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Question about referencing
« on: January 11, 2006, 12:51:43 AM »
I've had a problem with referencing the X-axis that I can’t solve. Z and Y reference normally but when it gets to X, it will move anywhere from a ¼ inch to 1 ½ in and stop. No reference LED lit on the Diagnostic screen and no error message. The DRO shows the distance it has moved. It doesn’t matter if the reference (home position is 2 inches or 20 inches away, it moves it’s short distance and stops. Once it is close enough to the home switch (within the 1/4 to 1 ½ inch range) it homes normally. The homing speed is set at 50%. The only workaround I have is to jog the X-axis after it references the Z and Y until the X is close to the home position, then reference it again.

There got to be something simple I’m overlooking, but I can’t find it

Louis
 ???
"There is no mechanical problem so difficult that it cannot be overcome by
brute strength and ignorance"
Re: Question about referencing
« Reply #1 on: January 11, 2006, 06:11:22 AM »
under config/logic try putting in a value of 200 for the debounce interval. This should fix your problem.

Thank you
Brian
Fixing problems one post at a time ;)

www.newfangledsolutions.com
www.machsupport.com
Re: Question about referencing
« Reply #2 on: January 11, 2006, 06:21:36 PM »
Well, changing the debounce to 200 helped some. It actually moved one time about 5 inches before stopping. Should I try a higher value?

Louis
"There is no mechanical problem so difficult that it cannot be overcome by
brute strength and ignorance"
Re: Question about referencing
« Reply #3 on: January 11, 2006, 07:09:43 PM »
try 2000 ...
Fixing problems one post at a time ;)

www.newfangledsolutions.com
www.machsupport.com
Re: Question about referencing
« Reply #4 on: January 11, 2006, 07:44:20 PM »
If it is stopping randomly before even reaching the home switch, and increasing the debounce interval helped, that pretty much confirmed that the problem is in shielding / crosstalk, probably with the stepper leads for that axis.

Debounce is intended to compensate for contact bounce in the switch when it is triggered, not for crosstalk. Increasing the debounce interval further will reduce the symptoms of the problem, but will do nothing to cure the underlying problem.

What you should do is inspect the routing of the wires for the home and limit switches on the problem axis to insure they are kept as separate from the stepper wires as practical. If it is not practical to physically separate the wiring then the wiring for the switches should be changed to shielded wire with the shield grounded at only one end, generally the control end.

Also note that the crosstalk can be occurring anywhere along the wire, not necessarily just where they meet on the axis. If the wires are close on the control end that could also be the source of the crosstalk.

Pete C.
Re: Question about referencing
« Reply #5 on: January 11, 2006, 08:06:48 PM »
You are right and that is where I am headed... But if he gets back to us and is saying "G it looks the same" there is an other problem like a loose wire on the switch.

Thanks for the input
Fixing problems one post at a time ;)

www.newfangledsolutions.com
www.machsupport.com
Re: Question about referencing
« Reply #6 on: January 12, 2006, 08:06:31 PM »
It turned out to be a combination of debounce and noise. I had forgotten I had left about 4 extra feet of cable when I wired the home/limit switch for the X axis---- and the excess was looped around a 120V outlet for the router motor.

I moved it an reset the debounce to 100 and it still had some of the problem but with it moved and debounce set to 200 it references flawlessly.

Thank you Brian and Peat.

Louis
"There is no mechanical problem so difficult that it cannot be overcome by
brute strength and ignorance"