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Author Topic: slave motor not in sync with master axis motor  (Read 6729 times)

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slave motor not in sync with master axis motor
« on: July 17, 2009, 12:59:02 AM »
I'll preface this with the fact that I'm fairly new to the CNC world.  I've got a Gecko G540 with the A-axis slaved to the X-axis.  I have two steppers moving the gantry of my router in the x direction.  I cut a lot of circles, some recessed, some through cuts.  What I've noticed is that when the router has made one complete pass it pauses to plunge down a little more in the z direction (I'm cutting 3/4" mdf or 19mm baltic birch typically) and then will start another pass. The A-axis motor will always start moving before the X-axis motor, making the gantry out of square, more and more.  I tried to use a ramp cut down so the motors don't necessarily stop all of the way, but for some reason Mach 3 or the Gecko ignores the Z move in my G-code if it is preceded by both an X and Y move.  The computer monitor shows the Z axis moving down, but the actual z-axis doesn't move.  If the Z move is on it's own line it will move fine. 

So, two questions.  Why isn't the slaved axis starting in sync with the master axis (or vice versa)?  Why won't Mach3 or the Gecko recognize a z move in a line of code like this (G1X6.8124Y3.9731Z-0.0017)?

Offline Hood

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Re: slave motor not in sync with master axis motor
« Reply #1 on: July 17, 2009, 08:22:20 AM »
Sounds like a drive/bob issue. Try Sherline mode and see if your problems stop.
Hood

Offline ger21

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Re: slave motor not in sync with master axis motor
« Reply #2 on: July 17, 2009, 09:21:35 AM »
Is the Z move showing correctly on the DRO's? I'm guessing it is.
Gerry

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Re: slave motor not in sync with master axis motor
« Reply #3 on: July 17, 2009, 01:17:51 PM »
Thank you for the replies.  I took my Gecko 540 apart and traded the Z card with the X card.  Now the X and A axis' are working in sync. 

In a ramp move for Z the DRO shows it moving down, while in actuality the Z-axis isn't moving. 
Re: slave motor not in sync with master axis motor
« Reply #4 on: July 17, 2009, 01:21:00 PM »
Oh, one more thing I didn't mention before.  When I would make through cuts, the passes would be off in the x direction causing a stepped through cut.  When I changed the code to Sherline that stepped problem went away.

Offline Hood

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Re: slave motor not in sync with master axis motor
« Reply #5 on: July 17, 2009, 04:17:24 PM »
So to recap, your X and A slaving is working fine now? Your Z is still not working?
 Sounds like there may be a bad connection or a config problem in Mach, can you attach your xml? Also if swapping X and Z drives cured the slaving problem its either X is a bad drive or connections were not god and swapping cured that.
Hood

Offline ger21

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Re: slave motor not in sync with master axis motor
« Reply #6 on: July 18, 2009, 06:36:44 AM »
I've seen a lot of G540 users that need to use Sherline mode to keep from losing steps and getting strange results. The problem is due to the PC not being able to deliver the correct voltage/ current through the parallel port. You might want to try a different PC, or possibly a PCI parallel port card.

It also appears you have a bad drive in your G540.
Gerry

2010 Screenset
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JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html