue Aug 28, 2012 6:34 pm

I'll second the vertical tube idea if its possible. For clamping, you could use silicone (cut up a silicone baking sheet) between your clamp and the laser tube.
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Re: Liberty4Ever's Laser Build Log

Postby Liberty4Ever » Tue Aug 28, 2012 10:52 pm

TLHarrell wrote:Any particular reason to bump up to a 60w tube with the issue of such an extremely long package?

I cut some nasty stuff, Santoprene tubing, a rubbery plastic. I'm currently using a 40W laser and it takes a couple of minutes for each piece. I can't set up a big job. There's a fixture with three different stations, including a rotisserie that I made to serve as a pseudo-4th axis for precision end trimming. I'd like to get the laser time down because it's very attended cutting time. There's about a minute in each cycle of staring at it with nothing to do. I minute isn't quite enough time to do anything else, although I've used those little breaks to surf for information on 3D printers, LinuxCNC conversions of machine tools, and lately... lasers!


TLHarrell wrote:Why not use a 40w? Or, consider mounting the 4' long tube vertically in the rear leg of the machine? Place the first mirror right at the tube, so the plane of the beam paths is around +50". The table surface would be below that, at a workable standing height.

I had definitely thought of mounting the tube vertically. In fact, that was my first thought. It would avoid the odd angle I'd need on the first mirror, simply trading the horizontal laser entry for vertical entry. I'm ashamed to admit that I was somehow thinking that the work area would be above the laser. No, I wasn't thinking of cutting from the bottom or anything. I had it modeled in my mind as below the laser, just like desktop lasers are configured, but when I started thinking in terms of the height of everything, I somehow thought the bed would be above the laser. Weird. How could my brain do that, other than persistent lack of sleep? What can I say? I'm an electrical engineer, not a mechanical engineer. :)

In thinking through the vertical laser tube, it seems likely that an air bubble would form at the top, where the laser emerges from the laser tube, which I believe is a hot spot that needs a lot of cooling. That wouldn't do. If so, a slightly smaller diagonal air bubble would form in the same place for a laser tube installed diagonally on the back wall. I had halfway worked through this in my mind as having a coolant fill tube that protrudes up, like the coolant filler neck for the radiator in a car. But I still think an air bubble would form above the upper coolant port on the laser tube. Even if there was coolant in that area, it wouldn't circulate well and would quickly overheat.

That would only leave the possibility of mounting the laser tube under the bed in a diagonal in the XY plane (horizontal, but from right front to left rear), and a 60W laser tube would still be 14" too long for that on a 16" X 24" bed with an inch of overhang on each end. I could either revert to a 40W tube, or keep the 60W tube I want and upgrade to a much larger 36" X 48" table. I wouldn't design that myself. I'd feel safe slightly increasing the size of the Laser 2.X design, but not that much. It wouldn't be rigid enough. I was already planning on cheating and buying a nice XY motion platform. 3'X4' is larger than I need for almost everything I do, but every now and then it would be handy for big projects like cutting acrylic sign stencils. I've been doing those in 1'X2' pieces and taping them together, which is a hassle. I do that infrequently enough that I couldn't justify the larger table, but if I need that large a table to get a 60W laser....

I could also use the larger cabinet to hold more water so I could lase longer without overheating, but I think a simple radiator and fan makes more sense at that point.

I could also make the vertical enclosure only as large as needed for the XY table, and build a rectangular box sticking out the back side on the right to house the laser tube and revert to a simple "horizontal across the back" design like everyone else. I could use the space in front of the laser tube for the PC and monitor, storing laser supplies underneath, etc. I need some horizontal work space to prep the next job (6" long tubes pressed onto 1" diameter mandrels), so I'd need some extra floor space other than just the laser anyway. That design certainly gets simpler and less problematic. Any time something new is tried, there is almost always time spent solving unforeseen problems, often stuff that's obvious in retrospect, and typically expressed as something like, "Oh, gravity works in THAT direction!" :roll:

Thanks for helping me think through this. It seems that I can only go so far with the design between my ears. I guess I should get better with 3D CAD tools. That's how most designers develop mechanical concepts in the virtual world.
Apparently, I didn't build that! :-)
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Re: Liberty4Ever's Laser Build Log

Postby TLHarrell » Tue Aug 28, 2012 11:38 pm

Once you have all the air purged out of the cooling system, you should not end up with any additional air unless you are doing something wrong. You would need to design in a method for checking the end of the tube though. Good thinking.

The larger the laser X-Y system, the harder it is to adjust it to proper alignment. Any tiny misalignment is magnified the farther along the laser path you go.

Most commonly available laser mirror mounts are designed for 90 degree angles. Having an odd angle, or even a compound angle, will likely result in additional cost. If horizontal won't work well, definitely vertical is the next best option. Always follow KISS... additional complications should be avoided.
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Re: Liberty4Ever's Laser Build Log

Postby StigOE » Wed Aug 29, 2012 5:56 am

TLHarrell wrote:Once you have all the air purged out of the cooling system, you should not end up with any additional air unless you are doing something wrong.

That's not my experience. After my system has been turned off for a while I have 'lots' of air in the cooling lines and I have no idea where it comes from. Both my pump and return line is fully submersed so there shouldn't have come any air in that way.
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PROJECT IS A GO! PARTS ORDERED!

Postby Liberty4Ever » Wed Sep 26, 2012 5:20 am

PROJECT UPDATE - PARTS ORDERED!

I'm completely project crazed. I previously said that I was going to retire one of my three other projects before buying parts to start my laser project. I lied.

I've been obsessed the last couple of days with building my own laser cutter/engraver. I've upgraded the design a bit since my earlier musings in this build log. It'll have twice the work area and twice the power of the laser I've been using, and it'll be water cooled instead of air cooled. I'm building an 80W laser with a true 24" X 24" laser area with a slightly larger bed that extends beyond the laser cutting area. I want to be able to load a 24" X 24" sheet and cut to the edges.

With a lot of valuable help from Marco at LightObject.com, I've finally decided to chop down a 36" X 48" XY table to make the 24" X 24" XY table I want. The 3' X 4' table is way more than I need, and I don't have the space for such a large laser, but the typical 11.5" X 20" desktop lasers were going to cramp my style too much. It'll cost more, but I think the 24" X 24" laser will be the best value for my dollar and square feet of precious floor space.

Yes, I'm definitely cheating by purchasing a high quality imported XY table instead of building my own. I'm hoping to earn back some geek points because of the degree of difficulty scoring, given that I'm running a small business and I have three other concurrent geek projects (a large CNC retrofit, my CNC lathe conversion, and a couple of Hadron ORD Bots).

Here's the XY table I'll be chopping down to make my 24" X 24" table.

http://www.lightobject.com/Pro-9001200-X-Y-Stages-for-DIY-CO2-Laser-P708.aspx

Note that the XY table includes all of the rails, timing belts, pulleys, stepper motors,etc. Definitely cheating! The part acquisition is probably the least fun part, IMO.

BTW - If you REALLY want to cheat, LightObject.com also offers an even more complete XY table that can be cut down. It includes the optics mounts and laser head. All that's missing is three 25mm mirrors and a 20mm focusing lens. The cost of either XY stage equally equipped is about the same.

http://www.lightobject.com/XLE-9001200-X-Y-Stages-complete-kit-for-DIY-CO2-Laser-P737.aspx

The next biggest purchase will be the laser tube and matching laser power supply. Probably something like this:

http://www.ebay.com/itm/NEW-RECI-BRAND-80w-80-watt-CO2-LASER-tube-long-life-with-POWER-SUPPLY-/251151358563?pt=LH_DefaultDomain_0&hash=item3a79c99a63

I'll hold off on the laser tube and laser power supply purchase until near the end of the project, unless I find a deal I can't refuse. I want to have the infrastructure in place to safely mount the laser tube to minimize handling, and pump coolant through it so I can quickly test the laser tube and power supply once I receive it, in case I need to file a claim for shipping damage or some other problem.

My next task will be collecting a lot of the other components so I can decide what goes where when I design a custom bolt-together extruded aluminum frame. It'll probably have a footprint about 34" deep and 72" long. I want to make sure it'll go through a standard 36" wide door. The rest of the ~72" length will consist of a work surface to the right of the laser table. Part of the reason for the addition of the work area is to allow space along the back of the frame for the 1200 mm (4+ foot long) laser tube. From many all night sessions spent laser cutting parts for my business, I know the work surface will be very handy.

This laser is turning out to be a bit bigger than I originally planned, but it'll be so nice to be able to cut 24"X24" sheets for a few hours as I assemble parts or watch a Netflix movie nearby while keeping an eye on the laser. And every now and then I need to make a laser cut acrylic or poster board spray painting stencil, and the larger cutting area will avoid the hassle of piecing a stencil together from smaller pieces.

The other major laser stuff I still need to buy (in no particular order) includes:

Used PC off Craig's List to control it all, with a big flat screen monitor
MESA Electronics integrated I/O and stepper controllers
Stepper motor drivers
DC power supply for the motors
DC power supply for the control electronics
A large Harbor Fright exhaust fan to remove the nasty smoke from lasing stuff
A large aquarium air pump to push clean air through the laser nozzle to keep the optics from gunking up with smoke
A water pump to circulate the coolant through the laser tube
A large coolant reservoir
Some sort of laser cutting bed and a method to raise and lower it so the material to be cut is at the laser focal point
Misumi extruded aluminum frame with body panels
Lots of small stuff like an emergency stop switch, water flow switch, water float switch, coolant temperature sensor....

I think I'll build the extruded aluminum laser frame and XY table at my friend's business across town. They have large granite surface plates for work tables that will allow me to bolt together very square and flat mechanical subassemblies.

I'll probably spend some time thinking about the possibility of using the clean inlet air for the fume exhaust to cool the coolant. It might also be nice to have a down draft exhaust system that pulled the smoke away from the optics and also functioned as a weak vacuum hold down assist for fixtures or flat sheet stock. Some of the sheet materials I cut are rolled for shipping and they don't want to lie completely flat. I can tape down the edges to keep them flat and prevent the material from moving while it's being cut, but it'd be nice if it was gently pulled flat so the 1/4" thick material is cut with very straight side walls.

I plan on using LinuxCNC as the CNC control system. I've been using LinuxCNC and MESA Electronics for the other CNC projects I've been doing lately, so a lot of that knowledge transfers, and the development and ongoing support should be easier. There are slightly cheaper solutions, but the MESA Electronics hardware is high quality, robust, and very capable. It's not the cheapest, but I consider it to be a very good value.

LinuxCNC won't allow me to draw something and print it to the laser like the Windows software for lasers. CorelDraw has been very handy for quick parts off the laser, like the acrylic Hadron ORD Bot feet I made. I'd want that sort of solution if I was laser engraving trophies or industrial device labels and one-off custom signage all day long, where every job is different, but most of my laser jobs are production jobs that I run a couple of days per month. Using less graphically oriented tools to piece together G code is slower but tolerable for the way I use the laser, and LinuxCNC does generate a nice graphical WYSIWYG interface that shows what will be cut, scaled to the work space, as well as the beam path as the job progresses. Maybe there will be a nice integrated Linux laser controller solution some day.

On the plus side, G code and LinuxCNC allows more direct control of the laser. One of my current laser jobs uses a fixture with a DC gear motor to turn a mandrel to cut rubber tubing. I call it "the rotisserie". It's sort of a poor man's 4th axis. The VersaLaser commercial laser software has a minimum laser speed, so I'm forced to make successive short cuts back and forth to cut the rotating tube. With LinuxCNC and G code, I can move the laser to the position I want and turn on the laser as the tubing rotates underneath, and avoid the back-and-forth cuts on the rotating tube, so I'll have smoother and quicker cuts.

I'm still trying to decide if I want stepper motors for the Z axis. A manual mechanical Z axis adjustment would be all I need, but I'm more of an electrical engineer than a mechanical engineer. It may be easier for me to design a system with two stepper motors wired together (ala 3D printers) to raise and lower the bed by jogging it up and down. Maybe a scissor jack mechanism on each end? Threaded rod in each corner of the bed?

Does anyone know of a good small & cheap integrated PC board that runs LinuxCNC with low jitter? The four year old chock-full-o-viruses Windoze PC on Craig's List is probably the most cost effective solution, but it'd be great to have a small and reliable PC that can be ordered off the internet and known to work with LinuxCNC, preferably with a 64 GB flash drive instead of a hard drive. When I make the Craig's List PC buy, I try to find one with a flat screen monitor for the best bundled price, and I arrange with the seller to allow me to plug in a LinuxCNC Live CD so I can make sure it boots from the CD and can run LinuxCNC with low jitter for acceptable realtime control response before I pay for the PC. It's something of a crap shoot. LinuxCNC doesn't need a fast PC. Most PCs are OK, but onboard video chips that use system memory as video memory and access it via DMA can wreck the realtime Linux kernel response needed for fast CNC control operations.

Here are the parts I bought from LightObject.com tonight.

Qty SKU Item Price
3 LSR-MIR25MO 25 mm Molybdenum (MO) Reflection Mirror $82.50
1 LSR-HD2520LR Pro laser head mount for 25mm mirror & 20mm focus lens. LR Type $69.00
2 LSR-PR25M2D Pro 25mm reflection mirror mount for Co2 laser machine $69.00
2 LSR-TUBEMNT80 Pro Laser Tube Mount 80mm (adjustable) $64.00
1 LSR-PRO90120XY Pro 900*1200 X-Y Stages for DIY CO2 Laser $950.00
1 LSR-EP4 CO2 10600nm Laser Eyes Protection Glasses/Goggle. CE certified $45.00
1 LSR-ZNSE2050HQ High quality 20mm ZnSe Focus lens (F50.8mm) $52.00
1 SHIPPING UPS Ground $78.97

I had a $100 coupon, so I paid $1,310.47. I'll start a spreadsheet to track costs, vendors and part numbers in case anyone wants to follow in my insane path, in whole, or in part.

This was probably the most expensive single order I'll make for this project, and it represents a lot of the hard work done for me, so I expect to be finishing this project instead of becoming mired in designing and redesigning. I should be able to bring this laser project in under $3,500.

Huge thanks to Marco at http://www.LightObject.com for all of the time he spent helping me. He went way beyond the call of duty. I feel very good about supporting vendors like that, but even if you're ruthlessly self interested, a vendor with low prices and excellent service is an unbeatable deal - way better than maybe saving a few pennies on eBay and regretting it later when it doesn't work out and you're left holding the bag.

The next project is always the best project, but I really do need to start wrapping up some of these projects instead of starting new ones. It's getting crazy around here.
Last edited by Liberty4Ever on Sat Sep 29, 2012 4:52 am, edited 1 time in total.
Apparently, I didn't build that! :-)
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Re: Liberty4Ever's Laser Build Log

Postby loopingz » Wed Sep 26, 2012 1:51 pm

I know this kind of issue. You start to think about something. Then you got obsessed about it. Now you really need it. And Oh wait, is it the best possible? Then you do order.
I might hard to explain/justify to madam...
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