SLS, MJF and SLA are the three industrial 3D printing processes most often used for production parts, and each one fits different parts. Picking the right one up front saves money, lead time and redesigns. Here’s how they compare on strength, surface finish, detail, size and finishing, and how to decide which one your part needs.
The short answer
- Choose SLS for strong, functional nylon parts, larger parts, and parts with snap fits, living hinges or moving assemblies.
- Choose MJF for medium runs of small to mid-size nylon parts where consistent properties and fine detail matter.
- Choose SLA for smooth, highly detailed cosmetic parts, clear parts, master patterns for molds, and very large single-piece resin parts.
How each process works
SLS (selective laser sintering)
A laser fuses nylon powder layer by layer. The unfused powder supports the part, so no support structures are needed and parts can nest in the build to make batches efficient. At SNL Creative we run SLS in-house on an EOS P396, printing PA12, PA11 and flexible TPU.
MJF (Multi Jet Fusion)
HP’s Multi Jet Fusion is also a nylon powder process, but instead of a laser it jets fusing and detailing agents across each layer and fuses it with heat. It produces dense, consistent PA12 nylon parts with crisp small features, and it is well suited to repeat production of small and mid-size parts.
SLA (stereolithography)
A UV laser cures liquid resin one thin layer at a time. SLA gives the smoothest surface and the finest detail of the three. We run SLA on our 800 and 450 machines and a Formlabs Form 3L. The 800 builds parts up to 800 × 800 × 600 mm, and oversize parts can be printed in sections and joined.
Side-by-side comparison
| SLS | MJF | SLA | |
|---|---|---|---|
| Material type | Nylon PA12, PA11, TPU | Nylon PA12 | Engineering and standard resins |
| Best for | Functional parts, larger parts, flexible parts | Medium runs of small to mid-size parts | Cosmetic parts, fine detail, clear parts, masters |
| Strength | Tough and durable | Tough and durable | Stiff; depends on the resin |
| Surface as printed | Slightly grainy, matte | Slightly grainy, matte | Smooth |
| Support structures | None | None | Yes, removed after printing |
| Finishing options | Vapor smoothing, dyeing, painting | Vapor smoothing, dyeing, painting | Sanding, priming, painting, clear coat |
Five questions that pick the process
- Does the part have to flex, snap or take impact? Nylon (SLS or MJF) handles repeated stress better than most resins. For rubber-like parts, SLS TPU.
- Is appearance the main goal? For display models, consumer-facing covers or parts you’ll paint, SLA gives the best starting surface.
- How big is it? Large one-piece resin parts go on our SLA 800. Large nylon parts go on SLS, and they can also be split and bonded.
- How many do you need? For repeat runs of small nylon parts, MJF and SLS both batch well. Ask us which is better for your part’s size and geometry.
- Will you make a mold from it? SLA is the usual choice for master patterns, and we make silicone molds from SLA masters in-house.
Finishing changes the answer
Raw nylon parts are matte gray or white. Vapor smoothing and DyeMansion dyeing give SLS and MJF parts a sealed, smoother surface and a consistent color, which makes them look and feel like molded parts. SLA parts aren’t vapor smoothed or dyed. Instead they’re sanded, primed and painted or clear coated for a show-quality finish.
When to use more than one process
Many products mix processes. A drone or robot might use SLS nylon for the frame and brackets, MJF for small clips and connectors made in volume, and SLA for a smooth, painted cover or a clear lens. A consumer product might start with SLA appearance models for photos and focus groups, then move to SLS or MJF for functional testing and the first production run. Because every part comes from the same CAD and the same shop, it is easy to switch processes as the design matures, without new tooling and without starting over with a new supplier.
Common mistakes
- Choosing SLA for a part that has to bend or take impact. Many resins are stiff and can crack where nylon would flex.
- Choosing nylon for a part that has to look glossy as printed. Nylon needs finishing to look smooth. If looks matter most, start with SLA.
- Ignoring wall thickness. Very thin walls can warp or break in any process. Send us your CAD and we’ll flag problem areas before printing.
Frequently asked questions
Is MJF stronger than SLS?
Both make tough PA12 nylon parts with similar mechanical properties. The better choice usually comes down to part size, geometry, quantity and finish rather than strength alone.
Which process gives the smoothest parts?
SLA. It prints smooth straight off the machine and takes paint well. SLS and MJF parts can be vapor smoothed for a sealed, smoother surface.
Can SLS and MJF parts be colored?
Yes. We dye SLS and MJF nylon parts with DyeMansion equipment and can also paint them.
Which is best for production parts?
For functional end-use parts, SLS or MJF nylon. For cosmetic production parts, SLA with finishing. Many products use more than one process.
How do I know which to choose?
Upload your CAD to our instant quote tool to compare options, or email orders@snlcreative.com and we’ll recommend a process for your part.
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Related services: SLS 3D printing · MJF 3D printing · SLA 3D printing · Vapor smoothing and dyeing
