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What is vapor smoothing?

Want to learn about vapor smoothing? Here’s a guide to using the post-processing technique, how it works, its common industrial uses, and more.

Even the most advanced 3D printers can produce parts with rough surfaces and visible layer lines, which can detract from their overall appearance and feel. In these cases, post-processing techniques are often used to eliminate unwanted part qualities. Vapor smoothing is one such process. 

What is vapor smoothing?

Vapor smoothing – also known as chemical smoothing – is a post-processing technique used to enhance the surface finish of 3D printed parts. The process often used for parts created with Multi Jet Fusion (MJF), Selective Laser Sintering (SLS), or other additive manufacturing processes, resulting in high-quality smooth surfaces that can be used for cosmetic applications.

How does vapor smoothing work?

The vapor smoothing process involves placing a cleaned 3D printed part into a sealed container – or a vapor smoothing machine – along with a solvent, such as acetone or ethanol. The solvent is heated to a specific temperature, causing it to vaporize and fill the container (or vapor smoothing machine’s chamber). The solvent vapor then condenses on the part's surface, before melting on and smoothing out the part’s outer layer, resulting in a polished finish. After the process is finished, the part is allowed to dry and cool. The process can take up to several hours, depending on the size and complexity of the part.

Do you need a vapor smoothing machine for vapor smoothing?

You do not necessarily need a vapor smoothing machine to perform vapor smoothing. While there are commercially available vapor smoothing machines that are specifically designed for this purpose, you can also perform vapor smoothing using DIY methods with materials that are readily available.

One common DIY method involves using a container with a tight-fitting lid and a layer of solvent at the bottom of the container. The 3D printed part is suspended above the solvent using a platform or a stand. The container is then sealed, and the solvent is heated to create a vapor that smooths the surface of the part. 

However, it is important to note that performing vapor smoothing without proper equipment and safety precautions can be hazardous, as solvents used in the process can be flammable and can release harmful fumes. With this in mind, we recommend using Protolabs Network's vapor smoothing service

What solvents and materials are used with vapor smoothing?

Vapor smoothing can be used on a variety of materials, including ABS, PLA, PA 12, Nylon, epoxy resins, polycarbonate, and polypropylene. However, the process is not suitable for materials that cannot withstand high temperatures or chemicals, such as TPU and certain specialty filaments.

A variety of solvents are also commonly used with vapor smoothing. Here are a few of them.

  • Acetone. Acetone is a highly effective solvent used for vapor smoothing parts created with ABS. 

  • Methyl ethyl ketone (MEK). MEK is commonly used for vapor smoothing thermoplastic materials such as ABS, polycarbonate, and acrylic, as well as some thermosetting plastics like epoxy resins.

  • Tetrahydrofuran (THF). THF is a strong solvent that is commonly used for vapor smoothing PLA parts. 

  • Dichloromethane (DCM). DCM is a fast-acting solvent that is sometimes used for vapor smoothing ABS parts. 

  • Ethyl acetate. Ethyl acetate is a less aggressive solvent that is sometimes used for vapor smoothing PLA parts. Because it is slower-acting, it may require longer exposure times to achieve the desired smoothing effect.

What are the benefits of vapor smoothing?

Vapor smoothing offers several benefits 

  • Improved aesthetics and surface finish. Vapor smoothing creates a smooth and polished surface, hiding any visible layer lines or imperfections. This can be especially useful for parts that require a high-quality surface finish, such as prototypes or parts for visual applications.

  • Improved water resistance. Because it creates a smooth outer layer on printed parts, vapor smoothing can improve water resistance. However, if water resistance is required, it is important to discuss this before production, as it can affect the vapor smoothing process. 

  • Increased durability and strength. The vapor smoothing process can increase a part's strength and durability as it fuses the outer layer, making it less prone to cracking or breaking. This can be particularly useful for parts that will undergo stress or wear and tear.

What are best practices for vapor smoothing?

By following these best practices, you can achieve optimal results when vapor smoothing your 3D printed parts.

  • Safety. Vapor smoothing requires the use of solvents, which can be dangerous if not handled properly. Acetone, for example, is highly flammable and volatile, and can ignite at room temperature. As such, always wear appropriate personal protective equipment, such as gloves and safety glasses, and work in a cool, well-ventilated area where there can be no exposure to flames or sparks.

  • Solvent choice. Different solvents work better with different types of 3D printing materials. You can find brief descriptions of commonly used solvents – and the materials with which they work best – in the above section.

  • Exposure time. The amount of time that a part needs to be exposed to the vapor depends on several factors, including material type, solvent temperature, and the desired level of smoothing. 

  • Temperature control. The temperature of the solvent can have a significant impact on the vapor smoothing process. Generally, higher temperatures will result in faster smoothing, but if the temperature is too high, the part can become deformed. 

  • Part orientation. The orientation of a part can affect the quality of the smoothing. Typically, parts are positioned so that the surface that needs to be smoothed is facing down, toward the solvent.

  • Part design and features. Whether a part can be vapor smoothed depends on its geometry and wall thickness. Parts with complex geometries, such as sharp corners and edges – and those with thin walls – may not be suitable for vapor smoothing.

  • Clean the part before smoothing. For best results, parts are thoroughly cleaned before smoothing to remove any residual debris or oils that may interfere with the vapor smoothing process.

  • Post-processing. Once a part has been smoothed, it may need additional post-processing to remove any remaining solvent or to enhance the surface finish. Sanding or polishing is sometimes used to achieve a higher level of finish.

How do you reduce cost and lead time for vapor smoothing?

These strategies can result in reduced cost and lead time for vapor smoothing and improve the efficiency of the manufacturing process.

  • A chamber or vapor smoothing machine. A chamber that can specifically be used for vapor smoothing – such as a vapor smoothing machine, will help to keep solvent vapor contained and reduce the amount of solvent needed. It will also speed up the process by allowing multiple parts to be smoothed simultaneously.

  • Optimize the process parameters. The amount of solvent and the exposure time required are carefully chosen to achieve the desired level of smoothing while reducing the amount of solvent needed and the time required for the process.

  • Automated equipment. Automated equipment can be used to control the temperature, pressure, and exposure time during the vapor smoothing process. This can help to reduce the variability in the process and improve the quality of the finished parts.

  • Part design. Design the parts in a way that minimizes the need for post-processing. This can help to reduce the overall cost and lead time for the manufacturing process. 

Which industries use vapor smoothing?

Vapor smoothing is used across a variety of industries for a variety of applications. Here are a few of them. 

  • Aerospace. The aerospace industry often uses 3D printing to create complex parts for aircraft. Vapor smoothing can be used to improve the surface finish of these parts.

  • Automotive. The automotive industry uses 3D printing for prototyping, tooling, and manufacturing parts. Vapor smoothing is used to improve those parts’ surface finish.

  • Medical. The medical industry uses 3D printing to create customized implants and prosthetics, with vapor smoothing used to improve their biocompatibility and reduce the risk of bacterial growth.

  • Consumer products. Vapor smoothing can be used to improve the surface finish of 3D printed consumer products, such as phone cases, jewelry, and toys. 

  • Architecture and construction. 3D printing is becoming increasingly popular in architecture and construction, and vapor smoothing can be used to improve the surface finish of building components, such as architectural models and façade elements.

  • Industrial manufacturing. Vapor smoothing can be used to improve the surface finish of 3D printed parts used in various industrial applications, such as machine parts, molds, and jigs.

CNC machining, 3D printing and sheet metal fabrication parts

Frequently asked questions

How long does vapor smoothing take?

Several factors affect the time it takes to vapor smooth a part but it is usually completed in a matter of hours.

Can you vapor smooth PLA or ABS?

We currently only offer vapor smoothing for MJF and SLS 3D printing (using PA 12), however, you can discuss custom requests and other recommendations with our team via

Can all 3D printed parts be vapor smoothed?

Not all 3D printed parts are suitable for vapor smoothing. Parts with intricate geometries or fine details may be damaged or distorted during the process.

Can multiple parts be vapor smoothed at once?

Yes, multiple parts can be placed in a vapor smoothing chamber at the same time, as long as there is enough space for the solvent vapors to circulate around each part.

Can vapor smoothing be used on parts with support structures?

Yes, parts with support structures can be vapor smoothed, but the support structures may also be affected by the process, and may need to be removed or post-processed separately.


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