Stall detection setup

sinned6915

I am trying to work out stall detection for my printer in conjuction with my scheme for Z-Probe pickup (different thread). I want to enable it as a failsafe for the condition if the probe is not picked up and the machine overtravels.

I am not clear on 2 things- if microstepping values affect the stall detection and Hmin. I am on Duet2 Ethernet, RRF 3.1.1, 24V psu if it matters.

My Z axis is TR8x8 screws that are driven by a belt reduction system. Here is the bit from my config.sys file for motors and esteps.

M350 X16 Y16 Z32 E16 I1                        ; configure microstepping 16 for with interpolation
M92 X80.00 Y80.00 Z1600.00 E397                ; set steps per mm

I understand that the detection is 1 in 4 steps. Do I need to fudge the Z estep number to use ustep of 16 to make use of interpoaltion instead of direct as 32 to make better stall detection?

Hmin- I am getting 84mm/s with my motor at 1/2 the rated current. that seems pretty slow already.
https://en.smath.com/cloud/worksheet/uNvQ8YSD

Do I only enable stall detection for the duration when I am trying to pick up the probe? This speed seems quite slow.

Phaedrux

Why not just use stall detection as the z probe? M558 P10

Or am I missing something?

Use x16 with interpolation always. You're not gaining anything but noise by running at x32.

84mm/s seems slow on the Z axis?

Veti

@sinned6915 said in Stall detection setup:

M350 X16 Y16 Z32 E16 I1 ; configure microstepping 16 for with interpolation
M92 X80.00 Y80.00 Z1600.00 E397 ; set steps per mm

unless you are using 0.9 steppers for your z axis, your steps are incorrect.
or are do you have a 2:1 reduction?

and yes the Duet2 Ethernet can only do interpolation at x16

sinned6915

i thought stall detection was useful for conditions where the machine could get hung up, like the nozzle snagging a print.

i am trying to prevent overtravel on the Z axis past the point of the probe.

I am not sold on sensorless homing= the thought of purposefully crashing into something to find where it is seems crude to me over a swtich.

Phaedrux

@sinned6915 said in Stall detection setup:

i thought stall detection was useful for conditions where the machine could get hung up, like the nozzle snagging a print.

Yes. Though you're talking about stall detection on the Z axis. Which isn't used very often, though I think it should it work.

Stall detection on the Z axis is actually a pretty attractive way to home Z. The nozzle is used as the reference point, so no offset, and the stall causes it to snap to a full step, so should have quite good accuracy and repeatability. The downside is that the Z axis design needs to be suitable for stall detection. Preferably natural high steps per mm and rigid enough to cause a reliable stall. There's also the downside that sensitivity can depend on motor temperature.