Printing Smooth Bottom Surface (especially with adhesives)
Generally I get a smooth bottom surface on a print and, if needed, could print upside down and use the bottom on the print bed as the top. Sometimes I get issues with that, but not often. The one time it is an issue is when I have to use an adhesive on the bed:
The "scratch lines" on this surface are from the adhesive I spread on the bed to keep the print on the bed. This is a large square object and when I print it, I generally prefer adhesive. While warping isn't really an issue for an open square (as opposed to a big square surface), sometimes I have issues. The adhesives I find work best for me are the ones resembling stick glue. I've tried spray on adhesives without much luck. The kinds that apply with a sponge on the bottle top can also leave lines or patterns on the bed that result in an issue like this.
While I'm interested in general tips to make sure the bottom layer is smooth (and let's skip the obvious - making sure the print bed itself isn't damaged), I'm especially interested in finding out how I can use adhesives and have a smooth surface, not one like in the photo.
RE: Printing Smooth Bottom Surface (especially with adhesives)
What material are you having adhesion issues with?
RE: Printing Smooth Bottom Surface (especially with adhesives)
What material are you having adhesion issues with?
PLA. Sometimes PETG.
RE: Printing Smooth Bottom Surface (especially with adhesives)
I should also have asked what sheet are you using?
In 99.9% of the cases, poor bed adhesion is the print sheet has oils on it. A trip to the sink, wash in hot flowing water. Use a half sheet of a fresh paper towel, a drop or two of Dawn dish detergent, and scrub the sheet, both sides, handling the sheet only by the edges. Rinse. If the flowing water doesn't sheet off leaving a dry surface, it is still dirty and needs more scrubbing. Once the hot water is sheeting off, take a fresh paper towel and dry the sheet -- again you must not touch the print surface with fingers.
Once dry, by the edges place the sheet back on the printer and start your print. With the smooth sheet, PLA is rather hard to remove after printing; with the textured sheet the PLA should pop off pretty easily. I've switched to using third party textured sheets because the Prusa sheets have been known to be finicky for PLA, so much that some folk have used abrasive Scotchgard scrubbers on them to get PLA to stick.
One fingerprint can ruin adhesion, so keep hands and fingers away from the print surface at all times, handle only the edges; use tools to remove parts.
RE: Printing Smooth Bottom Surface (especially with adhesives)
A bit more - some plastics, like ABS, often require adhesives with glue stick or ABS goo. But PLA sticks really well to the smooth sheet; and PETG sticks too well to the smooth sheet and can damage it if a person tries too hard to remove the part quickly (the PEI is laminated to the steel, and that glue separates leaving marks under the PEI. They self heal if not too large). Sometimes when reefing a PETG part off folk have torn the PEI, ruining the sheet. I pop the part and sheet into the freezer for a few minutes, and the PETG part will often pop off itself with a simply twist of the sheet.