Using the bed leveling screws leveling

Jacotheron · 10 Mar 2018, 14:40

I have tried to read up on the bed leveling using the screws and the probe, which should give instructions to get the bed level, rather than just compensating for an uneven bed, but have a few questions:

We define the screw locations using M671, along with the screw pitch, should these positions be where the probe can measure? I am converting a Wanhao D5S Mini, and I am a little worried that my probe will not be able to reach some screws, since they are outside of the printable surface; can I use Y coordinates greater than the maximum, or smaller than 0, or how do I probe there?
Do I need the Zmax endstop? I found a reference to the Zmax as possibly being required, but it was not very clear.
Are there anything else that I need to configure? I have configured the IR probe (standard one as sold on the Duet3d website), how should the bed.g be modified (it currently have my 4 points, Home and 3 as close to the screws I can get it)?

I have not yet inserted the board into the printer, and connected everything (it is quite a mayor upgrade), I first want to make sure I have as much as possible correctly configured.

dc42 · 10 Mar 2018, 14:54

1. The screw locations do not to be at points that can be probed. On my SCARA printer, one of the screw positions is 300mm from the nearest point that can be probed.

2. You do not need a Z max endstop.

3. Bed.g should contain enough points so that the tilt in both directions can be measured, for example one point close to each corner, or alternatively (and possibly better) a point close to the mid point of each side. Many people use one point close to each screw, but that isn't the only choice.

4. If you are currently using bed.g to do bed compensation, you won't be able to do that so easily any more. But if you need bed compensation after levelling the bed, you can use G29 mesh bed compensation for that.

HTH David

kraegar · 10 Mar 2018, 15:24

I've played with both many points (up to 9, in 3 rows of 3) and one point by each leadscrew.

I got roughly equal results with both methods, so went back to a point by each leadscrew, since it's faster. I can do full bed prints this way (but also have a very flat bed to print on, which is of course important)

Jacotheron · 16 Mar 2018, 14:36

Hi, thank you for the answers, they are exactly what I needed to know.

I only found them now, since I did not subscribe to the thread. Now set my settings to auto subscribe when I start one.