EPTAHUB’s vapor smoothing service offers low-cost finishing for additive-manufactured parts, delivering a surface finish that can compete with injection molding.
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3D printing is one of the primary methods for small-batch product manufacturing. However, plastic 3D printing typically has a significant drawback: the surface finish of parts is often poor. Powder bed fusion processes—such as Selective Laser Sintering (SLS) and HP Multi Jet Fusion (MJF)—produce a matte, grainy texture similar to a sugar cube. Fused Deposition Modeling (FDM), in contrast, leaves visible layer lines on the surface. Over the past 30 years, traditional post-processing methods such as media tumbling, manual sanding, and coating have only achieved limited improvements in surface quality. As a result, when aesthetics are critical, engineers often choose alternative manufacturing methods such as injection molding, CNC machining, or polyurethane casting.
With the development of chemical vapor smoothing—a technique that uses vapor-phase solvents to smooth the surface of 3D-printed parts and improve their mechanical properties—plastic 3D printing has become much more suitable for low-volume production. This process is compatible with most 3D-printable polymers and elastomers, including more than twenty materials offered by EPTAHUB.
EPTAHUB has adopted AMT’s PostPro3D chemical vapor smoothing technology. Unlike physical smoothing processes like sanding or media tumbling, vapor smoothing does not remove material from the workpiece. Instead, a vapor finishing agent (FA 326) is placed into a sealed processing chamber along with the parts. Although the finishing agent remains the same, different processing parameters are applied based on the materials and geometric features of the parts. Parts are racked or hung in a 600 x 400 x 400 mm chamber to maximize the exposure of their surfaces to the vapor. The vapor adheres to the part surface, where it causes a controlled chemical melt. This melt reduces the surface peaks and valleys by liquefying and redistributing the material, creating a more even surface. Additionally, the melt has the effect of enhancing the part’s shine.
Once the parts are finished, the chamber is heated to extract the finishing agent into a collection vat. No residue is left on the parts. The smoothed parts are then ready for shipping or for another secondary process, such as dyeing.
Compatible Materials for Chemical Vapor Smoothing through EPTAHUB
| Material Name | Process | Quoting Process |
|---|---|---|
| Nylon 12 | SLS, HP MJF | Instant Quote |
| Nylon 12, Glass Bead | SLS, HP MJF | SLS, HP MJF |
| Nylon 11 | HP MJF | Instant Quote |
| Thermoplastic Urethane, TPU 88A | HP MJF | Instant Quote |
| Polypropylene (PP) | HP MJF | Requires Review |
| Nylon 11 EX | SLS | Requires Review |
| Nylon 12, Carbon-Filled (CF) | SLS | Requires Review |
| Nylon 12, Aluminum-Filled (AF) | SLS | Requires Review |
| Nylon 12, Mineral-Filled (HST) | SLS | Requires Review |
The table above lists all the materials that EPTAHUB offers for vapor smoothing, including those that may need a manual review. You can get an instant quote for select materials by selecting "Vapor Smoothing" from the "Finishes" drop-down menu.
Easily compare 3D printing processes with our quick reference guides.
You can obtain instant pricing and lead times for vapor smoothing through the EPTAHUB Instant Quoting Engine®. These are determined by the process, material, quantity, and part geometry for the most popular HP MJF and SLS materials. Since the process is batch-based, the cost per part is relatively low and will decrease as the order volume increases. EPTAHUB typically adds 1-5 business days to the lead times for vapor smoothing.
For vapor smoothing orders involving specialty materials like SLS high-performance blends, Nylon 11 EX, Nylon 12 AF, Nylon 12 HST, and Nylon 12 CF, EPTAHUB will conduct a manual review. Please select “Other” as your finish option and submit the quote for an expert review.
Vapor smoothed parts have improved cosmetic appeal and their surface finish is comparable to that of injection molding. Standard SLS parts usually have a surface roughness of more than 250μin Ra, but with chemical vapor polishing, this can be improved to below 125μin Ra and as low as 40μin Ra. In some studies, chemical vapor smoothing has enhanced material surfaces by 800%-1000%. It is important to note that chemical vapor smoothing redistributes surface material to create a sealed, smooth surface – it does not produce a polished surface. There will still be visible surface topology and minimal layer lines.
Chemical vapor smoothing can greatly increase the practicality of 3D prints in food processing, medical devices, and consumer products. It is recommended for end-use applications in these industries. Notably, vapor-smoothed nylon 12 3D prints effectively reduce bacterial attachment and growth compared to standard nylon 12 3D prints. Studies have shown that vapor-smoothed SLS and HP MJF parts meet and pass multiple biocompatibility and safety tests.
Other benefits of chemical vapor smoothing include:
Vapor Smoothing Passes Health and Safety Tests
The chemical used for vapor polishing is safe, and the closed-loop process of AMT’s PostPro3D system ensures that no extra residue remains on the parts after smoothing. In fact, studies have demonstrated that vapor-smoothed SLS and HP MJF parts comply with and pass multiple biocompatibility and safety tests related to food contact, skin irritation, cytotoxicity, and bacterial growth. The results are summarized above, and more details can be found in this AMT PostPro3D document on safety certifications.
| Test | Results | Details | Normative Reference |
|---|---|---|---|
| Food Contact Test | PASS | SLS printed PA-12 parts chemically vapor smoothed with PostPro3D do not pose a risk to consumer health or affect food quality. | According to regulation (EC) 10/2011 Annex V, Chapter 3, Table 3, OM 3, 2 hours at 70°C; DS/EN1186-01:2002; DS/EN1186-03:2002; DS/EN1186-14:2002 |
| Skin Irritation Test | PASS | SLS printed PA-12 parts chemically vapor smoothed with PostPro3D did not cause skin irritation. | ISO 10993-10 (2013); ISO 10993-1 (2018); OECD TG 439 |
| Cytotoxicity Test | PASS | MJF printed PA-12 parts chemically vapor smoothed with PostPro3D did not cause a cytotoxic effect. | ISO 10993-5 (2009); ISO 10993-1 (2010); ISO 10993-12 (2012) |
| Microbiological Test on MRSA Bacteria | PASS | MJF printed PA-12 parts chemically vapor smoothed with PostPro3D showed a 99.88% reduction in bacterial growth against MRSA. | MOD ISO 22196: 2011 |
| Microbiological Test on E. coli Bacteria | PASS | MJF printed PA-12 parts chemically vapor smoothed with PostPro3D showed a 99.78% reduction in bacterial growth against E. coli. | MOD ISO 22196: 2011 |
Enhanced cosmetics, better coloration, and sealed surfaces can make vapor smoothed 3D prints stand out as impressive concept models.
Vapor smoothing does not significantly extend lead times, enabling the production of highly functional parts in record time
3D printing vapor smoothing is a bulk finishing process, making it an ideal solution for producing large quantities of customized parts.
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