Duet 2 Wifi sensorless homing experience

rschlachter

I just rebuilt the frame on my 3D printer. It's looking great and I'm excited to get it running again.

The design I followed seems to have forgotten about end stop placement with the upgrades I have. Given that my printer is down, I was going to cut some small blocks of wood to hold the end stops until I can print something so that things match. But as I was browsing the docs, it seems like sensorless homing is a possibility with this board. I run a BLTouch 3 so I'm not worried about the Z-axis, but it sounds kind of nice for the X and Y.

So I'm just curious if other folks have run their printers sensorless and what the experience has been? I doubt I'd ever need 100% of the build plate in either direction so if it's very slightly off occasionally, I don't think that'd be a huge deal... But yeah. Just looking for a little feedback before I commit one way or another.

dc42

@rschlachter, the E3D tool changer uses Duet 2 and sensorless homing by default.

o_lampe

@rschlachter
I used to use it on my Delta and Duet2 running RRF1.20!
It worked OK, sometimes I had to hit G28 twice, because it tripped to early.
Now I'm using the same printer/steppers with RRF 3.3RC3 and I couldn't use the same settings again.
Sensitivity+ 1 => triggers immediately
Sensitivity +2 => doesn't trigger at all
It depends on various parameters and the tryout-phase is not for the 'faint of heart'...carriers banging against the frame and trying to rip off the belts
(even at low current and different speeds)
Always had a finger at the reset button.

dc42

@o_lampe, I can't think of any reason why the stall sensitivity would change between RRF 3 and earlier versions, except that in earlier versions, if you use M913 to temporarily reduce and restore motor current, you needed to use M400 first to ensure that the previous moves had finished.

See also https://duet3d.dozuki.com/Wiki/Stall_detection_and_sensorless_homing#Section_Minimum_recommended_speed_for_stall_detection.

Before executing the homing move, it's also a good idea to back off from the endstops by at least 4 full steps in case the motors were recorded as stalled to start with. On my tool changer, I backoff and home each axis twice, to guard against premature stalls.

o_lampe

@dc42
The difference is, that I now have a Sherpa Mini on my offset-effector, before it was Bowden tube.
The effector drops on it's own when powered off/reset. Another source of 'joy'...but I don't have to care about the 4 fullstep rule.
My steppers aren't the best for stall detection: 0.9 degree, 2.4A, low inductance.

rschlachter

My motors are still whatever came on my wanhao duplicator i3+. Probably should have got new ones.

It sounds like my best bet is just to try it and see how it goes. Thanks folks!