Resin Print Layer Separation: Causes and Fixes

A resin part that splits cleanly along one layer plane had a layer bond weaker than the force pulling on it. Every one of the documented resin print layer separation causes sits on one side of that inequality: the new layer did not cure far enough into the layer below (exposure, temperature, layer height, dirty optics), or the peel off the release film was stronger than a normal bond can take (lift speed, suction cups, unsupported area, loose hardware).

Read the failure first

Formlabs defines delamination as cured layers separating from one another, with two signs: peeling between layers, and pieces of cured resin floating in the tank. That second sign rules out three lookalikes: a cured sheet on the film with nothing on the plate, covered in resin print not sticking to the build plate; a part that came off its supports intact; and a part that cracked days after printing, covered at the end.

A true split shows a flat, glossy fracture face at one Z height. FDM layer splitting is a cooling problem with a different path, at slicerguide.com.

Cause 1: the layer did not cure deep enough to bond

Each exposure must cure past its own thickness into the layer below. The relationship is the Jacobs working curve, and a 2024 interlaboratory study led by NIST found its penetration depth Dp varying up to 7x and critical dose Ec up to 70x across 24 labs.

Anycubic’s parameter description puts normal exposure for its resins on a monochrome Photon at roughly 2 to 3 s at the default 0.05 mm layer, lists model breakage and visible layer lines as the symptoms of too little, and notes that thicker layers and dark pigment both need more. Its support guide allows +0.5 to 1 s per trial. The stepped test is in how to calibrate resin exposure time.

Cause 2: cold resin

Anycubic states the optimal resin temperature is around 24 C, that cold resin needs more exposure, and that below 10 C it will not cure properly. Its support-separation guide gives the correction for a 15 to 20 C room: exposure +30% and lift speed -30%, with a pre-warmed bottle kept under 60 C.

Cause 3: peel force exceeds bond strength

Anycubic describes excessive lift speed as producing instantaneous tensile force between layers and between model and film, resulting in cracking, and recommends 60 to 150 mm/min. Elegoo’s Saturn firmware ships a four-stage lift that separates the first 3.5 mm at 2.0 mm/s before speeding up, and Elegoo caps anyone forcing a constant speed at 2.5 mm/s. Drop 30% from the default when a split appears.

Geometry multiplies the same force. Formlabs lists a large change in surface area between consecutive layers, because the big layer resists the peel while the small one under it does not, and suction cups. Reorient, add drain holes low on the model, or on Form 4 enable Cup Mitigation.

Cause 4: resin has not settled before the exposure

Anycubic’s off time, the pause between the plate stopping and the light coming on, is recommended at 1 to 3 s and lengthened for viscous resin, low temperature or a large layer. Phrozen’s profile reference adds that a fast retract causes instability, so slow the retract rather than cutting the pause.

Cause 5: supports and the bottom-to-normal transition

Formlabs’ first step is to find free-hanging sections and add supports. Anycubic adds that uneven support density concentrates stress, and that deeper insertion and a wider tip strengthen the join. A split just above the raft, where the long-exposed bottom layers meet the normal layers, is what transition layers exist to prevent, per Phrozen.

Cause 6: hardware, contamination and pauses

Prusa’s delamination article names a broken model or sliced file, a faulty UV LED panel, and dirt in the tank; its checks are a known-good pre-sliced sample, a tank clean, and the Display test. Formlabs adds a loose build platform, a worn tank film and contaminated optics. A flake of cured debris under the part blocks light on the pixels above it: a local under-exposure on one layer. Formlabs also lists prints paused for an hour or longer.

Cause 7: it separated after the print

Prusa’s warped layers article explains that most resins shrink by several micrometres after curing and that the forces warp and separate large solid layers; its remedy is hollowing. A crack that appears a day after curing is this or a wash and cure fault, covered in how to wash and cure resin prints; more exposure makes it worse.

Settings to change first

Anycubic Photon Mono-class printer, Anycubic standard resin, 0.05 mm:

Setting	Baseline	First change on a split
Normal exposure	2 to 3 s	+0.5 s per trial
Layer thickness	0.05 mm	Return to 0.05 mm if raised
Lift speed	Default, within 60 to 150 mm/min	Reduce 30%
Off time	1 to 3 s	Lengthen for viscous or cold resin
Resin temperature	24 to 30 C	Warm the bottle, never above 60 C; in a 15 to 20 C room, exposure +30% and lift speed -30%

Saturn owners already have the staged lift. Change one variable per print.

How to verify

1. Print a stepped exposure test at the layer height and temperature you will use. Wash, dry, then pick the middle of the range that produces complete geometry.
2. Reprint the part that split, tilted so the largest cross-section change is not flat. No floating flakes in the vat is the first pass criterion.
3. Inspect the old failure height. A line that catches a fingernail means another +0.5 s or another 30% off the lift.
4. If the split moved rather than vanished, the cause is force: check platform bolts, the film for a cloudy patch, and the model for an enclosed volume at that height.

Related across the network

• Resin Types Compared: Which Anycubic Resin to Print With — anycubicguide.com
• Photon File Validator: Check Files Before You Print — anycubicguide.com
• Resin MSLA or High Speed FDM: Which Process to Choose — anycubicguide.com
• How to Dry Filament: Temperatures by Material — 3dfilamentguide.com
• ansible-playbook Options: Flags That Change a Run — ansibleguide.com

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