BLTouch Only Descends Halfway on G29/G32

Zerbob

I have turned the Z acceleration down quite a bit, from 250mm/s^2 to 100mm/s^2. I also changed homez.gcode to utilize the endstop. With the new homez.gcode I get very consistent zeroing.

To test the probing I do the following set of commands.

M558 P9 F200 T9000 H5 A3     ; set probe type to BLTouch, feed rate to 200mm/min, travel between points to 9000 mm/min, dive height 3mm, probe three times

G1 X0 Y0 F9000     ; go to x0 y0
G28 Z                     ; home the Z axis
G1 Z4.5 F200          ; move 
G30                         ; perform single point probe

This code should cause the Z axis to be correctly home, then probe the same spot three more times. The result is similar to before. The homing probe will be performed correctly (it is using a G1 S1 Z-1300 F200, followed by a G92). I then make sure that the probe is within the dive height to the bed based off the measurement just performed. The probing move is then started but the probe will stop a mm or two short of the bed then state "Error: Z probe was not triggered during probing move".

On the probing move it is visibly not descending far enough before stopping and reporting the error. No heaters or fans are running during any of these tests.

dc42

Please try adding some recovery time to your M558 command, for example R0.5. If that works, you can try reducing it.

dc42

PS - P25 in your G31 command is very low. What happens if you use P500?

Zerbob

I've run it at 250 and 500 before, but I will try a little higher and see if that helps. Won't be able to test till tomorrow. Thank you for still checking in.

dc42

Just to be clear, please try both a M558 R parameter and a higher G31 P parameter.

Zerbob

Tried both and got the same result. It seems that the printer is resetting its height before a dive, causing it to dive too short. If you obstruct the probe early with your finger, it works as intended. However left to itself, it will not lower enough for the probe to even reach the bed.

dc42

Could it be that the bed is tilted, and the dive height is set too low to reach some points? You can change dive height, it's the M558 H parameter. The default is 5mm.