Printing head catches print and removes it from PEI sheet  

Re: Printing head catches print and removes it from PEI sheet

I'm similarly new. It would help if you could show a picture - but I had similar problems. Since I did all the first layer calibration stuff https://shop.prusa3d.com/forum/assembly-and-first-prints-troubleshooting-f62/life-adjust-z-my-way-t2981.html and also wiped the print bed with Isopropanol (and once Acetone), I believed that there couldn't be anything wrong with my print bed.

Oh boy. Finally convinced myself to take the steel sheet to the kitchen sink and give it a wash with warm water, a new sponge and some dish soap. And what a difference that made. All those streaks and smears, which were still visible after iso and acetone were gone, the water just ran smoothly off the bed - and the PLA stuck to it like on the first day.

Re: Printing head catches print and removes it from PEI sheet

[...] I've been trying to print a few bits and bobs but I am noticing that print head will sometimes catch the print/scrap against the print and this disconnects it from the PEI bed. The nozzle physically scraping the print can be caused by a couple of things:

You may have one or both of these issues contributing to your failed prints.

Crash detection never goes off, suggesting there isnt a great adherence to the bed. That does sound like the print is just coming loose and moving about.

I am printing in PLA, currently trying to print this, https://www.thingiverse.com/thing:925556 but 3 times and no success. That is a fairly ambitious print. I'd suggest spending some time with smaller calibration prints to be sure you've got a solid foundation before trying anything that ambitious.

I've been using isopropyl wipes on the bed to keep it in nice condition as suggested by my manual.The 2 wipes I received with my Prusa printer were 70% isopropyl alcohol. You'll want to pick up some 91%+ isopropyl for effective bed cleaning. If adhesion starts to weaken, try these things in this order:

The most important thing is to keep the bed clean and avoid touching it at all costs. It sounds like you've done some of these steps already, so I'd suggest starting with a dunk under the kitchen sink with some dish soap and making sure any accumulated crud is washed off.

[...] I wondered if maybe the bed needs to be hotter in Slic3r? A hotter bed can help with adhesion issues, but the Prusa defaults are already pretty warm (60-65C for PLA IIRC) which is getting close the temps it will deform at. You might wind up with the elephant's foot resulting from softened 1st layer material over the course of the print.

You can try adding a brim to prints you're having trouble with, although I find I rarely need to bother if I've calibrated my Live-Z and prepared the bed properly.