Inconsistent Z calibration - Heat issues?
I'm having an issue where I have to adjust the Live Z Adjust as much as 300um between prints. I've done the XYZ calibration, and printed the V2 calibration print (which only gets "fairly close"). My actual testing was with the Prusa Logo that I re-sliced (using Slic3r) for ABS filament.
When I print the logo I use the Live Z Adjust to get a nice first layer, then stop the print after the first layer (Let's say it was at -500um). I then print the same print again, same ABS, same gcode file, but this time I may have to adjust the Live Z Adjust to -800um to get the same quality first layer. It varies between -500 and -800 between prints. Is that normal? I don't know how to even begin troubleshooting this issue.
Re: Inconsistent Z calibration - Heat issues?
Try mobing the exytuder to day 100mm or more before rach print and see if it settled down
Therr appears to be an issue whenn the ponds probe is close to the heatbed during heating.
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
Re: Inconsistent Z calibration - Heat issues?
It could be your bed is not properly tighten or the pinda probe is loose and moving.
Re: Inconsistent Z calibration - Heat issues?
I have observed this for a while and been thinking about solutions. Certainly check everything is correctly tightened just to be safe. That said the pinda definitely has a thermal coefficient. It detects further away from the heat bed the warmer it is so you have to move lower as the temp rises. Parameters that will impact this are the temperature of the room and whether you have been using the printer immediately before. There has been a lot of opinion on this and i will be going counter to much of it but by my experience has been that it is better to warm the probe. I sit the head in the middle of the bed and pre-heat before kicking off the print. Many people say you should start cold but this does not work if you are going to kick off the next print immediately after the last one. The print head and bed will always be warm then. This may in fact be what you are observing. Starting cold and then starting again when warm.
You should also consider the material as this will affect the z-adjust to use (different print/bed temps). For example i set to -760 for pla, -800 for petg and -840 for abs.
To make the fully correct fix you would have to attach a thermocouple to the pinda and chart the coefficient then pick your z adjust depending on the current temp. I'm thinking about this but its a bit of work.
Last point. If you do choose to calibrate warm then be careful on first print. If you forget to warm up and it happens to be a cooler day you could get a bed crash. I have a nice dent at point zero where i did this and the hot nozzle crashed the bed. This is probably why people say calibrate cold.
Re: Inconsistent Z calibration - Heat issues?
Messages always look different when you write them on a smart phone...
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
Re: Inconsistent Z calibration - Heat issues?
I find it beneficial to make sure the extruder is above 100mm when you start a new print. Which ensures the pinda doesnt get affected by bed heat.
Regards joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
Re: Inconsistent Z calibration - Heat issues?
You all are on to something here. I added a couple extra lines of gcode to Slic3r in the "Start G-Code" section to have the printer autohome, then raise to 150mm before heating up. This has had a positive effect on the issue, but hasn't solved it completely.
My Start G-Code section now looks like this:
M115 U3.0.10 ; tell printer latest fw version
M83 ; extruder relative mode
G28 W ; home all without mesh bed level
G1 X0 Y200 Z150 F5000 ; raise extruder while heating
M104 S[first_layer_temperature] ; set extruder temp
M140 S[first_layer_bed_temperature] ; set bed temp
M190 S[first_layer_bed_temperature] ; wait for bed temp
M109 S[first_layer_temperature] ; wait for extruder temp
G28 W ; home all without mesh bed level
Re: Inconsistent Z calibration - Heat issues?
james.r6: where is the "G80 ; mesh bed leveling" in your g-code?
This is the Start G-code from slic3r prusa edition v1.33.8 (bundled with the v1.7.6 driver release):M115 U3.0.10 ; tell printer latest fw version
M83 ; extruder relative mode
M104 S[first_layer_temperature] ; set extruder temp
M140 S[first_layer_bed_temperature] ; set bed temp
M190 S[first_layer_bed_temperature] ; wait for bed temp
M109 S[first_layer_temperature] ; wait for extruder temp
G28 W ; home all without mesh bed level
G80 ; mesh bed leveling
G1 Y-3.0 F1000.0 ; go outside pritn area
G1 X60.0 E9.0 F1000.0 ; intro line
G1 X100.0 E12.5 F1000.0 ; intro line
With all the discussion about heat affecting the sensitivity of the pinda probe, wouldn't it make more sense to have the G28 and G80 codes before the codes for setting temps and preheating?
Is it really necessary to do the bed leveling at the start of every print? Couldn't it just be done occasionally when everything is at room temperature?
-Kevin
Re: Inconsistent Z calibration - Heat issues?
Bump: I'm wondering if the PINDA detection is further out when warmed, is it not preferable to preform the mesh bed leveling BEFORE issuing the pre-heat gcode? Once it has the measurements the temp of the probe shouldn't' matter correct?
I've noticed this issue since trying ABS with a heated enclosure, my live Z has been all over the place and until I read about the PINDA prob detection range changing with temperature I was completely lost as to why that may be.
Does anyone know How sensitive we're talking here? If we wait enough time for the heat bed to cool to room temp, is that enough between prints?
Re: Inconsistent Z calibration - Heat issues?
I'm guessing the difference in sensitivity of the PINDA is related to continuity. I haven't gotten my kit together yet but I do know that the higher the temp the less the continuity. I also have noticed in the posts the importance of keeping an even and constant temp on the PINDA. It seems, and I may have it bass ackwards or entirely wrong, that a "cold" PINDA tends to allow for a greater gap between it and the bed and a "hot" one wants to ram itself into the bed.
Hope that helps,
Neal