knock sensor to help ABL

[daveapplemotors]

Sometimes even with 3D touch auto bed leveling I must adjust the Z offset. If I hear the extruder skipping / jamming / not feeding due to being too close to the bed I stop the print reset Z offset 0.[02-0.04 mm] lower.

If I wired a simple automobile 'knock sensor' to listen for extruder trouble then I could program "Raise The Extruder and Nozzle 0.02" into the firmware. If I set the Z offset so it is always too close then it would always call up the knock sensor routine and thus my prints would never need my adjusting.

Please let me know if such an idea sounds good to you.

[cosmith]

I think your main problem is the auto leveling isn't working correctly. I had the same issue on my Pro C. It would compensate, but not enough. I switched to the latest RC of Marlin and now my bed could be skewed by 5mm and it will still print correctly.

--Colin

[daveapplemotors]

Mine works well. I just finished a couple of 60nm prints. I started at 0.012 mm with layers of 0.060mm.

I have done plenty of autoleveled prints. But sometimes the head is too high--the print doesn't stick-- and I correct with a larger Z offset. Sometimes the nozzle is too low--and I can hear the extruder grinding-- and I correct with a smaller Z offset.

I am just saying the the process could probably be automated with another sensor and addition to the firmware.

[cosmith]

Now you're just bragging.

I think this would be something for the Marlin folks. There are some input lines open on the board (axis MAX sensors come to mind). It would just be a matter of integrating it into Marlin.

--Colin