Design Guide - Quick Reference

Download the Quick Reference Guide - HERE

Download the HP MJF Design Guide - HERE

Multi Jet Fusion (MJF) is a powerful 3D printing technology that offers high accuracy and detail for functional prototypes and end-use parts. To ensure successful printing with MJF, here's a guide to consider during the design phase:

Wall Thickness and Features:

• Minimum Walls: Aim for at least 1mm wall thickness to avoid warping. Excessively thin walls can become distorted during printing.  Thinner walls are possible where supported on at least three sides
• Maximum Walls: Avoid overly thick walls (above 7-8mm) as they can lead to uneven surfaces and internal stresses.  Where areas of the model exceed 10mm thick, the model is likely to be hollowed before printing to ensure printability.
• Embossed Details: Ensure a minimum height and width of 0.8mm for embossed text or features to improve legibility after post-processing.
• Engraved Details: Ensure a minimum height and width of 0.4mm using bold fonts and engraved width of at least 0.8mm to minimise the chance of polyshot media becoming trapped finer details.
• Tapered Edges: Avoid tapering edges to zero and instead give a rounded edge of at least 1mm to avoid damage during post-processing

• Minimum Clearance: Design a minimum gap of 0.6mm between mating parts to prevent them from fusing during printing. Increase the gap for thicker walls (0.9mm for walls above 50mm).
• Interlocking Parts: Consider interlocking features for easy assembly and improved part strength.  For large parts that will be printed in multiple pieces we can section for you and automatically apply the correct tolerances and optionally features such as lap joints, tongue and groove or dovetail joining methods.

Additional Design Considerations:

• Minimum Feature Sizes: Holes and shafts should be at least 0.5mm in diameter. Minimum font size for text is 6pt.  Beware that long thin channels may be difficult to clean and may suffer from solidified powder in long thin channels where super-heating will fuse powder.
• Large Flat Areas: Break up large, flat surfaces with ribs or other features to minimize warping.
• Lattice Structures: Design lattice structures with a minimum gap of 1mm between elements for proper removal of excess material.
• Material Selection: MJF typically uses Nylon PA 12, offering a good balance of strength and printability.
• Strength:  MJF parts are fully isotropic producing parts with strength along all axis.  Consider using the freedom of design provided by MJF printing technology to add geometries which provide strength rather than simply adding material (and cost) to your designs.

Fused Deposition Modelling (FDM) is a popular 3D printing technology known for its affordability and wide range of filament materials. This guide will equip you with the knowledge to design parts that optimize the capabilities of FDM printing.

Wall Thickness and Orientation:

• Minimum Strength: Maintain a minimum wall thickness of 1.2mm for vertical walls to prevent warping. Walls with horizontal support can be slightly thinner (1.0mm).
• Overhangs and Bridges: FDM printers struggle with unsupported features that jut outwards (overhangs) or bridge gaps between unsupported areas. To avoid printing issues, limit overhang angles to 45 degrees or less. Consider adding support structures in your design software or redesigning parts to minimize overhangs and bridges.
• Warping Reduction: Thicker walls (around 3-5mm) at the base of your design can help reduce warping, especially for tall prints.

Holes and Threads:

• Minimum Feature Size: Design holes and pins with a minimum diameter of 1mm for accurate printing. Smaller features may become clogged or break easily.
• Thread Design: Avoid sharp corners when designing threads. Instead, opt for rounded roots and crests (ACME threads) for improved strength. Consider tapping threads after printing for parts requiring high precision.

Clearances and Assembly:

• Frictionless Movement: Include a clearance of at least 0.5mm between mating parts to prevent them from sticking together after printing.
• Snap Fits: Design snap-fit features with a slight interference between parts (0.1 - 0.2mm) for secure connections.

Surface Features and Text:

• Visible Details: Ensure embossed features have a height of at least 0.3mm and engraved features have a minimum depth and width of 0.5mm to be visible on the final printed part.
• Text Clarity: Use bold text with a minimum size of 16 points on the top or bottom surfaces, and 10 points on vertical walls. Vertical text may require removing support structures after printing, which can add time.

Additional Considerations:

• Filament Choice: The ideal filament material depends on your application. Consider factors like strength, flexibility, heat resistance, and desired finish.
• Strength: Think about how the part will be printed when designing.  FDM prints are usually orientated with the flattest surface on teh build plate and layer are built up from this face.  The natural weakness of an FDM print will be in the Z orientation so features requiring strength should be printed horizontally.