Having just switched to the Duet WiFi, I started experimenting with the automatic mesh leveling. The RepRapFirmware uses the Z-sensor to build a bed height map automatically by probing the bed in a grid pattern. Ideally the sensor should be as close as possible to the nozzles. The bracket I've been using sits a few cm behind the nozzles. By reshaping the bracket I was able to move the sensor forward 10 mm and closer to being centered between the nozzle by 2 mm. This should improve compensation and it means the calibration grid (set by M557) can go back 10 mm farther. The odd shape of the new bracket makes it a little tricky to print. If you look at the example on the left, you'll see it includes a brim like disk that holds it at an odd angle during printing. This makes various overhangs printable. After it prints, peel the disc off and sand any rough edges off. I've attached a zip file with two versions of the bracket. One has recesses for M2.5 square nuts. The other is my preferred version. It has undersized holes that can be tapped for M2.5 screws and no nut is needed. I printed 0.2 mm layers with a 0.4 mm nozzle. You will want to bend the three pins for the sensor connector 30-45 degrees outward. This will make fitting the cable easier. Bend the pins one at a time to minimize stresses. The bracket sits close to the hot-ends so a high temperature material like colorFabb HT is recommended. UPDATE: I forgot to include what it looks like installed so you can see the realigned pins.
That's a nice mod. If you are interested in designing a mod to place the sensor even closer to the nozzle e.g. below the heatsink, I'll send you a new IR sensor with SMD optical components and a straight 3-pin connector.
Success! DC42 was as good as his word and sent me the new version of the IR sensor built with mostly surface mount components. This moves the point where the height is measured by about 3 mm. I did a redesign of my bracket to pull it even farther towards the front. It's pretty weird looking but it still prints for me in HT with no support material. The new bracket tucks the Z-Probe up close to the right hotend fan. The net effect is I can now run the mesh leveling within 15 mm of the front bed edge! A 15x10 grid on 20 mm centers now has the mesh leveling mapping just over 500 cm^2 of the 600 cm^2 build area. You can download the stl file below. This version has the PCB mounting holes sized for a M2.5 tap. There is no provision for a nut. It's not really needed and I was trying to save every mm I could to shift the sensor towards the front.
Right now socks and I are taking a break HT eventually burns a hard brown residue onto the sock that builds up and can't be removed without tearing the sock
Ephemeris, very nice work! Does the new sensor work well? Are you doing the auto bed level or the Manual/Mesh?
Sensor works like a champ on the PEI/Al bed. I'm using the Duet WiFi's automatic mesh leveling. When I think to do it, I launch a Duet macro that runs a 150 point (15x10) grid. Unless I've been doing maintenance, it looks very similar from day to day which means the sensor is pretty repeatable. I discuss the leveling in detail here: https://forum.e3d-online.com/index.php?threads/my-guide-to-duet-mesh-auto-leveling.2456/
