Controlling PLA stick on a Mini

Hi,

I’m using a Mini, Cura and PLA.

I’ve noticed taht models with a small bed contact area sometimes come unstuck, those with a large contact area can be very difficult to remove.

How do I adjust the “stick” to the model?

I would’ve guessed that adjusting the bed temperature would be the ticket but reading through the forums I see a lot of talk
about adjusting the Z end stop to avoid first layer squish. Not sure how to make that adjustment on a Mini or in Cura.

TIA, Craig

First, are you printing at 60C and removing parts at 50C? I have not had any problems removing PLA parts from the bed using those temps.

Next, if it is actually sticking the parts too tightly to the bed, you can adjust the Z offset in your slicer software. I would start with 0.05 and experiment from there. Z offset just moves all the Z positions by the value entered. That will allow you to tighten or loosen the “squish” on the bed on the mini, since it doesn’t have a z endstop adjustment.

Also, make sure your nozzle is clean and that the nozzle is not deflecting the corner washers when it measures prior to the print. The nozzle should be just tapping the washers without any deflection of the washers and bed.

60/50 check, and it’s not a dirty nozzle issue. I’ve noticed the “squish” that manifests as a slight ridge on the first layer from day one. Thanks for the info I’m not crazy and there’s no mechanical adjustment on the Mini.

In Cura there seems to be no way to adjust the Z offset. In the Start/End-GCode there’s a G90 so we’re in absolute mode so no way to adjust that there. Not quite ready to jump to Slic3r just yet.

I’m making one of these and that’s about 90 hours of extruder time so I’m taking the opportunity to make fine adjustments to the Cura material profiles as I go.

Mostly Printed CNC / MultiTool
http://www.thingiverse.com/thing:724999

Lowering the bed temperature appears to be helping with the release for big bed contact parts. The “squish” thing I’ve seen mentioned doesn’t make a lot of sense to me but this does.

Out of box print quality help
https://forum.lulzbot.com/t/out-of-box-print-quality-help/2087/16

Thinking the firmware offset constant from the washers to the bed might be a little off on mine. M851 says the factory set it at -1.43 so I’m going to back that off a little and see what happens. Just out of curiosity, what’s your factory Z offset?

I don’t use Cura very much but I didn’t see anything for Z offset just now during my quick look.

A call to Lulz support might get some answers.

You could try placing a thin piece of tape under each of the corner washers to raise them a bit. That might get you running if nothing else seems to work.

The other thread said the guidance came from support. Tried it and got an arguably dimensionally perfect result by adding 0.1 (M851 Z-1.33, M500 for my Mini). That and lowering the bed temperature 10 to 15C has the PLA stick just about right. This is definitely seems to be going in a good direction.

Regarding the squash/squish, the extruded filament is basically being pressed more into the bed surface. Since the same amount of filament is extruded, the result is an oval extrusion… this wider which creates a better adhesion.