Designing a part for additive manufacturing differs from more traditional methods. First, the processes are additive (require material to be added to make the part) rather than subtractive (require material to be removed from a block), and something like part orientation can have major effects on cost and efficiency.
Designing for Multi-Jet Fusion differs even more from other 3D printing processes. In this blog, we’ll explore what to consider when designing a part for Multi-Jet Fusion and the benefits and pitfalls to avoid.
Crafting Precision: Key Design Tips for Mastering Multi Jet Fusion
Consideration: Wall Thickness—It should be consistent wherever possible. Typically, a minimum wall thickness of 0.8mm is recommended, while thicknesses ranging from 2.5 - 4.0 mm are ideal.
Benefit: MJF can provide many benefits regarding wall thickness on your part, including excellent control over the printing process and enabling uniform wall thickness throughout your part. This is important for maintaining consistent mechanical properties across the surface.
Pitfall: If your geometry has a thick area (> 4 mm), as a rule, hollowing out the part to a wall thickness of 2 to 4 mm will be required to avoid sink marks or even a machine crash. Protolabs will modify the CAD file. Un-sintered powder will remain within the hollowed-out part and cannot be removed unless a drain hole is added to remove the excess powder.
Consideration: Reinforcement—For thin walls or large/ flat surfaces, consider reinforcing with ribs or gussets and holes surrounded by raised bosses wherever possible. This will decrease stress and increase strength and dimensional stability.
Benefit: Reinforcement can enhance the dimensional stability and structural integrity of your part, meaning parts are less likely to lose their shape and buckle under load, offering higher strength and durability.
Pitfall: Large unsupported (especially flat) areas are prone to sag and warp. Thin and unsupported walls can warp and collapse. Parts can also be more prone to cracking and surface irregularities.
Consideration: Raised Text and Small Features should be no smaller than 0.5mm; otherwise, they may not survive secondary post-processing.
Benefit: Multi Jet Fusion allows for high resolution and detail, meaning that smaller text and features can be produced better than other processes.
Pitfall: Raised text and small features when minimum sizes and materials are not considered can lead to poor quality, difficult-to-polish/ finish areas, increased risk of breakage and loss of details.
Consideration: Part Orientation—At Protolabs, we will orient your part so that you can print it efficiently and effectively. Part orientation can affect finish, mechanical properties, and dimensional accuracy.
Benefit: Orienting your part correctly can offer significant benefits from reduced time, efficient material usage and cost-effectiveness to improved mechanical properties and optimal surface quality.
Pitfall: If orientation is not considered correctly, it can lead to higher costs and increased timescales. Consider a part that is 3cm tall and 1cm wide. It would be quicker and cheaper to print 1cm of layer over 3cm of layer.
Consideration: Material Choice—Ensure you have a thorough understanding of the properties of the material you wish to use. Select accordingly.
Benefit: Multi Jet Fusion offers a range of materials with excellent properties, such as excellent thermal and chemical resistance, biocompatibility, and enhanced surface finishes. To top it off, MJF materials are often more cost-effective than those used in other 3D printing technologies.
Pitfall: Part failure is not uncommon due to a material being selected that doesn’t match the mechanical or environmental needs.
Consideration: Design for Assembly – For parts that are being assembled post-print, interlocking features, snap-fits, or fasteners should be designed considering material properties and process precision.
Benefit: Using MJF for assembled parts provides a more streamlined process compared with other 3D printing technologies. Parts produced using MJF can speed up the overall process because they require minimal post-processing.
Pitfall: If not considered, pre-print parts may not assemble correctly, or at all.
Consideration: Avoiding Overhangs—Unlike some 3D printing processes, MJF does not require support structures. The surrounding powder acts as a natural support.
Consideration: Prototyping and Production – MJF is cost-effective for both prototyping and low- to medium-volume production. Designers can consolidate multiple parts into a single print when possible.
Consideration: Isotropic Mechanical Properties—MJF offers consistent isotropic mechanical properties in the Z-build direction compared to other additive processes.
Benefit: Functional Prototyping and End-Use Parts—MJF is good for both. This includes automotive parts, consumer products, medical devices, and industrial components.
Benefit: MJF allows for customisation and personalisation without additional tooling costs. This is particularly beneficial for parts that require bespoke solutions, such as custom-fit devices and personalised consumer electronics.
Benefit: Multi Jet Fusion uses powdered materials efficiently and can recycle unused powder. This reduces waste and lowers material costs.
Benefit: Fast production speed is offered. The layer-by-layer approach allows for quicker turnaround times when compared to other 3D printing processes.
Pitfall: Build Layer Visibility—MJF layers can sometimes be visible in the final part. This should be considered beforehand when using them for aesthetic parts.
Pitfall: Overly Complex Geometries—While MJF allows for complex parts, excessive complexity can complicate post-processing and increase costs.
Pitfall: Inadequate Venting or Escape Holes – Without proper venting, unfused powder can get trapped in hollow or enclosed parts. Including escape holes will allow for effective cleaning.
Pitfall: Not Accounting for Shrinkage – Parts can shrink during cooling. If this is not accounted for it can lead to problems with dimensional accuracy and fitting of assembled components.
Designers can leverage the strength and opportunities that MJF technology provides by addressing such considerations and avoiding common pitfalls as part of their design process.