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Author Topic: Inconsistent feed speeds - any help?  (Read 1852 times)

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Inconsistent feed speeds - any help?
« on: May 20, 2012, 03:50:51 PM »
Hi,
 Longtime lurker, first time poster here.  I can usually find a solution to my problem using the search function but I'm coming up empty handed on this one.

 I'm using Mach 3 on a small home-made milling machine.  Has run well for years.  Yesterday I thought "hey, I'll set the backlash on the Z-Axis, that should make my part depths more consistent".

  I set the Z backlash, previously set at zero, at .012".  This morning I noticed that the machine would slow on Y-Z axis feeds, which I attributed to the backlash; further investigation revealed that was probably not the case, as the backlash adjustment should only take place when the Z-Axis changes direction (I think).  At any rate, I have parts to make, so I set the Z-Axis backlash back to .000 and restarted the program.

  Now it appears that the problem was not related to the backlash, as it is still occurring randomly.  I'm feeding on the Y axis at 4ipm, the feed will randomly slow to .3-.4 ipm, then go back to 4ipm.  Sometimes once or twice a pass, sometimes more.

  Any help?


Thanks,
Steve
Re: Inconsistent feed speeds - any help?
« Reply #1 on: May 20, 2012, 03:59:32 PM »
Additional info - I just went to reset the machine and it does the same thing when jogging - I jogged up on the Z axis and it fed for a bit at 2ipm, the slows (audibly and on the DRO), then picks back up and goes 2ipm.  Probably some setting I monkeyed up when playing with the backlash...

Offline Hood

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Re: Inconsistent feed speeds - any help?
« Reply #2 on: May 20, 2012, 05:11:16 PM »
If you attach your xml I will see if I can find anything.
Hood
Re: Inconsistent feed speeds - any help?
« Reply #3 on: May 20, 2012, 05:38:16 PM »
Hood, thanks for the reply - here is a little more info...

I shut down the program per instruction after changing the backlash setting.

Just for grins, I rebooted the computer, and the problem disappeared.  To confirm, I re-set the Z-Axis backlash to .012, shut down the program, restarted and ran a part - the problem reappeared.

I then reset the backlash to zero, restarted the program, and the problem was still present.

Then shut down the program, rebooted the computer, restarted the program and ran a part - problem gone. (phew!)

Did I just "not do it right" or might the xml file tell you something is amiss?  If so, I can send it in the morning.

Thanks,
Steve

Offline Hood

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Re: Inconsistent feed speeds - any help?
« Reply #4 on: May 20, 2012, 05:57:07 PM »
Usually shutting Mach down would be enough so not sure why you are needing to reboot.
Your issue sounds like it may be the shuttle accel needing set, do a search on the forum for backlash and 555 rule or something like that.
Hood