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.
RE: Printing Smooth Bottom Surface (especially with adhesives)
I had read to clean the print bed with alcohol, which is what I have been using. I take a paper towel and fold it so I end up with a section I haven't touched, then use it to wipe off the entire bed (I'm using Prusa's satin surface bed), so I don't get any finger oil on it at all. Since I'm using PLA, it sounds like, somehow, I'm getting fingerprints on it. I do wash with Dawn, as described (keeping fingerprints off it and handling by the edges), but generally about ever 5th-6th print.
I did damage a smooth sheet the first time I printed PETG! I have a sheet that, for now, I use just for PETG. While on that topic, let me ask - what kind of sheet is best for printing TPU? I had no idea how flexible it was, printed it on my satin surface sheet and let it finish. Then I flexed the bed sheet, as I always do with PLA, but it wouldn't pop off so I carefully pulled it off using a putty knife and going really slow on separating it.
You are using too much glue.
Get the plate clean then draw one line of glue stick across the plate and spread evenly it with a little water and a wet paper towel.
Or: Use a spritz of Windex or similar window cleaner spread the same way.
Or: Use half a teaspoonful of of liquid *PVA glue and spread with water as above - if you are using soluble PVA filament as support you can use some of the wash water but beware PVA wood glues, some of them are blended with other adhesive, read the label carefully.
TPU bonds to all the common print sheets rather too well. Use glue and when it comes to removal it's easiest to stretch it off; get one corner started then pull it off slowly, stretching the attachment boundary as it frees. If it's really stuck then a small puddle of IPA against the attachment boundary often helps.
*Often sold for use in schools as it washes out of clothing.
Cheerio,
RE: Printing Smooth Bottom Surface (especially with adhesives)
I use a textured 3rd party sheet from Amazon. Cheap, filament holds better than the Prusa textured sheet. For some filaments, I'll pop the sheet with part into the freezer, the glass temp for TPU's is near 0, so once cold, it doesn't bend with the sheet and pops off.
Some people also use hairspray to add adhesion.
RE: Printing Smooth Bottom Surface (especially with adhesives)
Clarifying a few points, to make sure I'm 100% clear on them (I have a few reading issues, so I sometimes do this to be sure I get something.)
Or: Use a spritz of Windex or similar window cleaner spread the same way.
Do you mean Windex *only* instead of glue? Sounds interesting and easier to spread thinly than glue.
Use glue and when it comes to removal it's easiest to stretch it off
So using glue with TPU is one of those examples of when using an adhesive makes it easier to pull the print off at the end? And is that also a case where I could use Windex instead?
I use a textured 3rd party sheet from Amazon. Cheap, filament holds better than the Prusa textured sheet.
Do you mean something like this?