Delta printer motor stall calibration
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I like doing impossible things, so I wanted to give the delta calibration using motor stall detection a try.
I started with this basic script which is supposed to just probe a single point. I'm using a small cardboard box to prevent any damage, therefore the high values for probing height etc.
However, the issue I'm facing is that no stall gets detected at all. The head moves into the box, then the motors lose steps, and after a second I hit the emergency stop.
Did I configure something incorrectly?
M913 X30 Y30 Z30 ; Reduce motor currents to 30%
M915 PX:Y:Z S-20 F0 R0 ; Configure motor stall detection on X, Y, Z axisM558 P10 F1000 T1000 H1000 R.5 ; Set probetype 10 (motor stall), dive height and dive speed
M574 Z1 S4 ; Configure low z endstop??? doesn't change anything???G0 X16 Y-8 Z55 ; Move to center
G30 S-1 ; Probe point; Remember to set motor currents back after probing
M913 X100 Y100 Z100 -
What board do you have?
The Duet 2 maestro for example uses TMC2204 which don't have StallGuard.
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I've got a Duet2 WIFI
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see
https://duet3d.dozuki.com/Wiki/Stall_detection_and_sensorless_homing
The stepper drivers only update the stall detection state every 1 or 4 full steps, depending on configuration. So the actual position of the stall is uncertain to either +/- half a full step or +/- 2 full steps. This means that when using stall detection to replace endstop switches, the position defined by the stall is much less accurate than with typical endstop switches.
this is not accurate enough for deltas.
here is what i use.
https://de.aliexpress.com/item/32968709878.html
which i put on once for calibration, and if your endstops are good enough it will last several prints before you need to recalibrate again. -
I know that it's not accurate enough, but I wanted to give it a try anyway.
But as mentioned above the stall detection doesn't work at all
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M558 configures the probe
https://duet3d.dozuki.com/Wiki/Gcode#Section_M558_Set_Z_probe_type
P10 is for stall detection
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That's what I'm using in my macro above, but it doesn't seem to work
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The stall needs a short sharp shock to detect the back emf reliably. The squishy cardboard box may have too much give to it.
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Ah, ok. I thought it's actually able to detect the restisting force. But besides of that it's also not working when I just use my print bed. The nozzle hits the bed, the motors stutter a couple of times, but no probe measurement. Just horrible noises eek
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Well you're also trying to stall 3 motors at the same time. There's a lot of reasons it's not used with deltas. Stalling the carriages at the top of travel against the frame is one thing, but trying to probe the bed with stall is unlikely to work right.
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I know, I know, that's why I mentioned I like impossible things in my initial post. It's still kinda weird that I don't get any motor stall response at all.
I just wanted to give it a try, because it doesn't seem like people actually tried it. Everything I found so far were some calulations which said it's not possible. Therefore I just wanted to give it a try and post some more indepth details on that.
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It could work....
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Well, not as long the motor stall detection doesn't trigger at all. But for now I'll just play with an accelerometer, how hard can it be? xD
