Multi Jet Fusion3D Printing Design Guidelines
Our design guidelines for MJF include important information to improve part quality, minimize costs, and reduce overall manufacturing time. By following the guidelines, you can produce high-quality parts, reduce expenses, and improve productivity.
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Overview
Multi Jet Fusion (MJF) is an industrial 3D printing technology that chemically melts nylon powder layer by layer to create strong, precise, and highly detailed parts. This advanced powder-based process excels at producing functional components with excellent mechanical properties.
These MJF design guidelines outline critical considerations for wall thickness, surface details, clearances, and material behavior. Following these proven best practices ensures your parts achieve optimal quality, dimensional accuracy, and cost-effectiveness for both prototyping and high-volume production applications.
Maximum Build Volume
380 x 284 x 380 mm (15 x 11.2 x 15 inches)
If your parts require specific tolerances, please include an engineering drawing along with the part. Parts designed with large flat planes will likely warp, so this should be avoided if tight tolerances are required.
Parts with large flat surfaces are prone to warping and should be avoided for applications requiring tight tolerances.
Tolerances
Nylon PA 12: ±0.3%, with a lower limit of ±0.5 mm
If your parts require specific tolerances, please include an engineering drawing along with the part. Parts designed with large flat planes will likely warp, so this should be avoided if tight tolerances are required.
Always provide engineering drawings for parts requiring specific dimensional tolerances.
Layer Height
100 Microns
The layer height is the overall Z resolution of the part; we avoid stepping artifacts on important features of your models by orienting the part(s) along the Z plane or at a 20 degree angle on all sides.
Optimal part orientation minimizes visible layer lines on critical surfaces.
Surface Finish
Uniform, Matte
Parts are bead blasted and have a uniform grainy matte texture, similar to ultra-fine sandpaper.
The matte finish provides excellent grip and professional appearance for functional parts.
Wall Thickness
Thicker geometries and walls with variable thickness are at risk of deformation due to shrinkage and stress. In general, follow wall design rules for injection molding to achieve a more uniform and consistent part.
Minimum Wall Thickness
1.0 mm (0.039")
Supported walls are connected to two or more sides and are thick enough to support the model.
Thinner walls may warp or distort during the sintering process due to thermal stresses.
Minimum Unsupported Wall Thickness
1.5mm (0.059")
Unsupported walls are connected on only one side or edge.
Unsupported walls thinner than 1.5mm may sag or curl during printing, especially with larger layer heights.
Minimum Pin Diameter
2mm (0.07")
The minimum pin size depends on a combination of parameters such as; part orientation, nozzle diameter, and length of the pin.
Recommendations:
- Larger diameters required due to MJF layer adhesion characteristics
- Consider pin length and support requirements
- Test critical pin features for strength requirements
Minimum Detail Size
The quality of engraved and embossed features depends heavily on part orientation and the resulting thermal effects of printing. It is best to orient text or other small details facing down on the XY plane, or oriented vertically on the ZX or ZY plane (though layer height will limit resolution).
Debossed Details
Minimum Width: 1mm, Depth: 0.3mm
Debossed details are recessed features on your model. These features should be no shallower than 0.5mm (0.019").
Add draft angles to debossed features for better definition and easier support removal.
Embossed Details
Minimum Width: 1mm, Depth: 0.5mm
Embossed details are raised features on your model. These usually resolve better than engraved details. Extruded text should have a wall thickness of at least 1.5mm (0.059") when printed flat, and 2mm (0.079") when printed vertically.
Recommendations:
- Orient embossed features to minimize support requirements
- Use adequate thickness for layer adhesion
- Consider nozzle diameter limitations
Text
Minimum point size: 16pt
Minimum suggested text size on the top or bottom build plane of a MJF model is 16 point boldface. Minimum suggested text size on vertical walls is 10 point bold.
Recommendations:
- Use bold, sans-serif fonts for best results
- Orient text horizontally when possible
- Consider support elimination for vertical text
Part Clearances
The mechanical performance of printed assemblies is sensitive to variables such as print orientation, layer height and machine tolerances. It is best to test and refine any mated parts before committing to a full production run.
Minimum Clearance
0.5mm (0.019")
Clearance is the distance between two moving parts on hinges, joints, mating parts, etc.
Insufficient clearance can cause parts to fuse together during the printing process.
Minimum Press Fit
0.1mm (0.004")
For a tight press fit, add a small offset, and chamfer the leading edge to ease entry. Always print an initial test part to dial in dimensions.
Recommendations:
- Test press fits extensively before production
- Account for material thermal expansion
- Consider surface finish effects on fit
Printed Linkages
Minimum: 0.6 mm (0.023")
This defines the minimum allowed gap between a bush and a bolt, to avoid bonding of the hinge parts.
MJF excels at printing functional assemblies, but larger clearances may be needed compared to powder-based processes.
Holes & Gaps
Hole accuracy can vary depending on print orientation, thickness of surrounding material and support structures. For tight tolerances, consider printing center marks and post-machining them instead.
Minimum Hole Size
0.5mm (0.019")
Depending on orientation, circular holes can resolve as ovals – if higher accuracy is required, printing the hole smaller and then drilling it out is recommended.
Vertical holes print more accurately than horizontal ones due to layer stacking.
Minimum Gap Size
0.5mm (0.019")
Gaps or slots can fuse if made too narrow, and support material may be difficult to remove. If possible, orient gaps along the xy-plane for highest accuracy.
Recommendations:
- Orient gaps horizontally for best accuracy
- Consider support removal accessibility
- Account for material thermal expansion
Minimum Drain Hole Size
4 mm (0.15")
Hollow features may be filled with soluble support material, and must be designed with drain holes so that the support can be dissolved and removed during cleaning. Larger parts or parts with complex internal features may require larger holes to allow support material to fully dissolve.
Soluble supports make complex internal geometries possible with proper drain hole design.
Part Geometry
Part geometry can be optimized for 3D printing to reduce material usage, increase strength and rigidity, and take advantage of machine capabilities.
Fillets
Design Recommendations
Fillets can be used to reduce stress concentrations and increase the strength of your part. When designing fillet features across inside and outside corners, it is best to have them share a common center point in order to maintain a consistent wall thickness.
Recommendations:
- Use fillets to improve layer adhesion at corners
- Consider printing orientation when sizing fillets
- Larger fillets may improve part strength
Bosses and Ribs
Design Recommendations
Bosses and ribs are an effective way to add strength and stiffness to a part while keeping material consumption to a minimum, this can also reduce build time and use less support material.
Recommendations:
- Bosses and ribs can generally be matched to part thickness
- Use ribs to support large flat surfaces
- Consider heat set insert compatibility for bosses
Support Structures
MJF Printing
Parts do not require physical support structures. Parts are supported by the surrounding powder in the build chamber. This powder material is removed using compressed air glass beads leaving no defects or residual powder on the final part.
Self-supporting nature allows for complex geometries without support removal marks.
Infills
MJF Printing
Parts are always produced with solid walls. Infills are not applicable for MJF.
Solid construction ensures consistent mechanical properties throughout the part.
Threads & Inserts
Threads and inserts can increase functionality of your parts, but keep in account that printed threads will wear down through repeated cycles of assembly and disassembly, while heat set inserts can potentially deform or cause imperfections on part finish due to the heat processes of installation.
3D Printed Threads
MJF Guidelines
We recommend M6 thread sizes or larger, and use thread profiles designed for plastics. The rough surface produced from MJF printing will result in increased friction with connecting thread parts. We recommend using an offset of 0.5mm to compensate for thermal shrinkage.
Recommendations:
- Use coarse thread pitches for better durability
- Add 0.5mm clearance offset for thermal shrinkage
- Consider the naturally rough surface texture
Tapping & Threading
MJF Post-Processing
Design parts with holes sized for tapping, or center marks for drilling a pre-tapped hole. Tapping removes material, puts pressure on the surrounding geometry, and fastener locations are often points of stress, so make sure there is enough material surrounding the tapped hole.
Ensure adequate wall thickness around tapped holes to prevent cracking under stress.
Inserts
MJF Applications
Inserts are not required for MJF parts.
MJF parts can be directly threaded or machined for fastening without inserts.
Post Processing
While printed parts are highly functional and accurate, there are a variety of ways to modify them after printing to enhance durability or aesthetics.
Sectioning, Joining, and Bonding
MJF Post-Processing
Parts too big to fit on the print tray can be split in CAD and printed in multiple parts, then glued or press fit. Use joinery features, such as tongue and groove, to ensure the sections are aligned and bond tightly.
Recommendations:
- Use welding or brazing for permanent metal joints
- Design precise alignment features for assembly
- Consider thermal effects on joint integrity
Post-Machining
MJF Machining
Parts can be machined to tighter tolerances using traditional or CNC subtractive manufacturing equipment.
MJF parts machine similarly to conventionally manufactured metals.
Coatings
MJF Finishing
Parts can be treated with standard metal coatings (anodization, powder coating etc).
Recommendations:
- Choose coatings appropriate for the metal alloy
- Consider surface preparation requirements
- Account for coating thickness in final dimensions
Vapor Smoothing
MJF Post-Processing
Not applicable for MJF.
MJF parts achieve excellent surface finish through bead blasting and other mechanical processes.
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