Introduction
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 |
| Standard | Poor | High | High |
| Media tumbled & Vibro polish | Excellent | Medium | Medium |
| Dyeing | Medium | High | Medium |
| Spray paint & Lacquering | Excellent | Medium | Medium |
| Water-tightness | Medium | Medium | Medium |
| Metal coating | Excellent | Medium | Low |
Standard Finish
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.
| Finish type | Advantage | Disadvantage |
| Standard finish | Common finish otherwise specified
High accuracy as overall geometry Low cost |
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.
| Finish type | Advantage | Disadvantage |
| 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
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.
| Finish type | Advantage | Disadvantage |
| 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.
| Finish type | Advantage | Disadvantage |
| Spray paint & Lacquering | Improve mechanical properties
Improve UV protection Glossy smooth surface with color or clear |
Labor intensive
Impact overall dimensions Require good surface preparation |
Water-tightness
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.
| Finish type | Advantage | Disadvantage |
| Water-tightness | Further improve water resistance
Improve mechanical strength |
Coating thick affect overall accuracy |
Metal Coating
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.
| Finish type | Advantage | Disadvantage |
| Metal coating | Improve strength and functionality
Excellent aesthetic appearance Part conductivity Excellent surface finish |
Increase lead time
Increase cost greatly High level of skill Limited number of metals |