Beginner’s Guide to Understanding 3D Printed Part Finishing

3D printed part finishing is a crucial step that directly affects how your final part looks, feels, and functions. While many users focus on material selection or print settings, the post-processing stage can be just as important for both prototypes and end-use parts.

Upside Parts - 3D Printed Part Finishing

In this guide, we explain what finishing involves, compare methods across FDM, SLA, and SLS technologies, and outline how to choose the right 3D printing post processing approach for your application.

Why 3D Printed Part Finishing Is Essential

Finishing 3D printed parts serves several practical purposes. It improves surface finish, removes support marks, enhances dimensional accuracy, and allows for additional functionality such as painting, sealing, or coating. In industries like product design, healthcare, and automotive, well-finished prints can make the difference between a rough prototype and a polished presentation model or end-use component.

Each 3D printing technology comes with unique surface characteristics. For instance, FDM prints often have visible layer lines. SLA parts may retain minor resin residue. SLS prints typically have a powdery surface texture. 3D printing post processing helps correct these features and tailors the final output for its intended use. Even small adjustments to surface quality can enhance usability, safety, or the professional appearance of your part.

Techniques for Finishing 3D Printed Parts

Support Removal

Support removal is typically the first step when finishing 3D printed parts. The process varies depending on the print method used.

• FDM prints use breakaway or dissolvable supports that can be manually removed.

• SLA prints require clipping supports and washing in isopropyl alcohol to remove uncured resin.

• SLS prints do not require supports, but unsintered powder must be cleared.

Proper removal without damaging critical features is important for quality control. For best results, use tools designed for the specific technology or material type.

Surface Smoothing

The surface finish of 3D printed parts depends on the post processing methods applied.

Common options include:

Technology	Common Methods
FDM	Sanding, vapor smoothing for ABS, filler priming
SLA	Wet sanding, polishing, and coating
SLS	Bead blasting, tumbling, and dyeing

These techniques help reduce layer visibility and improve appearance. Bead blasting is especially effective for SLS nylon parts and works well to prepare prints for dyeing or sealing.

UV Curing

In SLA 3D printing, UV curing is necessary to fully harden the resin. This step is important to ensure that printed parts achieve their designed mechanical properties. Typical curing times range from 10 to 30 minutes depending on the material and wall thickness.

Painting and Coating

Painting transforms basic prints into display-ready components. Before applying paint or coatings, make sure the surface is clean and sanded. Priming is particularly important for FDM prints to hide layer lines and ensure even coating. Surface preparation plays a major role in achieving a professional finish, especially for parts intended for visual presentation or client demos.

Choosing Finishing Methods Based on Technology

Finishing strategies vary depending on the 3D printing process used. Below is a comparison across major technologies.

FDM

• Offers ease of sanding and bonding

• Has visible layers that often require manual smoothing

• Works best for durable, large-scale prototypes

SLA

• Produces high detail and smooth surfaces

• Requires UV curing and delicate handling

• Well-suited for presentation models and castable patterns

Learn more about resin properties in our comparison of standard resin vs tough resin.

SLS

• Needs no support removal

• Requires powder cleanup and often sealing

• Suitable for functional parts and low-volume production

See our post on SLS vs FDM 3D printing for more on process capabilities.

How to Achieve a Smooth Surface Finish on 3D Printed Parts

The surface finish of 3D printed parts depends on multiple factors including print orientation, material, and geometry. A good surface finish improves not only visual quality but also functionality, especially for mechanical or user-facing components. Whether you are prototyping or preparing a final-use part, the choice of finishing method has a direct effect on the surface finish 3D printed parts can achieve.

Here are several factors to consider:

• Horizontal surfaces often show better detail than vertical ones

• Some materials are easier to sand and coat than others

• Intricate designs may be harder to reach during finishing

• Intended use determines how much effort should go into finishing 3D printed parts

3D printing post processing techniques like sanding, coating, or polishing can reduce surface irregularities, seal porous textures, and enhance the look and feel of the part. These improvements are often essential in fields such as product design, medical devices, or architecture, where tactile feedback and appearance matter.

Practical Considerations on 3D Printing Post Processing

Post processing takes time and resources, so it is important to plan accordingly. Follow these best practices:

• Design parts with access points for sanding or painting

• Conduct small-scale tests before committing to a final method

• Use proper safety equipment when handling resins and solvents

• Allocate space for curing, drying, or painting operations

• Understand the finishing limitations of each technology upfront

Choosing the right finishing process depends on your timeline, budget, and project goals. Whether your aim is function or appearance, finishing 3D printed parts correctly can add significant value.

If you need guidance on how to finish your FDM, SLA, or SLS parts, our experts are ready to help. We offer 3D printing in Boston MA as well as 3D printed part finishing and ship completed parts nationwide.