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  1. #531
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 4 Hours Ago Has been a member for 5-6 years. Has a total post count of 1,169. Received thanks 212 times, giving thanks to others 5 times.
    I saw exactly the same problem on my machine. X and Y were fine, but Z looked as if it were losing steps on complex 3D work. In my case, it didn't show up on single test runs; what seemed to happen was that you lost one step every time you changed direction. Fix was simple - as Jazz said, just change step polarity. I think this is more likely to happen with the CSMIO controllers as they have differential outputs - brilliant for noise rejection, but too easy to get the two wires swapped!

    My only reservation about this diagnosis is that I wouldn't expect to see any significant error on a single movement, as the effect is cumulative with movement direction changes. But Jazz's test (I did exactly the same thing when I was chasing the error) will soon show the truth!
    Last edited by Neale; 29-01-2018 at 11:10 AM.

  2. #532
    Quote Originally Posted by Neale View Post
    what seemed to happen was that you lost one step every time you changed direction.
    That's exactly what happens because the last pulse gets sent after the next direction change happens so it gets dropped.

    To be honest, can happen on any system. The reason it tends to happen on these is that of the flexibility both drives and controller give. Meaning it's easy for one or other to be set wrong. Majority of older or lesser drives only allow rising edge which is ok for most sytems until you get controller that use's the falling edge.!!

  3. Thanks Dean, I'll have a look and see. I don't think anything is loose or falling off!! Only one I'm not sure on is how tight the square shaped nuts on the BK bearing block should be and whether they are perfectly set up. I've done the best I can, but when jogging the machine rapidly in alternating directions on the X axis it does sometime make a noise and appears to momentarily stall. I'm not sure what that's about and it doesn't do it consistently but wondered if that could be connected to differing tension on the two ball screws? I did not get this when cutting or doing the calibration tests at the weekend. I'll try and video it so you can see what I mean...

  4. Thanks Neale, on a single movement there is very little error, only when cutting a test pocket with changes in direction did i see the error so I'm hoping this is the explanation. Whilst I've taken care throughout the build and asked a lot of questions, I have made this machine with basic tools and basic skills, so I'm sure it's not just down to calibration!

  5. #535
    I read sometimes the seals on the ballscrew can be tight when new so when you first run the machines they can stick a little, the solution run it up and down the full length of the travel a few times. Greasing can help to.

    I had a sticky bit right at the end of my travel on one of my Y ballscrews kept firing a stall detect at me, after 10 to 15 running up and down the lengths occasionally stalling the problem disapeared. The area where it stalled is now part of my homing sequence so it gets travelled over regulary never stalled again.
    Last edited by Desertboy; 29-01-2018 at 05:48 PM.
    http://www.mycncuk.com/threads/10880...60cm-work-area My first CNC build WIP 120cm*80cm

    If you didn't buy it from China the company you bought it from did ;)

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  7. #536
    Quote Originally Posted by Desertboy View Post
    I had a sticky bit right at the end of my travel on one of my Y ballscrews kept firing a stall detect at me, after 10 to 15 running up and down the lengths occasionally stalling the problem disapeared. The area where it stalled is now part of my homing sequence so it gets travelled over regulary never stalled again.
    That's most likely to be alignment issue not sticky seals. To be honest I've fitted 100's ballscrews and never had sticky seal on the ballnut(presume you mean ballnut seal)

    Now what can happen is often the spacers on the BK bearings are not long enough and the seal in BK bearing can rub on the screw.
    This tends to happen mostly on cheap BK bearings. Also on cheap BK bearings, like what Chai Sells, the bearings are not always shimmed correctly or even in wrong way round so when tightening the nut they will bind.

    Joe If BK's came from Fred at BST then you can tighten them fully and they won't bind. Fred BK bearings are light years better than Chai's.

  8. I think I have found the culprit, there was (much to my annoyance) a loose grub screw on one of the y pulleys which I noticed whilst running Jazzís pulse test. With this tightened down and thread locked all seems to be well... The test results can be seen here:
    Last edited by JoeHarris; 30-01-2018 at 12:21 AM.

  9. Quote Originally Posted by JAZZCNC View Post
    That's most likely to be alignment issue not sticky seals. To be honest I've fitted 100's ballscrews and never had sticky seal on the ballnut(presume you mean ballnut seal)

    Now what can happen is often the spacers on the BK bearings are not long enough and the seal in BK bearing can rub on the screw.
    This tends to happen mostly on cheap BK bearings. Also on cheap BK bearings, like what Chai Sells, the bearings are not always shimmed correctly or even in wrong way round so when tightening the nut they will bind.

    Joe If BK's came from Fred at BST then you can tighten them fully and they won't bind. Fred BK bearings are light years better than Chai's.
    My Hiwins came from Fred but ballscrews and bk/bf bearings from chai.... not wild about taking them apart especially now!

  10. #539
    I hadn't squared the gantry up at this point so very possible it was alignment, if would be about the same time. It has taken me ages to get dual homing working.

    Hmm interesting with the bearings will have a look, I have a spare BK12/BF12 fitting to strip down. But will make sure I buy my bearings from Fred next time I keep seeing his name mentioned.
    http://www.mycncuk.com/threads/10880...60cm-work-area My first CNC build WIP 120cm*80cm

    If you didn't buy it from China the company you bought it from did ;)

  11. #540
    It has taken me ages to get dual homing working.
    If you have this now working with 2.8 master would you mind posting the hal & ini files.
    ..Clive
    The more you know, The better you know, How little you know

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