Replacing the PEI on a damaged smooth sheet - easy and done.  

Replacing the PEI on a damaged smooth sheet - easy and done.

Many of you have experienced your first PETG or ABS prints tearing the smooth PEI sheet because you didn't know you needed release agents on the sheet before printing with super-sticky materials.  Prusa shop sells replacement PEI coatings (in the spare parts section) - and they are a good alternative for buying a brand new steel sheet.

I decided today was the day.  I've been sitting on the replacement PEI (comes with instructions) and the materials you need to do the job (freezer and Limonene) - so I got an old shallow baking pan from my wife and permission to potentially make it a shop sheet, popped the damaged sheet in the deep freeze overnight and was ready to try the job this morning.

Frozen, the PEI sheet peels off very easily - leaving the glue layer behind.  The new sheet comes with the 3M glue already applied, so the next part of the job is to take all of the old glue off of the steel sheet.  You do not want to just apply the new sheet over the old glue because that will make the extra thickness throw off the PINDA sensor on your Prusa printer.  So into the shallow pan went two small bottles of limonene (smells like orange peels) and I used a plastic scraper to start pushing the glue.  The limonene does a good job softening up the glue - and it comes of in surprising quantities.  I ended up with a half quart of old glue at the end.  Once _all_ of the glue is off - not even a thin remnant, it's on to laying down the new PEI sheet.

As I said before, the replacement kit comes with two PEI sheets - you really can't do only one side.   The kit also comes with very clear instructions, color pictures, and cautions on what to not do.  Very advisable to read that a few times over before you start.

Putting down the new sheet was not a long job, but you need to be careful to go slow and keep air bubbles out of the mix.   Then you trim the sheet back to the size of the steel sheet - and you're ready to print.

So if you have a damaged PEI smooth sheet - think about fixing the one you have instead of buying a new one.  Even if you bought a new one, fix your old one and you'll have more sheets to swap (faster printing while the old print cools)