Design Optimization for MJF Technology: Tips for Engineers and Designers

Multi Jet Fusion (MJF) technology has opened new horizons for product designers, allowing the creation of complex parts with high precision but without the need for support structures. It also enables the production of functional, end-use components that do not require additional assembly. However, to fully unlock the potential of this technology, it’s important to take its specific characteristics into account at the design stage.

In this article, we’ll look at the importance of design for additive printing. Specifically, we’ll explore how to best adapt designs for MJF printing, why support structures are not required in this process, and how topology optimization can help reduce part weight without sacrificing strength. Our 3D printing design guidelines also cover key limitations to be aware of in order to avoid mistakes and achieve high-quality results.

Why MJF Doesn’t Require Support Structures — and How That Impacts Design

In most 3D printing technologies like FDM or SLA, overhanging features require support structures that are removed manually after printing. This complicates the process and can damage the surface of the part.

MJF works differently. The model is surrounded by unused powder, which serves as a natural support. This powder stabilizes the part during printing and eliminates the need for additional support elements. As a result, post-processing becomes simpler, and designers gain more freedom — allowing for the creation of internal cavities, complex curved shapes, integrated joints, and hidden channels.

Even with this design freedom though, it’s important to keep in mind some minimum technical tolerances:

• Minimum wall thickness: 0.7 mm
• Gaps between moving parts: at least 0.5 mm
• Recommended fillet radius: from 0.3 mm

How Topology Optimization Reduces Weight While Maintaining Strength in MJF

Topology optimization is a digital method for redistributing material in a structure to achieve the best balance between weight and strength. Unlike the traditional approach — where the shape is manually defined — topology optimization uses algorithms to “grow” the geometry based on load conditions, constraints, and functional requirements. This assists with weight reduction, as well as stress distribution in load-bearing structures

The essence of the method is not just to reduce weight however, but to preserve structural integrity and performance while minimizing material volume. This is particularly effective in MJF, as the technology easily handles organic and unconventional shapes resulting from the optimization process.

Topology optimization can be implemented using specialized software. For this purpose, the following tools can be used:

• nTopology — a powerful tool focused on complex lattice structures
• Altair Inspire — an intuitive platform with extensive analysis and simulation capabilities
• Autodesk Fusion 360 (with Generative Design) — suitable for quickly generating multiple design alternatives based on predefined constraints

The typical optimization process involves the following steps:

1. Defining load conditions and constraints (fixations, external forces)
2. Creating the design space — the zone where material can exist
3. Generating the geometry and analyzing the results
4. Refining the final geometry to meet manufacturing tolerances and preparing it for printing

Key Limitations to Consider When Working with MJF

Despite its flexibility, Multi Jet Fusion (MJF) technology has certain limitations that need to be considered. When developing a model, we recommend paying attention to the following aspects:

• Powder removal. Internal cavities may be difficult to clean. In such cases, it’s necessary to design escape holes to allow for the removal of unused powder.
• Overheating of thin walls. In some lightweight 3D printed parts, if the wall thickness is below the recommended minimum, there is a risk of warping or loss of strength.
• Color and surface texture. Parts made from PA 12 typically have a gray color and a slightly grainy surface. Additional finishing (e.g., painting or vibratory polishing) is required if aesthetics are important.

By taking these factors into account to ensure MJF design optimization, you can achieve high-quality prints without unnecessary iterations and redesigns.

Practical Tips for Preparing Models for MJF Printing

For successful projects using MJF, we recommend following these tips and MJF best practices:

Define the purpose of the part before starting the design. It’s important to know whether the part will bear load, require sealing, or include moving elements. This will help in selecting the right material and setting appropriate design constraints.

If the part includes hollow areas or internal channels, ensure that the powder can be removed. If not, add escape holes or design the part for assembly.

Use simple geometry without excessively sharp angles, thin walls, or fine details. This simplifies post-processing. These considerations are especially important if the part will be painted or polished.

For multi-part assemblies, plan the assembly process in advance. We recommend incorporating features like guides, snap fits, or other tool-free connections.

For batch production, plan the layout of models inside the printer’s build chamber ahead of time to improve efficiency and reduce manufacturing costs. Useful tools for this include:

• Materialise Magics — one of the most powerful tools for model preparation and nesting
• HP SmartStream — HP’s native ecosystem for MJF platforms, featuring chamber packing optimization tools

Why MJF Is Ideal for Functional and End-Use Parts

MJF is more than just a fast printing method, it’s a technology that allows you to:

• Create prototypes and small production runs without tooling costs
• Design parts with high accuracy and consistent repeatability
• Combine multiple functions into a single part, eliminating the need for assembly
• Accelerate product development and time-to-market

Ensuring additive manufacturing efficiency makes MJF an ideal solution for startups, design firms, and industrial companies that need to rapidly test ideas as part of their generative design process and transition to manufacturing.

The successful use of MJF technology depends not only on the equipment but also on how well the part is designed. Understanding design optimization principles, knowing the limitations, and using modern tools enables engineers to get the most out of what MJF has to offer. By considering all these aspects from the very beginning of the design phase, you can do more than just print a part — you can create a competitive solution from effective and functional 3D printing designs.