Adjusting For Different Beds - Am I Missing Something
So the printer has been great, and love the removable bed sheet. I purchased several of the Buildtak Flexplate sheets, added a PEI sheet to the back of each to protect the heatbed, then I apply PEI, Buildtak, DOBSTFY, to the top and print away. Well not really, here is the problem. The MK3 is not really tolerant to different Z base heights.
On all my other non-Prusa printers, changing the bed material usually takes a simple re calibration with a business card, and I'm done in 10 minutes. Not on the MK3. Recalibrating involves running the ZXY calibration which brings the printhead to the top (Z), then attempts to calibrate X and Y. So first it does the base heatbed without the bedplate, and that takes 10 minutes, then you add the bedplate and find out if the P.I.N.D.A. sensor is too high or low. Raise or lower the P.I.N.D.A. and repeat over and over until its right. Then load PLA (it will only use PLA) and print out the calibration and adjust the Z-height.
In the end its not unusual to spend 2+ hours doing this. So, am I missing something? The P.I.N.D.A sensor does not appear to be something designed to adjust often, but I must play with it OVER and OVER to get it to work. After that I never touch it until I want to change bed material and then I have to start again. What a pain. So is this 2 hour adjustment procedure the "auto bed leveling" Prusa touts in its ads?
Re: Adjusting For Different Beds - Am I Missing Something
I have found the live Z to be more complicated than just adjust for the thickness of the material. Someone can correct me if I am wrong, but it is just not that simple.
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Chuck H
3D Printer Review Blog
Re: Adjusting For Different Beds - Am I Missing Something
Hi Allen,
you don't need to do the whole re-calibration,
changing live Z should be all that's needed for a simple print surface change!
it's always wise to back off live Z, on a new surface, before trying live Z calibration, just in case the previous live Z would result in a nozzle crash on the new build surface
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: Adjusting For Different Beds - Am I Missing Something
Yep, what the others have said. The end result is that you should end up with a live-z value for each print surface. No recalibration required when you change print surfaces. Just change the live-z to the appropriate value.
Re: Adjusting For Different Beds - Am I Missing Something
I get what everyone is saying. I guess the challenge is getting the PINDA low enough so the nozzle is high enough to clear the sheet. But the PINDA can't be lower than the nozzle. The trick is to put the PINDA just slightly higher than the nozzle and hope for the best.
I have some thin Phenolic (0.8mm) that I got for printing nylon, but I don't think I will ever be able to use it because the PINDA will hit it during calibration even if the PINDA is just below the nozzle, which is the lowest it will go.
So yes, the Z-height adjustment works for thin beds, but for thicker material, your out-of-luck. Ideally I'd like to use the Phenolic clamped to a bed with PEI or Buildtak, but there is no PINDA adjustment where that would work.
Re: Adjusting For Different Beds - Am I Missing Something
Well that's an entirely different issue to the one you started with.
Yes. If a bed material is too thick, so that the PINDA can't sense the steel sheet through it, then it won't work (barring the glass sheet workaround, where you pause, clamp the sheet in place, and dial in an offset, after the Z-homing).
So, phenolic (0.8mm thickness) clamped on PEI (~0.3mm thickness) = 1.1mm + a nozzle gap = very close to the 2mm range of the PINDA.
However, PEI on one side of the bed (0.3mm thickness) and Printbite+ on the other (0.8mm) is a very workable combination, and I simply run -0.40 mm live-Z-adjust for the Printbite, and -0.90 mm for the PEI (Or something like that. Can't remember exact numbers).