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Thread: LaserCut losing steps?

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    LaserCut losing steps?

    Hi All,

    I'm trying to run a very long job... approximately 500 small parts. The process is to cut all of the holes, and then come back on a second pass and do the cutouts. I have each one set up as a different color in LaserCut.

    Once all the holes are cut (1000), it starts doing the cutout pass. The farther into the job it gets, the more the cutout skews from where it should be on each part.

    If it were my CNC machine, I'd think it was losing steps. I tried turning the acceleration down in the machine settings.

    Any ideas?

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    No idea but I hope you find the answer soon.

    It must be loosing a fair few steps to become visible, is it out by eye or are you measuring them?



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    Quote Originally Posted by jasonharris22 View Post
    No idea but I hope you find the answer soon.

    It must be loosing a fair few steps to become visible, is it out by eye or are you measuring them?
    You can see it in the part. Now, the machine cuts 1000 holes, then 500 little lines, so whatever little issue there may be is multiplied 1500 times before it even starts the cutout.

    My interim solution was to set up the job in blocks... cut the holes in a section, cut out the parts, then move on to the next.

    I'm sure it's a config thing... probably a very simple fix.



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    Sounds like the stepper motors are not set up correctly. Is there any way to set up your steps per inch ?



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    It does seem like a stepper setup issue, but I'm leaning more towards acceleration issues than steps per inch... I'd think if the steps per inch were off, it should still be repeating the cuts, they'd just be the wrong size.

    I tried decreasing acceleration, and probably need to turn the rapid speed down as well. Right now I'm so far behind on this parts job that I don't have time to experiment with it. I'm not even sure that the changes I made posted to the machine? I had it plugged in with the USB, and the computer was able to control it, but I don't know if there's something I have to do to post or reflash the DSP.

    We ran all night with the jobs broken into smaller clusters... cut a section of holes, cut the parts out, cut another section, those those parts out. It's just as fast, but requires a little more setup. Still something I'd like to resolve.



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    Personally I have never had a problem with acceleration making the part not cut right, I have had acceleration make the steppers loose a step or two then of course the part is toast. What if you cut a series of round holes, is the first one accurate ? (round) or does it just get bad when your four or five holes down the line ?



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    If you make changes to the machine settings in LaserCut, they won't take affect unless you re-download the config file to the laser. You should hear a beep after a successful download to the machine.



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    Quote Originally Posted by bundysax View Post
    Personally I have never had a problem with acceleration making the part not cut right, I have had acceleration make the steppers loose a step or two then of course the part is toast. What if you cut a series of round holes, is the first one accurate ? (round) or does it just get bad when your four or five holes down the line ?
    They're all round, and the correct size, however, after I cut a few hundred and start the next process, the second pass is not aligned with the first cuts.

    Basically, if I cut 1000 circles, and then tried to have it come back and cut them all a second time, it would be cutting 1/8" to the left of the original set, and get progressively worse as it went.

    Last edited by Asynchronism; 03-13-2012 at 05:49 PM.


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    Quote Originally Posted by Asynchronism View Post
    They're all round, and the correct size, however, after I cut a few hundred and start the next process, the second pass is not aligned with the first cuts.

    Basically, if I cut 1000 circles, and then tried to have it come back and cut them all a second time, it would be cutting 1/8" to the left of the original set, and get progressively worse as it went.

    1/8th" (3.2mm) is a hell of a lot. I don't know what the gearing is on these things but to achieve the dpi they have I would think that is a hell of a lot of steps it must be loosing to get that far out.

    Makes me think it is something else, I have no idea what though, maybe a software bug, if it was Gcode I guess you could tell by seeing what the software is telling it to do but I don't know anything about the lasers equivalent.



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    Basics to try

    To figure out it it is losing steps, I think your best bet it is push the speed of the machine, even if that means just marking a scrap piece and seeing if the skewing gets worse. And, of course, see if slowing it down makes it better.

    Next thing to try would be slowing down the acceleration, as it could be losing steps there too, although less likely.

    Was the problem is just one axis or both?



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    I found the download button and dialed back the rapid speed and acceleration a little. I still need to get this job out, but I'll test as I can... if not, I'll run a full test next week.



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    Rapid speeds.

    Yes, I think for the testing, setting the rapid speed lower and to match the "stress test" cutting speed would be a good idea. I would probably first set the acceleration back to the factory settings, keeping those issues separate.



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