mesh bed compensation not applying correct corrections
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@necrorat said in mesh bed compensation not applying correct corrections:
inconstant very small gaps between the extruded lines in a couple of patches on the bed
that is either a problem with under extrusion or backlash in your printer. not a problem with mesh bed leveling.
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@Veti 90% of the bed layer is perfect there are two patches where the gaps are observed so if it was under extrusion or backlash would it not be consistently like that all over the bed with mesh levelling working as it should?
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post a picture
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@necrorat said in mesh bed compensation not applying correct corrections:
The image seems to show a bowed gantry. What areas are not touching the bed?
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not the best pictures but best i can do at the moment.the main area is the region 3 threes what appears to be a island where the print head is too far from the bed
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Where are those locations in relation to the heightmap?
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I see you're using the BLTouch. You can attempt to get a bit more accuracy and repeatability out of it by modifying your M558 a bit.
M558 P9 H5 F60 T6000 A10 R0.75 S0.003 B1Slower probe speed, with repeated attempts if 2 consecutive probes don't match to within a tighter tolerance. Probing will take longer because of the slower dive height and it will do at least 2 probes per point. But you will be far less likely to get outliers.
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@Phaedrux so 1 is the rear right of the height map and 3 is the front centre on the height map. sweet thanks for the tip ill change that out and give it a try probably wont be till tomorrow till ill get to try it now though.
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can you measure the z trigger heigh at different positions?
it is possible that you have different trigger heights based on position.
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@Veti so i measured the z trigger height and it didn't vary by more than 0.005mm at each of the 9 points i measured at, it did vary from point to point but thats kinda the point of bed levelling isn't it ?
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@necrorat said in mesh bed compensation not applying correct corrections:
so i measured the z trigger height and it didn't vary by more than 0.005mm at each of the 9 points i measured at, it did vary from point to point but thats kinda the point of bed levelling isn't it ?
no the z trigger height has to be constant across the entire bed otherwise you have the effects that you are seeing.
to clarify i am not refereing the the result of a G30 but the valude of of Z for G31 when calibrating it. -
@Veti just ran though a 3x3 grid to check and i am consistently getting 2.31 for the trigger height
01/02/2020, 15:16:27 M98 P"0:/macros/probe test"
Current reading 0, threshold 25, trigger height 2.31, offsets X-29.5 Y11.4 -
@necrorat said in mesh bed compensation not applying correct corrections:
01/02/2020, 15:16:27 M98 P"0:/macros/probe test"
does that macro do this?
https://duet3d.dozuki.com/Wiki/Test_and_calibrate_the_Z_probe#Section_Calibrate_the_Z_probe_trigger_height -
@Veti ive wrote it as this to probe 3 times per spot:
G1 Z10
G30 S-1
G1 Z10
G30 S-1
G1 Z10
G30 S-1 -
so have just run it again and i am getting quite a large variance now in the region of 0.11mm is this a mechanical issue? the machine is set up on linear rails and i have ensured that they are as square and parallel as possible
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@necrorat said in mesh bed compensation not applying correct corrections:
G1 Z10
G30 S-1
G1 Z10
G30 S-1
G1 Z10
G30 S-1that determines repeatability, but does not determine z probe trigger height as you do not determine z=0 before probing as described in the above linked document
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@Veti so do i have to go though the full calibration procedure for each point that i probe on the bed?
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@necrorat
do one at the point where the lines where ok and one where the lines where not ok -
@Veti so just did a test over 5 point and theses are the results :
2.064
2.068
2.066
2.059
2.046 -
thats a lot different than your original trigger height of 2.31
