Machine home zeroing with no motion from G code.

I'm using a stepper spindle on my lathe for threading, and it works great, but I have to unwind the spindle back to the home position or the machine limit will eventually be reached. Setting A to zero with G54 does no good because the machine limit is unchanged.

Is there a way to set the machine home position to zero, with no motion, from within a G code program?

Sherline lathe
Gecko drivers
Standard XYZA (Y unused) stepper setup wizard settings.
No HAL tweaking done.

I'm working in G91 mode, and manually writing the G code.

You should see the nice lead-ins and lead-outs on these threads -- perfect! I could bore and thread a hole, and fill it perfectly with a threaded rod. ("perfect" meaning "theoretically/mathematically/geometrically perfect, with so-so execution")

Thanks.

Have you tried G92?

linuxcnc.org/docs/html/gcode_main.html#sub:G92,-G92.1,-G92.2 ,

Also look at G10

Rick G

jodhner wrote:

Is there a way to set the machine home position to zero, with no motion, from within a G code program?

No, that is not possible.

Are you trying to thread without any position feedback from the spindle?

John

jodhner wrote:

I'm using a stepper spindle on my lathe for threading, and it works great, but I have to unwind the spindle back to the home position or the machine limit will eventually be reached. Setting A to zero with G54 does no good because the machine limit is unchanged.

You could set the machine limit very high indeed, that might work. I doubt that any of us will live long enough to see 10^38 spindle revs.

Are you using an encoder and index, or using G-code with coordinated Z,A moves?

Whoa, just lost my reply when I hit "submit". It said "Code not correct". I'll have to recompose my reply ...

I'm using open loop steppers with no spindle encoder.
Everything is coordinated.

This is a hobby where the process is just as important to me as the product.

If I were vanilla threading I'd use a spindle encoder and canned cycles, but I'm particular about my threads, and I will also be making worms, ornamental turning, and who knows what else. I'm using the spindle more like a fast rotary table.

If the machine limit parameter is astronomical I'll just zero with G54, but my object oriented sensitivities will suffer. I'd like my subs to leave the machine as they found it.

You guys do a lot of work, and I appreciate your attention. Thank you.

--Justin