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Vapor Smoothing

3D-print & moulding post-processing · Chemical bath

Vapor smoothing briefly softens the outer skin of compatible powder-bed polymers so surface peaks flow together.

3D printingPremium cost $$$Unchanged
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Vapor Smoothing on a machined part

What is Vapor smoothing?

Qualified systems are used on PA12 and PA11 MJF or SLS parts and selected TPU grades.

How it works

Parts are exposed in a controlled chamber to a solvent vapor matched to the polymer. A shallow surface layer swells and reflows, reducing powder texture and partially sealing connected surface porosity; controlled drying removes residual solvent. Typical finished Ra is about 0.8–6.3 µm (32–250 µin), compared with rougher as-printed powder-bed surfaces. Exposure, drainage, geometry, dye, and exact polymer grade require a validated recipe.

Why specify it

  • Reduces Ra to about 0.8–6.3 µm (32–250 µin)
  • Improves cleanability and gloss
  • Can reduce surface-connected porosity
  • Reaches complex external geometry

Where it falls short

  • Only works with qualified polymer and chemistry pairs
  • Rounds fine texture and small edges
  • Can trap condensate in cavities
  • Does not guarantee pressure tightness

Vapor smoothing at a glance

Vapor smoothing is strongest on cosmetic quality (80 of 100), at a premium cost. Corrosion protection and surface hardness are not rated: a plastic part does not corrode, and the finish leaves the part's own surface.

Corrosion protectionNot rated—
Surface hardnessNot rated—
Cosmetic qualityVery good80 / 100
LubricityFair35 / 100
Relative costPremium55 / 100
CorrosionHardnessCosmeticLubricityEconomy

Each score is 0–100 against every finish in this catalog. Corrosion comes from salt-spray life (ASTM B117, log scale) and hardness from the finish layer's Vickers or pencil hardness; cosmetic, lubricity and cost are FabDigit's engineering assessment. Economy on the radar is the inverse of cost.

Vapor smoothing key numbers

Typical values from the governing specifications and shop practice; bars are this finish against the highest value among 3d-print & moulding post-processing finishes.

Thickness0 µm0 mil
Thickness
No deposited coating; typical finished Ra 0.8–6.3 µm (32–250 µin).
Electrical
Unchanged
Appearance
Smoother satin to glossy polymer surface with reduced powder grain.

Specifications for Vapor smoothing

The documents a drawing cites to define this finish, with the Type / Class rows that apply. Each links to a page explaining the standard.

Drawing call-out

VAPOR SMOOTH MJF PA12 EXTERNAL SURFACES TO Ra 3.2 µm MAX; MASK DATUM A AND THREADS; NO POOLING OR BLOCKED PASSAGES

Which materials take Vapor smoothing?

Verdict per material family, with the grades that behave differently. Each family links to its datasheets in the material library.

Material familyVerdictNotes
MJF
YesPA12 and selected PA11 or TPU grades are common qualified applications.
  • Qualify exact material and dye
SLS
YesPA12 and PA11 are common qualified vapor-smoothing applications.
Polymer
With careOnly qualified PA12, PA11, selected TPU, and a few other thermoplastics reflow in commercial vapor systems.
FDM
LimitedUse chemical-smoothing for solvent-compatible FDM polymers; commercial PA vapor systems are not an FDM default.
Aluminum
NoThis is a polymer additive or moulded-plastic finishing step, not a bulk-aluminum process.
Brass
NoThis is a polymer finishing step, not a brass process.
Copper Alloy
NoThis is a polymer finishing step, not a copper-alloy process.
DMLS / SLM
NoMetal AM does not vapor-smooth.
Magnesium Alloy
NoThis is a polymer finishing step, not a magnesium process.
SLA
NoThermoset photopolymer does not reflow like powder-bed nylon.
Stainless Steel
NoThis is a polymer finishing step, not a stainless process.
Steel
NoThis is a polymer finishing step, not a steel process.
Titanium
NoThis is a polymer finishing step, not a titanium process.
Zinc Alloy
NoThis is a polymer finishing step, not a zinc process.

How Vapor smoothing is applied, and what it does to the part

  1. 1Clean and depowder
  2. 2Load with drainage orientation
  3. 3Run polymer-specific vapor cycle
  4. 4Dry and condition
  5. 5Inspect dimensions Ra and cleanliness
DimensionsSurface reflow can round edges, close small gaps, and shift precision fits; validate coupons and machine tight interfaces afterward.
Build-up per side0 µm — Surface reflows rather than receiving a coating; edge rounding and local dimensional shift are possible.
MaskingUsually needed. Mask precision interfaces where the qualified system permits; otherwise machine critical fits after smoothing.
ElectricalUnchanged
AppearanceSmoother satin to glossy polymer surface with reduced powder grain.
Added lead time2–7 working days on top of the bare part

Design rules for Vapor smoothing

What to decide on the drawing before the part goes to the finisher.

  1. Name the exact polymer grade.PA12, PA11, and TPU recipes are not interchangeable.
  2. Provide drain paths.Condensate can pool in cavities.
  3. Keep tiny text and edges oversized.Reflow softens fine detail.
  4. Validate pressure requirements separately.A smoother surface is not proof of leak tightness.

Vapor smoothing versus the alternatives

Finishes engineers weigh against Vapor smoothing, and when each wins.

FinishCorrosionHardnessCosmeticCostThicknessChoose it when
Vapor smoothing
this page
——80$$$0 µm—
Chemical Smoothing
Vapor smoothing vs Chemical Smoothing →
——75$$$0 µmwhen FDM ABS or a resin-specific liquid solvent process is intended
Surface Sealing
Vapor smoothing vs Surface Sealing →
30—55$$$≥ 0 µmwhen pore sealing rather than reflow is primary
CorrosionHardnessCosmeticLubricityEconomy
Vapor smoothingChemical Smoothing

The radar overlays Vapor smoothing with Chemical Smoothing, its most common alternative — chosen when FDM ABS or a resin-specific liquid solvent process is intended. Scores in the table are 0–100 across every finish in the catalog.

Cost, lead time and compliance

Relative cost

Vapor Smoothing is a premium-cost finish ($$$): more expensive than about 63 % of the finishes FabDigit quotes.

Finishing is priced per part with a lot minimum, from FabDigit's own China-side rates cross-checked against US job-shop pricing. The exact figure appears on the instant quote once the part is uploaded.

Lead time and compliance

Added lead time2–7 working days
RoHSCompliant
NotesClosed equipment must recover solvent and verify residual-solvent limits appropriate to the application.

What Vapor smoothing is used for

  • MJF PA12 manifolds
  • SLS PA11 housings
  • Selected TPU wearables
  • Cleanable medical-device prototypes

Vapor smoothing — frequently asked

vapor smoothing MJF

Qualified vapor systems can smooth MJF PA12 and selected PA11 or TPU grades to roughly Ra 0.8–6.3 µm (32–250 µin). Exact chemistry, exposure, and conditioning are proprietary and grade-specific.

does vapor smoothing make PA12 waterproof

It can reduce surface-connected porosity, but it does not automatically make a part pressure-tight. Leak testing at the required pressure and duration is still necessary.

can TPU be vapor smoothed

Only selected TPU grades work with qualified commercial systems. Flexibility, swelling, tack, and dimensional change must be tested on the exact grade.

does vapor smoothing change dimensions

It can round edges, soften small text, close narrow gaps, and alter fits. Machine precision interfaces afterward or qualify them with coupons.

vapor smoothing vs bead blasting MJF

Bead blasting removes loose powder and evens the matte appearance but commonly leaves Ra 1.6–6.3 µm. Vapor smoothing reflows the polymer skin and can create a smoother, glossier, more cleanable surface.