Fix needed: Printing many copies at the same time, why is brim easy to remove on some, hard on others?
I'm using Prusament PC Blend natural to print 20 copies at a time of a small (2 cm x 2 cm x 4 cm) functional part on an MK3S+ in an enclosure on the Prusa textured sheet.
With no brim and no Magigoo PC, some of the identical parts will warp and separate from the bed. Most of these parts are on the left half of the print bed.
With Magigoo PC, the warping problem is reduced but not completely eliminated. Parts in on the left quarter or third of the print bed still tend to separate, and I think it's worst in the middle (front to back) third of the bed.
With a brim and Magigoo PC the problem is completely eliminated, BUT there's a new problem. There is a gradient from right to left in which the brims are easy to remove (on the right) to very hard to remove (on the left).
Two explanations came to mind:
1) The print bed is not heating evenly. I tried with a non-contact thermometer and a cheap thermal imager, but I don't think the resolution is good enough in either case to confirm this hypothesis.
2) The print bed is not completely flat. I know I can micro-adjust using the settings, but I don't know which direction. Do you think that a hard-to-remove brim is the result of a bed that is high relative to the nozzle, or low?
Best Answer by Dan Rogers:
enable 7x7 bed mesh leveling in the control panel. this should help with bed flatness adjustments. The printer is capable of mapping the bed surface with each print and adjusting Z for localized hills and valleys. Brim "tenacity" is a function of localized live Z. You may find you can go without brim or your favorite sticky stuff once you have enabled this.
Start with 7 x 7 mesh leveling
enable 7x7 bed mesh leveling in the control panel. this should help with bed flatness adjustments. The printer is capable of mapping the bed surface with each print and adjusting Z for localized hills and valleys. Brim "tenacity" is a function of localized live Z. You may find you can go without brim or your favorite sticky stuff once you have enabled this.
Supplied glue stick
FWIW As Prusa supply PC filament with a glue stick, I guess it's reasonable to assume it's necessary.
RE: Fix needed: Printing many copies at the same time, why is brim easy to remove on some, hard on others?
Before the start of printing, let printer heat up for longer time. With doors closed. How hot does the printer get inside, maximum is 40 or 45 degrees, higher the cooling will not work as good. I leave door often a little open in summer.
Z-calibration.
(Put plate in a freezer, possible better to release.)
Z-live , adjust a little higher.
Check if bed is flat.
Print less parts, print only in the middle of bed.
Use glue stick, possible better to release after print.
Thanks! It was a group effort!
It's a gold for @dan-rogers 's contribution to the solution. The 7x7 mesh leveling suggestion made a huge improvement. I'm still not confident enough to try it without Magigoo PC, but I am able to reliably print 20 copies without a brim using Prusament PC Blend. They all stick well to the textured sheet.
Silver for @peter-m ! The freezer trick works really well to loosen the completed parts from the textured sheet. FYI, I have an AC Infinity fan that I set to 44 C and "smart mode", which means it starts at low RPM at about 41 C.
Bronze for @towlerg . Yes, you'd think that if Prusa included the glue stick it would make all the difference. But, having made dozens of this print (hundreds of individual parts), I can say that it doesn't. As far as I understand it, the glue stick acts as an interface between the plate and the print to improve release, not to improve adhesion. I have found that when printing with Prusament PC Blend there are several things I must do to prevent warping and separation of the print:
- Make sure the textured plate is very clean. I use dish soap and scrub it. Then rinse it with RODI H2O. Then never touch it with bare fingers.
- Optional Magigoo PC -- I suspect that Magigoo is probably a successful marketing scheme for some cheap substance, but this stuff is well worth it for me. My prints take 10-12 hours. IF they fail, they fail past the halfway point, which is a lot of wasted time and expensive filament. Magigoo does seem to increase the likelihood of a successful print.
- Set the Z really close to the sheet to cram the first layer down on the sheet.
- A draft-free enclosure with an internal temperature of around 40 C, which is at the upper limit of Prusa's tolerances.
- Upgrading the E axis components to Prusament PC Blend for improved resistance to the heat required for printing PC.
Freezer and PEI are not meant to be
If you want to remove your PEI sheets, put your steel sheet in the freezer. If you have over-adhesion and are looking for the freezer to be a magic bullet, be prepared to rip holes in your frozen PEI sheet = the glue is designed to release at temps just above freezing - it makes fixing a ruined sheet a not-too-bad project.