SLS and MJF 3D printing: how it works, costs and design rules

Powder bed fusion prints strong nylon parts without support structures. Selective laser sintering (SLS) and HP Multi Jet Fusion (MJF) are used for functional prototypes, low-volume production parts, housings and clips.

Typical tolerance

±0.3 mm or ±0.3% of the size

Quantities

1 to several thousand

Lead time

3–7 working days

Materials

PA12, PA11, glass-filled PA, TPU

How it works

A thin layer of nylon powder is spread over the bed and fused where the part should be, by a laser (SLS) or by inkjet agents and infrared heat (MJF). Unfused powder supports the part, so overhangs are free.

Benefits

• Strong, durable nylon parts close to moulded properties.
• No supports, so complex and nested designs are possible.
• Economical for batches of hundreds when parts are packed together.

Limitations

• Slightly grainy surface (can be smoothed or dyed).
• Large flat parts may warp.
• Trapped powder must be able to escape.

What drives the cost

• Part volume and bounding box height in the build.
• Finishing such as dyeing, vapour smoothing or painting.

Design rules

• Walls at least 0.8–1 mm.
• Add escape holes (5 mm or more) to closed hollow parts.
• Leave 0.4–0.5 mm clearance between moving parts printed together.

Preparing your STEP file

• Export STEP in millimetres.
• Combine small parts into one order; the build is priced on volume, not count.

See also the full STEP export checklist and the comparison of all processes.