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Glossary · Part

3D printing

FEP film

The transparent film in the bottom of the vat of a resin printer. Light passes through it onto the resin, and each finished layer peels away from it again.

Explained in more detail

FEP stands for fluorinated ethylene propylene, a fluoroplastic with a smooth, non-stick surface, related to PTFE. The film is stretched taut in the vat frame and is translucent, so each cured layer stays on the build plate when the plate lifts and separates from the film. Besides FEP there are nFEP and PFA films, which suppliers advertise with lower peel forces. Deep scratches, dents, a permanent milky haze or holes scatter the light or let resin run onto the screen. In that case it is time to replace it. There are no fixed replacement intervals; what matters is the condition of the film.

Where does the term come from?

FEP is the abbreviation of the English fluorinated ethylene propylene. Like PTFE (known under the brand name Teflon), the plastic belongs to the fluoropolymers.

In practice

  • Hold the empty, cleaned vat up to the light: cloudy spots, deep scratches and dents show that the film should be replaced.
  • Remove leftovers from the vat only with a plastic spatula, never with metal.
  • Tension a new film evenly: if it sags, parts are more likely to stay on the film instead of the build plate.
  • Films differ in size and hole pattern from vat to vat. Buy replacement films that match your model.

Not to be confused

The FEP film is not the protective film on the display: the display film protects the LCD, while the FEP film forms the bottom of the vat and touches the resin.

Frequently asked questions

When does the FEP film need replacing?

If it is permanently cloudy, has deep scratches, dents or holes, or parts stick to the film instead of the platform despite suitable settings. Light streaks can often be removed with isopropyl alcohol and a soft cloth.

What is the difference between FEP, nFEP and PFA?

All three are fluoroplastics with a non-stick surface. nFEP and PFA are advertised with lower peel forces. Which film fits your vat is stated by the printer manufacturer.