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Author Topic: Z losing zero position in rapid move up  (Read 326 times)

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Z losing zero position in rapid move up
« on: September 12, 2018, 11:59:07 PM »
I've got a Sieg KX1 and have had it for since 2011, and just recently I've noticed that the z will lose a position after a rapid manual move up. Doesn't seem to be having any issues while running a program, only after I rapid the z up and recheck the zero postion, usually only by .003" to .007"

Any ideas?
Re: Z losing zero position in rapid move up
« Reply #1 on: September 13, 2018, 12:48:10 AM »
Hi,
sounds like its losing steps, try reducing the acceleration of the z axis a bit.

When running a job the machine tends to run at a percentage of max speed/acceleration whereas
your jogging will be at max.

If that fixes it you might have to look further as to why its doing it now but not before, maybe some
mechanical binding or similar.

Craig
My wife left with my best friend...
     and I miss him!
Re: Z losing zero position in rapid move up
« Reply #2 on: September 13, 2018, 01:02:25 AM »
I'll give that a try and see what happens. I was thinking more along the lines of a backlash problem. But I've read of others having problems losing steps.
Re: Z losing zero position in rapid move up
« Reply #3 on: September 13, 2018, 02:37:31 AM »
Hi,

Quote
I was thinking more along the lines of a backlash problem
You may very well be right, I hadn't considered backlash. If backlash is an issue why is it that it occurs when you are jogging
not during a Gcode job?

A reduction in acceleration or velocity or even both may prove effective and therefore point you in the right direction. If the problem remains unchanged
then you can all but rule it out, either way its still a useful experiment.

Craig
My wife left with my best friend...
     and I miss him!
Re: Z losing zero position in rapid move up
« Reply #4 on: September 13, 2018, 09:48:30 AM »
Unlikely to be backlash especially on the Z as gravity mostly keeps the nut down against the screw. Likely to be loosing steps because you say it doesn’t occur when jogging which is done at the maximum torque part of the motor speed curve. Rapids take the motor into the part of the curve where torque falls way off.

For best performance I would try reducing maximum motor speed not acceleration first. Reducing acceleration will make cutting times go way up when lots of short moves are needed. Reducing max speed only slows long rapid moves
Re: Z losing zero position in rapid move up
« Reply #5 on: September 13, 2018, 12:44:20 PM »
Good points, I wasn't sure about the backlash theory, since it doesn't seem to be a problem when running g code. Only when rapid up then back down manually. So I'd imagine it's losing steps as y'all have suggested. I'll try reducing the speed and see if that helps.