Sensor-less homing, is it possible to tune the sensitivity?
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Hi guys
Having a small issue with my E3D Toolchanger running duet 2 wifi, the sensor-less homing for the X-Axis is a little bit temperamental
Sometimes I have to home the X-Axis 4 or 5 times to get a good homing on the X, it will home every time but sometimes it will do it and the home sound is more of a bang than a subtle homing noise, when it’s a louder bang the homing position is slightly off which becomes apparent when changing tools
With my super limited knowledge of sensor-less homing it takes the resistance detected as a home position, is it possible to tune this value to make the sensor-less homing a little more sensitive?
It performs great on all other axis where present too
Thanks
Tom
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@filamentfrenzy There is some documentation on the background of stall detection here:
https://duet3d.dozuki.com/Wiki/Stall_detection_and_sensorless_homing
The command to modify in your config.g or homing files is M915
https://duet3d.dozuki.com/Wiki/M915
You can try reducing the S value by 1 and retesting (and keep reducing by one until the issue stops) however if you have to go too far below 0 then you may find you get a false trigger before the motor reaches the end of the axis. -
@filamentfrenzy you may find the sensitivity adjustment provided by M915 rather course. If that's the case, you can adjust the motor current to fine-tune it.
If it sometimes detects a stall right at the start of the homing move, try reducing acceleration before homing, and restore it again after homing. In 3.4beta6 this will be done automatically.
On my TC I have set the homing files to back off 5mm and do the stall homing move twice, in case the first one fails.
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I tried lowering the S value from S5 to S1 in increments of 1 and these seemed to make the issue more apparent each time, so i then adjusted upwards settling on a value of S8 which so far after testing the home position roughly 30x seems to provide a good solid repeatable homing position, I’m super happy with it now!
Thankyou for you’re replies, I really appreciate the help
Thanks
Tom
