SLS & MJF | Post-Production Finishing
Vapor Smoothing & Deep-Dye Coloring for SLS and MJF Parts
Surface finish and color are part of the manufacturing specification. Plan them alongside geometry, material, tolerances, and inspection requirements before releasing a part for production.
SNL Creative provides in-house vapor smoothing with the DyeMansion Powerfuse S and deep-dye coloring with the DyeMansion DM60. This guide covers PA 12 parts produced by SLS and MJF, with material-specific review for SLS TPU 1301.
Why finish a powder-bed printed part?
After depowdering, SLS and MJF parts retain a textured surface. That texture may be acceptable for a fixture or internal bracket, but a handled enclosure, visible housing, or fluid-contact component can have different surface requirements. Finishing is selected to meet those requirements; it is not mandatory for every printed part.
Vapor smoothing / VaporFuse Surfacing
A controlled vapor process reflows the outer polymer surface, reducing roughness and accessible surface porosity. It can produce a smoother touch and a more uniform, molded-like appearance.
Reduced surface texture can make cleaning easier and reduce places where dirt collects. Surface sealing can support fluid-handling applications, subject to part-specific validation.
Surface treatment does not make a part injection molded or change its manufacturing origin. A leak-tight, pressure-rated, food-contact, or other qualified application requires evaluation of the complete part and process.
Deep-dye coloring
Dye penetrates the near-surface polymer rather than forming a separate paint film. It adds color without the film build of a coating and avoids paint-layer peeling.
Color can identify variants, distinguish assemblies, and define the appearance of a finished product. Dyeing alone does not smooth the printed texture.
Dye is not bulk coloration through the full wall. Deep scratches or machining can expose the underlying material. UV, chemical, and abrasion performance depend on the material, dye, environment, and use.
Choose the finish by the required result
| Finish route | Result | Review before production |
|---|---|---|
| Cleaned / blasted | Printed texture remains; typically matte. | Powder removal, handling requirements, and acceptable surface texture. |
| Deep-dyed | Color is added while printed texture remains. | Base color, dye compatibility, color reference, and sample approval. |
| Vapor-smoothed | Smoother surface and altered sheen. | Thin features, fine detail, critical fits, and required surface performance. |
| Smoothed + dyed | Combined surface and color treatment. | Approve the complete process sequence and inspect after final finishing. |
| Custom coated | Specified coating appearance or function. | Coating thickness, masking, adhesion, and final dimensions. |
Before and after: illustrative comparison
Finished-part examples
These are finished-part examples, not a matched before-and-after comparison. Compare approved samples of the same geometry and material under consistent lighting when defining a production finish.
Deep-dye color reference
Standard color references below follow the existing SNL Creative PA2200 / PA 12 palette. They are visual references, not measured acceptance standards.
White 09 is a palette reference for a compatible white base; it is not a promise that grey MJF parts can be dyed white. Screen colors are approximate.
DfAM: design for the finished part
The following are engineering review points for the complete print-and-finish route. There is no universal minimum wall thickness or dimensional allowance that applies to every material, geometry, and smoothing recipe.
| Feature | What to evaluate | Planning action |
|---|---|---|
| Thin walls, fins & lattices | Fragile features can be sensitive to handling and surface reflow. Thin or translucent walls can also show color differences. | Review local wall thickness and handling; qualify representative features with the intended recipe. |
| Sharp edges, texture & lettering | Smoothing can soften edges or change the visibility of fine detail. | Identify details to preserve and approve a finished sample. |
| Holes, threads & mating fits | Final dimensions and fit must account for the finishing route. | Specify final tolerances; agree any machining, masking, or compensation before printing. |
| Sealing faces & critical surfaces | A smooth appearance alone does not establish a seal. | Mark functional surfaces; inspect dimensions and test leakage under operating conditions. |
| Channels & cavities | Powder removal, process access, drainage, and drying depend on geometry. Trapped air can prevent dye contact; enclosed cavities can cause parts to float in the dye bath. | Provide accessible openings, consider rounded internal corners, and review internal surfaces before design release. |
| Visible faces & contact locations | Orientation, handling, and processing contact can influence appearance. | Identify cosmetic faces and acceptable contact locations on drawings. |
| TPU flexible features | Texture, feel, and functional response must be evaluated in the final condition. | Test flexibility, fit, and appearance after the complete finish route. |
Plan finishing into production
- Define requirements. Supply CAD, material, quantity, final tolerances, cosmetic faces, color reference, and operating conditions.
- Review the process route. Agree cleaning, surface treatment, dyeing, coatings, machining, and assembly sequence. Smoothing and dyeing order is established for the qualified route.
- Approve representative finished samples. Include thin walls, fine details, mating features, and the intended color. Evaluate appearance and fit after all finishing steps.
- Set acceptance criteria. Define color and sheen reference, inspection lighting, dimensions, and application-specific tests. Measure roughness or color difference where the specification requires it.
- Release the complete route. Record the approved material and finish, allow time for sampling and drying, and inspect production parts in their final condition.
Including finishing in DfAM helps identify dimensional and cosmetic risks before production, reducing the likelihood of rework after parts have already been printed.
Common questions
Does vapor smoothing make every part waterproof?
No. It can reduce surface porosity, but wall thickness, geometry, material, joints, and processing affect performance. Qualify the complete part for the required fluid, pressure, temperature, and duration.
Is deep dye the same as paint?
No. Dye colors the near-surface polymer; paint creates a separate film. Dye does not provide every protective or functional property of a coating.
Can the same color specification be used for SLS and MJF?
The same target reference can be requested, but the different base colors and material/finish combinations require separate sample approval.
When should finishing be specified?
During design and quoting, before geometry and tolerances are released. Final acceptance should be based on the finished part.
Related capabilities
Process references: DyeMansion Print-to-Product and color guidance; DyeMansion VaporFuse Surfacing and DyeMansion color database. Manufacturer examples do not establish part-specific acceptance values.
