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Ben's 2.x Laser Build

PostPosted: Fri May 27, 2011 5:40 am
by BenJackson
What slowed me down when I decided to build the project was an actual list of what to buy and where, so I wanted to include that in my build log. I finally got around to updating it now that I'm halfway through the build:

Bill of Materials

Note I did not get the Electronic kit (but I did get some custom DIN stuff).

Notable missing items:

  • Flow switch
  • 24V PSU. I will probably use a bench supply initially.
  • Electronics tray I will fab from stuff in the garage
  • Heatsinks for the Pololu boards. Not sure if they're required.
  • Microswitches -- the ones I have are too small, oops.
  • Assist air pump.

Re: Ben's 2.x Laser Build

PostPosted: Fri May 27, 2011 5:51 am
by BenJackson
Here are the kits fresh from Bart (skins not shown -- the packing on those is amazing). You see the E-stop out of its bag because my wife found it and decided the button action was great. I might have to get one for her so I can have that one for the laser...
Kits and Misumi Parts

I invented my own method of gluing up the V rails. My two longest rails had enough twist that pressing one end down flat caused the other to pop up in two dimensions by several mm. In order to have enough even clamping force I put lots of rubber bands around the 2040, then slipped the V-rail under them (by sneaking down the T slot). I used some bits of cheap chopstick to prop them off the rail, sort of like you'd glue down a laminate top:

Work the rail toward the edge and tug on the rubber bands so they're not dragging the rail away from the edge. I then applied the glue (a bit too much, I went over the 4g total in the end and there was a bit of squeeze out). When the glue was ready I used one hand to pull forward on the rail and the other to pull out the chopsticks. You definitely want to practice that maneuver without glue a few times. The results were very good. After an hour I used the same rubber bands to do the other side. I cleaned up as much squeeze out as I could while wet and used acetone and Q-tips to remove the rest later. I did superglue a few rubber bands to the rail but it cleaned up fine.

Re: Ben's 2.x Laser Build

PostPosted: Sat May 28, 2011 6:49 pm
by BenJackson
I hit "buy now" and paid for the laser on May 22 with an estimated delivery of May 25-31. It arrived today (Saturday!) via USPS. Unfortunately the PSU did not arrive at the same time so I probably won't have it until Tuesday. The mailman was quite curious to know what it was and really surprised it was a laser. He asked if I was going to do light shows.

I had seen pictures of the giant delivery tube but with nothing to give you scale, so here's the tube as it arrived on top of my laser frame:
40W Laser Tube as packed by love-happyshopping of eBay fame

Last night I printed a couple of bits to help aim the laser. Two 50mm discs, one which holds a laser pointer and one with an aiming pinhole. The laser pointer will go in the rearmost laser support and the pinhole in the front to ensure it is aimed squarely:

If anyone wants to print their own I have attached the STL files... as a ZIP because it won't let me attach STL files.

Re: Ben's 2.x Laser Build

PostPosted: Mon May 30, 2011 11:20 pm
by BenJackson
Here is my innovative Del Monte Gantry Alignment system. The table was adjusted so the cans would rest in the T slots of the table rails:

The limit in forward "Y" movement (gantry toward user) seems to be the SHCS on the left side idler. Replacing that with a button head M5x12 would give a bit more travel. Could also notch the gantry end plate but that seems like overkill.

Here's my 3d-printed laser holder/pinhole mounted in the laser brackets. I only did very minor adjustments here (mostly on the gantry mirror) to get the laser to hit the final mirror. The red spot is visible on the bottom of the frame, but it is actually very far forward of the carriage.

One of the mirror holders has a poorly made thread on the mirror retaining ring and it can "cross thread" while being unscrewed and jam up. When you catch the threads right it's as smooth as the others but I ended up removing it from the "bridge" entirely to mess with it before I figured out what was going on.

This final shot shows how close my aiming laser is coming to the X idler. I guess it's missing it so that's good enough! I might have put that idler over too far attempting to get more travel on X without realizing where the beam would be:

Re: Ben's 2.x Laser Build

PostPosted: Tue May 31, 2011 12:28 am
by BenJackson
BenJackson wrote:The red spot is visible on the bottom of the frame, but it is actually very far forward of the carriage.

The problem here was twist in the final mirror (the one on the carriage). I had not realized that the mirror holder rotated in the plate. Mine was frozen together (perhaps assembled while the parts were hot) and I ended up having to use two sets of soft jaws to get it apart. Nerve wracking because I was 99% sure it had to rotate to be square but it was darn tight.

First motion!

PostPosted: Tue May 31, 2011 5:19 am
by BenJackson
I hooked up a L298 stepper driver (half-stepping only) just so I could drive the carriage around a bit. Here's a video!

The noise is probably due mostly to the half-stepping driver in concert with a few loose items (like the final mirror/lens assembly which is not screwed down). If Bart feels the racket will scare away potential builders I can have Youtube replace it with inspiring music. ;-)

Re: Ben's 2.x Laser Build

PostPosted: Tue May 31, 2011 10:06 pm
by dirktheeng
Wow Ben, this came together quickly! I may just be slow, but I've been working on this for a few weeks and haven't tested the motors yet. However, I am just about ready to. Once I get the arduino's here, I can run GRBL to get teh motors moving. That will be an exciting day!

Looks good! keep up the good work!

Re: Ben's 2.x Laser Build

PostPosted: Tue May 31, 2011 11:19 pm
by BenJackson
It's not as fast as the post history suggests: The Misumi parts came in the second week of May and I started building when Bart's kits arrived about a week after that. After I saw how fast those parts were going to go together I ordered the laser just in time to get it for the Memorial Day weekend. Unfortunately the laser PSU didn't make it so I eased up on the build. Tonight I should be able to fire the laser and maybe even cut something (with my hacked up X-Y control). I won't be ready for Mach3 or EMC2 control until Bart's next batch of Pololu control boards turn up.

Engraving will have to wait until I build/write some kind of engraving solution. :)

Re: Ben's 2.x Laser Build

PostPosted: Wed Jun 01, 2011 3:32 am
by dirktheeng

I will be interested to find out how valuable the led pre-alighnment turns out. I've thought about doing this myself, but I can't help but think that there is no way to make sure that the pen laser is on the exact same axis of the CO2 laser once you swap them out. I mean, they will be close, but I would dare say it would be just dumb luck if one got the CO2 laser put in there and it was aligned to a good focus right off the bat. My question is whether or not it is worth the time/expense/effort for a guy (mainly me) without any CNC stuff available here to try to use a red LED laser to align the stuff given that I am relatively certain I am going to have to do it again after taking out the red laser and putting in the CO2. Is the idea that one is just getting the CO2 laser close enought that it hits the mirrors and such without bouncing around dangerously or are you expecting to get a true alignment out of it? Just curious if you've thought about it and what your stratagy is. I have been seriously thinking of asking bart or one of the fab shops to make me something simmilar, but I'm not sure what I will gain. I don't mean to sound at all accusatory by my comments/questions, I am trying to make up my mind and playing a bit of devils advocate as well as hoping you have a really good strategy to address these concerns as the alignment part of this project scares me some (if there's a chance for me to get hurt it would be here... through the years as a scientist I have seen some aweful laser accidents).


Re: Ben's 2.x Laser Build

PostPosted: Wed Jun 01, 2011 4:03 am
by BenJackson

I'd be happy to send you the holders I made. My laser PSU arrived today so I hope to be firing it for real today. As soon as I can find the !@#$% picture I know is on this forum somewhere verifying the direction of coolant flow.

My theory goes like this: The mounting discs are 50mm (same as the tube). The aiming of the laser pointer is guided by the pinhole in the forward disc so the beam is very close to parallel to the tube mounts (less than 1mm off across the ~500mm gap, which in a linear system of mirrors I would expect to translate to a proportional error on the other legs). My primary goal is to make sure I don't have any gross errors in the system. It would have been very hard to figure out that my lens assembly was twisted with an invisible beam. I suspect that people who are hitting the inside of their air assist nozzles might have that problem.

When I swap in the real tube I am going to back off one screw entirely in each mount (if I can still get the tube in!) so that the tube will be registered against two of the screws exactly like the aiming discs were. When I tighten that screw the laser should be aligned exactly where the laser pointer was (assuming the beam leaves the center of the tube and is parallel to the tube).