SLS Design Guidelines

Our EOS SLS machines (EOS P396 and EOS P110 Velocis) offer a maximum build volume of 340 x 340 x 600 mm (13.4 x 13.4 x 23.6 in), allowing for the production of both small, intricate components and large, durable parts. They operate with a standard layer thickness of 100 µm, ensuring fine detail resolution while maintaining efficiency.

CriticalParts designed with large flat planes will likely warp, so this should be avoided if tight tolerances are required.

If your parts require specific tolerances, please include an engineering drawing along with the part. Parts designed with large flat planes will likely warp, so this should be avoided if tight tolerances are required.

NoteTolerances differ for TPU. Tight tolerances or axis-specific requirements available on review.

The layer height is the overall Z resolution of the part; we avoid stepping artifacts on important features of your models by orienting the part(s) along the Z plane or at a 20 degree angle on all sides. Our EOS SLS printers (P396 and P110 Velocis) support layer heights of 60 µm, 100 µm (standard), and 120 µm, allowing for a balance between detail and print speed. Lower layer heights produce finer details and smoother surfaces but increase print time, making them ideal for precision components.

SLS parts feature a uniform, matte finish with a fine, powdery texture, making them ideal for functional prototypes and end-use applications. The self-supporting nature of SLS eliminates the need for support structures, ensuring consistent quality and design freedom without post-removal marks. The surface is naturally durable and can be further enhanced through bead blasting, tumbling, or vapor smoothing for a refined aesthetic and improved performance.

Supported walls, which are connected on at least two sides and thick enough to support the model, require a minimum thickness of 0.8 mm (0.017"). For optimal strength and durability, we strongly recommend 0.8 mm – 1.0 mm to ensure sufficient rigidity and structural integrity.

CriticalWalls thinner than 0.45 mm may experience over-sintering, where excess laser energy causes unintended thickening, leading to loss of detail and potential warping.

Unsupported walls are those extending freely without additional support—a minimum thickness of 1.5 mm (0.059") is required to maintain structural stability. Thinner unsupported walls are prone to warping, bending, or breaking due to thermal stresses during the sintering process.

Freestanding features such as pins require a minimum diameter of 0.8 mm (0.031") to ensure structural integrity and printability. Pins below this threshold may become fragile, prone to breakage, or fail to print accurately due to the sintering process and powder removal.

Engraved details are recessed features designed into a model, requiring a minimum width and depth of 0.5 mm (0.019") to ensure clarity and visibility. Features smaller than this may become partially or completely filled with unsintered powder, leading to closed gaps and loss of detail during post-processing.

Embossed details are raised features on a model, generally resolving better than engraved details due to their prominence above the surface. To ensure clarity and definition, embossed details should have a minimum width and depth of 0.5 mm (0.019").

NoteExtruded text requires at least 1.5 mm (0.059") thickness when printed flat and 2 mm (0.079") when printed vertically to maintain legibility.

For legible and well-defined text, a minimum line thickness and depth of 0.5 mm (0.019") or a minimum font size of 14pt is recommended for all orientations. Text smaller than this may lose sharpness, become illegible, or blend into the surface.

Clearance refers to the gap between moving or interlocking parts, such as hinges, joints, and mating components, ensuring they function properly without fusing together during printing. A minimum clearance of 0.5 mm (0.019") is required to prevent parts from sintering together.

CriticalInsufficient clearance can lead to tight fits, difficulty in assembly, or complete bonding of parts, while excessive clearance may cause looseness or instability.

For a secure press fit, a minimum offset of 0.1 mm (0.004") is recommended to allow parts to fit together tightly without requiring adhesives or fasteners. Adding a chamfer or slight taper at the leading edge helps guide the parts into place more smoothly.

SLS 3D Printing allows for the printing of fully assembled mechanical linkages, such as hinges, chains, and moving joints, in a single build without the need for assembly. To ensure free movement and prevent parts from fusing together during sintering, a minimum clearance of 0.6 mm (0.023") is required.

Minimum hole diameter varies based on wall thickness to ensure proper powder removal and dimensional accuracy.

Minimum gap size varies based on wall thickness to ensure proper powder removal and prevent fusing.

Escape holes are essential for removing unsintered powder from hollow or enclosed parts. A minimum hole diameter of 4 mm (0.157") is required when using a single escape hole to allow efficient powder removal.

TipFor larger parts exceeding 50 mm x 50 mm x 50 mm, at least two escape holes are recommended, each with a minimum diameter of 2 mm (0.078").

Fillets are smooth, rounded transitions between surfaces that help reduce stress concentrations, improve part strength, and enhance durability, especially in load-bearing or high-stress areas. Sharp corners can act as weak points where stress builds up.

Bosses and ribs are structural reinforcements that enhance strength, stiffness, and durability while keeping material usage efficient. These features are particularly valuable in thin-walled or load-bearing components.

SLS does not require support structures since parts are fully supported by the unsintered powder in the build chamber. This allows for complex geometries, overhangs, and internal features without additional material or post-processing to remove supports.

TipFreedom in design enables lightweight, intricate, and fully functional parts with minimal post-processing.

Unlike FDM, SLS parts are always produced with solid walls, as the process does not use variable infill patterns. The entire part is built with fully sintered material, ensuring consistent mechanical strength, durability, and density.

NoteHollow sections can be designed with escape holes to remove unsintered material, reducing weight without compromising structural integrity.

For functional, reliable threading, we recommend using M6 thread sizes or larger and employing thread profiles designed for plastics to accommodate the unique properties of SLS-printed parts.

For strong, functional threads, parts should be designed with holes sized for tapping or center marks for drilling pre-tapped holes. Ensure sufficient wall thickness is maintained around tapped holes, especially in load-bearing areas.

NoteUnlike FDM, SLS prints are isotropic, meaning layers bond more uniformly, reducing the risk of thread delamination.

Threaded inserts can be glued in or heat-set for stronger, more durable connections. Heat-set inserts require a soldering iron with an installation tip, which softens the plastic walls as the metal insert is pressed in.

For parts larger than the build volume, designs can be split in CAD and printed in multiple sections, then glued, press-fit, or mechanically joined. Adding alignment features like tongue-and-groove joints ensures precise positioning.

SLS-printed parts can be machined using traditional or CNC equipment to achieve tighter tolerances, smoother surfaces, and precise fitments. This is particularly useful for critical features such as bearing surfaces, threaded holes, or mating components.

SLS parts are naturally white when printed but can be dyed black for a uniform appearance. Additional coatings, such as lacquers, varnishes, or clear coats, offer custom finishes while enhancing durability and performance.

Vapor smoothing is not applicable for Selective Laser Sintered parts.

NoteOther post-processing methods like bead blasting or tumbling can be used to improve surface finish.