Learn · Comparison

Vapor smoothing vs other finishing methods.

Vapor smoothing reflows the surface of a 3D printed polymer part with a controlled solvent vapor, so it smooths and seals in one automated step. The other common finishes work differently: media finishing, tumbling and sanding remove or flatten material, dyeing changes color, and coatings add a layer. In production they are often combined.

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Four ways a finish changes a printed surface Four cross-sections of the same rough printed surface. Abrasive finishing cuts the peaks down and leaves the pores open. Dyeing leaves the shape unchanged and colors the surface layer. A coating adds a layer on top. Vapor smoothing reflows the part's own surface into a smooth, closed skin. Section · printed surface Schematic · not to scale Abrasive Peaks cut pores open Dyeing Color in, shape unchanged Coating Layer added on top Vapor smoothing Own surface reflowed, sealed
DiagramThe same rough printed surface after four kinds of finish, drawn as sections. Schematic: shapes and sizes are illustrative.

Side by side

Six ways to finish a 3D printed part.

What each finish does to the surface, whether it seals the part, whether it reaches inside, and what it costs in labor. Vapor smoothing figures are AMT’s published results, with the material they were measured on.

Finishing methods for 3D printed polymer parts, compared
Question Vapor smoothing PostPro Media finishing Abrasive beads or grit Tumbling Vibratory, rotary Sanding Hand finishing Dyeing Dye bath Coating Paint, sealant
How it works A controlled solvent vapor reflows the outer skin in an automated cycle.1 Abrasive beads or grit are driven at the part with compressed air. Parts rotate or vibrate in a bowl of abrasive media. Abrasive paper, files and polishing by hand. Parts soak in a heated dye bath. A layer is sprayed, dipped or brushed on, then cured.
Surface after 13.42 → 1.18 µm22022 roughness on BASF Ultrasint TPU01 · HP MJF. Even and matte. Smoother, edges rounded. As smooth as the operator makes it, on faces they can reach. Texture unchanged, color through the surface layer. Whatever the coating gives.
Seals the surface Yes, with the part’s own material3 No No No No Yes, while the layer is intact
Internal channels Reached by the vapor1 Line of sight Barely No Where the dye flows Hard to coat evenly
Dimensions ≤ 0.4%42024 change on PA12 · voxeljet HSS. Removes a little material; edges soften. Rounds edges and fine detail. Depends on the operator. Geometry unchanged. Adds the layer’s thickness.
Labor Hang parts on a rack, start the recipe: 1.5–2 h1 per cycle on the SF50 and SF100. Manual cabinet or automated machine. Low touch, long cycles. High: every part, every face. Batch, with handling and rinsing. Masking, coating and curing.
Typical role End-use parts that are handled, worn, washed or must look molded. Cleaning and a uniform matte look; preparation for the next step. Robust parts without fine features. One-offs, show models, prototypes. Color, often together with smoothing. Color, UV or chemical protection, special surfaces.

YesPartlyNoResults depend on material, printer and recipe.

01Abrasive

Vapor smoothing vs media finishing

Media finishing fires abrasive beads or grit at a part. It cleans off loose powder and evens the surface into a uniform matte finish, which makes it a common step for powder-bed parts. What it does not do is close the surface: the pores between powder grains stay open, so the part still takes up water, dirt and dye.

Vapor smoothing starts where media finishing stops. It reflows the cleaned surface, so the pores close and the part comes out sealed and smoother. In a production cell the two are steps in one route: clean, then smooth.

02Color

Vapor smoothing vs dyeing, and combining them

Dyeing and vapor smoothing answer different questions. Dyeing decides the color of a part; vapor smoothing decides its surface. A dyed part keeps its rough, open texture, and a vapor-smoothed part comes out darker and more polished than it went in.5

That is why they are so often combined. Orthotics and prosthetics makers that vapor smooth their devices also offer custom colors and graphics on them.5,6 The best order of the two steps depends on the material and the dye, so ask an AMT engineer for your parts.

03Abrasive

Vapor smoothing vs tumbling and sanding

Tumbling smooths by wearing material away in a bowl of media. It needs little attention, but cycles are long, edges and fine detail round off, and nothing inside the part is touched. Sanding by hand can make a face very smooth, but the time grows with every face and every part, and the result depends on who holds the paper.

Vapor smoothing finishes every exposed surface at once, inside channels too, without removing material: dimensional change in AMT’s published tests was ≤ 0.4%42024 (PA12 · voxeljet HSS) and ≤ 0.4%72024 (PA2200 · SLS).

04Layer

Vapor smoothing vs coating and painting

A coating seals a part by adding a layer on top. It can bring color, UV or chemical protection, but it adds thickness, needs masking around fits and threads, and protects for as long as it stays intact: a chipped or worn coating opens the surface again.

Vapor smoothing seals with the part’s own material, so there is no layer to chip or peel, even on parts that flex, such as TPU seals and lattices. Where a coating is still needed, a smoothed surface is a cleaner base for it.

05Decide

Which finish for which job

  • A sealed, cleanable end-use part: vapor smoothing, dyed first or after if it needs color.
  • Color alone, on a part that is not handled or washed: dyeing.
  • A clean, matte prototype: media finishing.
  • A one-off show model: sanding and paint.
  • UV or chemical protection: a coating, ideally over a smoothed surface.
  • Machined plastic parts: vapor polishing.

Not sure? Send AMT a part and judge the finish in your hand. More terms in the glossary; the process itself in What is vapor smoothing?

Questions

Finishing methods: questions.

Short answers. For your own parts, ask an engineer.

Is vapor smoothing better than sanding?

For production parts, usually. Vapor smoothing finishes every exposed surface of a batch at once, seals it and barely changes dimensions, while sanding is manual, face by face, and leaves the surface open. For a single show model, sanding and paint can still make sense.

Can you dye parts and vapor smooth them?

Yes. Dyeing sets the color and vapor smoothing sets the surface, and the two are often combined. The best order depends on the material and the dye, so ask AMT for your parts.

Does a coating seal parts as well as vapor smoothing?

A coating seals while its layer is intact, but it adds thickness and can chip or wear through. Vapor smoothing seals with the part’s own material, so there is no separate layer to lose.

Which finish changes dimensions least?

Dyeing leaves geometry alone. Vapor smoothing changes it very little: ≤ 0.4%42024 on PA12 · voxeljet HSS parts in AMT’s published test. Abrasive methods remove material at edges, and coatings add a layer.

Does vapor smoothing make parts watertight?

It seals the surface, which is what keeps water out of the part’s pores. In AMT’s published test on PA2200 · SLS parts, the burst-pressure result was up to +7%72024. Whether a finished part holds pressure also depends on its design and wall thickness.

Next step

See the price. Run the numbers. Hold the part.

List prices are public and the cost-per-part math is yours to check, with no email needed for either. The free benchmark puts your own parts, vapor smoothed, in your hands.

  1. 01Quote

    Build your quote

    Pick a system and its options and get an itemized total on screen, from AMT’s published list prices.

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  2. 02ROI

    Calculate your ROI

    Compare your cost per part with manual finishing, using your own labor rate and volumes. Every assumption is editable.

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  3. 03Benchmark

    Test your parts, free

    Ship us your parts with a prepaid label. We vapor smooth them and send them back with before-and-after photos and a benchmark report.

    Test your parts, free

    No cost to evaluate · Parts returned · Typical turnaround 2–3 weeks8

Prices: AMT list prices, excluding tax and shipping; confirmed in your formal quote.

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