Post-Processing of MJF-Printed Parts: Methods, Comparison, Tips

HP Multi Jet Fusion (MJF) is one of the most flexible and reliable technologies in industrial 3D printing. It enables the production of geometrically accurate and durable parts without support structures, with minimal defects and high repeatability. However, even high-quality printed parts require post-processing — to improve aesthetics, enable assembly, ensure sealing, or prepare the surface for painting.

This article explores MJF post-processing in detail — including key Multi Jet Fusion finishing techniques and how they differ from SLA, SLS, and FDM. We explain what tools and materials are needed, and which engineering and organizational methods can help reduce finishing costs and boost process efficiency. We’ve also added a helpful table which includes a time comparison in 3D printing post-processing.

Stages of Post-Processing: From Cleaning to Assembly

Post-processing begins with the removal of unfused powder. This is typically done using air compressors with a pressure of 6–8 bar, blasting cabinets with plastic media, and vibratory cleaning systems. Cleaning a medium-sized part takes 5–10 minutes. Special attention is given to internal channels, where flexible nozzles and angled air blowers are used.

Sanding MJF prints is necessary when a smooth surface is required, such as for painting. It’s usually done manually or with a vibratory sander, starting with P180 grit and finishing with P600. Manual sanding takes 20–40 minutes; mechanical sanding reduces this to 10–15 minutes. To evaluate surface smoothness, a “test painting” method is often used — spraying inexpensive paint or marking the surface with a pencil to reveal defects.

Painting is carried out by dip-dyeing MJF parts (for fast batch coloring), aerosol spraying, or coating with paint and varnish systems. When 3D printed parts painting is required, it’s crucial to account for adhesion, color durability, and visual result. Drying time between coats for this surface treatment is typically 15 to 30 minutes.

Assembly and sealing are carried out using superglue or epoxy compounds. Fixation time ranges from a few seconds to an hour. If the part is going to be exposed to moisture or chemicals, additional polyurethane or acrylic coatings are applied.

Comparison with Other Technologies: When to Use What

MJF is the best choice when you need to replicate functional parts. It’s optimal for projects with repeatable geometry.

SLA is suitable for visual models where surface smoothness is important, but mechanical strength is not required.

SLS is a good fit for complex geometry and structural integrity, though additional finishing may be needed for aesthetic quality.

FDM is cost-effective but lags behind in surface quality and post-processing efficiency.

How to Simplify Post-Processing at the Design Stage

Certain design features directly impact post-processing complexity. Here are some tips:

• Avoid sharp internal corners and narrow gaps — they are difficult to sand and clean.
• Design internal channels to allow airflow for cleaning (e.g., add through-holes).
• Surfaces that require painting should have acceptable roughness — avoid unnecessary recesses.
• If gluing is required, add mechanical connectors such as tabs and slots to simplify assembly.

To optimize the workflow, it’s helpful to keep a post-processing log. It can include:

• Date and part type
• Methods used (sanding, coating, painting)
• Duration of each step
• Tools and materials used
• Defects found and how they were resolved

Documenting helps detect recurring problems such as material compatibility, refine work instructions, and train personnel more effectively.

Post-processing is not just about aesthetics — it’s a full-fledged technological stage that affects the functionality and durability of the final product.
In the case of MJF and its extensive range of industrial applications, it is relatively fast and efficient, especially when design-specific nuances are considered from the very beginning.

At Makerly, we help clients not only with 3D printing, but also with delivering results that are ready for use. We know how to turn a 3D model into a high-quality product — quickly, accurately, and with minimal effort required from the client.