Z Axis Homing and Movement Issue

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01 May 2024 07:34 - 01 May 2024 07:44 #299445 by N3pu
Hey Guys,

during the setup of the last axis (Z) I copied the section from X and Y Axis in the Ini file and adjusted the Limits of movement for Z and the changed the Sign for the Homing Search and Latch. Z will be homed in High Position (Z+).

Two Issues I can not resolve:
1) During Homing (Z Axis moving Up in direction Z+ to Ref-Sensor) the UnitCount in LinuxCNC is about 1000 mm (and then linux cnc Stops and prompt a message "J2 Bewegungsende im Referenzstatus 7"). If I press again Z-Ref the the Homing proceeds well until Z-Ref Sensor is reached.

So the travel of such long way (like the display) says is crazy. I just have a travel of about 500 mm on Z.

2) After Homing processed discribed in "1)" I can move the axis DOWN with the right measurement count.
BUT if I like to move the Axis UP again it didn´t works. Just a few µm and then linux CNC says "0.000" position of Z.

It seems like it rehomed during the DOWN move. Can´t understand.
I rechecked Positions with measurement tools and in the Servodrive. Everything is real, exept the value on LinuxCNC Z Position.

 
Last edit: 01 May 2024 07:44 by N3pu.

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01 May 2024 13:20 #299460 by N3pu
I created a video for issue 2)

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01 May 2024 19:00 #299499 by tommylight
That helps in bringing up more questions, so
-what controller
-what drives
-what control type (step/dir, analog, PWM)
One thing is for sure, not a LinuxCNC issue with homing or whatever, the only thing i can think of in a hurry is too short step time or motor skipping.

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01 May 2024 19:38 #299505 by PCW
As tommylight suggests I would try lengthening the step pulses
just to eliminate that as a possible issue (say to 1000 ns)
The following user(s) said Thank You: tommylight

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03 May 2024 18:21 #299651 by N3pu
Yeah, you could be right, that the problem is outside LinuxCNC.
My though was it´s linuxCNC (config) because of I copied the Z Axis by hand in the Ini-File (X and Y which are working are created in PNC-Conf) AND moving the Z Axis DOWN there seems to be no difference in way of moving.

I also have on X, Y and Z the same Servo Drive (Kollmorgen S346 with Firmware 3.89). Maybe the drives have different Hardware configuration - I will recheck. Motors are slightly different on X/Y and Z. Motors have Multiturn-Encoders connected to the Drive and they are in closed loop (drive and motor). So if something should be wrong it only can only be the step / dir signal between Mesa 7i76e and Servo Drive.

Servo Drive is rated at 1,5 MHz frequence for the step / dir interface. Cable is 30 cm.
I will recalc everything and give it a try on the weekend to change the timing for test, even if this timing is working fine on X and Y Axis...

I also noticed the resistor in the rs485 line - at the moment I havn´t insert this end-resistor. Could be an issue too.
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04 May 2024 17:19 #299742 by N3pu
Today I increased the step timing from 0,5 µS to 1µs each (high and low) but there was no change.

Then I was thinking again about that down seems to work (maybe only better) and up is more crazy.... So I recheckt my cabeling from Mesa to Drive - specially the DIR signal.

Here there was a missing contakt on DIR - (I think I crimped without stripping or someting like this). So crimped again and everything seems to work fine! Because of the floating DIR- the step count was sometime Up and sometime Down...

Thank you guys!

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