Auto_Bed_Leveling: Z-Probe Repeatability code

[brucehvn]

Roxy, I've got a question about how the z position numbers are calculated in your M48 code compared to other commands. I've been battling a problem all day that started with a wire falling off my z-probe. After fixing that, I noticed that the microswitch was slightly tilted and when coming down to the bed, the lever would hit first, but before tripping, the opposite side of the switch would hit the glass and move the arm slightly. I adjusted that and since I haven't been able to get a good print. I've gone around and around adjusting the z probe offset value and storing it in EEPROM, but every time I try to start a print, it's just smashing the filament down on the glass making blobs and wide streaks.

Anyway, what I've noticed is that if my current offset is set to say -10.65, when I run the G29 command, the 4 points it probes list z values close to and around that offset. However, when I run the M48 code, the numbers it reports for each sample are around the 10.24 range. The test comes out very acceptable. I can't see that there's any great fluctuation or problems with the probe, but I'm curious why the numbers are different as that amount of difference looks to be in the ballpark of what might actually get it printing properly again. I'd guess it's about .4mm off.

Bruce

[MichaelBrock]

Anyway, what I've noticed is that if my current offset is set to say -10.65, when I run the G29 command, the 4 points it probes list z values close to and around that offset. However, when I run the M48 code, the numbers it reports for each sample are around the 10.24 range. The test comes out very acceptable. I can't see that there's any great fluctuation or problems with the probe, but I'm curious why the numbers are different as that amount of difference looks to be in the ballpark of what might actually get it printing properly again. I'd guess it's about .4mm off.

Bruce

Bruce,

Did you figure this out? I'm having the same issue. G29 results seem to vary quite a bit but M48 results are very consistent and differ from the G29 resutls. And, like you, the difference seems like it would explain my occassional air prints. It seems the two should produce similar measurements. If not, it would be nice to have an explanation as to why.