Polynomial Temp Compensation for Probes?

[Kolbi]

Looking at the data for a bit, I believe the curve actually represents the thermal effects on the entire machine and the disparities (saw tooth pattern up/down) represent the probe's ability.

I zip-tied a bltouch3.1 to the extruder and ran the same test, the only problem is that there was no probe temp to base the curve off so I based it off bed temp.

[Kolbi]

@evan38109 I tackled the temp comp issue by changing to a BLTouch - had to modify the BMGm in CAD but it was worth it, very clean and accurate install. I believe you also have a BMGm, so this might interest you:

Cheers,
Kolbi

[evan38109]

Hey @Kolbi,

Sorry, I have email notifications off and missed your latest posts until I came to the forums to check something else!

That BLTouch mount is pretty impressive. How did you print it? Also: are the files available on Thingiverse or elsewhere? I'm pretty happy with my PINDA for now, but I do tend to get itchy for new experiments...

I'm racking my brain for why your measurements wound up so much different than mine. I've found my PINDA to be pretty darn stable. I've never needed more than +-0.10 babystepping for a nice first layer, regardless of the temperature at which I zero the machine. I'll keep turning it over in my brain, but...I've got nothing.

[Kolbi]

@evan38109 No worries at all on posts. The modified BMGm housing with BLTouch is working extremely well, I have a couple tweaks to make to the design files and then I'll post them. Just like the ones purchased through bondtech, mine were printed using MJF / Nylon.
On the Pinda, I never had major issues because I always did a probe warming routine to keep all measurements on an even temp offset. I had random problems with offset because of it - more noticeable with certain build plates then others. What was enlightening to me was the probe measurement disparities between runs - didn't think it would be that bad but the saw-tooth patterns above depict it - those metrics were derived over at least 5 runs.

For the BLTouch - it's totally great. No more offsets for different build plates, no temp comp, and reliable repeatability.

Cheers,
Kolbi

[Phaedrux]

@Kolbi said in Polynomial Temp Compensation for Probes?:

mine were printed using MJF / Nylon.

That's quite the hardware to have access to, or was it printed through a service? It looks quite nice.

[Kolbi]

@Phaedrux Hehe, not mine - it was sent off for mfg. I have to modify it slightly, tighten the pocket where the mosquito sits with a set-screw to make for a no-compromising tightness. Also thinking about adding part cooling ducts into the housing sections with just a replaceable air nozzle/deflector.

[dc42]

@Kolbi, the forthcoming 3.2beta firmware supports 2nd order temperature compensation for trigger height.

[Kolbi]

@dc42 Nice! How will the temperature offset/calibration process work?

[dc42]

You will have to work out the calibration manually as you have done already. Once you have worked out the first and second order temperature coefficients, you can enter them in the M558 C parameter, e.g.

M558 ... C0.01:0.005

[Kolbi]

@dc42 Thanks! Was just reading this as you replied:
Z probe trigger height second order temperature compensation is now supported. To use it, specify a 2-element array as the temperature coefficient, e.g. "M558 ... C0.01:0.0005"