Sliptonic has a (frickin) laser!

Well, not quite….yet.

I found an old Universal Laser Systems model 25A for sale at a surplus auction.  It looked to be in good shape and went cheap.  After I got it home and cleaned up, I found that I couldn’t get the laser head to fire.  I called in some expert assistance from Columbia Gadget Works, but no luck was to be had.  I’ve since learned that RF laser tubes have a life expectancy of about 10 years before they need to be re-gassed.  Re-gassing this one is prohibitively expensive and would *only* get it back to 25W.  Instead, I’m looking at replacing the RF laser with a chinese glass tube.  This should take it to 40W.

Either way, this looks to be a fun project.  Here’s a picture.



2011-11-15 10.49.19

15 thoughts on “Sliptonic has a (frickin) laser!

  1. Hey Man,

    I just obtained an identical laser machine, with an equally dead laser tube. I’m planning on making exactly the same modifications you did, and have enjoyed reading your blog as now I know it’s possible! I would love to stay in touch if you dont mind me asking questions when I inevitably run into any problems…

    Hope to hear from you,



  2. Hi Ben,
    By all means, please stay in touch. Would love to see some pictures as your (re)build progresses. I’m sure you’ll make some improvements as well. Overall, I’ve been thrilled with the machine and have had a lot of fun with it.

  3. Hey Sliptonic,

    We collected it and started work on it this weekend. We removed all the flying optics, and cleaned the whole lot before reassembling them so now it is moving nice and smoothly.

    I have a quick question for you already i’m afraid – the 40W chinese tubes i’ve been looking at seem to quote a beam width of around 20mm, wheras the optics on the ULS-25 seem to have appertures which are a little smaller than this. Did you have any problems getting a chinese beam to fit through the original optics?



  4. Sounds like things are going great. Did you figure out how to tension the belt running on the gantry? I figured out how to tension the fixed axis (my Y-axis) but never figured out how the other one tensions.

    As for the beam size, I think someone dropped a decimal point. The tubes I’m seeing on ebay, which is where I got mine quote the beam diameter at about 1.95mm and that seems about right.
    See this one for reference:

  5. Oooh, that makes much more sense. Thanks!

  6. Nice blog!
    When you had the XY gantry disassembled, did you see how to tighten the the belt that moves the last optical element? For me, that’s the X axis and runs from the front to the back of the machine.

    It’s clear to me how to tension the other belt with screws on the right end but I’ve never figured out how to tension this one.

  7. Hey man!

    So we’ve made some excellent progress on our U25A conversion! We even managed to sell the old defunct laser tube to photovac laser for $375 (you should look into this if yours is still lying around). The only problem we are having now is that the motors seem to be skipping steps on small detailed items… Am I right in thinking your system also uses pololu stepper drivers? I dont seem to be able to stop it from loosing steps by upping the motor current, so I’m thinking maybe I need to go deeper into the stepper driver timing settings in Linux CNC. Did you have to mess with these at all to get yours cutting accurately? If so, are there any pointers you could give me?



  8. Hi Ben, I’m glad to hear it’s going well. I’ve checked in on your blog from time to time and it looks great.

    You’re right that mine uses Pololu’s. I’m using the the board from My experience with 3D printers is that there’s a lot of variability with Pololu stepper drivers. I’ve had some go bad but the failure mode didn’t look like what you’re describing.

    I was using Mercury motors on a 3D printer and they DID fail exactly this way — All three of them one at a time. Still, if you’re loosing steps in both directions, I’d look elsewhere.

    LinuxCNC tuning shouldn’t be any more complicated than 1) Making sure the PC has appropriately low latency 2) tuning the axes with stepconf.

    Just a note for future readers: As happy as I’ve been with the Buildlog board (very) I’d do it differently if I was doing it today. I did a milling machine conversion and used Mesa’s products. They were a bit more expensive and a bit more complicated to set up but wow. Very powerful, very flexible, tons of extra pins, and great support.

  9. Cool, thanks. I’m hoping its not a driver failure as it has been this way from the start. I did notice that Linux cnc actually has published recommended settings for pololu drivers here, so I will try these next as I think my system is still on the defaults. Also I am using 1/16th micro stepping right now so maybe I should try switching it up to 1/8th. What do you end up going for in terms of micro stepping?



  10. Hey man,

    So I’ve been playing with my stepper settings, motor currents and belt tensions, and I haven’t been able to correct the missed steps. I’m wondering now if maybe the 19v laptop power supply I’m using just isn’t up to the job. Would you be able to let me know how many volts you’re running your motors on, and what kind of power supply you’re using?



  11. Hi Sliptonic,

    I found that you started to convert your laser from parallel port to mesa 5i25 card.
    Is this migration to mesa card finished? Are you satisfied with the result?

    I want to use 7i90 card to drive my laser but I am not sure if all time critical settings can just transferred from par-port to hostmot2 settings in hal file. Did you change something ? Could you share the hal file?

    Thanks for the answer in advance.

    Best regards:

  12. I’m sorry to say I didn’t get much traction on this project. I started the conversion and ended up reverting to the parport because it was ‘good enough’. I still have the 5i25 unused and would like to tackle it again but it just hasn’t been a priority. I also have an unused Beagleboneblack and a CRAMPS board and I’ve thought about doing a full conversion to it so everything is on the laser. Sorry I can’t be more help. If you go forward, please let me know how it goes. You might inspire me to get off my butt 🙂

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