Polynomial Temp Compensation for Probes?

evan38109

Hmm...not sure what's going on there, but that doesn't look right at all. It definitely shouldn't be going down as temperatures get higher, and the magnitude also looks off, too. I don't know, but I suspect the probing method is not very accurate:

while sensors.endstops[2].triggered = false
    G1 Z-0.00625 F300

I don't understand the intricacies of RRF, but it feels like there's plenty of room for timing oddities there with the command queue.

I much prefer G30 S-1 ... :

G1 Z3                        ; move to first probing height
G30 P0 X100 Y102 Z-99999 S-1 ; probe #1
...

It's cleaner, simpler, more accurate, and it also follows your M558 parameters. I love how it will take samples until it reaches the requested tolerance; it means that each of my "samples" is actually a sample group. For instance, when probing like this, I like to set the tolerance tight, with lots of available iterations and a very slow feed rate:

M558 ... H1.0 F180 T99999 A20 S0.001

For data , I just made a quick Google Doc with columns aligned to make data entry with the keypad easy:

I suppose it would be possible to script that, but...ehh, that's too close to the day job for a hobby.

Kolbi

@evan38109 Yeah, I'm not sure on the scripts accuracy either and I had/have a hard time believing the results too. Or maybe I have a poopy pinda?
I do find it interesting that the detection height goes back down after 43c - even if the method is deemed not accurate, it still shouldn't be seeing a drop in detection height. I also noticed that once the pinda is triggered, you have to move it up a little to get back to an untriggered state.
Eh, it's a rainy Saturday morning here, will likely toy around with it some more.

Kolbi

Ok, made some macro changes and I think I had more accurate results.
Take a look:
Screen Shot 2020-07-18 at 10.28.27 AM.png

Macro:


	G32

	G1 X100 Y100 F2000

	M558 P5 C"^zprobe.in" H1.0 F180 T99999 A20 S0.001              ; Set probing to slow and precise
	M140 S100
	M104 S240

while sensors.analog[2].lastReading < 50


	G30 Z-99999 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S0
	G1 Z2
	M400

	G30 Z-99999 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S1
	G1 Z2
	M400
	
	G30 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S2
	G1 Z2
	M400
	
	G30 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S3
	G1 Z2
	M400
	
	
	G30 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S4
	G1 Z2
	M400
	
	
	G90 ; set true
	G1 Z2 F2000
	M400
	G1 Z{(state.restorePoints[0].coords[2] + state.restorePoints[1].coords[2] + state.restorePoints[2].coords[2] + state.restorePoints[3].coords[2] + state.restorePoints[4].coords[2]) / 5} F100	
	G60 S5

	G90 ; set true
	G1 Z4 F2000
	M400


	echo "Pinda at " ^ sensors.analog[2].lastReading ^ " average trigger at " ^ state.restorePoints[5].coords[2] ^ " millimeters."
	echo "Trigs: "^state.restorePoints[0].coords[2]^", "^state.restorePoints[1].coords[2]^", "^state.restorePoints[2].coords[2]^", "^state.restorePoints[3].coords[2]^", "^state.restorePoints[4].coords[2]

	M28 {"0:/macros/Probe Comp/"^ sensors.analog[2].lastReading ^","^state.restorePoints[5].coords[2]}  
	M29

Kolbi

Granted, I am not sure about the accuracy of the macro, but I did make some additions to it where once it finishes probing on heat up, then it probes on the cool down too. I've run it several times to collect a good average, lots of points. Interesting data. Making me think that maybe I should try raising the pinda temp slower, to stabilize it at every few degrees?

@evan38109 I am curious, what variant of pinda-v2 you and I actually have. I read somewhere there are three PindaV2 variants out in the wild. I am fairly certain I have the latest revision with black wire - it's only about 2 months old as I got it for my Zaribo build. Also would be interested if you ran the macro on your machine to see if it comes close to the data you have already gathered, but if not - I don't blame you

Screen Shot 2020-07-18 at 6.17.33 PM.png
Screen Shot 2020-07-18 at 6.19.28 PM.png


	G32

	G1 X100 Y100 F2000

	M558 P5 C"^zprobe.in" H1.0 F180 T99999 A20 S0.001              ; Set probing to slow and precise
	M140 S100
	M104 S240

while sensors.analog[2].lastReading < 45


	G30 Z-99999 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S0
	G1 Z2
	M400

	G30 Z-99999 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S1
	G1 Z2
	M400
	
	G30 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S2
	G1 Z2
	M400
	
	G30 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S3
	G1 Z2
	M400
	
	
	G30 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S4
	G1 Z2
	M400
	
	
	G90 ; set true
	G1 Z2 F2000
	M400
	G1 Z{(state.restorePoints[0].coords[2] + state.restorePoints[1].coords[2] + state.restorePoints[2].coords[2] + state.restorePoints[3].coords[2] + state.restorePoints[4].coords[2]) / 5} F100	
	G60 S5

	G90 ; set true
	G1 Z4 F2000
	M400


	echo "Pinda at " ^ sensors.analog[2].lastReading ^ " average trigger at " ^ state.restorePoints[5].coords[2] ^ " millimeters."
	echo "Trigs: "^state.restorePoints[0].coords[2]^", "^state.restorePoints[1].coords[2]^", "^state.restorePoints[2].coords[2]^", "^state.restorePoints[3].coords[2]^", "^state.restorePoints[4].coords[2]

	M28 {"0:/macros/probe-comp-going-up/"^ sensors.analog[2].lastReading ^","^state.restorePoints[5].coords[2]}  
	M29	


M140 S0
M104 S0
G4 S60

while sensors.analog[2].lastReading >23
G4 S60

	G30 Z-99999 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S0
	G1 Z2
	M400

	G30 Z-99999 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S1
	G1 Z2
	M400
	
	G30 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S2
	G1 Z2
	M400
	
	G30 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S3
	G1 Z2
	M400
	
	
	G30 S-1
	echo "" ^ sensors.analog[2].lastReading ^ "," ^ move.axes[2].userPosition
	G60 S4
	G1 Z2
	M400
	
	
	G90 ; set true
	G1 Z2 F2000
	M400
	G1 Z{(state.restorePoints[0].coords[2] + state.restorePoints[1].coords[2] + state.restorePoints[2].coords[2] + state.restorePoints[3].coords[2] + state.restorePoints[4].coords[2]) / 5} F100	
	G60 S5

	G90 ; set true
	G1 Z4 F2000
	M400


	echo "Pinda at " ^ sensors.analog[2].lastReading ^ " average trigger at " ^ state.restorePoints[5].coords[2] ^ " millimeters."
	echo "Trigs: "^state.restorePoints[0].coords[2]^", "^state.restorePoints[1].coords[2]^", "^state.restorePoints[2].coords[2]^", "^state.restorePoints[3].coords[2]^", "^state.restorePoints[4].coords[2]

	M28 {"0:/macros/probe-comp-going-down/"^ sensors.analog[2].lastReading ^","^state.restorePoints[5].coords[2]}  
	M29	

M558 P5 C"^zprobe.in" H0.7 F400 T8000 A20 S0.003
M140 S0
M104 S0
G4 S60

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.
Screen Shot 2020-07-20 at 3.19.42 PM.png

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:
Screen Shot 2020-08-01 at 10.40.16 AM.jpg

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"