Changing to different thickness print bed sheet  

Re: Changing to different thickness print bed sheet

I think part of my problem is the new filament I'm trying is thinner than what I've been using. Running Matt's extrusion multiplier calibration, hope that will fix it.

https://mattshub.com/2017/04/19/extruder-calibration/

Re: Changing to different thickness print bed sheet

I think part of my problem is the new filament I'm trying is thinner than what I've been using. Running Matt's extrusion multiplier calibration, hope that will fix it.

https://mattshub.com/2017/04/19/extruder-calibration/

shouldn't be more than a few microns off for any filament, .02 is considered good. so yes that would affect it in a small way, but has more to do with your idler tension.

only thing you should need to change is Z.

Re: Changing to different thickness print bed sheet

Monte:

I have a Prusa PC sheet and the The KKIINNGG sheet and here is what works for me.

I get a good live z on the Prusa PC sheet using the 75x75mm square from the life Z thread in the assembly and troubleshooting subforum. Then, once that is good, i run from the Calibration menu, calibrate z to fix that live z adjustment in the eprom ( to prevent wandering live z issues). That locks my live z in. I then change sheets (and found that the The KKIINNGG sheet is about 100 microns thinner in Live Z than the Prusa PC sheet) and do a 75X75MM calibration square) and get that dialed in. I write both live Zs down on a sticky and stick it on my LCD screen as a reminder. Then I make sure to change the live Z after preheat, but before printing, in the settings, live adjust z submenu depending on the sheet I am using.

It seems kind of burdensome, but if you change nozzles or filaments, you have to redial the live z, so it is a necessary evil. If you find a better way, please post it because I would be interested in using it. Theoretically, you could enter an offset in the Gcode for each sheet, but that seems to me to limit the gcode to the specific sheet which I do not want to do.

with this system, there are pros and cons

pro:
live z is set to one sheet and adjusted to the other sheet until you change nozzles or other major adjustment
GCODEs can be created regardless of the sheet used.

con:
you have to adjust the live z in settings live z depending on the sheet you are using.
switching filament type requires an adjustment, just like if you had one sheet and went from PLA to PETG a minor live z adjustment is necessary.

here is a pic. you can see the Prusa Sheet is (0.577) and the KKIINNGG is (0.485) for live Z

Hope that helps.

Re: Changing to different thickness print bed sheet

I have tested many steel sheet beds and each is subtling different in live Zs.

Re: Changing to different thickness print bed sheet

If you are using different sheet al the time you dont need to alter the live Z at all between sheets. All you do is set up a printer profile for the differnt sheets.
I use the offset adjustment in the printer profiles to set up for each sheet. I have one that it almost 1.5mm thicker than the rest and is just compensated for in the offset. But be carefull as the first purge line seems to print at the same height all the time. So my thick coated sheet has the front portion removed where the purge line prints.
Very rarely do i have to alter the live Z between sheets. I even use the printer profile offset to compensate between filament materials to get the correct squish for bed adhesion.

RE: Changing to different thickness print bed sheet

This is exactly what I wanted to do, but I hit problems as follows:

I made a bed to use for nylon by glueing some Garulite to an old Prusa Steel bed so it is 2.3mm thicker than the one that is usually on the printer.  I put a positive 2.3mm Z offset in a new 'Physical printer' in Prusa slicer and thought that would solve the problems.

However when the print starts and the printer executes the standard home and bed levelling gcode, the extrider decends, hits the thicker bed and stops the print.

I checked the gcode and the 2.3mm offset is there, but too late to stop the extruder crashing into the bed and stopping the print.

So I edited the gcode and moved the offset to earlier, but it doesn't seem to make any difference - the extruder still crashes into the bed and aborts the print.

This all sounds like your comment about the purge line always being at the same height.

Do you or anyone else have any suggestions?  I've thought about changing the start gcode to either remove the G28 home instruction or change it to G28 X0 Y0, but I suspect this will just leave the Z position wherever it hapens to be, and then the 2.3mm Z offset will add 2.3mm to it and start printing from there.

Thanks for any suggestions.

Andy

RE:

Problem is that your garolite sheet is too thick. I'm using a garolite sheet of 0.5mm. glued with 468MP tape to a plain flex steel plate.  Therefore, I'm able to calibrate Z in the regular way, because it stays within the range of 0 to -2.0mm.   No need to create new printers or to modify the start gcode.

For instance,  the Z of my Prusa smooth sheet is -1.085 mm and the Z of my garolite sheet is -0.625mm.