Auto_Bed_Leveling: Enhanced G29 command

[RobH2]

Excellent Bruce. Doing it now. Will report back. Kudos...

[RobH2]

Nope, not working for me. After I do all the steps, adjust, flash, EEPROM commands and then go to print, my hotend is about 1.5 mm off of the bed in both Cura and Simplify3d. Slic3r in Pronterface is on the bed and preventing extrusion. Hmmmm... I'm at a loss now. I was hoping that Slic3r in Pronterface would be perfect. That's the host I used after I flashed the RAMPS to issue M502 and M500. I expected that it at least would be correct. If I now to into Slic3r in Pronterface, without a print running and do a G28 and then a G1 Z0, it's perfect. But, go to print and it's on the bed with no gap. I don't have an offset for Z in Slic3r. My setting in Slic3r for Z offset is 0mm.

Edit:

Here's a test. See anything odd?

SENDING:G29 n3 T V4
Roxy's Enhanced G29 Auto_Bed_Leveling Code V1.01:
Bed x: 25.00 y: 30.00 z: 7.54
Bed x: 92.00 y: 30.00 z: 6.91
Bed x: 159.00 y: 30.00 z: 6.22
Bed x: 25.00 y: 95.00 z: 7.54
Bed x: 92.00 y: 95.00 z: 6.99
Bed x: 159.00 y: 95.00 z: 6.30
Bed x: 25.00 y: 160.00 z: 7.62
Bed x: 92.00 y: 160.00 z: 7.00
Bed x: 159.00 y: 160.00 z: 6.33
Eqn coefficients: a: -0.01 b: 0.00 d: 7.75
Mean of sampled points: 6.937500

Bed Height Topography:
--0.71750 --0.02950 +0.59850
--0.64125 +0.05500 +0.59825
--0.60875 +0.06675 +0.67850

planeNormal x: 0.01 y: -0.00 z: 1.00

Bed Level Correction Matrix:
0.999954 0.000000 -0.009559
0.000000 1.000000 0.000731
0.009559 -0.000731 0.999954
echo:endstops hit: X:-8.99 Z:6.33

Edit #2: (I manually releveled my bed with the corner bolts/springs and ran the grid again)

SENDING:G29 n3 T V4
Roxy's Enhanced G29 Auto_Bed_Leveling Code V1.01:
Bed x: 25.00 y: 30.00 z: 7.10
Bed x: 92.00 y: 30.00 z: 7.12
Bed x: 159.00 y: 30.00 z: 7.07
Bed x: 25.00 y: 95.00 z: 7.05
Bed x: 92.00 y: 95.00 z: 7.16
Bed x: 159.00 y: 95.00 z: 7.29
Bed x: 25.00 y: 160.00 z: 7.17
Bed x: 92.00 y: 160.00 z: 7.19
Bed x: 159.00 y: 160.00 z: 7.30
Eqn coefficients: a: 0.00 b: 0.00 d: 6.99
Mean of sampled points: 7.159583

Bed Height Topography:
--0.08908 --0.04158 --0.05733
+0.12717 --0.00158 --0.11333
+0.13867 +0.03117 +0.00592

planeNormal x: -0.00 y: -0.00 z: 1.00

Bed Level Correction Matrix:
1.000000 0.000000 0.000850
0.000000 1.000000 0.000933
-0.000850 -0.000933 0.999999
echo:endstops hit: X:-8.96 Z:7.30

[brucehvn]

Ok, so in slic3r, what do you have your first layer height set to? Whatever that is, then look at the gcode generated and see what the first printing G1 command is that sets the Z height. It should be the same as your first layer height. In slic3r there is the regular layer height setting but a separate one for the first layer.

Bruce

[RobH2]

I appreciate your time. I'm not a noob. I just can't seem to get things settled in.

Here's a screen shot:
1stLayer.jpg

The Slic3r default recommended is 0.35. Maybe I'm misunderstanding this setting for 'First layer height:' and need to set it to be 0.20 also. Is that what you are trying to get across to me? Now that I think of it, if the 'First layer height:' is set to 0.35mm, then the hot end needs to be 0.35mm away from the bed to do that. Hmmm, this is probably it now that I wrap my head around it.

Off to do a new test. Thanks for checking in and getting me to do better analysis of parameters.

[brucehvn]

I appreciate your time. I'm not a noob. I just can't seem to get things settled in.

Here's a screen shot:
1stLayer.jpg

The Slic3r default recommended is 0.35. Maybe I'm misunderstanding this setting for 'First layer height:' and need to set it to be 0.20 also. Is that what you are trying to get across to me? Now that I think of it, if the 'First layer height:' is set to 0.35mm, then the hot end needs to be 0.35mm away from the bed to do that. Hmmm, this is probably it now that I wrap my head around it.

Off to do a new test. Thanks for checking in and getting me to do better analysis of parameters.

.35 is not a bad first layer height. Can you paste about the first 25 lines of the generated gcode here, so we can see what Slic3r is outputting? And yes, if your first layer height is set to .35, then the first printing move should place the nozzle .35 off the bed.

Bruce

[RobH2]

Zeroing in now. So if .35 is not a bad first layer height why is everyone struggling so hard to get that perfect .2mm gap? I guess in reality, as long as the filament is getting pushed into the bed, you'll have good adhesion. And if you have a .5mm nozzle, the .35 is still being pushed in 30% of that diameter. So it you are at least pushing it in and not having it "fall" onto the bed, then the most important thing is "level" and, that's what this whole autoleveling thing is all about. Getting that first layer as consistent as possible. Whether it's .2mm or .35mm, it's about level. Correct?

I'm convinced that the 'First layer height:' setting was my culprit. I kept having to adjust the head down manually and about .15 was what I was finding it off. Now I know. I'll go check my other slicers for similar 'First layer height' parameters. I bet I'll be surprised and will solve this.

[brucehvn]

Zeroing in now. So if .35 is not a bad first layer height why is everyone struggling so hard to get that perfect .2mm gap? I guess in reality, as long as the filament is getting pushed into the bed, you'll have good adhesion. And if you have a .5mm nozzle, the .35 is still being pushed in 30% of that diameter. So it you are at least pushing it in and not having it "fall" onto the bed, then the most important thing is "level" and, that's what this whole autoleveling thing is all about. Getting that first layer as consistent as possible. Whether it's .2mm or .35mm, it's about level. Correct?

I'm convinced that the 'First layer height:' setting was my culprit. I kept having to adjust the head down manually and about .15 was what I was finding it off. Now I know. I'll go check my other slicers for similar 'First layer height' parameters. I bet I'll be surprised and will solve this.

In reality Z=0 should mean the nozzle is touching the bed. However, we usually calibrate the bed with the nozzle cold, so we allow for heat expansion by leaving just a paper width gap (or about .1mm). So theoretically, when the nozzle is at temperature, Z=0 will have no gap. During printing, the nozzle will always be the height corresponding to the layer height. So in your case, the first layer will put z=0.35, the second layer will have z=0.55, etc. The adhesion comes from the volume of filament being extruded. In Slic3r, the default is to use a 200% extrusion width on the first layer. So while your nozzle is still 0.35 above the bed, the volume of filament is causing it to get smooshed onto the bed and hopefully causing good adhesion. Cura just recently in the latest version allows you to set the extrusion width for the first layer. It does have the first layer height setting and I think it limits it to less than Slic3r's default. Triffid Hunter's calibration guide says that you should really never print at a layer height > 80% of your nozzle width and I usually try to respect that when setting the first layer height. I have a .4mm nozzle, so I don't set the first layer height > .32. I think Cura won't allow me to set anything above .30.

Bruce

[RobH2]

Understood. I'm getting predictable performance now. It was all about that 'First layer height' that I was misinterpreting. I have my paper gap (just measured that paper and it's 0.11mm) so I''ll now respect that 'First layer height' properly. Thanks for all of your guidance. We all know a lot of stuff but none of us knows everything. That's what makes forums so powerful. The expertise that is shared in collaboration is just priceless. Sometimes we get so wrapped up we can't see the forest for the trees.

Thanks again. I'm really pleased with the consistency in gaps that I'm getting now.

[Roxy]

Sorry for needing the hand holding.

When I place the case 499 code in Marlin_main.cpp I get the following compile error:

I apologize... I was intending to make that change a separate 'Enhancement' and did not get it done yet. I edited in yet-another small change to post #75. Marlin_main.cpp #include's the ConfigurationStore.h file and that is where the invalidate EEPROM command is declared (so Marlin_main.cpp can call it) It is just one extra line in the ConfigurationStore.h file.

Rob, do you know about the M851 command? It has to be turned on in Configuration.h but it lets you very quickly set the Z-Probe offset. It is kind of the opposite of the EEPROM_INVALIDATE stuff. But with that you could figure out the magic number each slicer needs and just have a table where you feed the printer the right number for the slicer you are using prior to starting the print. <---<<< Probably this can be ignored! I see your first layer height numbers were causing some issues.

[RobH2]

I apologize... I was intending to make that change a separate 'Enhancement' and did not get it done yet. I edited in yet-another small change to post #75. Marlin_main.cpp #include's the ConfigurationStore.h file and that is where the invalidate EEPROM command is declared (so Marlin_main.cpp can call it) It is just one extra line in the ConfigurationStore.h file.

Rob, do you know about the M851 command? It has to be turned on in Configuration.h but it lets you very quickly set the Z-Probe offset. It is kind of the opposite of the EEPROM_INVALIDATE stuff. But with that you could figure out the magic number each slicer needs and just have a table where you feed the printer the right number for the slicer you are using prior to starting the print. <---<<< Probably this can be ignored! I see your first layer height numbers were causing some issues.

No problem Roxy, just plugging along. No, I don't know about M851 but will read up on it. Might still be good to know about.