Mach III losing 'z' zero position

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jimwill2
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Mach III losing 'z' zero position

Post by jimwill2 »

I have had this happen in all three axis at one time or the other... I was vcarving some text and the router suddenly plunged about .25 and continued routing. I checked the homing limit on 'z' and it was still fine. The 'z' zero had changed by the .25 amount. I thought before that it was the cnc losing it's position but that would cause the homing limit to screw up also. The only thing I can think of is a slight power sag when my central air kicks on. I bought a UPS power backup for the computer and I'm going to hook that up. Just wondering if anyone else has had this problem?
Jim Williams

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zeeway
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Re: Mach III losing 'z' zero position

Post by zeeway »

Jim,

Hmmm....for your router to plunge .25 based on an electrical sag would seem counterintuitive to me. I can see the sag perhaps causing less steps than programmed, but not more. Are you sure you don't have a mechanical problem, like a loose set screw on a coupling...or something like that? Over on the Mechmate Forum (when it was free), I had read they use a spring or gas cylinder as a counterbalance for the z axis...but unless you have a very heavy z slide, I would not think that is the problem. I guess you should also check for backlash.

Good luck,

Angie

cac67
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Re: Mach III losing 'z' zero position

Post by cac67 »

I've had that problem. I got rid of my wireless keyboard and mouse, got a new controller, updated mach, replaced that computer. None of that fixed it. Finally I made one change to my mach profile: I set if for incremental mode. No more problems.

Before a bunch of people jump in here to tell me that setting doesn't have anything to do with it, I know. That's why I did all that other stuff first. That setting is superseded by the gcode generated by aspire so it shouldn't matter what that setting is, and even if it wasn't superseded by the gcode incremental mode would be the wrong mode. But that's what stopped the problem.

scrapmaker
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Re: Mach III losing 'z' zero position

Post by scrapmaker »

I used to have that problem where the bit would plunge for the center of the earth and I had to keep one hand on the e-stop. I dedicated the computer to the cnc and removed all background and excess programs. No screen saver, no link to the internet or network to other computers. I haven't had the plunge since. It is just an old computer but works fine now.

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miopicman
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Re: Mach III losing 'z' zero position

Post by miopicman »

jimwill2 wrote:I have had this happen in all three axis at one time or the other... I was vcarving some text and the router suddenly plunged about .25 and continued routing. I checked the homing limit on 'z' and it was still fine. The 'z' zero had changed by the .25 amount. I thought before that it was the cnc losing it's position but that would cause the homing limit to screw up also. The only thing I can think of is a slight power sag when my central air kicks on. I bought a UPS power backup for the computer and I'm going to hook that up. Just wondering if anyone else has had this problem?
I had a similar problem until I changed from a laptop to a relatively old desktop PC with separate (non-motherboard) graphics card, no anti-virus software running, not connected to the internet or LAN and running as little in the background as possible.

jimwill2
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Re: Mach III losing 'z' zero position

Post by jimwill2 »

I installed an UPS that protects the computer and the CNC machine (the router is on it's own) and haven't had another problem.
Jim Williams

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