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GREAT NEWS! Backlash working on USB board...

Discussion in 'Troubleshooting and Build Support' started by Flashsolutions, Jan 26, 2011.

  1. Flashsolutions

    Flashsolutions Active Member

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    I just completed beta testing Andrej's backlash fix. I am estastic to say that it is working well! :doubleup: :dance3:

    I don't think the beta version is online yet but expect that it will be very shortly. I just sent Andrej the results of my testing and it works as well as Mach 3. Can't ask for more than that!

    THANK YOU Andrej :fantastic:

    Now maybe I can give my wifes computer back to her.


    The photos of the 2" circles show the Mach 3 cut on the left and the USB board cut on the right. Both were set to compensate .014" which is the amount of backlash I have after fine tuning my Phlatprinter . Attached files [​IMG]
     
  2. Kroko

    Kroko Member

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    :D
    It will be published in beta 2.10.1101.2601 little later. I need to finish and test some other things first.
     
  3. 3DMON

    3DMON Moderator Staff Member

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    AWESOME!!!!! :doubleup:

    Andrej, you the man!

    I can't wait to try it out.
     
  4. kram242

    kram242 Administrator Staff Member

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    Andrej that was fast! Thank you for looking into this and taking care the problem.
    Your skillz are amazing :gimmefive: Well done Brother! :D
    Thank you for testing this out Larry! :good:
    Mark and Trish
     
  5. rcav8r

    rcav8r Moderator Staff Member

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    Good news for the USB folks.... Question: How do you calculate/figure out the value used?
     
  6. kram242

    kram242 Administrator Staff Member

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    Here is a step by step
    Of course we will be using the material as our Axis of measurement for the X. We may find we need different settings for different material used (different hardness/less give for example fff vs. epp vs. mdf) and may be a good idea to keep a list of these settings for future reference.
    Although our Phlatprinters are relatively the same and most of us can get by with a standard setting for starters, it would be nice to have these standards on hand to trouble shoot.

    This information can be found here.
    http://www.cncexpo.com/MeasuringBacklash.aspx
    Hope this helps
    Mark and Trish
     
  7. rcav8r

    rcav8r Moderator Staff Member

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    THANKS Mark. I'll check later when I get home. As part of my check for skew, I wrote a little g-code file to move a sheet of foam 35" and back to 0 a bunch of times, and then ran it a few times. After about 25-20 moves, it is about 1/32" from home; but more importantly NO Skew. I have tried to re-calibrate with calipers and it always seems to check spot on, but I am limited to 6" with the calipers I have. I would think that a "longer" calibration check would yield more accurate results. But a ruler isn't anywhere near as accurate as calipers.
     
  8. Flashsolutions

    Flashsolutions Active Member

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    I was about to send my response, but Marks response covers it pretty well.

    One thing you need to do is zero your X axis before you start each move. This was not mentioned and it will cause erroneous readings if you forget to do it.

    If you don't have a dial caliper, you can always guess. Start with .010 and see if that helps. If not, double it and check again. Trial and error should get you there within a few tries.
     
  9. Flashsolutions

    Flashsolutions Active Member

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    By the way... I use .1 moves when checking with a dial indicator. I cut 1" circles to test the results.

    You cannot expect to see 1/32" backlash in a 10" circle. It is the little circles, 1/4", 1/2", etc that show up backlash the worst.

    You can input the move values in the text window at the lower right of the display.

    Example G1 X .1 F10 to move forward and G1 X -.1 to move reverse. Just be sure you zero the axis each time.
     
  10. rcav8r

    rcav8r Moderator Staff Member

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    OK, from what you mentioned (and now that you mentioned it I remember reading before) I don't think backlash is the issue as all the circle cuts I did, were spot on, even smaller ones. The 1/32" I was seeing was after about 25-30 runs back and forth. At this point I am guessing this is a calibration issue, all-be-it rather small.

    Also for the moves, I just used
    X30
    X0

    I am guessing this is OK?

    THANKS
     
  11. Kroko

    Kroko Member

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    Beta 2.10.1101.2601 is published.
     
  12. Bob-n

    Bob-n New Member

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    Great News !!!
    Can't wait to try it out this evening !
    Thanks Andrej :doubleup:
    :dance3:
     
  13. Bob-n

    Bob-n New Member

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    Andrej,
    We now have Round Circles !
    You Nailed it !
    Many Thanks
    Bob-n
    :banger:
     
  14. Flashsolutions

    Flashsolutions Active Member

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    I don't think calibration will cause the X not to return fully to its home position, especially if circles are true and you are tracking well. I would tend to guess that you just lost a few steps. Could be you are accelerating too quickly which could cause slippage.

    I would not be too concerned if all you are getting is 1/32nd over 30 passes. This is not going to show up in most anything you will be cutting. Most parts are going to be two passes typical. If you can go from one end of a sheet of FFF a couple times and return back to home position, you should be just fine.

    I have my settings set to ramp up the X axis slowly. Think of it as stomping the accelerator on your car and spinning the tires.

    What we want to achieve is accurate cuts, not see how fast we can do them. If you want to try to improve your accuracy, try turning down the acceleration property and let the X axis startup very slowly and gain speed then ramp down. You should be able to hear the difference.

    Other things that might cause this are the material itself. Try the same test with different material and see if the results vary or remain the same. I have several different materials I run thru it and some have a tendency to drag on the table top or just have more flex to them than others.

    I would say you have your machine dialed in pretty well as is.



     
  15. Anonymous

    Anonymous New Member

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    WOW! So many changes and updates, when I get back "up" to working on my PP, I'm gonna hafta relearn everything! Great stuff! :banger:
     
  16. 3DMON

    3DMON Moderator Staff Member

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    Make sure the deceleration box is checked as well. I had issues in the beginning with my Y axis losing steps and found out from Andrej I should of had that checked.
     
  17. rcav8r

    rcav8r Moderator Staff Member

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    Good point about the acceleration. I'll adjust and try again, but as you said I don't think about 1/32 off will hurt much. I've only really cut foam so far and haven't had any issues with parts fitting. After trying some aircraft ply, I had some really severe skewing ( which made me run the back and forth test as well as the circle) but that only convinced me I needed a fence setup like I had on my MK1.5 After seeing your post on the topic, I knew I had to make a fence set up.
    I also didn't think about different materials behaving differently. I'll toss a sheet of balsa in there and check it too.
    THANKS
    Dave
     
  18. Flashsolutions

    Flashsolutions Active Member

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    Aircraft ply is another story... I would recommend putting masking tape at least along the edges. Ply is so hard that it is very easy for slippage to occur.

    Depending on size of material, use enough tape to permit rollers to have something solid to grab onto.

    You could also tape the ply to a sheet of FFF as a carrier, but the other thing to watch out for is where the rollers meet the ply. They must be centered over the ply or you will get skewing from uneven pressure on the upper rollers.

    Feed rate and spindle speed also comes into play with harder materials. If the bit cannot cut the material as fast as the drive train wants to move it, something has to give, and it is usually the ply that will slip.

    Guide rails of course will help keep minor skew/slippage under control, but push comes to shove, the path of least resistance wins.


     
  19. ToxicToast

    ToxicToast Down in the weeds. Staff Member

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    Color me a little slow on this. I get the idea of what backlash is and how it can be set in USBCNC. What I don't get is how to measure and calbrate for it on my Phlatprinters, particularly the P.

    Can somebody translate the cnc expo into a step by step relevant to our machines? Perhaps a video would be nice but not expected. My calipers are standing by!

    I don't have the roller issue resolved and am holding out for when I can get the fixed versions of it. However, I do think this will help improve some of the accuracy on travels, where I can observe overshoot that results in enough error to affect the cut starts.
     
  20. Flashsolutions

    Flashsolutions Active Member

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    I will do a video later, but just to give you a quick tutorial, You need to move the X axis in one direction in .1" increments, measuring the amount of actual travel each time. Do this at least 4 times. Average those values. Now reverse the travel again by .1" and measure the actual travel. It will most likely be less than your forward values.

    That is the value of your backlash.

    Go in reverse a few more times .1" at a time. These values should be close to your forward values.

    Reverse again, the next .1" increment will give you the backlash in the opposite direction.

    Average the two backlash values. Enter this in the control software.

    It is best to use MDF or something solid to get a good reading with your calipers. I have even used a cutoff yardstick...

    Hope this helps.


     
  21. ToxicToast

    ToxicToast Down in the weeds. Staff Member

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    Great explanation, Larry. Exactly what I was looking for. Clear lucid and to the point, thanks! I'll give it a go tonight.

    I think you mentioned before that different material loads would have an effect on the backlash value. If so, how do you compensate for this?
     
  22. Flashsolutions

    Flashsolutions Active Member

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    I don't know for sure that different material will give different readings on backlash, but I suspect it could simply because some material is so much softer than other. 1/2" foam comes to mind, or EPP.

    Your best bet is to cut a 1" circle and see what it looks like. That will tell you if you need more correction.

    I did a video this morning showing the process. It is kinda rough but should help if it is still unclear.



     
  23. rcav8r

    rcav8r Moderator Staff Member

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    Way back in this thread you mentioned acceleration as a possible solution to an issue that I thought was backlash. Well the different was so small, it's hard to tell for sure, but I think that solved the issue of it re-homing. Then as you suggested I tried a different material. Boy I really wish I didn't try that. :shock: I put a piece of 4" balsa in the machine, and the thing nearly slid across the rollers as it was traveling on the X axis. Along 35" of balsa, it slid about 4". I re-ran the foam and all was OK including tiny circles. Not sure why the foam and balsa are SO different, but looks like I'll be looking into "the fix" as I really want to cut some wood. But I'm half afraid of screwing up how it cuts foam.
     
  24. Flashsolutions

    Flashsolutions Active Member

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    There are so many variables which come into play it is hard to know what is causing what. For balsa, you need to center the wood in the machine and try to get the upper pressure rollers to evenly apply pressure, as this will skew balsa very easily.

    Try taping the balsa to a sheet of FFF as a carrier. This may be a quick fix if you are tracking FFF just fine.





     
  25. kram242

    kram242 Administrator Staff Member

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    Great video tutorial Flash! thank you for putting this together it really helps to explain the basics of backlash.
    A while back, while using mach. I found a video on you tube that shows you how you can check X/Y axis and how to set your shuttle acceleration in mach (great tip) to use it without the the jerky movements you may be seeing.
    Hope this helps
    Mark and Trish
     

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