Hard time cutting Thread G76 on Lathe

I am having some trouble cutting thread on Lathe using LinuxCNC.

I use G76 P20 z-20 I-2 J0.05 K1R1 command



It seems to drift 90 degrees on each pass cutting thread ?

Donno wrote:

I am having some trouble cutting thread on Lathe using LinuxCNC.

I use G76 P20 z-20 I-2 J0.05 K1R1 command

It seems to drift 90 degrees on each pass cutting thread ?

First is the are the x and Z moving the correct command distance ie if you command Z20 does it actually move 20mm

This is the code I use
G0 G40 G18 G80 G21 G49 G95
G90 G7
F1.5 S470
M3
G4 P1
M7
(Change the fist X to the Dia P = the Pitch K = Thread depth)
G0 X10 Z10
G76 P1.5 Z-12 I-0.1 J0.1 R1 K1.5 Q29.5 L0 H1

I just choose P20( Pitch = 20mm) to show the problem the X and Z is moving the correct distance. I will test your code above.

Donno wrote:

I just choose P20( Pitch = 20mm) to show the problem the X and Z is moving the correct distance. I will test your code above.

Also not teaching you to suck eggs but is the encoder geared 1:1 to the spindle with a toothed belt

The Belt Pulley is 22:22 or 1:1 but i think you might be on to something. I ran the spindle at 1rpm and waited for the spindle index signal. I made a mark on top of the spindle and rotated it and the spindle index signal not triggering on the same spot. I remember reading about electronic gear ratio in my spindle manual, might have to check spindle settings.

Edit: It Seems the pulley is 22:24 ratio is there a way to config LinuxCNC or should the spindle be configured with an electronical gear ratio ??

Donno wrote:

The Belt Pulley is 22:22 or 1:1 but i think you might be on to something. I ran the spindle at 1rpm and waited for the spindle index signal. I made a mark on top of the spindle and rotated it and the spindle index signal not triggering on the same spot. I remember reading about electronic gear ratio in my spindle manual, might have to check spindle settings.

Edit: It Seems the pulley is 22:24 ratio is there a way to config LinuxCNC or should the spindle be configured with an electronical gear ratio ??

You just need the index to be 1:1 so if you could put a sensor to do that on the spindle it would be fine

At least you have found the problem

I just got the correct pulley and everything seems to be working fine.



Thanks for the help

Donno wrote:

I just got the correct pulley and everything seems to be working fine.


Thanks for the help

Glad to be of assistance