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Author Topic: Z axis cutting too deep  (Read 3700 times)

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Offline Pico

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Z axis cutting too deep
« on: December 18, 2009, 03:17:48 PM »
My cnc computer has been off for about 1 1/2 months; previously I used it for about 60 hours, spread over 2 weeks with no problem. Recently I have attempted to cut a piece about 2"X4"X.85". The X and Y axis are alright but the Z axis continually cuts too deep. The first several pieces I cut seem to be about 100% too deep - the cut was through the 1 " material, the 3/8" plywood that it was contact cemented to, and into the table about 3/16". Other cuts I made have not been as extreme, the cut this morning maybe 50% too deep. The program limits reads Z range =.85". I don't think the DROs are reading correctly, the tool retract height is +.15 but after it has cut deeply into the material, and the cutter has retracted to +.15, I can look across the top surface of the material and the bottom of the cutter will be beneath it. I checked Ports and Pins-Motor Tuning and the Z axis steps are identical with the X and Y axis. I've looked over this board but can't find a similiar problem. Any idea about how to solve this?    Thanks,   Pico

Offline Hood

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Re: Z axis cutting too deep
« Reply #1 on: December 18, 2009, 03:26:18 PM »
Sounds like your Z is losing steps on its upward movements, check to see that it is not binding.
Hood

Offline Pico

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Re: Z axis cutting too deep
« Reply #2 on: December 18, 2009, 04:39:58 PM »
It's not binding, I just checked. I have run 7 samples and it seems that in all the Z axis has been "stretched" a consistent amount, but the DROs and program limits give the correct amount. At first I thought that the Z axis steps were off, but that isn't it. Sure got me baffled.   Thanks,    Pico

Offline Hood

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Re: Z axis cutting too deep
« Reply #3 on: December 18, 2009, 04:42:03 PM »
Lower the accel on the Z by half and see if its still wrong.
Hood

Offline Pico

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Re: Z axis cutting too deep
« Reply #4 on: December 18, 2009, 06:03:38 PM »
Will do, Thanks.     Pico

Offline Pico

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Re: Z axis cutting too deep
« Reply #5 on: December 19, 2009, 05:25:58 PM »
Tried that, doesn't change anything. I'll be gone for a week and will return on the 28th to continue experimenting with a solution. Thanks,     Pico

Offline Hood

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Re: Z axis cutting too deep
« Reply #6 on: December 19, 2009, 05:37:14 PM »
Have you verified that if you command a move from the MDI that it moves that distance? Try both G1 and G0 moves.
If you can swap drives around to see if the problem fllows the drive, same with motor if possible.

Hood

Offline Pico

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Re: Z axis cutting too deep
« Reply #7 on: December 19, 2009, 05:46:13 PM »
Thanks for the advice, will try when I get back.      Pico

Offline Tweakie.CNC

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Re: Z axis cutting too deep
« Reply #8 on: December 20, 2009, 06:52:38 AM »
Another possibility that may be worth investigating is that the tool is moving in it's collet.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.