How both processes actually work
SLS, selective laser sintering, and MJF, multi jet fusion, are both powder-bed fusion processes for nylon. A thin layer of polymer powder is spread across the build area, and in SLS a CO2 laser scans and sinters the cross-section; in MJF an inkjet array deposits a fusing agent along the cross-section and infrared lamps fuse it.
Neither needs support structures, because the surrounding unsintered powder holds each part rigid during the build. After cooling, parts are extracted from the powder cake, cleaned, and optionally finished. The two share the same material family - PA 11 and PA 12 - but differ in heat source and speed.
When SLS is the better choice
Choose SLS when you need the widest material library - PA 12, PA 11, filled nylons, and specialty powders - or when full three-axis isotropy is required and batch size is small. Its simpler, mature machines are available from more service providers, which widens sourcing options.
SLS is also a strong default for functional prototypes, jigs, and low-volume spares where the uniform grain matters more than a mirror finish. If you may later need a different powder, SLS platforms tend to be more flexible.
When MJF wins
MJF generally builds faster and yields a smoother, more uniform grey surface with finer feature detail than SLS, which makes it attractive for enclosures, consumer-facing parts, and batches where appearance and throughput both count.
Its faster cycle and lower per-part cost at volume make MJF the economic pick for runs of a few dozen to hundreds of identical parts. When deadline and finish are both tight, MJF usually edges ahead.
Cost and the break-even point
For very small quantities both processes price similarly, driven mainly by build volume and powder consumption. The difference appears as quantity rises: MJF's faster builds and denser packing lower the per-part cost more steeply than SLS.
There is no hard tooling cost in either, so the break-even is not against molding but against each other. Roughly, once you move past a few dozen parts, MJF's throughput advantage often makes it cheaper per piece; below that, SLS stays competitive.
Tolerances, accuracy and materials
Both hold typical nylon tolerances around plus or minus 0.3 mm on small parts, with accuracy influenced by part orientation, packing density, and cooling. Dimensional stability is good, and features like snap fits and living hinges print reliably in either process.
Material choice is where they diverge most: SLS offers more powder variants and colors, while MJF concentrates on a tighter, optimized set, notably PA 12, with very consistent mechanical results. Pick the process that carries the powder your application needs.
Surface finish and post-processing
MJF parts emerge with a fine, uniform, slightly sandy grey surface and minimal visible layering; SLS shows a faint grain and a marginally rougher touch. Both accept dyeing, media blasting, smoothing, and painting to reach a cleaner or colored look.
If the part is visible to end users, MJF often needs less post-work to look finished, saving time and cost. For hidden structural parts, the difference is cosmetic only and either process is fine as-printed.
Lead time and iteration speed
Both are fast from file to part - typically days, not weeks - because there is no tooling and no programming beyond part layout. Design changes are cheap: revise the model and reprint, with no mold to modify.
MJF's faster build cycle can shorten a given batch's turnaround, especially when many parts share one build. For rapid design spirals, either process lets you print, test, and revise within the same week.
Strength, isotropy and end-use suitability
Both produce isotropic nylon with similar tensile, flexural, and impact strength, far more uniform than FDM printing. Parts are tough, chemical-resistant, and suitable for end-use in many non-food, non-medical applications.
SLS is uniform in all axes; MJF can show a small variation in the Z, build, direction, though in practice it remains strong and is widely used for functional and semi-structural parts. Neither matches CNC metal for load-bearing duty.
Typical applications by industry
Robotics and automation use both for brackets, enclosures, and end-effector tools; automotive and aerospace use them for lightweight ducting, clips, and interior components where consolidation of assemblies saves weight.
Consumer product teams print housings and wearables; medical and dental labs use biocompatible nylons for guides and devices under appropriate certification. The support-free capability makes complex one-piece parts routine.
A practical decision checklist
Ask: Do I need a specific powder only SLS offers? Is the batch very small? Then SLS. Do I need the smoothest finish, fastest turnaround, and dozens-plus of parts? Then MJF. If both are close, let cost per part decide.
Also weigh color and material availability, and whether Z-direction uniformity is critical. When unsure, request quotes for both from the same model and compare delivered price, finish, and lead time.
How FabProto supports both processes
FabProto runs industrial SLS and MJF under one roof, so you are not locked to one technology. Send a CAD model and we will recommend the process that fits your quantity, finish, and material, then return a clear cost and tolerance comparison.
That dual capability means we can start you on SLS for early low-volume validation and shift to MJF as your batch grows - or vice versa - without changing partners. One source, both nylon powder processes, the right part every stage.