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  1. #1

    cutting Acrylic with New Machine

    After many struggles of my own making, I finally have my 1500x1500 machine up and running. I cut some 3/4 plywood yesterday at a pretty good speed, around 150ipm with no issues and a great looking cut.

    Today I tried cutting 15mm acrylic and had some issues with the machine stalling. I was cutting very conservatively, I thought. 18000rpm, 60ipm, .1" doc. I'd get about halfway through the cut and it would start stalling.

    My drivers are set for 1/8 microstepping and I have 48V PSU.

    Anyone have any ideas why this would be happening?

  2. #2
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    Re: cutting Acrylic with New Machine

    Not enough information.Spindle power?Stepper size?Drive mechanism?Cutter size and rpm?

  3. #3

    Re: cutting Acrylic with New Machine

    Ah, right.

    It runs on 1610 ball screws on all axes with a 2.2KW spindle. The steppers are Leadshine DM856. Motors are NEMA 23 425oz, 3.8 inductance.

    Cutter is 1/4" upspiral running at 18000RPM

  4. #4
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    Re: cutting Acrylic with New Machine

    the spindle may be a little week... and the acrylic may be melting on.. causing even more load

  5. #5
    Community Moderator ger21's Avatar
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    Re: cutting Acrylic with New Machine

    Is it stalling while cutting, or during rapids?

    There should be practically zero cutting forces with what you're doing. (your RPM is likely way too high, btw).
    Gerry

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  6. #6

    Re: cutting Acrylic with New Machine

    Yeah, that's what I thought too? It is stalling in the cut. Could the high RPM be melting the acrylic? The finish it's leaving is not great.

  7. #7

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    Re: cutting Acrylic with New Machine

    Quote Originally Posted by Frankmali17 View Post
    the spindle may be a little week... and the acrylic may be melting on.. causing even more load
    I was wondering about it melting as well, don't think it has anything to do with the spindle power since I think the steppers are stalling not the spindle.

    Try 140ipm 16000 rpm leave the doc at 0.1 and see if you get better results you have way to low of a chip load for acrylic, if you're machine can't handle 140ipm try 100ipm 12000rpm same doc. Do yourself a favor and start reading up on chiploads and search for recommended ipt and look up some of the feeds and speeds calculator and start playing around with them. You just need to know the correct chiploads for the type of material you are cutting as well as the recommendations from the tool manufacturers. Once you know your machine limitations just try to get in the ballpark for the material and the endmill. For example acrylic recommend chiploads is 0.004-0.015 the speed and feed I gave you gives you 0.0045 and 0.0042, your current feed and speed is giving you a 0.0017 IPT. Alot of people try to slow down the feed rate, but unless you slow down the spindle your usually just going to dull your cutter, with 18000 rpm you would need to be cutting at 150 ipm to have a chipload of 0.0042. All of the information is assuming you are using a 2 flute endmill, if you are using any thing else the chiploads would be different than what I listed.

    Hopefully you can find some of the information I posted useful, if you make the changes and you are still having problems you will need to lower the spindle speed and feed rate while still keeping the proper IPT. You may find that you need to make some changes to your machine, but I would start with playing with your feeds and speeds first.

    Dan

  8. #8

    Re: cutting Acrylic with New Machine

    Thanks so much for the help! I will give these a shot tomorrow.

  9. #9
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    Re: cutting Acrylic with New Machine

    Something is seriously wrong here if you are stalling at 0.1”depth of cut in acrylic. If the cutter is sharp and you are not welding it into the plastic or plugging the flutes then I’d look into a mechanical issue. But before that take a good look at the cutter.

    The thing is a cutter can easily gum up on plastics due to excessive RPMs in the spindle and slow feed rates (actually the plastic itself can start to heat up too). Due to the high speeds one gets with router spindles you generally want with two flute or single flute cutters. These need to be run at tooth engagements that result in good chip removal and minimizes heating of the plastics. In any event looking at your cutter and the chips you are getting will tell you a lot.

    In any event, assuming that the cutter isn't causing the load, I’d take a close look at your build. It is very easy to have missed something in a build that will result in something coming loose. I’d even try some wood products again to see if your performance there is the same.

  10. #10

    Re: cutting Acrylic with New Machine

    Yeah, I don't get it. I tried plywood today @ 100ipm 18000RPM brand new and sharp .25 2 flute cutter .25" DOC and it stalled? It's like the motors have no torque? Changed it to .125 DOC and it did fine, but this thing should cut at these setting easily. I designed it to cut at at least 200ipm. It only seems to do this on the X axis, but Everything seems OK with the axis. Everything is straight, square and tight.

  11. #11

    Join Date
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    Re: cutting Acrylic with New Machine

    Start with the simple stuff, loose wires bad connection, loose bolts and so on like Wizard suggested. I honestly didn't even think about that since you said you had no issues cutting wood. Welcome to the wonderful world of dyi cnc machines, honestly even a new factory built machine will break down on you. Look at the bright side since you built it you can work on it and don't have to pay a tech $150 hr to come out and milk his hourly pay on your dime. I would suggest posting some pictures that might help someone maybe point you in the right direction. Pictures of the machine electronic enclosure and so on, the more information you give the better chance you will have that someone will recognize the problem.

  12. #12

    Re: cutting Acrylic with New Machine

    Thanks for the help. I'll go over it some more and try to find something. Any chance it could be my microstepping at 1/8?

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