Vapor Smoothing
Chemical vapor process that smooths the surface of 3D printed nylon and ABS parts. Seals porosity, improves aesthetics, and creates a semi-gloss appearance without dimensional distortion.
About Vapor Smoothing
Vapor smoothing is a chemical surface finishing process specifically designed for 3D printed polymer parts, most commonly produced by Selective Laser Sintering (SLS) and Fused Deposition Modeling (FDM). The process exposes parts to a controlled chemical vapor that selectively melts and redistributes the outermost layer of the plastic surface. This action eliminates the characteristic layer lines, staircase effects, and surface roughness inherent to additive manufacturing, producing a smooth, sealed, semi-gloss surface that closely resembles injection-molded quality.
Vapor smoothing is the preferred finishing method for 3D printed parts that require improved aesthetics, sealed porosity, or enhanced mechanical performance. The sealed surface prevents moisture absorption, gas permeation, and bacterial growth, making it essential for fluid-handling components, food-contact parts, and medical devices. The smoothing process also improves the fatigue life and elongation at break of SLS nylon parts by eliminating stress-concentrating surface defects and inter-layer voids.
The process is highly repeatable and can be applied to complex geometries, internal channels, and undercuts that would be impossible to reach with mechanical polishing or bead blasting. Parts maintain their dimensional accuracy within 0.1 mm, as the smoothing only affects the outermost 50-100 µm of material through redistribution rather than removal. This makes vapor smoothing suitable for functional prototypes, end-use parts, and short-run production where both appearance and dimensional accuracy are important.
Finish Properties
How It Works
Vapor smoothing is performed in a sealed, temperature-controlled processing chamber. Parts are placed inside the chamber, which is then filled with a vaporized solvent specific to the target polymer—typically a proprietary blend of fluorinated solvents for nylon (PA12, PA11) or acetone-based vapor for ABS. The chemical vapor condenses on the cooler part surfaces, forming a thin liquid film that dissolves the outermost layer of plastic. Surface tension causes this liquid to flow from peaks into valleys, effectively leveling the surface topography and eliminating layer lines. After a precisely timed exposure (typically 5-30 minutes depending on part geometry and desired smoothness), the vapor is evacuated and the parts are cooled, causing the redistributed surface to solidify into a smooth, sealed, semi-gloss finish. The entire process is automated and monitored to ensure consistent results.
Design Guidelines for Vapor Smoothing
Design minimum wall thickness of 1.0 mm for vapor-smoothed parts—thinner walls may warp or become translucent during the smoothing process as the solvent penetrates too deeply.
Avoid sharp edges and fine details smaller than 0.5 mm, as vapor smoothing will round and soften these features through surface redistribution.
Orient parts during 3D printing to minimize support contact points on cosmetic surfaces, as support witness marks may remain visible even after vapor smoothing.
Account for the sealed surface when designing fluid-handling parts—vapor smoothing seals the inherent porosity of SLS parts, enabling pressure-tight applications up to approximately 3-6 bar.
Text and engravings should have a minimum depth of 0.5 mm and width of 1.0 mm to remain legible after smoothing, as the process will soften and partially fill shallow features.
Compatible Materials
Materials that can be finished with vapor smoothing.
Vapor Smoothing FAQ
Vapor smoothing generally improves the mechanical properties of 3D printed parts. By sealing porosity and eliminating inter-layer voids, the process increases elongation at break by 20-50% and improves fatigue life. Tensile strength and stiffness remain largely unchanged. The sealed surface also reduces moisture absorption in nylon parts, maintaining dimensional stability and mechanical performance in humid environments.
Vapor smoothing is most effective on SLS nylon (PA12, PA11, PA12-GF), FDM/SLA ABS, and certain TPU elastomers. Each material requires a specific solvent chemistry. It is not compatible with PLA, PETG, polycarbonate, or resin-based (SLA/DLP) photopolymers. Metal 3D printed parts cannot be vapor smoothed. Always confirm material compatibility before specifying vapor smoothing in your project requirements.
Vapor smoothing is faster, more consistent, and reaches internal features that are inaccessible to sanding or tumble media. Manual sanding is labor-intensive, inconsistent, and can alter part dimensions. Tumble finishing works well for external surfaces of robust parts but cannot smooth internal channels or delicate features. Vapor smoothing produces a more uniform result across complex geometries in a fraction of the time, though at higher per-batch cost than tumble finishing.
Yes. Vapor-smoothed parts accept dyes and paints well. The smooth, sealed surface provides excellent adhesion for spray painting, and the elimination of porosity prevents paint from being absorbed unevenly. For SLS nylon parts, dyeing before vapor smoothing produces richer, more uniform colors as the dye penetrates the porous structure before sealing. Painting after vapor smoothing is recommended when an exact color match to a RAL or Pantone standard is required.
Vapor smoothing typically changes dimensions by less than 0.1 mm. The process redistributes surface material rather than adding or removing it, so the net dimensional change is minimal. However, sharp edges and fine features may experience slightly more rounding (up to 0.2 mm). For parts with tight tolerances (±0.05 mm or less), critical dimensions should be verified after smoothing on a first-article sample.
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