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Author Topic: Sudden wild axis movements during program run  (Read 3582 times)

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Sudden wild axis movements during program run
« on: July 08, 2014, 11:34:59 PM »
I am suddenly having X-Axis missed steps issues.  I tore down the X-Axis to check for problems, I swapped stepper motors, I changed outputs between X & Y axes on BOB, but it still misses steps on the return to zero.  I slowed the motor tuning settings to 100 ipm.  I lowered acceleration to 5.  I turned off tool path view.   I changed the parallel cable.  I tightened all screws on electronics.  I am rastering a 6"x26" dome-shaped object and it started missing steps on the return leg towards zero on every pass - thus making a parallelagram.  Then it would go fine for 15 minutes & suddenly loose a bunch of steps and be off by 1-2 inches as if a lot of skipped steps.  I have been repeating the same program dozens of times, & it fails in different spots each time now.  The last time it was on the return leg to zero on X when it stopped X travel, suddenly rose about 2-3" on Z, moved on towards zero, then lowered back to surface.I stopped the program & it thought it was 2 inches further down the X Axis.  I checked gcode - the endmill was not where the gcode said it should be.  I was as if the gcode kept moving in the X direction while the mill was moving in the Z direction up & down.  The errors are so random, I am thinking about getting a different BOB next.  I am running ssd computer with WinXP Mach3 R3.043.066 for some time now without problems.  Any suggestions would be greatly appreciated.

Offline Tweakie.CNC

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Re: Sudden wild axis movements during program run
« Reply #1 on: July 09, 2014, 02:35:46 AM »
Hi Marv,

Pretty ugly problem you are describing, it could have many causes but I would be inclined to make a clean re-install of Mach3 (possibly an earlier version .056 ?) and see if that resolves the issue. Don't forget to back-up your Mach3 folder so you can copy all your settings etc. to the fresh install.

Tweakie.
PEACE
Re: Sudden wild axis movements during program run
« Reply #2 on: July 09, 2014, 11:01:47 PM »
So today I loaded Mach....062 in place of ....066 & it failed.  I switched to a Win7 machine with usb-to-parallel cable & it failed.  I changed out the BOB & it failed.  I connected X-axis motor directly to controller & it failed.  I switched X & Y controllers & it failed.  I'm done for the day, but wondering what is left.  X-Axis motor?  The program fails in different places in the code each time.  Any other suggestions? 

Offline Tweakie.CNC

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Re: Sudden wild axis movements during program run
« Reply #3 on: July 10, 2014, 01:48:01 AM »
Hi Marv,

If you have swapped stepper motors then it is unlikely that the problem lies with the X axis stepper.
You could try reducing your Velocity and Acceleration settings further and see if that makes an improvement.
Perhaps a silly suggestion but I trust you are using a genuine Mach3 license ?

Tweakie.
PEACE

Offline RICH

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Re: Sudden wild axis movements during program run
« Reply #4 on: July 10, 2014, 06:22:05 AM »
Your motors may be fine for 2 D work but lack the power for 3D work.

Reduce your velocity and acceleration and see how it goes.

RICH
Re: Sudden wild axis movements during program run
« Reply #5 on: July 11, 2014, 07:34:45 PM »
I spent a lot of time tacking down the problem, & turns out the X-Axis coupling was the culprit.  I had changed from LoveJoy spider type to a split type quite some time ago. I checked it when I tore down the X-Axis and went on to other possiblilites.  After rewiring, swapping BOB, slowing down tuning, etc. it got worse & just sat in one spot on X & went up & down on Z axis.  I checked the X stepper & noticed the motor turned but not the lead screw.  The set screws were tight on the coupling but slipping.  It is some kind of plastic.  So I went back to LoveJoy & it works fine now.  I ran the same job twice without a hiccup.  I guess lesson learned is don't give up and don't assume - recheck what you already checked!  Thanks so much for you assistance.