Post Processing for SLA Parts

Jack Lie CNC machining expert

Specialize in CNC Milling, CNC Turning, 3D Printing, Urethane Casting, and Sheet Metal Fabrication Services.

SLA is able to produce very fine details and features as small as 0.3 mm. This technology always produce very small parts, and require orientation at an angle. This need support structures to attache on the parts surface, leave marks on surface and create uneven surfaces. However, most SLA resins are easily post processed. SLA parts are suitable for a wide range of finishing options, we will describe the most common ways as following:

Finish typeVisual rankToleranceSpeedApplied area
Basic removalLowMediumHighAll SLA parts
Nibs sandingLowMediumMediumAll SLA parts
Wet sandingMediumMediumMediumAll SLA parts
Mineral oil finishMediumMediumMediumAll SLA parts
Spray paintingGoodLowLowAll SLA parts
Clear transparent polishingExcellentLowLowClear resin parts

Basic Removal

Process: support structure is cut off or broken form SLA parts, and leave a bumpy surface with support materials. High quality surface requires at least 0.1mm extra materials, then sanding afterwards for better dimensional accuracy.

Finish typeAdvantageDisadvantage
Basic removalComplete control of finishes

Drilling on vertical for high accuracy

High accuracy for overall geometry
Not aesthetic

High level of skills

Nibs Sanding

Process: only small support nibs need to be sanded. This process is most suitable for flat surface. In reason of this process only sand support nibs area, there is no effect on the overall geometries.

Finish typeAdvantageDisadvantage
Nibs sandingAccurate surface

Matte finish
Uneven surface on side area

Not aesthetic

Wet Sanding

Process: Wet sanding is able to provide the smoothest surface finish, which depend on sandpaper graduations. On unsupported side, we just need to sand the build lines, this process only require a single high grade sandpaper. On supported side, this process is more labor intensive, it requires at least 4 sandpaper graduations. So we recommend that the support structure should be placed on the least visible part. There will be some accuracy loss as materials is removed at support placement.

Finish typeAdvantageDisadvantage
Wet sandingExcellent smooth finish

Perfect for complex geometries

Best surface preparation for painting
Lower accuracy at supported area

Result white or light spots

Mineral Oil Finish

Process: This process is similar to wet sanding, just add a mineral oil layer after sanding process. This mineral oil will hide the white or light spot on parts surface, in order to create a nice even finish. This surface finish is most suitable for mechanical parts with fiction reducing and surface lubrication.

Finish typeAdvantageDisadvantage
Mineral oil finishSemi transparent finish for clear resins Not suitable for paint adhesion

Spray Painting

Process: Spray painting will conceal layer lines, in order to reducing the sanding of unsupported area. In addition, it will also limit UV exposure, and avoid yellowing and post curing on parts. Acrylic paint cannot adhere well on flexible resin surface, so a glossy thin layer will need on parts surface. However, this will affect parts tolerance and details dramatically.

Finish typeAdvantageDisadvantage
Spray paintingClear finish on complex geometries

UV protection
Orange peel on surface

Increase overall dimensions

Not suitable for sliding or moving parts

Clear Transparent Polishing

Process: SLA parts will be sanded by increased grit levels of sandpaper, then polished with polishing compound. This will get the most clear surface, but it is very time consuming and only possible for easy sanding surfaces. This finish is most suitable for simple shapes with less details, but less suitable for complex geometries parts.

Finish typeAdvantageDisadvantage
Clear transparent polishingClear finish

Very smooth surface
Labor intensive

Not suitable for complex geometries