>>11601762the FEP is the plastic layer that comes into contact with the LCD screen, and your resin, as your model prints, it stretches out the FEP.
When the printer starts curing, the resin hardens, and sticks to the FEP, this is when the build plate pulls of the model off of the plastic FEP sheet.
You want to minimize how much pulling distorts your freshly cured resin print, this is where printing at a angle comes in handy. there are other tools, like the speed the build plate that raises off of the FEP film, but for the most part, printing at a angle solves a lot of these issues.
