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Replace the FEP Film on Your Saturn 4 Ultra 16K

  • Bryan Cawthon



Resin Printing · Maintenance Guide

Replace the FEP Film
on Your Saturn 4 Ultra 16K

A complete step-by-step walkthrough to swap your release liner, protect your LCD screen, and get back to crisp 16K prints.

DifficultyBeginner
Time~30 min
Screws24 total
PrinterSaturn 4 Ultra 16K
What you'll need
Replacement FEP film
2.0 mm hex wrench
2.5 mm hex wrench
3.0 mm hex wrench
80 × 80 × 8 mm foam spacer
Utility / craft knife
Nitrile gloves
Isopropyl alcohol (IPA)
Paper towels
Small dish for screws
⚠ Always wear nitrile gloves when handling uncured resin. Work in a well-ventilated space. Dispose of resin-contaminated materials per your local hazardous waste rules.
When to replace your FEP

Cloudiness or hazing
Can't see clearly through it when held to light.

Deep scratches
Visible gouges from spatula that catch light at an angle.

Print failures
Prints not sticking despite correct settings.

Punctures / leaks
IPA test: wet spots on paper towel below = holes.
Step-by-step guide
1
Empty & clean the resin vat
resin (to be poured out) bottle IPA wipe Saturn 4 Ultra resin vat — FEP film at base FEP release film

// Pour resin back into bottle, then IPA-wipe all internal surfaces

Pour all resin back into its bottle using a funnel and filter. Wipe the inside of the vat with IPA-dampened paper towels. Let it dry fully — you don't want uncured resin trapped under your new film.

Pro tipHold the old FEP up to a bright light and look for micro-punctures, not just obvious damage. Even tiny pinholes cause adhesion failures.
2
Remove the vat & unscrew the frame
FEP film hex wrench 24 screws secure the inner + outer frames — remove all

// The 24 screws (yellow) hold the two frame halves together around the FEP

Lift the vat straight out of the printer and place it on a flat surface. Use your hex wrenches to remove all 24 screws. Keep them in a small dish — you need every one.

CriticalLoosen screws in a diagonal / cross pattern — opposite corners first, then work inward. This releases tension evenly and prevents the aluminium frame from warping.
3
Separate the frames & remove the old film
outer frame inner frame (lifting) old FEP film — cloudy, scratched IPA clean both frames IPA-wipe both frames clean — no resin residue, no fingerprints

// Lift the inner frame away — old FEP comes with it

Lift the inner frame away — the old FEP comes with it. Peel the film off and dispose of it. Wipe both frames thoroughly with IPA to remove all residue and finger oils, then let them dry completely.

4
Place the foam spacer & lay the new FEP
outer frame — face down on table foam 80×80×8 mm new FEP film — laid over frame, centred on all sides equal equal correct slack created by foam height foam lifts FEP to correct tension — not too tight, not too loose

// Foam spacer in centre gives the FEP the right amount of sag

Place the outer frame face-down on a clean flat surface. Set the 80 × 80 × 8 mm foam block in the centre — this is the most skipped and most important step. Lay the new FEP sheet over the frame, centred evenly from all four edges.

NoteThe FEP film has no front or back — either side can face up.
5
Sandwich the frames & tighten all screws
FEP 1 2 3 4 1 tighten first (corners) tighten after hand-thread all 24 first, then tighten diagonally — do two full passes

// Always tighten corners first (1→2→3→4), then fill in the rest

Place the inner frame on top of the FEP, aligning all 24 screw holes. Check orientation: the side of the black inner frame with the larger screw-hole openings must face down toward the table. Hand-thread all 24 before applying any torque, then tighten diagonally. Do two full passes. The film should feel taut and springy — not drum-tight.

Common mistakeTightening sequentially around the frame warps it and creates uneven tension. Always use the diagonal method.
6
Trim the excess FEP film
utility knife excess excess trim flush to frame edge blade flush to frame edge — smooth controlled strokes

// Run the knife flush along the frame edge to trim the overhang

Run your utility knife along the outer edge of the frame to trim off the overhanging FEP. Hold the blade flush against the frame and use smooth, controlled strokes. A clean edge ensures the vat seats flush in the printer.

SafetyKeep fingers on the frame, away from the blade path. A fresh blade cuts easily with minimal pressure — no forcing needed.
7
Reinstall the vat & run a test print
LCD screen — protected vat with fresh FEP build plate ✓ Re-level build plate ✓ Run residue detect ✓ Test print first ✓ Check for leaks always re-level after any vat removal

// Run auto-level, then a small test print before committing to a long job

Lower the vat into the printer and lock it in. Inspect the new FEP from below — it should be perfectly clear with no wrinkles. Fill with resin, then run the auto-leveling routine. Do a small test print first and check the underside of the vat during the first few layers for any leaks.

After replacementThe Saturn 4 Ultra's residue detection will flag anything amiss before a full run. Use it as your first check every time you reinstall the vat.

Back to 16K Perfection

With fresh FEP installed correctly, you should see crisp prints immediately. Most users get 20–40+ prints per sheet with good care.

Use a plastic or silicone scraper — metal spatulas are the #1 cause of premature FEP damage.
Inspect the FEP every few prints by holding it up to a light source and looking for cloudiness or texture changes.
Don't leave resin in the vat for weeks — it can partially cure onto the film, especially near windows.
Keep a spare pack of FEP sheets on hand so you're never waiting for delivery before your next session.
After 60,000 uses the printer will prompt you to replace the film — reset the counter in Settings → Self-Test after installing the new sheet.
Elegoo Saturn 4 Ultra 16K — FEP Replacement Guide Use Elegoo official FEP / PFA film for best results

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