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THC axis selection?
« on: January 13, 2011, 04:13:51 AM »
Hello and a pleasure to meet you all.

First, I want to congratulate and thank everyone on the excellent job they've done with this forum and for providing some much needed answers, you were able to shed some light on many problems I've encountered so far.Keep up the good work!

Second, I've been wrapping my head around a feature for my CNC machine that I just can't find an answer for.I have a 4 axis machine and I want to be able to jog the axis freely while I run a G-code program (something like the THC up/down feature for Z).My questions is how can I change the axis the THC controls?If someone could point me in the right direction  I would really appreciate it.

Regards,
Shorty

Offline stirling

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Re: THC axis selection?
« Reply #1 on: January 13, 2011, 10:39:06 AM »
Hi Shorty - welcome.

As far as I know - and I'm happy to be corrected, the THC control of the Z axis is hard coded and can't be moved to another axis. You could of course wire the Z pins to any physical axis you want or you could use swapaxis(). But I'm guessing that's not really what you want. I'm also guessing you want to run XYZ gcode whilst you manually control the 4th (rotational?) axis. Can you explain in a bit more detail - someone may have something.

Ian
Re: THC axis selection?
« Reply #2 on: January 13, 2011, 05:50:36 PM »
Thank you for the reply Ian.

I have 4 axis: standard up/down , left/right, front/back and the 4th one is another up/down for a more precise control.What I want is to be able to jog all the axis freely while running a G-code program, something similar to what happens when you use THC up/down function assign to keys.Mach interprets this beautifully and recalculates all the G-code relative to the new position from what I saw.I was wondering if I could achieve the same effect on all 4 axis, if it's even possible.

Hope I explained things a little better this time :)

Regards,
Shorty

Offline stirling

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Re: THC axis selection?
« Reply #3 on: January 14, 2011, 09:03:39 AM »
What I want is to be able to jog all the axis freely while running a G-code program
Can't see you being able to do that - why would you want to do this?

something similar to what happens when you use THC up/down function assign to keys.Mach interprets this beautifully and recalculates all the G-code relative to the new position from what I saw
I think you may be misunderstanding something here (or I'm misunderstanding you). Mach doesn't recalculate anything as such. It just moves the Z axis as prescribed by the THC up/down signals (and of course keeps track of Z position in the DRO). During this time Mach can not simultaneously perform Z axis gcode i.e. commanded movements. In fact I just tested this out before posting and if you command any Z movement, simultaneous THC up/down is ignored. (which is kind of what I'd expect - if you don't want anarchy)

Ian