Go to System and use the "upload system files button" in DWC2.

To me, it looks like it is under extruding and the Z0 isn't close enough to the bed.

@tetele Sounds like the bed is warping when it heats up. The bed mounts needs to be able to allow the bed to expand.

@uca I dont't one. One way is when you home one, make sure the other isn't triggered. For example: in the homeall.g file: home x, move x away from the endstop so it's not triggered, home z. Just put a move away form the endstop for one, to use the other. You may have to connect them to both endstop connectors until the firmware can freely assign endstops.

@crchisholm DWC 2.0, it's under machine-specific. DWC 1.22.6, it's under settings->list items

@army61 One wire to the ground pin and the other to the signal pin. The 3.3v pin is not used.

Update:

The pi4 was showing the low voltage lightning on the screen. Now powering from a 5vdc Meanwell.

Fan 1 defaults to thermostatic. Did you turn that off?

https://duet3d.dozuki.com/Wiki/Connecting_and_configuring_fans

G29 S1
if result > 1
G29 S0
When I deleted the heightmap.csv:
G32
Error: G29: Failed to load height map from file heightmap.csv: Could not find file '/opt/dsf/sd/sys/heightmap.csv'.
35 points probed, min error -0.170, max error 0.168, mean 0.000, deviation 0.089
Height map saved to file heightmap.csv

After a system page refresh, it's there.

Then I changed it to:
G29 S1
if result > 1
G29
It works with no errors

@roaminginterests For 24v all you need is a 24v heater for the hotend & bed(if DC) and 24v fans. The motors will not need to be rated for 24v, since the drivers control via current. You will need to know the steps/mm, the acceleration and jerk values.

@campeancalin PID doesn't set a max temperature, the M143 does.

@rzi You don't have any fans defined in that config.g you posted.
That file also looks incomplete.

Goto https://configtool.reprapfirmware.org and set up your config.g

@tetele Going to more than 5mm won't help. What the bed heater is made of, isn't thick enough to prevent warping. Make sure you use black glass or black paper underneath clear glass, otherwise the IR won't see it.

@Rudy2A I use a Raspberry PI 0 W with a PI camera. The software used is from https://elinux.org/RPi-Cam-Web-Interface

I set its network name to picamera.
Webcam url set to http://picamera.local/html/cam_pic.php
When you click on the webcam image is set to http://picamera.local/html/

@tetele You might enlarge the hole in the bed mounts on the 2020, to allow the screws to pivot.

One way is enlarge the holes where mounting screws go through the bed. From looking at a photo of the heater portion, you don't have much space around the holes before it get to the heating trace.

On my corexy printer, I use 310mmX425mm 1/4" MIC6 aluminum as my bed base, with a heater and insulation attached to the bottom. 300mmX400mm PEI sheet attached to the surface. I also use the three point mounting for the bed.

@tetele Sounds like the bed is warping when it heats up. The bed mounts needs to be able to allow the bed to expand.

@dc42 It would do a double tap on the bed. It would do it when homing Z, and doing the G29.

Watching it do it, the moment it would hit the bed, it would fully retract, but it would imediately redeploy and trigger again.

Watching the 3.1, it would trigger and not rectract completely, the full retract was delayed,

@npm1 Check to see if the V_Fan Jumper Select is set to VIn.

https://duet3d.dozuki.com/Wiki/Gcode#Section_M911_Configure_auto_save_on_loss_of_power