How to design parts for SLS printing

For PA12 Formlabs specifies minimum 0.6 mm for vertical wall and 0.3 mm for horizontal. These are printing limits, not the finished dimension of a loaded wall. A thin wall may exit the chamber correctly, then bend during assembly.

In the working part, mark bending locations and mounting points. There, match the cross-section to the force, and guide thickness changes gently. Rounding at the base of a pin or a rib on a long wall limits local stresses. A freestanding pin should have at least 0.8 mm diameter according to specifications.

Powder surrounds the part during printing and remains in enclosed cavities. For a hollow housing or internal channel, provide access to the interior. Formlabs recommends at least two powder drain holes, each with a minimum diameter of 3.5 mm each. Place them so that powder can be poured out, air can reach the interior, and cleaning tools can enter.

A long curved channel may trap powder despite having two openings. For functional channels, show us the cross-section or CAD model before series production. Access to the interior determines the possibility of inspection after cleaning.

The recommended minimum diameter for a standard hole is 1.0 mm. The finished hole dimension also depends on the wall thickness through which it passes. If the hole is to define an axis or accept a screw with a precise fit, plan for drilling or reaming after printing. Formlabs recommends a pilot hole in such cases.

For assembled parts after printing, the PA12 specification provides clearance 0.2 mm for contact areas below 20 mm² and 0.4 mm for larger contact areas. A mechanism printed entirely requires 0.3 mm or 0.6 mm. This is the distance between surfaces, not an allowance on each element.

For snap-fit, sliding bearing, or sealed joints, make a fit sample before the full series. Other powders, including PA11 and TPU 90A, have their own clearance requirements.

A large thin plate with a sudden thickness jump accumulates stress during cooling. Maintain as uniform wall thickness as possible, and increase stiffness with ribs or by changing the cross-section shape. Reinforce long, narrow protrusions at their base.

Placement in the chamber also matters. Formlabs recommends a slight tilt for wide, flat parts as a way to limit warpage. Leave orientation selection for the build preparation stage; mark in your inquiry the surfaces where flatness and appearance are critical.

Raised letters should have a minimum height of 4.5 mm and engraved letters 3.0 mm. For both, Formlabs specifies 0.3 mm protrusion or groove depth. After cleaning and surface treatment, the smallest details may lose sharpness.

Place the part number on a surface easily accessible for cleaning. Do not place it on a mating plane or sliding surface. For serial delivery, such a number facilitates identification without a separate label.

Check mesh integrity, units in millimetres and dimensions. The preliminary PA12 size limit in the calculator is 159.8 × 159.8 × 295.5 mm. We confirm print feasibility and part orientation after reviewing the model. Specify required tolerances, mounting surfaces and areas where powder must not remain in your enquiry.

If the part must mate with an existing component, attach a drawing with critical dimensions. The STL describes nominal geometry but does not indicate which fit must be verified after printing.