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Author Topic: Problems threading on the lathe  (Read 330272 times)

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Offline ART

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Re: Problems threading on the lathe
« Reply #510 on: October 11, 2009, 12:23:31 PM »
Rich:

 Interesting that the 6th pass didnt trigger at the wrong time.. it appears to have a much greater pitch is all.. so almost as if the rpm locked in
at a higher rate than the previous ones locked in at. Higher rate of RPM caused the feedrate to be higher.. so the pitch increased..

Ill give this some though. Interesting too that the pitch still decreased by .006" , better than .008 .. but we may be seeing come correction
error since this uses toally different correction coding.


 I think Ill change the RPM to do time based on the old single pulse and see what the outcome is..

Thx
Art

PS: Love the document from previosu post. Says it all very well.

Offline ART

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Re: Problems threading on the lathe
« Reply #511 on: October 11, 2009, 01:10:32 PM »
Rich:

  Sorry this one is harder to test. You need to run the enclosed Mach3SpindleTime.exe AND load the enclosed driver to test it. Turn off Advanced threading for this test,
it basically changes the spindle RPM under the old system to a time based measurement. I suspect youll find your reading slightly higher RPM's, and this will
lead to a slightly higher pitch, so its quite possible the lagged thread will be correct. That , at least woudl be one bug poisoned.. :)

Thx, Good luck
Art

Offline RICH

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Re: Problems threading on the lathe
« Reply #512 on: October 11, 2009, 01:25:20 PM »
ART,
WIll try it out later today. A couple of honey do's to do. Should post after 6 pm or so.
RICH

Offline RICH

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Re: Problems threading on the lathe
« Reply #513 on: October 11, 2009, 06:01:25 PM »
ART,
Only one test @ 115 rpm / .1p / 40 passes.
Single scribed line, pitch improved. The lead decrease now  0.005" / inch instead of .008".
I didn't make note of the rpm range changes , DRO stayed at 115.
Want more tests or you going to tweak on your end?
RICH.

Offline ART

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Re: Problems threading on the lathe
« Reply #514 on: October 11, 2009, 06:10:37 PM »
Hi Rich:

Do you know if SpindleAveraging was turned on or off? Id prefer it off.
Good sign if the RPM stays constant with averaging off though, that would
 mean the time nature of it is much more stable
than the old way, that may explain the better pitch.

  Im trying now to think what elese may be inaccurate. If we know RPM is now accurate,
( or we assume so due to stability ), then a couple things are possible..

Its possible the PCI clock is misreporting the number of clocks per second, which I base the RPM on.
Since compuiters tend to the binary.. a second can really mean 1024ms or 1.024 seconds. That would explain
another .24% of error. Im leading to the RPM being the trouble since its about the only thing that could explain
why higher rpm's are close to pitch than lower RPM's.

  SO I think Ill try a tweak that assumes the reported pci base clock is counts per 1024ms just in case the chip
designer had a prediliction to think in binary when describing a second.

Thx
Art

Back to you soon.



Art

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Re: Problems threading on the lathe
« Reply #515 on: October 11, 2009, 06:21:32 PM »
Hi Rich:

  This one is an experiment. Same driver you just used.. But Im correcting by 1/2 the assumption of 1024ms per second. Seems to large a correction,
but Im interested in the resullt.

Art

Offline RICH

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Re: Problems threading on the lathe
« Reply #516 on: October 11, 2009, 07:16:41 PM »
The spindle speed averaging was on but i'll turn it off for reply 515 test.

RICH

Offline ART

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Re: Problems threading on the lathe
« Reply #517 on: October 11, 2009, 07:40:03 PM »
Rich:

  Thx., Probably doesnt matter if on or off, in fact since you normally have it on and it varys , that shows its more stable with
the changes anyway. So in the end it probably doesnt matter. Might be better on in fact.. hard to say though. ( Am I dithering enough.? :-) )

Art

Offline RICH

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Re: Problems threading on the lathe
« Reply #518 on: October 11, 2009, 09:02:01 PM »
ART,
TEST:  REPLY #515 / NO SPINDLE SPEED AVERAGING / NO ADVANCED THREADING / VER.028
115rpm / 40 passes/.1P
The real time rpm increased some to 115.75 and fluctuated by about .5 rpm.
The application rpm increased to 116.6 to about 117.1, DRO read 117.

During the thread:
Real Time application 115.6 ,while application was 116.6 to 117 rpm ( roughly)
I noticed the elongation of the scribing about pass #10 ( didn't have the microscope attached to the lathe ).
So picture #2 shows the cutting about 1.6" from the start of the thread. Notice how it gradualy tapers inward as
each pass was made. That just says the Z axis and timing seem rather consistant, and if it varied a lot
 ( up and down ) then backlash or or something else is going on.

The lead increased.

RICH

Offline RICH

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Re: Problems threading on the lathe
« Reply #519 on: October 11, 2009, 09:04:32 PM »
ART
To late, test done.....you be the judge.
What next?
RICH