Help needed: Just one axis will work!?

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27 May 2013 00:30 #34727 by cncbasher
as the z axis depths show an increasing depth of cut

the most likely problem is one of loosing steps ..
probable cause is too high acceleration and velocity settings , coupled with using too high microstepping ,

the higher the microstepping less torque you have available , and because also the z axis has to fight against gravity , it slips down
for z axis you need as much torque available as possible to counteract

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27 May 2013 00:59 #34730 by andypugh

What could be the reason for such change in Z axis during the processing of the G-Code?


You could be losing steps, or it is possible that the bit is pulling out of the collet.

Losing steps seems the most likely. Try half the accelleration you currently have on the Z.

You can test the settings by jogging with the jog speed set high. I think you have to restart LinuxCNC for INI file changes to stick, though.

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28 May 2013 01:35 #34776 by Alex_HH
Hello Andy,

I changed my settings back to
5000ns
5000ns
20000
20000
1/2 steps mode
75% current.

and reduced the acc to 200mm/s2 (before it was 381mm/s2).
But unfor. nothing changed.
I touched the surface of the part and homd z to 0.
Within the second G-Code I change Z-2 to Z0 to have a clear visual indication of the tool.

The first line was fine - the tool touch the surface.
But the second line was bad - the tool dived nearly 5mm deep into the material....

What can I do to narrow the problem?

I'm lost...
Alexander

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28 May 2013 01:38 #34777 by andypugh

The first line was fine - the tool touch the surface.
But the second line was bad - the tool dived nearly 5mm deep into the material....


What do you get if you set the jog speed fairly fast and jog the Z-axis up and down?

Do you see any sign of it stalling?

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28 May 2013 01:52 - 28 May 2013 02:12 #34778 by Alex_HH
Andy,

at acc of 200mm/s2 II set jogspeed to 1524mm/min (it is the max jog speed), at that rate I see problems - the motor is running, but the axis (threaded rod) is not moving smootly or just little by little.

In steps I reduced the max speed and acc to the following - at that rate there was no stalling during max jogspeed test. My settings are now:
max speed 12.5mm/sek
acc 70mm/s2

I will test this setting now with a g-code programm.

Alexander
Last edit: 28 May 2013 02:12 by Alex_HH.

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28 May 2013 02:38 #34785 by andypugh

In steps I reduced the max speed and acc to the following - at that rate there was no stalling during max jogspeed test. My settings are now:
max speed 12.5mm/sek
acc 70mm/s2


That sounds plausible. My milling machine runs at 11mm/s and 100 accel.

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29 May 2013 01:51 #34864 by Alex_HH
Hello Andy,

I tested the new setting some minutes ago. It seems everything on Z axis is now correct!
Many thanks for your help!
My new settings for z axis are:
acc = 70mm/s2
max speed= 11mm/s

Best regards from Germany
Alexander

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