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Author Topic: Problems threading on the lathe  (Read 330273 times)

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Offline RICH

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Re: Problems threading on the lathe
« Reply #130 on: March 16, 2009, 07:48:18 PM »
Hi Art,
The gcode i used for testing was per reply #118 to this thread.

SMOOTHSTEPPER: MACH VER: 3.042.020
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The G32 code will give you the weird XZ move in both CV and exact stop when the spindle is slowed down.

PP TESTING: MACH VER: 3.042.018  & .020
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The G32 code will give you the weird XZ move in both CV and exact stop when the spindle is slowed down.
A  50 to 60% reduction in RPM seems to trigger it.

NOTE: 1.The testing was done without BACKLASH COMPENSATION for the PP.
            Values for Shuttle acceleration other than "0" may create a problem in the axis travel from
            a weird slow down in travel over distance to an actual stop of the other axis. Shuttle causing values
            may vary depending on used computer and were posted in a different related posted.
            Those values are posted in another thread on the backlash problem.

           2. The weird pass also seems to accur in the G76 therading cycle about every four passes.

in light of all of this heree are some happy pics of a 0-80 threrad using the g32 CODE.

Rich
« Last Edit: March 16, 2009, 08:45:23 PM by RICH »
Re: Problems threading on the lathe
« Reply #131 on: March 16, 2009, 07:59:36 PM »
Smooth stepper test.I have had this issue with pp and ss.
With alot of effort I managed to slow my spindle and I get the error
with cv and no cv.I tried a g78 and a G32.same issue.I am free tonight to run
tests if any one needes a hand

Offline ART

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Re: Problems threading on the lathe
« Reply #132 on: March 16, 2009, 09:11:15 PM »
Woody:

  Thx, very nice description. You seem to have narrowed it to a single sentance, ( I like that.. ). So ..

"If the spindle speed is varied signifigantly during a pass, subsequent passes will show a X move during their pass. "

  Does everyone agree this seems to describe this error.

Thx
Art
Re: Problems threading on the lathe
« Reply #133 on: March 16, 2009, 09:20:38 PM »
yes
Re: Problems threading on the lathe
« Reply #134 on: March 16, 2009, 09:21:05 PM »
Art, Yes that is exactly what I believe several of us are describing, I can say that for me the variation in spindle speed has to be over 10rpm.  The lathe diag screen says variation percentage, but I think that it is showing a variation in rpm, not a percentage, for example 400 rpm set point dipping to 380 rpm shows a 20% spindle speed error which is actually more like 5% I think.  Thanks

Trevor

Offline RICH

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Re: Problems threading on the lathe
« Reply #135 on: March 16, 2009, 09:21:54 PM »
YES, and the amount is aroound 50 to 60% .
RICH

Offline ART

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Re: Problems threading on the lathe
« Reply #136 on: March 16, 2009, 09:37:47 PM »
interesting..

  OK, Me and Brian will put on our thinking caps and see what kind of diagnostic we can put in for this,or see if we can deduce
from your tests whats happening. I must say, this one defies logic. But that CAN happen.

  The way the driver works , Mach3 has no real knowledge that the spindle has slowed, so its an interesting trigger point
to find.. Sorry for all the delays here, but its taken me awhile to fully understand .. and its confusing as hell. :)

 Im sure we'll soon have an Ah-ha moment and Ill spend days or weeks kicking myself.

Art

Offline RICH

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Re: Problems threading on the lathe
« Reply #137 on: March 16, 2009, 09:54:03 PM »
HMM........Just a thought, but what did you guys change from when it worked?
Version 3.041?? or so ago??
RICH
Re: Problems threading on the lathe
« Reply #138 on: March 17, 2009, 10:30:01 AM »
Yep, Art, that summarises it for me. Also, I'd say about 10 to 20% speed dip triggers it on my machine.

If you want to suggest I test with an older / newer version of Mach, let me know.

Woody.

Offline ART

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Re: Problems threading on the lathe
« Reply #139 on: March 17, 2009, 10:55:41 AM »
Hi Guys:

  Found it. In actual fact a RPM change of exactly 50% or more was required to trigger the error. It was not an application error, but a driver error, and a very weird one at that.
This one has been hanging in there awhile. For the person with 20% reduction causing it, I suspect one rotation was measured at 50% and thats all it took. From then on the
error woudl present itself.

  Thanks to all of you, good reports, good help in troubleshooting and you made it much easier to find this rather bad driver fault. It might also have affected PP probing in very rare cases.

A fix will be out soon.

Art