Surface Finishing Options for 3D Printed Parts

Parts coming off a 3D printer often contain layer lines, excess powder, support witness marks and internal roughness that demand postprocessing. However, there’s no single “additive manufacturing (AM) surface finishing” process. Choosing the right sequence depends on material, geometry (especially internal features), required surface roughness and the part’s end-use requirements.

Listed below are 9 of the most common postprocessing and surface finishing techniques used in AM today:

1. Media Blasting (Bead, Sand or Soda)

This is a first step for many metal and polymer AM parts. Pressurized media strips loose powder, knocks down minor surface defects and produces a uniform matte finish. This method is quick and cost-effective.

Materials manufacturer Himed provides an example of media blasting with hydroxyapatite (HA), an apatite abrasive commonly used as both an abrasive for surface preparation and a coating for medical implants to encourage osseointegration. 

READ HERE

2. Abrasive Flow Machining (AFM)

A viscous, abrasive-laden putty is pumped back and forth through internal passages under pressure. This is a popular method for smoothing AM fuel nozzles, manifolds and hydraulic blocks.

3. Tumbling and Vibratory Finishing

Parts are loaded into a bowl or barrel with abrasive media and agitated for hours (or days). This process is well-suited for batch processing small-to-medium parts and for breaking edges. 

Manufacturers like Mass Finishing Inc. (MFI), a provider of industrial parts polishing and deburring machines, are zeroing in on centrifugal barrel tumbling as a quicker, quieter alternative to vibratory finishing. Centrifugal barrel finishing is said to operate on the “Ferris Wheel” principle, using a 1:1 ratio of barrel rotation to turret rotation. The approach is achieved by loading one or all four chambers to an estimated 50-80% capacity with a combination of components, water, compound and media. 

READ HERE

4. Manual Grinding, Sanding and Polishing

These processes can be critical for large structural parts, prototypes and removing support witness marks. Hand finishing remains the dominant cost driver in many low-volume metal AM workflows. 

5. Chemical and Electrochemical Polishing

Submerging parts in a chemistry that selectively dissolves peaks while leaving valleys relatively intact. Suitable for both external and internal surfaces, it is advantageous for lattice structures, conformal cooling channels and medical implants.

For example, Holdson, a provider of electrochemical solutions, has released an acid-free electrochemical polishing system, Electroform, as a sustainable surface finishing solution for AM parts. 

READ HERE

6. Laser Polishing

A defocused laser remelts a thin surface layer, enabling surface tension to smooth out asperities. No consumables, no media to clean out of internal features and tightly controllable. Often an option for small, high-value parts like dental and aerospace components.

7. CNC Machining

Popular for critical mating surfaces, bearing journals, sealing faces and tight-tolerance features. Hybrid manufacturing machines that combine directed energy deposition (DED) or laser powder bed fusion (LPBF) processes with milling in a single setup are increasingly common.

For example, Addman Advanced Manufacturing Solutions is combining its metal AM operations with precision CNC machining for surface finishing. Compact metal parts are additively manufactured via LPBF, then finished using an array of in-house options for CNC machining. 

READ HERE

8. Vapor Smoothing

Clean 3D printed parts are submerged in a solvent within an airtight vessel, which is then heated to a specific temperature, creating vapor that smooths and polishes the part’s surface over a matter of hours. Automated systems are popular options for vapor smoothing, though the process can also be performed within a sealed container.

9. Coatings and Plating

Anodizing, physical vapor deposition (PVD), electroless nickel and powder coat can be applied to AM parts after mechanical prep. Coatings may mask minor surface defects, add wear or corrosion resistance or provide a uniform cosmetic appearance.

An example of this is a UV powder coating process developed in collaboration by Streamline 3D and powder coating supplier Keyland Polymer for AM parts. UV powder coatings are formulated to melt and flow at a lower temperature, around 220°F. Following this stage, the UV powder coating is exposed to UV light and immediately cured, reducing the heat exposure to the part. The total process time, 8 minutes, offers vibrant, consistent colors with a low scrap rate and high scalability.

READ HERE