Petg adhesion warning
So I'm brand new to 3-D printing and I purchased an mk3s kit and built it with success. I've had about a 99.9% success rate on my prints and have been very happy with my results. I always do a lot of research when delving into a new hobby. With that being said, I watched a video with Josef Prusa stating that the best way to clean the heat bed is with Isopropyl Alcohol. So thats been my go to cleaner and the results have been amazing. Then.... I print out a phone case with Petg. Took 7 hours and the finished product was as usual wonderful. I bend the heat sheet and the case pops right off with no difficulty whatsoever. Felt no different than any other print popping loose from the bed. But then I noticed where each of the three corners were adhered to the bed, there were medium sized hills, or mounds that the print had pulled up from the bed. Now I can feel about 5 millimeter in diameter mounds whenever I run my fingers across those areas. So after I see this I go onto the Prusa website and lo and behold, under the description for Petg properties it states: "Do not use Isopropyl alcohol to clean bed before printing with Petg". I felt a little misled by the video but also responsible for not researching more. I just think when the designer of the machine says in a video addressed to new users that when cleaning the heat bed to use Isopropyl alcohol because its the best, that he should've gave the caveat of not using Isopropyl alcohol with Petg. I thought I had researched Petg enough and found that most people had a lack of adhesion problem so this took me by surprised. So I guess I'll have to purchase another sheet:(
RE: Petg adhesion warning
Yeah the info about using IPA is for PLA only. For PETG you need a release agent. Rubbing your hand across the sheet or spritzing it with Windex are the common suggestions.
Also, never use the same side of the plate that you use for PLA. PETG will leave a residue that will keep the PLA from sticking well.
That said, when using Amazon's PETG at 230 I've been able to get away with prepping the sheet just like I do for PLA. I expect that it's because it likes to print colder than most others that is letting me get away with it.
RE: Petg adhesion warning
IIRC, the info on PETG is in the manual. I believe the video (assuming I saw the same one) is describing "how to clean with isopropyl alcohol" not "how to prepare the bed for every filament".
Try printing on the other side for a bit. It's amazing how resilient the PEI sheets are if not actually torn. If you do opt for replacement, ordering a new double-sided sheet is well worth the time saving. Unless you're really fond of the strong citrus smell of limonene. The Prusa pricing on the spring steel sheets is very good, even with shipping.
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RE: Petg adhesion warning
But then I noticed where each of the three corners were adhered to the bed, there were medium sized hills, or mounds that the print had pulled up from the bed. Now I can feel about 5 millimeter in diameter mounds whenever I run my fingers across those areas.
Do not worry about those. The PETG, with its strong warp forces did pull the PEI off the steel sheet, stretching the 3M acrylic glue inbetween a little. Flip the sheet around and keep using it that way. After some time of exposure to heat and pressure the acrylic glue will regenerate and be flat again.
So after I see this I go onto the Prusa website and lo and behold, under the description for Petg properties it states: "Do not use Isopropyl alcohol to clean bed before printing with Petg". I felt a little misled by the video but also responsible for not researching more. I just think when the designer of the machine says in a video addressed to new users that when cleaning the heat bed to use Isopropyl alcohol because its the best, that he should've gave the caveat of not using Isopropyl alcohol with Petg. I thought I had researched Petg enough and found that most people had a lack of adhesion problem so this took me by surprised. So I guess I'll have to purchase another sheet:(
Do use IPA for prepping before printing PETG. But also do spray the sheet with Windex or a similar window cleaner afterwards, wipe off and let dry. The problem you saw isn't nearly as bad as what PETG can do - it can fuse to PEI so much that it's not possible to remove at all. A separating agent, like the Windex is a good safety net.
Many warping (ABS, Nylon, ...) materials will cause the mounds you've seen, and this can't really be avoided, particularly on long prints, because if the material didn't stick and pull on the bed, it'd pop off in the middle of the print instead.