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General Mach Discussion / G76 Threading Mach3 Denford Orac Z Stuttering

« on: January 27, 2017, 07:26:03 AM »

Hello all,

My Denford Orac has threaded with G76 many times without failing, but is now
stuttering in the Z axis. It stutters from Z6 to Z-22, comes out in X ok, but then struggles to return to Z6
again for the next pass. It then thinks it is at Z6, according to the Z axis DRO on mach screen. So with each attempted pass
it is getting closer to the chuck each time.

Works fine if I untick "use spindle feedback in sync modes", so Z mechanically good, but threads obviously ropey.
General turning is good and Z repeats very well.

Old pc died, so using the pc (Dell GX270) that I normally use for my Denford Triac
I'm sure I copied the Mach3 folder from the old pc (Dell GX260) to this one ok with my usb stick.

I'm using ver 040, but not 100% this is what I had on old pc.
I can't find other versions on Artsoft website to download and try.
I copied my original licence from my email into the mach3 folder just to make sure.
I don't know how to paste my latest xml file onto here.

I've cleaned the opto sensors and LED on board works for each rev when I rotate by hand.
Debounce set to 0, I've tried other values with only a slight difference.
Spindle speed averaging ticked.
I soldered onto pin 12 from 13 and changed Index to pin 12 and no difference.

Here's my G code:

G18 G40 G49 G90 G94 G80 G55
M03 S350
G04 P5
T0202
G00  X27.5 (M27 THREAD)
G00 Z6
G00 X27
G76 X25.16 Z-22 Q2 P1.5 J0.1 L45 H0.5 I29 C0.5 B0.05 T0
G0 Z20
G0 X40
M5
M30

I can only think it is either the pc, noise, version of Mach or faulty opto sensors.
Waiting to get another pc.


Any help would be much appreciated,

Thanks,
John