Monitoring of extruder head using laser distance sensors

tylersuard

Hello. My printer often has layer skips due to collissions with up-curling prints. These often happen while I am away and can't catch them, and that often ruins a 40+ hour print.

I mounted 2 laser distance sensors to the extruder head. How can I monitor the extruder head position from the board, compare that to the laser distance sensor readings, and pause the printer if there is a mismatch?

o_lampe

@tylersuard said in Monitoring of extruder head using laser distance sensors:

My printer often has layer ~~skips~~ shifts due to collissions with up-curling prints.

Sorry to sound like a smarta$$,
but I'd try to avoid layer shifts, instead of trying to find a 'band-aid' after the layer shift happened.

Finding a solution for real-time reading two analogue sensors and compare them to the coords in the object model sounds "optimistic" to say the least.

If you want a quick solution, you could probably pause the print and home X and Y after every 'n' layers.

breed

@tylersuard closed loop steppers. The newer ones from mks work great. Everyone will tell you here to fix the printing problem first, which is fine on a 20 hour print. I print 100+ hours quite often on big machines, fixing the printing problem only goes so far. Id much rather have a completed print with a small blemish, that is still usable.

OwenD

@tylersuard
Assuming that you can have one laser give a reference value of where the bed is and the other laser can give an accurate reading for the highest part of the print, then simply doing the math for

bedPosition + Z position <= highest part reading

In practice , it might be difficult to implement
Maybe if you scan the part at the end of each layer, but after raising the Z height.
At that point there should be at least LayerHeight difference.

tylersuard

@breed @o_lampe I have tried everything. I am printing with TPU, and I get upcurls on certain parts. Those upcurls collide with the nozzle. I have tried using cura's "make overhangs printable" setting on 25 degrees and 30 degrees. I have tried using TPU supports and PETG supports, cooling with a floor fan, playing with nozzle temp and speed... nothing is working. I just want a way to catch it when the layer shift happens (usually only once in a 100 hr print.

tylersuard

@OwenD I'm not sure what you mean by this, my layer shifts are horizontal, not vertical.

OwenD

@tylersuard said in Monitoring of extruder head using laser distance sensors:

@OwenD I'm not sure what you mean by this, my layer shifts are horizontal, not vertical.

Your original post said the issue was upcurling prints.
I assumed you were trying to detect that BEFORE you had a collision and layer shift.
Which would require measuring in the Z axis.
Anything else is shutting the gate after the horse has bolted.
Apart from fixing the underlying issue of course.

dc42

@tylersuard you might want to reduce travel speed when printing TPU, so that the nozzle melts the upcurl and goes through it instead of ramming into it. Or perhaps you can reduce the amount of upcurl by adjusting cooling fan speed or some other parameter.

tylersuard

@dc42 Thank you.

tylersuard

@OwenD Understood now, thank you.