To polish 3D printed parts to achieve a refined finish, engineers employ a variety of industrial finishing techniques, including coating, sandblasting, and hand-finishing methods. Although 3D printing can produce complex parts, initial prints often exhibit rough surfaces and pronounced layer lines, especially in parts produced using fused deposition modeling (FDM). For this reason, post-processing is an extremely important part of part production, smoothing the rough surface of the unfinished part by adding or removing layers of the part. In this article, Antarctic Bear will systematically introduce and compare two mainstream surface finishing processes currently on the market—steam smoothing and vibration fine polishing, so as to facilitate the understanding of the respective processes, advantages and disadvantages of each method.
steam smooth
Vapor Smoothing, also known as chemical vapor smoothing, is a surface treatment technique that exposes printed parts to an evaporating solvent environment. The industrial vapor smoothing process requires careful suspension of single or multiple components in an airtight chamber for maximum exposure. A chemical solvent mixture, such as FA 326, is injected and sprayed into a chamber where it condenses and hardens on the part, eliminating surface irregularities through a controlled melt. As the chamber temperature increases, the residual solvent evaporates and is recovered. The final part becomes waterproof and retains its smooth inner cavity, precise dimensions and original material volume. For best vapor smoothing results, it is recommended that the process be performed in a controlled environment using industrial-grade equipment designed for 3D printing vapor smoothing. For those interested in a DIY method, vapor smoothing can be achieved using acetone or ethanol as a chemical solvent, or in this case known as solvent impregnation. However, caution must be exercised and proper safety measures and equipment must be in place.
△The steam smooth part is on the left, and the standard surface treatment is on the right (photo source: ProtoLabs)
Vibration fine polishing
Vibratory finishing, on the other hand, does not use chemicals for surface preparation. Instead, it relies on abrasive media to enhance the surface of the 3D printed part. During the process, multiple 3D printed parts are placed in a vibrating bucket filled with selected abrasive media and compound lubricating fluid. When the machine is turned on, the barrel begins to move, creating mechanical friction between the part and the grinding media. This subtractive process improves the surface quality of the part by minimizing and gently removing the outermost layer of material. Vibratory fine polishing requires special measures and equipment, and offers two methods: vibration method and tumbling method. The vibration method is especially suitable for larger objects with less detail and can achieve the desired result more quickly.
The choice of abrasive or chips is critical in vibratory fine polishing. Abrasive chips can be made of ceramic, plastic, or steel, each producing different results. Ceramic abrasives are especially suitable for deburring and achieving a shiny surface. Due to their high density, they can withstand high pressures and are suitable for machining stainless steel, metal and plastic parts. Plastic abrasives are ideal for soft, delicate surfaces that require gentle finishing. They come in both pyramidal and conical shapes. In addition, Walther Trowl has developed nipple shaped abrasives for very small, delicate parts in hard to reach areas. Steel abrasives are mostly spherical and have minimal material removal, making them ideal for polishing and mechanical cleaning of metal, silver or aluminum parts to ensure a smooth and scratch-free surface.
△Abrasives made of ceramics can withstand high pressure. (Source: Vibrafinish)
In addition to abrasives, the vibratory fine polishing process also requires lubricating fluids, ie compounds. Compounds are used to absorb and remove wear from parts, and to clean and degrease parts. Acidic compounds can be selected for machining metal parts for pickling. After processing, drying is required. These parts can be dried in a vibratory dryer where they are placed with a heated drying medium such as corncob meal, nutmeal or wood blocks and vibrated. Alternatively, belt dryers are especially suitable for sensitive and bulky parts with internal channels and holes. In a belt dryer, the 3D printed parts are passed through a hot air system on the belt and dried in this way.
Steam smoothing and vibratory finish polishing treatments vary in time, from ten minutes to several hours, depending on the number and complexity of the parts being processed.
compatible material
Vapor Smooth is compatible with most 3D printing polymers and elastomers. Common materials for vapor smoothing include Acrylonitrile Styrene Acrylate (ASA), Acrylonitrile Butadiene Styrene (ABS), High Impact Polystyrene (depending on machine), Nylon 11 (PA 11), Nylon 12 (PA 12), polypropylene (PP), and polycarbonate/acrylonitrile butadiene styrene (PC-ABS). It's worth noting, however, that steam smoothing with TPU and certain specialty filaments is not recommended. Each solvent, such as acetone, methyl ethyl ketone (MEK), tetrahydrofuran (THF), dichloromethane (DCM), and ethyl acetate, has its own effectiveness and application considerations.
However, vibratory fine polishing is compatible with many other different materials. For example, vibratory fine polishing is not only available for 3D printed parts made of thermosets, thermoplastics and elastomers such as polyethylene (PE), polypropylene (PP) or polyethylene terephthalate (PET) , can also be used for metals such as aluminum, stainless steel, brass or copper. This makes it a more versatile method that can be used as a post-processing method for various 3D printing techniques such as FDM/FFF and powder bed fusion.
△Before and after comparison of vibration-polished metal parts (Source: Acton Finishing)
Limitations and advantages of post-processing techniques
Both processes offer many advantages in terms of surface appearance and performance. Steam smoothing can obtain smooth and water-resistant surface finish parts comparable to injection molding, and improve the elongation, tensile properties, bending properties of parts, maintain characteristics, strength and precision. Vibratory finishing, on the other hand, does not achieve a water-resistant finish, but also provides an exceptionally smooth surface, removes coating marks and produces a scratch- and stain-resistant surface. Components processed by vibrofinishing and vapor smoothing methods produce smooth surfaces with a glossy appearance. However, steam smoothing provides a shinier finish than vibratory fine polishing. In addition, parts treated with vibratory fine polishing exhibited a significantly softer, more pleasant tactile experience.
However, it's worth noting that vapor smoothing isn't the best solution for every print. Models that are too complex, too small, too large, or too flat may distort or lose detail, and artifacts may be visible afterwards. After steam smoothing, parts may exhibit defects such as bridging, blisters, bite marks, edge pools, spots, holes, or incomplete features. In addition, it is worth noting that flexible materials are more prone to surface defects than rigid materials. Therefore, careful timing must be taken when steam smoothing moving parts or components with joints to avoid compromising joint integrity or causing sticking due to overexposure to steam.
On the other hand, vibratory fine polishing is suitable for a wider range of 3D printed parts than steam smoothing, since it can be adapted to any individual requirements, material properties and structure of the part by choosing different abrasives and methods. Vibratory finishing is suitable for almost all 3D printed parts, as long as the process is always done professionally by specialists. However, vibratory finish polishing can lead to loss of part geometry. For example, the corners and tips of components can be overly rounded and lose their shape, which doesn't happen with steam smoothing. In addition, vibration finishing sometimes requires subsequent further drying procedures, which prolongs the process.
Application field
Vapor smoothing is a technology favored by industries such as medical, automotive and aerospace for the treatment of water-resistant, antimicrobial and chemical-free components. When it comes to vibratory fine polishing, the medical, automotive and sports industries especially benefit from this technology. In every field, smooth surfaces, especially metal parts, are important to ensure proper functioning and safe conditions of components. However, vapor smoothing and vibratory fine polishing can be implemented throughout the product development cycle, from concept models to prototypes to final products, and are used in a wide variety of industries including medical, automotive and consumer goods. Examples of parts processed with vibratory fine polishing are car parts for the automotive industry or roller skates and fitness equipment for the sports industry. In addition, jewelry and tableware are vibrationally finely polished for consumer use. An example of a vapor-smoothed part that is often used in the automotive industry is the interior components of vehicles, such as dashboards, door handles and center console elements. Vapor smoothing is also used in the aerospace industry for aircraft parts such as wings, air ducts and engine parts, among others.
picture
△Vapor smoothing is often applied to aircraft parts in the aerospace industry (Image source: Fast Radius)
suppliers and prices
Various service providers, such as SPALECK GmbH, VibraFinish or Rohde AG, offer vibratory fine polishing for private customers and companies. For vapor smoothing, Xometry, AMT, DyeMansion, Protolabs, and Hubs are prominent service providers offering vapor smoothing services either by specified post-processing solution machine or material based. 3Faktur is a German company offering steam smoothing and vibratory fine polishing services. Well-known VaporSmoothing machines such as the AMT PostPro3D series and the Powerfuse S series are solutions provided by Xometry and DyeMansion, while Protolabs and Hubs use SLS and MJFHPA 12, PA 12 and MJF Ultrasint™ TPU-01 materials respectively.
For vibratory fine polishing, large industrial machines from manufacturers such as Walther Trowal, AVAtec or Garant cost around $18,000 to $21,000 (€17,000 to €20,000). 2 kg of abrasives cost between $21 – 44 (€20 – 40) and 5 liters of compound around $21 – 44 (€20 – 40). Prices vary widely depending on the quantity and size of parts to be machined. For steam smoothing, the service charge for smoothing individual parts can be $5-$15 (€4-€14) depending on the complexity of the part, although many manufacturers typically only offer the service in bundles of 10 or more parts. Purchasing the steam smoother itself can cost around $10,000 to $30,000 (€11,000–33,000), depending on region, manufacturer, and quality.
