Bed Leveling?

Just curious if anyone was able to get bed leveling working.

I’m pretty close… I have a probe mounted to the carriage and UBL enabled in the latest marlin firmware… but it wants to probe the entire area of the table… I just want to probe the stock, not the clamps and the parking area, etc. It has some kind of sanity check so if it starts probing below the stock it just gives up and tries the same spot over and over. The G92 command doesn’t seem to help it goes back to the original Y=0. Starting to think it’s just not going to work.





Interesting, I think you might try G29 specifying left, right, front, and back limits of your workpiece, like

G29 L50 R150 F50 B150

It sounds like the probe coordinates are relative to internal absolute machine coordinates and not the work offset specified by G92, so you will have to know your workpiece location relative to what the machine thinks its home position is. I suppose you could use M114 to find the location of your workpiece and then do the math to set “L”, “R”, “F”, and “B” coordinates from that.

I’m mostly guessing based on this:


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Thanks! I missed that… it’s not in UBL but its in ABL so maybe I will enable that in firmware and give it a shot.
It’s a shame to miss out on some of the newer features but maybe it’ll work.


It worked ! Here’s a map of my table with a 4x8 foot sheet of 1/4" hardboard clamped to it.

It’s pretty interesting… even though there is a 0.5mm sag in the middle of my table, after the 1/2" foam spoil board and hardboard are on it, it’s a couple mm higher in the middle from the clamps around the outside.

I guess the take away is don’t sweat a few mm here and there on your table. Maybe I can talk the guys at marlin into adding this feature into the UBL levelling. It would be handy to be able to store a map for each thickness of stock you use.


What visulizer is that?

Why do you like UBL? I still use bilinear on my 3D printers. The UBL seemed much too complicated.

I’ve found that with squishy spoil boards, clamps on the outer edge of materials will bow the center up. That’s why I swapped out the half inch insulation panel with a half inch mdf panel. It will still bow, but not as much. Oddly enough, wood compresses. ¯_(ツ)_/¯

I took the output of the bed leveller and imported it into excel as a space delimited file then copy and pasted into this website:

I don’t actually like UBL… I tried it on my 3d printer running marlin 1.x and it was horribly unpredictable I think it was buggy. After upgrading my carriage to some aluminum plastic sandwich material and the bed with a silicone 24v heater and buildtak magnetic plate I found it all stayed pretty flat and I didn’t need bed leveling anymore so I turned it off entirely and just use a bltouch clone to probe the Z height.

I wanted UBL because hopefully the bugs are fixed under 2.x. You can have it do multiple bed probes and store them in different eeprom ‘slots’. So slot 1 could be hardboard, slot 2 could be 1/2" MDF, etc. with ABL you can only store the results of one probe in EEPROM which isn’t the greatest for my uses.

After seeing this I was wondering if I should swap mine out… hopefully the bed leveling works out so I can at least cut tabs in big cutouts of thin stock… I am not sure if swapping out the foam spoil board will get me that level of accuracy. Hmm… maybe if I just make a thin 1/2" mdf strip around the outside the same height as the spoil foam for the clamps to push on?


That might work.

Just to test I took off the clamps and it’s still higher in the middle though not quite as bad. I think either the hardboard acquired a curve or maybe the foam being squeezed on the guides on the table is getting pushed up in the middle. I can see the bulge visually and if I push on it it flattens out. If I had a hard spoil board I could probably fix it with a strip of double sided tape.


Managed to get multiple probes working with ABL by writing some code to generate the GCODE to write the mesh into marlin… I generate the gcode for each stock I probe and assign it to a button in cnc.js

The probe mounts and spreadsheet visualizer/gcode generator are here:


Cool idea, I even have some of those pressure plates already.