Machine Interruption - high speed higher accelation

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26 Oct 2017 19:42 #100848 by probamo
Shortly! Machine run with 3 stepper motors, one per axis. To provide movement each axis has the screw diameter 16mm, 5 mm pitch and related ball nut 16mm. For all axis, there are limit switches connected, homing is doing well. Speed of machine of each axis easily 7500 mm/min with acceleration of 350 mm/s2. While cutting 2D, or curving 2.5D no problem at all. I am fine. Running 3D model, works as well fine. However, I wanted to speed it up, thinking with low acceleration I am loosing time. When I set the acceleration to 500 mm/s2, and pressing respective arrows key on keyboard, movement engaged at max speed, no loosen steps, but when the key was released machine stopped immediately and interrupted (machine is set OFF), saying ''the home switch triggered", though there is still room to reach limit switch.

is there anybody facing at least similar issue, to advise me what to do?

Thank you

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26 Oct 2017 20:11 - 26 Oct 2017 20:12 #100849 by PCW
Sounds like an electrical noise issue (noise triggering false limit switch detection)
This may be solvable by re-routing the limit switch wiring (away from power and motor wires)
or use of the debounce component on the limit switch signals in HAL
Last edit: 26 Oct 2017 20:12 by PCW.

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04 Nov 2017 19:25 #101319 by probamo
I checked cables, that was not issue. Regarding ''debounce'' could you please help me a bit more in detail?

Thank you.

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05 Nov 2017 17:36 #101361 by PCW
You can get the manual page of the debounce component with

man debounce

Basically the debounce component is put in series with the limit switch signal in hal

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05 Nov 2017 20:01 #101367 by BigJohnT
A short description of the debounce component is in the Documents.
linuxcnc.org/docs/2.7/html/hal/rtcomps.html#_debounce

JT

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06 Nov 2017 18:35 #101448 by probamo
I tried to modify HAL file following this instruction:
forum.linuxcnc.org/38-general-linuxcnc-q...al-debounce?start=10

Unfortunately no improvement made. Hereafter enclosed INI and HAL files. The latest one with (lines 10, 11, 46 - 54) and w/o modification, if somebody could help me.
With modified HAL acceleration of 350mm/s2 works, but with higher e.g. 500mm/s2 machines stopped and screen-shot of message is attached.
Thank you.

File Attachment:

File Name: HAL.txt
File Size:4 KB

File Attachment:

File Name: HALmodified.txt
File Size:4 KB

File Attachment:

File Name: INI.txt
File Size:2 KB
Attachments:

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06 Nov 2017 19:14 - 06 Nov 2017 19:16 #101453 by PCW
OK, this is not a limit switch problem but more likely an issue with the stepgen (following error)

If you look at your maximum step rate (160 steps/mm*125 mm/S = 20 KHz), its _very_ close to maximum possible step rate
at your base thread period (1/48076 = 20.8 KHz)

I would try lowering the the maximum velocity (say to 100 mm/S) to see if that solves the issue

EDIT

If you set the acceleration to 500 mm/S^2 you must also set the stepgen max-accel parameter to about 625 mm/S^
Last edit: 06 Nov 2017 19:16 by PCW.

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07 Nov 2017 18:54 #101504 by probamo
Thanks PCW.

Indeed I passed through stepconfig once again. Started with max velocity 100mm/s and increased acceleration up to 500mm/s^2. Started machine - run well. Then I reset max velocity to 125mm/s^2, and acceleration 1000mm/s^2. Due to less velocity in reality, manually adopted velocity in INI file for each axis. In stepconfig reported that with given settings, acceleration should take place as fast as 0.1s to reach max velocity. I'll give a try in coming days, with some 3D curving project and see benefits.

To make sure, I left ''debounce'' modification I made the other day in HAL file.

Once again thanks a lot for support.
Cheers,

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