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Author Topic: Spontaneous Z axis movement  (Read 1621 times)

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Spontaneous Z axis movement
« on: January 04, 2015, 07:58:03 AM »

I've recently upgraded from Mach2 to Mach3 and I'm experiencing some strange Z movement when in step jog mode. I'm running a
3-axis gantry router.

When I'm in step jog mode, and I change from stepping one axis to another, or even from positive to negative, the Z axis travels
down exactly one unit, then back up, then the requested axis makes its instructed step! This does not happen in continuous mode, only in step.

Additionally, when the Z is travelling back up, the program line number box displays "2" (see http://imajeenyus.com/temp/mach3_screen.jpg) and then goes back to "0"
once the Z has finished travelling. There is no G-code program loaded, and the program line number is "0" normally.

I've looked through the settings and fiddled with anything that says 1 unit, but nothing seems to have any effect. I'm understandably
wary about using this, so I've gone back to using Mach2 for now, until I sort this out.

Does anyone have any ideas what might be causing this? It's probably some feature I've never used/understood before - I've never worked
with safe heights, tool offsets, coordinate systems etc., just basic G-code and jogging.

Best regards,

Lindsay Wilson

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Re: Spontaneous Z axis movement
« Reply #1 on: January 04, 2015, 01:10:04 PM »
Is this jogging via  the keyboard?
If it is can you possibly try a different keyboard just in case it is that.
Re: Spontaneous Z axis movement
« Reply #2 on: January 05, 2015, 06:52:50 AM »

I feel like an idiot, but I think I found what was the problem (a few hours after posting this topic - there must be some corollary to Murphy's law that says you'll
discover the solution to a problem soon after asking someone else about it). I was going through the screens yet again and noticed that "tangential approach mode"
was active. Not knowing what it was, I had left it alone previously, but this seemed to be causing the effect. The lift distance was set to 1 unit, and when
I disable it, the strange behaviour went away. I think I understand why it's doing it, if the purpose is to realign a cutting knife or similar.