SLA vs DLP: Which Resin 3D Printing Technology Is Better?

Two Approaches to Resin Printing

SLA (Stereolithography) and DLP (Digital Light Processing) both create parts by curing photopolymer resin with light. The fundamental difference is how that light is delivered. SLA uses a laser that traces each layer point by point. DLP uses a digital projector that flashes an entire layer image at once.

This difference affects speed, accuracy, surface quality, and cost in ways that matter for choosing the right technology for your project.

How SLA Works

SLA uses an ultraviolet laser guided by galvanometer mirrors to trace the cross-section of each layer on the surface of a resin vat. The laser cures the resin point by point, building up fine detail with layer heights as low as 25 microns. After each layer, the build platform shifts and a fresh layer of resin is spread.

Because the laser traces every contour individually, SLA produces exceptionally smooth surfaces and sharp edges. The trade-off is speed: a complex layer with many features takes longer to trace than a simple one.

How DLP Works

DLP replaces the laser with a digital light projector (similar to a cinema projector) that flashes a 2D image of the entire layer at once. Every pixel in the projected image cures a corresponding point on the resin surface simultaneously.

This means DLP speed is independent of layer complexity — a layer with one small feature takes the same time as a layer filled with intricate detail. This makes DLP faster for dense, complex builds.

Accuracy and Detail

SLA accuracy: plus or minus 0.1 mm with minimum feature sizes down to 0.15 mm. The laser spot is extremely small (approximately 85 microns), enabling fine details on any size part.

DLP accuracy: plus or minus 0.1 mm but minimum feature size depends on the projector resolution and build area. Smaller build areas produce finer pixels and sharper details. On larger build areas, pixel size increases and fine details become less crisp.

For small, highly detailed parts (dental models, jewellery masters), both technologies perform excellently. For larger parts where fine detail matters across the entire surface, SLA has an advantage because laser resolution does not vary with build area.

Surface Finish

SLA produces marginally smoother surfaces than DLP. DLP parts can show a subtle pixelated texture on curved surfaces (called the voxel grid effect) because each cured point is a tiny square rather than a round laser spot. In practice, the difference is small and disappears with light post-processing.

Speed

DLP wins on speed for most geometries. Projecting an entire layer at once means build time depends only on the number of layers (part height), not the complexity or footprint of each layer. SLA build time increases with both height and cross-sectional complexity.

For a single small part, the difference may be minimal. For a full build plate packed with parts, DLP can be 2 to 5 times faster than SLA.

When to Choose SLA

• You need the finest possible detail on medium to large parts
• Surface finish is critical and you want to minimise post-processing
• You need biocompatible or certified dental resins
• Part dimensions exceed 150 mm and detail must remain crisp across the entire surface
• You are producing architectural competition models where visual quality is paramount

When to Choose DLP

• Speed matters more than surface perfection
• You are producing batches of small identical parts (dental aligners, jewellery)
• Parts are relatively small (under 100 mm) where pixel resolution is sufficient
• Cost per part needs to be minimised through faster cycle times

What We Offer

At 3D On Demand, we use SLA printing for maximum quality and versatility. Our SLA printers use Standard Resin for visual prototypes and Tough Resin for functional parts needing impact resistance.

Not sure which resin technology suits your project? Upload your file for a free quote or contact us to discuss your requirements.