Tips on PLA bed adhesion for textured PEI sheets?

[m00dawg]

I would rarely print PLA on textured sheets on my Prusas but never quite recalled why it was to be avoided. I found out when I took a wing at using a textured sheet on my 2.4 for some larger PLA prints. It started great but adhesion started to get worse over time.

I've switched to smooth PEI for now and while it still does look good, not nearly as good as that gorgeous texture. For the parts I'm printing, I would prefer to use PLA over PETG or ABS/ASA. Are there any tips to improve adhesion easily? I would guess no based on what I've read but thought I would ask just the same to get the Voron community thoughts.

 

[Yezariael]

Soap and water, kitchen sponge and then IPA wash. If it does not help maybe a short scrub with Acetone (not too often or it will damage the sheet).

 

[m00dawg]

Yep that's about what I was doing. Actually I wasn't using a sponge so I'll try that next time, good thought! The bed adhesion is "good" but I've started to get corner lifting with the PLA/textured combo.

 

[NoGuru]

PLA requires less squish for me so If I am printing with it I do a PROBE_CALIBRATE before printing it.
If the part is small I will add a brim.
If I don't care about Elephant's foot, I will add 5 to 10 degrees to the bed.

 

[Indeed]

To print PLA on the textured PEI sheet that came with my formbot kit I have to set the bed temp to 70C to make it stick.

Unless I take the time to spread some sugar solution (syrup) over the PEI sheet.
When I do I can have the bed at 60C or even lower.
It's a bit of a hassle though, so I mostly print without sugar at 70C.

Before a print I spread a tiny amount of solution over the PEI sheet, with a finger.
It doesn't take much, I usually spread it as thin as possible.
I have also found that it doesn't matter much whether the finger is clean or not.

I make my own syrup:
Half fill a tiny bottle with ordinary sugar and then add water until the bottle is maybe 3/4 filled.
It takes a while for the sugar to dissolve completely. Shake the bottle now and then.
Then wait an hour or two until the bubbles are gone and the solution is clear.
There's usually a solid cake of undissolved sugar left at the bottom, that's ok.

 

[Yezariael]

I usually print ABS and PETG, today I wanted to use the rest of an old role of glow-in-the-dark PLA... I switched to smooth PEI because it did not stick to the textured sheet In my case no problem because of object and because I don't print PLA normally.

 

[m00dawg]

That's really interesting @Indeed! I might have to try that! Do you clean the plate in between or just keep putting a thin layer down each time?

The bed temp is an interesting one. On my Prusa's I run at 65-67 for PLA. I bumped that to 70 on my Voron and it works quite well (with my alcohol + purple glue slurry, some one I use on the Prusas). With texture I think I went all the way to 80 but I was still getting lifted corners. I read somewhere that it might be counter-intuitive and that was too hot but ran out of time to pursue that for the moment. Something I wanted to come back to though.

 

[Indeed]

Often I just start a print on the dry sugar leftovers from previous print, but after maybe two or three prints I spread some more syrup where needed. When too much cat hair or dust has stuck to the surface I wash the steel sheet in the kitchen under running water, with some soap and a dish brush. Usually after a day or two.

I haven't tried glue slurry or glue stick, maybe I will. It's probably just as good or even better. The syrup solution doesn't really wet the PEI surface and it has to be quite thick (saturated) to avoid having it curl up into islands due to surface tension. That's why I spread it with a finger, to press it down into the valleys of the textured surface.

About bed temp, I haven't yet done any experiments other than increase it until the PLA stuck at 70C. I never went any further to see if PLA would lift in the corners at even higher temperatures.

Going forward I'll probably use a BuildTak standard sticker for PLA instead of PEI. One of my other printers has a buildtak sticker, and PLA stick really well at 40C and even lower. Sometimes too well. I have to make sure the first layer isn't squished or it is difficult to get the parts to release.

I have ordered a cheap steel sheet that I'm going to put a sticker on and use for PLA. The buildtak surface won't be as textured as the PEI sheet so the parts won't look as nice anymore, but at least I'll be able to print PLA without removing the panels to avoid melted parts. Or so I assume, we'll see...