Masked Stereolithography (MSLA / DLP)
Masked stereolithography cures a whole resin layer at once through an LCD or DLP image, so build time depends on height rather than part count.
- Part
- Forming
- Revised
- 2026-08-11
At a glance
- Family
- Additive Manufacturing
- Typical tolerances
- About ±0.004–0.008 in (±0.1–0.2 mm) on general geometry; ±0.002 in (±0.05 mm) is achievable on small parts with fine-pitch panels and a compensated first article.
- Surface finish
- Ra 20–120 µin (0.5–3 µm) — close to laser SLA, but with a faint pixel texture on curved walls that laser scanning does not produce.
- Typical volumes
- 1–5,000 small parts; cost per part falls in proportion to how densely the plate is filled
- Lead time
- Same day to 3 business days. A 4 in (100 mm) tall build runs roughly 3–8 hours plus wash and post-cure, regardless of how many parts are on the plate.
- Materials
- Plastic
What it is
Masked stereolithography cures an entire resin layer in a single exposure by projecting the whole cross-section at once — through an LCD panel acting as a photomask (MSLA) or from a digital micromirror device (DLP) — rather than tracing it with a laser as SLA does. Exposure takes 1.5–4 seconds per layer regardless of how much of that layer is solid, so build time depends only on part height. One part or a full platform of them costs the same machine hours.
XY resolution equals the mask's pixel pitch: roughly 0.0008–0.002 in (20–50 µm) on current mono LCD panels, and 0.0012–0.004 in (30–100 µm) with DLP projection optics depending on the projected field size. Layers are 0.001–0.004 in (25–100 µm).
Build volumes are small — typically around 8 × 5 × 9 in (200 × 125 × 220 mm) — because enlarging the field either costs resolution or requires a bigger, more expensive panel. That makes the process ideal for high-volume small parts: dental models and surgical guides, aligner thermoforming molds, castable jewelry patterns, hearing aid shells, and miniatures.
How it works
- Slice into images. Each layer becomes a bitmap at the native pixel resolution of the mask. Anti-aliasing and gray-scale exposure are used to soften the pixel staircase on curved walls.
- Dip and settle. The build platform lowers into the vat until the gap between the last cured layer and the transparent film at the vat floor equals one layer thickness. Resin must flow into that gap before exposure — viscous resins need a longer settle time.
- Expose the whole layer. A 405 nm LED array shines through the LCD mask, or a DLP projector images the cross-section directly. Exposure is typically 1.5–4 seconds per layer on a mono LCD. Because the whole layer cures simultaneously, adding parts to the platform does not add time.
- Peel. The platform lifts, separating the cured layer from the release film. This is the critical mechanical event of the process: peel force scales with the cured cross-sectional area, and large flat layers are the usual cause of a part tearing off its supports or delaminating.
- Repeat. Vertical build rate is commonly 0.4–1.2 in/h (10–30 mm/h).
- Wash and post-cure. Isopropyl alcohol wash of 5–15 minutes, support removal, then UV post-cure — 15–60 minutes, often warmed to 60 °C (140 °F). As with any photopolymer process, published mechanical properties assume a completed post-cure.
Design guidelines
Orient to minimize cross-sectional area
This is the dominant rule of the process. Peel force is proportional to the area cured against the release film, so a flat plate printed parallel to the platform will fail where the same plate tilted 20–30° succeeds. Tilting also breaks the layer up so no single exposure has a large continuous area.
Hollow and vent
Hollow shells reduce both resin cost and peel area. Use a 0.060–0.080 in (1.5–2 mm) wall and at least two vent holes of 0.12 in (3 mm) or larger. A sealed hollow section also creates a suction cup against the vat film, which is a separate and equally destructive failure mode.
Feature size versus pixel size
Nothing smaller than one pixel can be resolved, and features under about three pixels reproduce unreliably. On a 50 µm panel, that means 0.006 in (0.15 mm) as an absolute floor for a rib or engraved line. Fine dental and jewelry work is done specifically on panels with the smallest available pitch.
Wall thickness
0.016 in (0.4 mm) supported and 0.032 in (0.8 mm) unsupported. Thin walls fail during peel, not during cure.
Supports
Use many small contact points rather than a few large ones — typically 0.3–0.6 mm tips at a density that spreads peel load. Keep them off cosmetic and fitting surfaces, and orient so the first layers land on sacrificial geometry.
Dimensional compensation
Photopolymer shrinks on cure and again on post-cure, and light bleed through the mask grows XY features slightly. Fitting features are usually compensated by 0.002–0.004 in (0.05–0.1 mm) per side after a first article; expect to iterate once on any press or slip fit. The ISO 286 fits and tolerances chart is a useful reference for what fit class you actually need.
| Feature | Recommended | Limit | Why |
|---|---|---|---|
| Orientation | 20–30° tilt | Flat only for thin parts | Peel force scales with layer area |
| Wall thickness | 0.032 in (0.8 mm) | 0.016 in (0.4 mm) | Peel loading, not cure resolution |
| Detail size | 3 pixels | 1 pixel | Sub-pixel features do not reproduce |
| Vent hole | 0.16 in (4 mm) | 0.12 in (3 mm) | Prevents suction against the vat film |
| Layer height | 0.002 in (50 µm) | 0.001 in (25 µm) | Time scales directly with layer count |
| Hollow wall | 0.080 in (2 mm) | 0.060 in (1.5 mm) | Shell must resist peel without support |
Cost drivers
The defining economic feature of masked SLA is that build time is a function of height alone. A platform holding fifty dental models costs the same machine hours as one, so unit cost falls almost linearly with how many parts fit on the plate. This is why the process took over dental and jewelry production while laser SLA stayed in engineering prototyping.
Resin volume is the second cost, which is why hollowing pays twice — less resin, lower peel force. Consumables are the third: LCD panels degrade under constant UV and are replaced periodically, and release films are changed regularly.
Labor for support removal, washing, and post-curing does not scale down with quantity and eventually dominates. Production shops mitigate it with automated wash-and-cure stations and support layouts designed for fast breakoff.
Volume breakpoints: masked SLA is economical from 1 part and stays competitive to a few thousand small parts a year. Beyond that, or where a tougher material is needed, look at molding.
- Fill the plate — it costs nothing extra in time.
- Hollow everything with a wall over 0.16 in (4 mm) and vent it.
- Use the largest layer height the surface finish tolerates.
- Design supports for fast manual removal; labor is the cost that does not scale.
- Match panel pixel pitch to the smallest feature you actually need rather than buying resolution you will not use.
Questions
6 questionsWhat is the difference between MSLA, DLP, and SLA?
All three cure photopolymer with UV light. SLA traces each layer with a scanning laser, so time scales with how much area is solid. MSLA masks an LED array with an LCD panel and DLP images the layer with a micromirror chip — both cure the whole layer in one exposure, so time depends only on part height.
Why does build time not increase when I add more parts?
Because the entire layer is exposed at once. Whether one part or thirty occupy that layer, the exposure is the same 1.5–4 seconds. Only the number of layers — that is, the height of the tallest part — determines build time.
What resolution can MSLA achieve?
XY resolution equals the mask pixel pitch, roughly 0.0008–0.002 in (20–50 µm) on current mono LCD panels. Features smaller than about three pixels reproduce unreliably, so on a 50 µm panel plan on 0.006 in (0.15 mm) as the practical minimum detail.
Why do my large flat MSLA prints fail or delaminate?
Peel force is proportional to the cured area contacting the vat film, and a large flat layer generates enough of it to tear the part off its supports. Tilt the part 20–30°, hollow it, and add vents — tilting reduces the area cured in any single exposure.
Do MSLA parts need vent holes?
Any hollow section does. Without vents, uncured resin is trapped inside and the sealed cavity acts as a suction cup against the vat film during peel. Use at least two holes of 0.12 in (3 mm) or larger, placed so resin can drain and air can enter.
Is MSLA accurate enough for dental and jewelry work?
Yes — it is the dominant process in both. With a fine-pitch panel and a compensated first article, ±0.002 in (±0.05 mm) is achievable on small parts, which covers dental models, surgical guides, aligner molds, and castable patterns for investment casting.