A 3D-printed part is rarely finished when it comes out of the printer. Whether it’s removing support material, smoothing surfaces, or inserting threads – post-processing determines whether a component looks like a prototype or an end product.
Overview: The Most Important Finishing Processes
| Process | Purpose | Suitable for |
|---|---|---|
| Blasting | Uniform surface, powder removal | SLS, MJF, SLM |
| Tumble finishing | Smoothing and edge rounding | SLS, MJF, FDM |
| Vapor smoothing | Chemical smoothing, closed pores | SLS, MJF (PA12) |
| Dyeing | Through-coloring of the material | SLS, MJF (Nylon) |
| Painting | Color application, protection, aesthetics | All processes |
| Threaded inserts | Load-bearing connections | All processes |
| Sanding / polishing | Surface refinement | FDM, SLA, SLM |
| Annealing | Increased strength & heat resistance | FDM (PEEK, PLA) |
Blasting: The Foundation of All Post-Processing
For powder bed-based processes (SLS, MJF), blasting is the first step. Glass beads or corundum remove sintered-on powder and create a uniform, matte surface.
- Glass beads (fine): Gentle cleaning, slightly silky finish
- Corundum (coarse): Stronger material removal, rougher surface
Blasting is included in the standard price of all SLS and MJF parts at DREI-DE.
Tumble Finishing (Vibratory Finishing)
In tumble finishing, parts are placed together with grinding media (chips) in a vibrating drum. The chips remove material layer by layer, creating rounded edges and smooth surfaces.
- Typical roughness afterward: Ra 3 – 6 µm (previously Ra 10 – 15 µm for SLS)
- Duration: 2 – 12 hours, depending on the desired result
- Advantage: Uniform, automated, cost-effective for larger quantities
- Limitation: Fine details and interior areas are barely reached
Vapor Smoothing: Industrial Quality Without Sanding
Vapor smoothing is one of the most exciting post-processing techniques in 3D printing. SLS or MJF parts made of PA12 are smoothed in a controlled solvent atmosphere. The surface briefly melts and closes pores.
Vapor smoothing reduces surface roughness by up to 90% and makes 3D-printed parts visually and tactilely almost indistinguishable from injection-molded parts.
Advantages:
- Closed, smooth surface (Ra < 1 µm possible)
- Watertight and food-contact suitable (depending on material)
- No mechanical stress – details are preserved
- Consistent results even in interior areas
Limitations:
- Primarily for PA12 and PA11 (Nylon)
- Slight dimensional changes possible (±0.1 mm)
- Cost approximately 20 – 40% surcharge on the part price
Dyeing: Color That Penetrates
In dyeing, SLS or MJF parts are immersed in a hot dye bath. The dye penetrates up to 0.5 mm into the material. The result: uniform, abrasion-resistant color without any layer build-up.
- Standard color: Black (most common, covers MJF gray)
- Other colors: Blue, red, green, yellow – depending on the provider
- Advantage over paint: No layer thickness, no chipping
Ideal for parts that are handled frequently (grips, housings, consumer products) – the color does not wear off like paint would.
Painting: From Functional Part to Design Object
Painting remains the most versatile way to visually enhance 3D prints. Options include:
- Primer + topcoat: For uniform coloring
- Soft-touch paint: Rubber-like feel for controls
- Metallic / chrome finish: For design models and showpieces
- UV protection coating: For outdoor use and UV-sensitive materials
Important: The surface must be smoothed before painting (sanding, tumble finishing, or vapor smoothing), otherwise layer lines and roughness will show through the paint.
Threaded Inserts: Load-Bearing Connections
3D-printed threads have limited durability. For repeated screwing or higher loads, brass threaded inserts (heat-set inserts) are used.
- How it works: Knurled sleeve is melted in with a soldering iron
- Sizes: M2 to M8 are standard
- Pull-out strength: Up to 10× higher than printed threads
- Ideal for: Housings, assembly fixtures, end products
Alternatively, with SLM metal parts, threads can be cut directly – the strength of the sintered metal allows this without inserts.
Annealing: More Strength Through Heat
In annealing (tempering), printed plastic parts are heated in a controlled manner to optimize the crystal structure of the polymer. This increases strength and heat resistance.
- PLA: +40% strength, heat resistance up to 120 °C (instead of 60 °C)
- PEEK: Increased crystallinity for high-temperature applications
- Caution: Shrinkage and warping possible, must be accounted for in the design
Which Post-Processing for Which Application?
| Application | Recommended post-processing |
|---|---|
| Functional prototype | Blasting (standard, included) |
| Visible housing | Vapor smoothing + dyeing or painting |
| Medical component | Vapor smoothing (closed pores) |
| Architectural model | Primer + painting |
| Assembly part with screws | Threaded inserts (heat-set) |
| Outdoor use | UV protection coating + dyeing |
| Consumer product (series) | Tumble finishing + dyeing |
| High-temperature part (FDM) | Annealing |
Post-Processing Costs
Post-processing can increase the part price by 15 – 80%, depending on the process and effort involved. A rough guide:
| Process | Surcharge | Note |
|---|---|---|
| Blasting | Included | Always included with SLS/MJF |
| Tumble finishing | +10 – 25% | Automated, efficient from 10+ parts |
| Vapor smoothing | +20 – 40% | Depends on part size |
| Dyeing | +10 – 20% | Black is cheapest |
| Painting (single color) | +30 – 60% | Manual work, highly dependent on geometry |
| Threaded inserts | +2 – 5 CHF per piece | Depends on size and quantity |
More on overall costs: How Much Does 3D Printing Cost? Pricing Factors at a Glance →
Conclusion: Post-Processing Is Not a Luxury
The right post-processing transforms a 3D print from a prototype into an end product. It significantly influences appearance, feel, functionality, and lifespan. Those who factor it into component planning from the start save time and achieve better results.
Unsure which finishing is optimal for your part? Upload your 3D model – we’ll advise you personally.
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