Selective laser sintering fuses nylon powder layer by layer in a heated chamber, and the surrounding unfused powder supports the part. That single fact, no supports, changes what can be made and how it is priced: parts nest in three dimensions throughout the build volume, so the machine hour is shared among everything in the box.
Why it is the functional default
Sintered nylon parts behave enough like moulded ones to test with. Snap fits snap, living hinges flex, clips clip, threads take a screw. Properties are reasonably consistent in every direction compared with filament printing, so a part that survives a test is telling you something about the design rather than about the build orientation.
Pricing and packing
The machine sells build volume rather than part volume, so a full box is much cheaper per part than a nearly empty one. Bureaux run shared builds, which is why lead times cluster around when the next box goes in. Ordering several parts, or several copies, rides the same build and costs far less than ordering them one at a time across separate builds.
Surface and appearance
The as sintered surface is matte and slightly grainy, which suits functional parts and disappoints on appearance models. Bead blasting evens it out. Dyeing, usually black, is cheap and gives a uniform colour. Vapour smoothing produces a sealed, near moulded finish and is worth asking about where the part is handled or must be cleaned.
Limits
Dimensional accuracy varies across a densely packed build because thermal history differs by position. Very thin walls are fragile. Trapped powder must be able to escape, so fully enclosed voids need drain holes. And the material is nylon, which absorbs moisture and changes dimension and properties with it, exactly as moulded nylon does.
Questions people ask about sls printing service
Does SLS need supports?
No. The unfused powder supports the part, which is why geometry can be freer and parts can be nested throughout the build volume.
How strong are SLS parts?
Strong enough to test functionally. They behave much more like moulded nylon than filament printed parts do, and they are far more consistent between directions.
Why is my quote cheaper for ten than for one?
Because the machine sells build volume. Ten parts in one box share the build, so the marginal cost of each additional part is small.
Can SLS parts be finished?
Yes. Bead blasting, dyeing and vapour smoothing are all common, with vapour smoothing giving a sealed near moulded surface.