FDM vs SLA vs SLS vs MJF: a plain-language comparison

Ask three print services for a quote on the same part and you can get back three different acronyms with no explanation of what any of them mean for your part. Here’s the plain version, technology by technology.

FDM is the cheapest and most common. A nozzle extrudes melted filament layer by layer; most desktop printers use it, and it’s what most online services default to for a low-cost quote. The tradeoff is layer adhesion: strength along the layer direction is fine, strength across layers is the weak point, and parts can delaminate there under load. Finish is the coarsest of the four unless you pay for post-processing. Good for prototypes, brackets, jigs, and anything where cost matters more than surface finish.

The same bracket in all four clips, built from its real slices. FDM draws each outline before the infill and puts a lattice under the arm, whose flat underside would otherwise print in mid-air. Drawn as 38 layers, 4× thick; at 0.2 mm it would be about 150.

SLA cures liquid resin with a laser, layer by layer, and the jump in surface quality over FDM is immediate: smooth surfaces, sharp edges, fine detail. What you give up is toughness. Depending on resin, SLA parts run more brittle than FDM plastics, so it suits presentation models, dental and medical models, and anything where how it looks matters more than what load it carries.

This is MSLA, the resin process on most desktop machines, which cures with a screen where SLA proper uses a laser. The screen cures the whole slice in one exposure; the plate then peels up and comes back one layer higher, so the part grows upside down.

SLS fuses powdered nylon with a laser. No supports needed, since unsintered powder holds the part up as it prints, which is part of why it handles complex geometry well. It’s a step up in cost from FDM and SLA, and it’s the one most often chosen for functional end-use parts that actually have to survive mechanical stress in a small production run.

A blade spreads the nylon powder and the laser draws the outline, then the hatch, turning the hatch 67° every layer so the lines never stack. The loose powder holds the arm up while it prints. No supports anywhere.

MJF is HP’s powder-bed process: same general idea as SLS, but inkjet arrays and printing agents do the fusing instead of a laser, and it prints noticeably faster in raw throughput. Cost sits around SLS or slightly above it. Where SLS and MJF actually differ on strength, density, and consistency is not a one-line answer, and we’ve written the sourced version of that comparison separately rather than compress it into a bullet here: SLS vs MJF: what the published research actually shows.

MJF starts from the same powder bed. The printhead lays fusing agent only where the slice is, and the dark agent soaks up the lamp's heat while bare powder doesn't, so a layer takes one pass however much of it is part.

Technology	Cost	Best for
FDM	Lowest	Prototypes, brackets, jigs, cost-sensitive parts
SLA	Mid-range	Presentation models, dental/medical models, fine detail
SLS	Higher	Functional end-use parts, complex geometry, small runs
MJF	Comparable to SLS	Same as SLS, plus higher-volume orders where print speed matters

None of this tells you what a specific provider will charge for your part; that depends on volume, complexity, and the vendor’s own pricing model, which is what we’re building the comparison tool for. If you’ve already got quotes using different technologies and want a check on whether the tech actually fits your part’s requirements, that’s worth asking before you order, not after.