First layer issues / bed level correction feature
A couple of questions about this.
I've been having issues on my just build MK3S achieving a good first layer across the whole bed. Line slightly thick on the right side of the printer (closest PSU) and thin on the left side. The printer comes up as being perpendicular through the initial calibration fine.
Anyway, I've maxed up the mesh settings (7x7, 5) which doesn't really seem to help. Reading the manual the Bed level correction facility it sounds like just the job, and by experimentation I have values that appear to give a nice uniform layer.
This raises a couple of questions:
1) Why does the manual specify "kit only" for this? Is it that factory Prusa units have this step already performed, or something else happens during assembly to ensure they don't need this?
2) I've seem posts saying this option gives more problems than it solves and is deprecated since moving to 7x7 mesh. Is that so?
3) The wording of the section in the manual is terrible and the direction of adjustment for + vs - on bed level correction is very unclear. First it says:
For example, if the first layer seems to be ever so slightly more squished on the right side, you can virtually raise the nozzle by +20 microns on the right side.
+20 is in bold, implying this is what you set it to to "raise the nozzle". At the end of the paragraph however it says:
A negative value will act as lowering the bed in the selected direction.
Now unless I'm being thick, raising the nozzle and lowering the bed are the same net effect!
RE: First layer issues / bed level correction feature
And if you get this feature to work, let us know. I've tried swinging the value +100 to -100 with no discernible change in layer 1 properties.
RE: First layer issues / bed level correction feature
And if you get this feature to work, let us know. I've tried swinging the value +100 to -100 with no discernible change in layer 1 properties.
It seemed to work fine once I worked out which direction the control functions in; my biggest frustration was the first time I tried I followed the second note in the manual and it had the opposite effect to desired. Positive numbers appear to increase the gap between the print head and bed surface, negative numbers decrease it (so the last sentence in the manual paragraph appears to be incorrect)
As I had one side high and one side low I did about +50 on one side and -50 on the other and that gave me uniform extrusion all the way around the print.
RE: First layer issues / bed level correction feature
Except that the PINDA is position insensitive. It senses height, so it is theoretically impossible for one side of the bed to be higher or lower after a PINDA based mesh correction. It also compensates for differences like debris lodged under the steel sheet, and changes in the heat bed and platter as the ambient temperature changes between prints.
Let's say the PINDA detects at 1.93 mm instead of 2.00 mm. It will record the true position and set this "height offset" at each and every point it measures. The recorded offset array is used to compensate for all of the sheet. Even large variations are included - 0.5 mm for example. Live-Z offset then adjusts for the actual trigger offset - and a user adds 0.07 to their Live-Z value.
The only variables would be the actual PEI thickness variation on the sheet being measured, and thermal response of the PINDA. Since the mesh level is serial, thermal variation would be averaged side to side, and advancing front to back.
If the PEI thickness varies on the sheet, it would be measurable.
So - my question is: is your steel sheet thickness the same side to side?
RE: First layer issues / bed level correction feature
I'll measure my build plate (powder coated) later. As it happens the finish isn't brilliant from the factory (both sides have lighter diagonal streaks in the powder coat finish) but I hadn't thought to measure it.
I also have a smooth PEI sheet - bought both with the printer - so I'll swap them and see how that behaves too.
I guess the only way I can see that the PINDA could be out across the length of the x-axis is if somehow the x-carriage were somehow rotating slightly as it traversed the axis such that the relationship between the PINDA the nozzle and the bed were changing. I guess the filament could pull on the x-carriage slightly as the carriage travels and cause it to twist slightly but sounds unlikely...
RE: First layer issues / bed level correction feature
I've proven to myself that in 3.7.1 bed correction doesn't work, at all. But as with all things, you may have a different experience. In the end, all that is important is that you get the mesh level that works for you, and it seems you have. So call it a success ... lol.
RE: First layer issues / bed level correction feature
I'm running the current release which is 3.7.2 I believe and that does seem to work as expected. The difference isn't particularly subtle as you adjust the setting
RE: First layer issues / bed level correction feature
I've proven to myself that in 3.7.1 bed correction doesn't work, at all. But as with all things, you may have a different experience. In the end, all that is important is that you get the mesh level that works for you, and it seems you have. So call it a success ... lol.
I have found that the "Bed Level Correct" values are not used when you are running the "1st Layer Calibration" It seams to only apply the values during the printing process. Try running a first layer calibration print from your SD card. Also if you are having to resort to "Bed Level Correct" to get a good first layer, you may want to set"Mesh Bed Level" settings to Mesh=7X7, Probe=5
RE: First layer issues / bed level correction feature
I've proven to myself that in 3.7.1 bed correction doesn't work, at all. But as with all things, you may have a different experience. In the end, all that is important is that you get the mesh level that works for you, and it seems you have. So call it a success ... lol.
I have found that the "Bed Level Correct" values are not used when you are running the "1st Layer Calibration" It seams to only apply the values during the printing process. Try running a first layer calibration print from your SD card. Also if you are having to resort to "Bed Level Correct" to get a good first layer, you may want to set"Mesh Bed Level" settings to Mesh=7X7, Probe=5
I was using 7x7 before it was a glimmer in Prusa's eyes. LOL