After a failed resin print: vat cleanup and FEP check

A big failure rarely ends with the print. Cured layers stuck to the FEP, chunks floating in the resin, and sometimes a punctured film are left behind, and starting the next print straight away can turn one failure into a damaged FEP or a resin-covered screen. ELEGOO's advice is simple: don't start the next print immediately. Clear the vat first, filter the resin, inspect the release film, check the build plate, and only then reprint (ideally after fixing whatever caused the failure).

Most likely causes (in order)

Cured layers or a whole failed print stuck to the FEP: Formlabs notes a failed print can leave hard cured resin stuck to the tank film. If it stays there, the build plate presses down on it on the next print; Anycubic warns leftover cured bits can destroy the FEP and hurt the next print.
Small fragments floating in the resin: Formlabs says failed prints often leave small, partially cured pieces floating in the tank, and that if you can see or feel cured resin in the tank, the next print will fail unless you clean it out.
A punctured or dented FEP: Anycubic explains that cured debris sinking to the bottom of the vat can be pressed into the film by the build plate, puncturing it and causing resin leaks.
Resin on the LCD screen: Anycubic says that if you remove the vat and find resin on the screen, the FEP is most likely damaged and needs replacing.
A dirty build plate: CHITUBOX notes that residue left on the build plate or in the vat blocks UV light and raises the risk of another failed print.

Settings to change

Setting	Change	Why
Pause before reprinting	Don't start the next print until the vat has been cleared and checked	ELEGOO warns that leaving impurities in the tank can cause further damage to the printer.
Lift debris with a cleaning layer	Use your printer's vat-cleaning or exposure tool to cure one thin layer across the screen (Anycubic uses about 20 seconds), then peel it off; on Formlabs printers, print the cleaning sheet from the Maintenance menu	The thin layer binds stuck and loose cured bits into one piece you can remove together (Formlabs); Anycubic uses the same quick method after a print failure.
Give the layer a handle	Before exposing, rest a clean piece of support with a raft (raft down) in a corner of the vat	Formlabs suggests this as an alternative to its cleaning sheet holder, so you can lift the sheet out by the support.
Tools	Plastic or silicone scraper only, used flat; never metal or sharp tools	ELEGOO, Anycubic and Formlabs all warn that sharp or metal tools can damage the release film.
Filter the resin	Pour the resin through a funnel and fine paint strainer (Formlabs uses a "Fine" or 190 micron filter) into an opaque container	Removes the small fragments you can't see; Anycubic recommends an opaque container to keep light off the resin.
Leak test the FEP	Pour a little IPA into the empty vat and set it on a paper towel; wet spots mean holes	Phrozen and Anycubic both use this test to find punctures that aren't visible.
Light test the FEP	Hold the empty vat up to a light and look for dents, scratches, holes and cloudiness	Phrozen's inspection step; minor scratches or slight loss of tension are still usable.
Replace the FEP	Replace if it is punctured, deeply scratched or dented, very cloudy or has lost tension, or if resin got onto the screen	Phrozen and Anycubic list these as replacement signs; Anycubic notes holes can't be repaired.
Build plate	Remove cured residue, clean the plate and re-level if the failure knocked it out	CHITUBOX: residue on the plate or in the vat impedes UV light and raises the risk of another failure.

Exact values depend on your printer and resin. Start from the resin maker's recommended settings and change one thing at a time.

Where to change it in your slicer

Setting names and locations for Lychee, CHITUBOX, Anycubic Photon Workshop and UVtools. Where we could not confirm an exact menu location, we list the setting name only. Names can differ slightly between versions.

Lift debris with a cleaning layer : Use your printer's vat-cleaning or exposure tool to cure one thin layer across the screen (Anycubic uses about 20 seconds), then peel it off; on Formlabs printers, print the cleaning sheet from the Maintenance menu

Lychee: Lift Distance and Lift Speed (Burn-in and Normal layers)

Set in your resin profile.

CHITUBOX: Settings > Print tab > Lifting Distance / Bottom Lift Distance, Lifting Speed

Anycubic Photon Workshop: Slice settings > Print Control > Z Lift Distance, Z Lift Speed

UVtools: Tools > Edit print parameters > Lift height and Lift speed

UVtools edits an already-sliced file, so make the change there after slicing.

Quick checklist

Wear nitrile gloves; uncured resin can irritate skin
Don't start another print yet
Run your printer's vat-clean or exposure tool with a support-and-raft handle in one corner, then peel the cured sheet out
Scrape any remaining bits gently with a plastic scraper held flat, never metal
Filter the resin through a fine paint strainer and funnel into an opaque container
Take the vat out and check the LCD for resin; if there is any, the FEP needs replacing
Hold the empty vat to a light and do the IPA-on-paper-towel leak test
Replace the FEP if it's punctured, deeply dented, very cloudy or slack
Clean the build plate and check leveling
Fix the cause of the original failure before reprinting

FAQ

How do I get a failed print out of my resin vat?

Use your printer's vat-cleaning or exposure function to cure a thin layer over the whole screen, then peel it out. It traps the failed print and loose bits in one sheet. A support with a raft placed flat in one corner gives you a handle. Formlabs printers have a built-in cleaning sheet that does the same job.

Can I reuse the resin after a failed print?

Usually yes, after filtering it. Pour it through a funnel and a fine paint strainer (Formlabs uses 190 micron) to catch the fragments, and store it in an opaque container away from light.

How do I check my FEP for holes?

Pour a little IPA into the empty vat and set it on a paper towel. Wet spots on the towel mean holes (Phrozen, Anycubic). Also hold the vat up to a light and look for dents, deep scratches and cloudiness.

When should I replace the FEP film?

Replace it if it's punctured, has deep scratches or dents, is very cloudy, has lost tension, or if you found resin on the screen. Light surface scratches are normal and usually fine, according to Phrozen, Anycubic and ELEGOO.

There's resin on my LCD screen. What now?

Anycubic says that means the FEP is damaged, so replace the film. To clean the screen, soften cured resin with high-concentration IPA, wipe it off with a microfibre cloth, and gently use a plastic spatula on anything stubborn. Never use a sharp metal tool, as it can damage the screen.

Not sure which one you've got?

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Sources

Related fixes

Wear nitrile gloves and eye protection when handling uncured resin, and work in a ventilated space.