HP Multi Jet Fusion (MJF) has revolutionized 3D printing for production, offering high-strength, detailed, and scalable parts. But to get functional, precision-fit components—especially those with threads or mating features—you need to design with MJF’s unique characteristics in mind.
Unlike machining, where tolerances are precise and controlled, MJF parts experience shrinkage, powder residue, and slight thermal expansion, all of which can affect how parts fit together and how well threads hold up under repeated use. Understanding how to design for these factors can mean the difference between a seamless assembly and a frustrating mismatch.
Mastering Fit: Why Shrinkage and Clearance Matter
Because MJF parts shrink slightly as they cool, designers must account for tolerance adjustments to ensure parts fit correctly. Clearance fits—where parts slide together easily—need extra spacing to prevent friction or binding. Interference fits, which rely on tight compression, must be carefully tested to avoid parts being too tight to assemble.
For mating components, it’s common to oversize holes or undersize pins slightly to compensate for shrinkage and powder residue. If extreme precision is needed, features like pilot holes can be post-machined to final size.
Threads in MJF: What Works, What Doesn’t
Threads can be tricky in MJF because fine details may not resolve cleanly, and printed threads tend to be weaker than machined ones. Larger threads print better, but for frequent use or high loads, machining or inserts are the way to go.
Self-tapping screws work well for one-time assembly, but for durability and repeated fastening, threaded inserts are the best option. These metal reinforcements provide strength, longevity, and reliability far beyond what printed plastic threads can handle.
Post-Processing for Better Fit and Thread Performance
After printing, cleaning off powder residue is crucial for smooth assembly. Compressed air, ultrasonic cleaning, or light sandblasting help remove fine debris from threads and mating surfaces. Dyeing is preferred over painting since paint can affect fit and engagement.
For smoother assembly and less wear, dry film lubricants or coatings can be applied to reduce friction and extend part lifespan.
Design Smarter, Print Better
HP Multi Jet Fusion delivers incredible speed, strength, and scalability, but getting fit and threads right takes planning. Adjusting for shrinkage, choosing the best threading method, and using post-processing wisely can transform an average print into a production-ready component.
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