Auto_Bed_Leveling: Enhanced G29 command

[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