SLS parts have high accuracy and good strength, which is always applied for functional parts. However, in reason of the nature powder based fusion in SLS, SLS parts normally have a powdery and grainy surface finish. So post processing techniques are available to increase surface finishes, and costing is normally applied to improve performance.
There are common SLS post processing methods as following:
|Finish type||Visual rank||Tolerance||Speed|
|Media tumbled & Vibro polish||Excellent||Medium||Medium|
|Spray paint & Lacquering||Excellent||Medium||Medium|
This is the most common finish for SLS parts. Compressed air is used to remove all powder form parts once printing finish, then apply plastic bead blasting to clean any un-sintered powder sticking on surface. This finish is rough like medium grit sandpaper or slight matte grainy, which is best surface preparation for painting or lacquering.
|Standard finish||Common finish otherwise specified|
High accuracy as overall geometry
|Matter, grainy surface|
Limited color option(typically white)
Media Tumbled & Vibro Polish
Media tumbled or vibro polish are applied for SLS parts, in order to polish parts into smoother surface texture. Small ceramic chips in a tumbler can vibrate against parts and erode outer surface to polished surface. In order to have less effect on part dimensions and get rounding sharp edges. However, it is not suitable for parts with fine details and intricate features.
|Media tumbled & Vibro polish||Excellent smooth surface|
Multiple parts in one process
Remove sharp edges
|Unsuitable for delicate features|
Remove sharp edges with negative effect on part geometry
Dyeing is the most cost-effective way to color SLS parts, the porosity in SLS parts are perfect for dyeing. In this process, SLS parts are immersed in a hot color bath with a wide range of available color, this color bath will guarantee full coverage of internal and external surface. However, the typical dye only penetrates parts with a depth of 0.5 mm, which means continued wear will expose the original powder color on surface.
|Dyeing||A wide range of colors|
Never affect part dimensions
Multiple parts in one process
Cost effectiveSuitable for complex geometries
|Dyeing penetration depth is only 0.5mm|
Not glossy finish
Spray Paint & Lacquering
SLS parts can be spray painted or coated with lacquer. These processes will make parts surface with various finishes, like high gloss, or metallic sheen. Lacquer coating can improve parts surface hardness, wear resistance, water tightness, and limit marks or smudges on parts surface. In reason of SLS parts nature porous, we recommend to apply 4-5 thin coats rather than 1 thick coat. This will increase the paint drying time and reduce the likelihood of paint moving.
|Spray paint & Lacquering||Improve mechanical properties|
Improve UV protection
Glossy smooth surface with color or clear
Impact overall dimensions
Require good surface preparation
Normal SLS parts have some inherent water resistance. Coating is always applied to enhance this properties. Silicones and vinyl-acrylates are verified to improve this properties greatly, while Polyurethane (PU) is not recommended. For complete water resistance, a dip coating method is required.
|Water-tightness||Further improve water resistance|
Improve mechanical strength
|Coating thick affect overall accuracy|
Electroplating can be applied of SLS parts, stainless steel, copper, nickel, gold and chrome are able to deposited on parts surface, in order to increase strength, electrical conductivity in shielding applications. Parts are cleaned and a conductive layer is applied on surface, then the parts go through traditional metal coating process.
|Metal coating||Improve strength and functionality|
Excellent aesthetic appearance
Excellent surface finish
|Increase lead time|
Increase cost greatly
High level of skill
Limited number of metals