Bed level probing with Duet Ethernet and DC42 IR probe

3DTyro

I'm setting up a Duet Ethernet with the DC42 IR probe for Z probing on a Wanhao I3 Plus clone (Powerspec). The probe shows the expected 4 flashes on startup, but in the Duet web control display the value for the height level is always zero, instead of the expected values around 500 when the probe is near the bed.

I've set the correct M558 command G31 as follows in the config.G file:

M558 P1 X0 Y0 Z1 H5 F120 T6000 ; Set Z probe type to switch, the axes for which it is used and the dive height + speeds
G31 P500 X34 Y0 Z2 ; Set Z probe trigger value, offset and trigger height
M557 X25:175 Y25:175 S20 ; Define mesh grid

The problem is that when trying to probe the bed height using the Auto Bed Compensation button, the nozzle drives about .250" into the top of the print surface, so obviously it can't be probing the bed correctly. It does seem to want to move around to the various check points, each time crashing the bed.

So what am I doing wrong? Should I comment out the mesh grid command- I thought that might be the result of a bed probe… Or is there another problem?

dc42

When you lower the nozzle towards the bed, does the red LED on the sensor light up before the nozzle touches the bed?

3DTyro

No, it doesn't. What does that mean? And why doesn't the display show the values in the DWC?

dc42

It could mean that you have mounted your IR sensor too high. The bottom edge of the sensor PCB should be between 1.0 and 2.0mm higher than the nozzle. If you put a piece of paper below the sensor, does it light up?

3DTyro

Yep- that's it! The Z-probe display also shows numeric values with the paper test. Now to make a new mount…

Thanks!