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Author Topic: Threading on lathe issues  (Read 7074 times)

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Offline RICH

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Re: Threading on lathe issues
« Reply #20 on: March 07, 2015, 07:07:49 PM »
DICKEYBIRD,
Still using the PP.

RICH
Re: Threading on lathe issues
« Reply #21 on: March 08, 2015, 10:02:58 AM »


Thanks Rich.

Hey Raul did you make any progress?  Coincidentally I had a little threading job to do in aluminum yesterday that came out great.  Even at 300 rpm in direct drive (too lazy to switch to 4:1 belt reduction) everything stayed in sync.

Couple things I changed, dunno if it was part of my problem.  I checked "Spindle speed averaging" in the spindle tab and set my debounce to 2.  The rpm DRO was WAY more stable after that.  I ran the thread several times with good results.

I don't know if the spindle rpm is read by Mach (when threading) via the rpm DRO or directly off the index pulse input but my setup appears to work better now.  May have been the alignment of the stars & planets...or maybe the tinfoil hat I wore yesterday. ;D

Oh almost forgot, I generated the code in Dolphin which shouldn't have made any difference but was easier (for me) than the Simple Threading Wizard.  I also chose 14 roughing and 4 finish passes.  In retrospect I should have doubled the roughing passes to reduce the load a bit as the last few roughing cuts were peeling off a healthy sized chip (for my little lathe.)  It all came out OK so I'm a happy camper today.  We'll see how things go down the road when I have to do "real" threads in steel.
Milton from Tennessee ya'll.

Offline RICH

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Re: Threading on lathe issues
« Reply #22 on: March 08, 2015, 11:53:30 AM »
Quote
rpm is read by Mach (when threading) via the rpm DRO or directly off the index pulse

Directly off the timing of an index pulse, before, during , and at the end of the threading the DRO just shows results of the COMPLEX cycle.
Spindle speed averaging is the average of the upper and lower timing ( if i recall...) so helps but is not a cure all for a varing or way off
pc kernal / pulse frequency, spindle speed variation, etc. Not sure, but, the rpm used in the cycle is to 4 decimal places ( there were at least 20 different versions
of thread testing routines and just don't recall specifics.)



FWIW,
RICH
« Last Edit: March 08, 2015, 11:55:56 AM by RICH »
Re: Threading on lathe issues
« Reply #23 on: March 08, 2015, 12:12:10 PM »
Spindle speed averaging is the average of the upper and lower timing ( if i recall...) so helps but is not a cure all for a varing or way off
pc kernal / pulse frequency, spindle speed variation, etc. Not sure, but, the rpm used in the cycle is to 4 decimal places ( there were at least 20 different versions
of thread testing routines and just don't recall specifics.)
Ahh, OK, thanks!
Milton from Tennessee ya'll.
Re: Threading on lathe issues
« Reply #24 on: May 09, 2015, 06:45:19 PM »


Thanks Rich.

Hey Raul did you make any progress?  Coincidentally I had a little threading job to do in aluminum yesterday that came out great.  Even at 300 rpm in direct drive (too lazy to switch to 4:1 belt reduction) everything stayed in sync.

Couple things I changed, dunno if it was part of my problem.  I checked "Spindle speed averaging" in the spindle tab and set my debounce to 2.  The rpm DRO was WAY more stable after that.  I ran the thread several times with good results.

I don't know if the spindle rpm is read by Mach (when threading) via the rpm DRO or directly off the index pulse input but my setup appears to work better now.  May have been the alignment of the stars & planets...or maybe the tinfoil hat I wore yesterday. ;D

Oh almost forgot, I generated the code in Dolphin which shouldn't have made any difference but was easier (for me) than the Simple Threading Wizard.  I also chose 14 roughing and 4 finish passes.  In retrospect I should have doubled the roughing passes to reduce the load a bit as the last few roughing cuts were peeling off a healthy sized chip (for my little lathe.)  It all came out OK so I'm a happy camper today.  We'll see how things go down the road when I have to do "real" threads in steel.

Sorry guys for not responding to the post. Work has swallowed me in entirely and just spit me out. I got around to playing around with my lathe again. One of the problems I had was that the axis rapid was moving to slow so I made the adjustment there.

The problem that I am still having is that once the rpm reading goes out of whack for a split second, the threading stops working. I have played around with the debounce but I have had no success. I am using the C3 card from CNC4PC.

Does anyone have any idea how I can fix this issue?

Thanks,
Raul
Re: Threading on lathe issues
« Reply #25 on: May 10, 2015, 12:18:48 AM »
Hi, it can be a problem in the Index, it may be entering your signal noise index, if you use an inductive sensor, check that the distance from the sensor to the disk is correct.

In configuration check, Use Spindle feedback in Sync. Mode and Spindle Speed Averaging is actives.

regards
Renato
Re: Threading on lathe issues
« Reply #26 on: May 10, 2015, 02:39:33 PM »
hi
i have a denford orac lathe  & do a lot of threading on this machine doing a thread of 1mm pitch this is done at 600 rpm both for internal & external threads , a 1/4" bsp thread 19 tpi is done at 250 rpm
i am using the parrallel port to run my machine and using mach version 062 which i have found very stable over the last 12 months
i think the pick up slot on your spindle disc is not wide enough mine is at least 1/2" wide & i get a very stable speed with very little variation also very stable in the threading cycle . when threading the cycle is always started at 15 mm away from the job to give it time to pick up the pitch & settle itself before it starts cutting
robert