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  #1  
Old Sun 11 December 2011, 13:14
kwang90020
Just call me: krod
 
California
United States of America
Zero point changes while cutting

I need help on home zero changes middle of cutting.
I searched the forum but could not find the same problems.
I finally finished with machine and tried to cut test patterns.
It's working fine most of time.
But sometimes it goes to wrong place in the middle of cutting. When I checked the zeros, home zero is changed.
x coordinate was changed by about 20 inches.
Everything else is seems fine.
I thank you in advance for help.

Last edited by kwang90020; Sun 11 December 2011 at 13:37..
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  #2  
Old Sun 11 December 2011, 13:19
Alan_c
Just call me: Alan (#11)
 
Cape Town (Western Cape)
South Africa
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Check if you are in absolute or relative mode.
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  #3  
Old Sun 11 December 2011, 13:54
kwang90020
Just call me: krod
 
California
United States of America
It was in relative mode.

Last edited by kwang90020; Sun 11 December 2011 at 13:59..
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  #4  
Old Sun 11 December 2011, 14:44
Alan_c
Just call me: Alan (#11)
 
Cape Town (Western Cape)
South Africa
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Try in absolute mode - that works relative to the table 0-0 point. if in relative mode where it stops becomes the new zero, next time you run the file it starts from that position - Hopefully my explanation is clear?
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  #5  
Old Sun 11 December 2011, 22:38
Kobus_Joubert
Just call me: Kobus #6
 
Riversdale Western Cape
South Africa
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He is not loosing steps..pushing it too hard ?
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  #6  
Old Sun 11 December 2011, 22:56
hennie
Just call me: Hennie #23
 
Roodepoort JHB
South Africa
I agree with Kobus if your cutter is blunt/cutting to deep at a pass or even to fast one can lose steps.(start at 0-0 point and run an air cut straight across the x-axis as fast as the machine allows you to go let it come back to 0-0 and see if you lost steps).
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  #7  
Old Mon 12 December 2011, 00:22
Alan_c
Just call me: Alan (#11)
 
Cape Town (Western Cape)
South Africa
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He's losing 20 inches in the X, if he was losing steps he would know about it - the noise would be horrendous. I have had this happen, especially when doing testing or if there was a problem and the machine was stopped mid process. After doing a rewind and starting again the machine would start moving off into the distance away from where it currently was to start the job - not exactly sure why it did it, only way I could get it right was to close Mach3 and start again - cant remember all the details of when it happen - it was some time ago. One thing though when it happened to me it offset in both X and Y.
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  #8  
Old Mon 12 December 2011, 01:40
KenC
Just call me: Ken
 
Klang
Malaysia
Alan Is right. 20 in is a lot of error & very noisy if there are lost steps happens continuously for 20 inch of travel in X-axis.
Kobus & Hennie are right to point at on over feeding blunt tool too hard.
A 3rd possibility is motor tuning. If I were you, I'll re-tune the motor setting by reduce the acceleration &/or max. velocity combo of the X-axis just to be sure it isn't due pushing the motor over its capability.
If this doesn't fix the problem... than it is very likely that it is a noise/signal interference thingy which is another can of worm...
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  #9  
Old Mon 12 December 2011, 22:34
kwang90020
Just call me: krod
 
California
United States of America
The machine was not stopped mid process. It was cutting and moving to another path but did not move all the way but 20 inches short. All the cutting was correct before the move.
If I was feeding too fast, wouldn't the cut be shorter than supposed to cut?
The movement was changed while tool was not cutting.
I'll tune the motor again and try.
Thanks guys.
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  #10  
Old Tue 13 December 2011, 00:28
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Krod,

You are not providing any data on what you have your acceleration and velocity set for each motor? What kind of file are you cutting when this happens? What kind of test pattern are you cutting?

What CAM software are you using to create you G Code? Run the same file in your CAM software, does it do the same thing? Air run the software in Mach, does it do the same thing? (Air Run, either run it on your computer or have the bit not touch any material).

It would help to have some data.
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