All 3D Labs Blog // MJF vs FDM: What is the Difference?

Originally posted on All 3D Labs

Since the mid-1980s 3D printing has slowly started to infiltrate the manufacturing industry. What started as a tool solely for the prototyping stage nowadays impacts the whole value chain through to end-part production. Far from being a single technology, 3D printing is a term used for seven (at the time of writing!) broad categories of technology with dozens of different methods of deployment.

Two of the seven categories are material extrusion and binder jetting — two very different types of 3D printing with relatively few overlapping features. While both aim to turn digital files into physical parts layer-by-layer, they do so through very different mechanisms. Multi Jet Fusion (MJF) is a powder-based process that produces high-quality parts with excellent surface finish, while Fused Deposition Modelling (FDM) is an extrusion-based process capable of processing a wide range of materials. Both technologies have their advantages and disadvantages, and picking a winner when it comes to MJF vs FDM will depend on the job in hand.

MJF

Multi Jet Fusion (MJF) is a type of advanced binder jetting 3D printing that uses multiple materials in the parts creation process. The base material (which is the material of the final part) is a polymer powder which is spread across the build area. Liquid fusing and detailing agents are then inkjetted with exceptional accuracy on top, after which the layer is exposed to an infra-red heat source. The polymer powder treated with the fusing agent then fuses in the heat, while the detailing agent inhibits powder fusing. MJF is an industrial-grade 3D printing technology.

Fused Deposition Modelling

Fused Deposition Modelling (FDM) is the original and most popular form of material extrusion 3D printing, dating back to 1989. FDM is most usually a filament-based 3D printing process that involves melting a thermoplastic filament and depositing it layer-by-layer via a heated nozzle to build up the object. FDM is the technology most frequently found in desktop 3D printers for hobbyists and casual users thanks to its relative simplicity, but industrial grade FDM 3D printers are used extensively across nearly all manufacturing verticals.

MJF vs FDM: Pros and Cons

MJF Pros

MJF technology has several advantages. As the inkjet print heads cover the whole build area in a single pass the process is much faster, especially for multiple parts, meaning low- to medium-volume production runs are viable. One of the biggest advantages of MJF is the high-quality surface finish it produces even before post-processing. The parts created with MJF have a smoother finish, sharper edges and crisper details than those made with FDM.

Another advantage of MJF is its ability to create complex geometries and intricate internal structures as the powder in the build chamber supports the part during the 3D printing process, so additional support structures are not required.

FDM Pros

FDM is well-established and can produce parts in a wide range of materials, including thermoplastics and composites. The relative simplicity of the FDM process means good reliability and the length-of-service in industry means many issues have been resolved over the years, leading to highly-refined and reliable systems.

MJF Cons

One of the main disadvantages of MJF is the limited range of materials that can currently be used, but future developments will expand the options. The upfront costs and complexity of MJF systems may also be off-putting for users, though MJF parts are cost effective when using a service provider thanks to the speed of production.

FDM Cons

One of the main disadvantages of FDM is the lower-quality surface finish it produces. FDM parts have a rougher surface finish and are more anisotropic than MJF parts, and require more post-processing. FDM is also slower than MJF as it processes at a single point (the nozzle), rather than across the whole build area — the lower print speed and longer production times add cost to the final parts and reduce the viability of manufacturing at scale.

Another disadvantage of FDM is its limited ability to create complex geometries and intricate internal structures. Parts 3D printed by FDM are limited by the need for support structures for overhanging features, which must be considered in the design phase and can be time-consuming to remove and affect the final part’s accuracy.

Which One is Right for You?

A good project for FDM looks like:

• One-offs and prototypes
• Parts that need highly specialised material properties
• Parts where anisotropy is tolerated
• Applications that don’t require smooth surface finish
• More simple parts without intricate internal geometries

A good project for MJF looks like:

• Complex, intricate parts
• Short- to medium-run production
• Isotropic parts
• Parts that have to look and feel good
• Applications that require fully sealed and watertight surfaces (with post processing)

Conclusion

Can you really pitch MJF vs FDM in the real world? Yes, but both MJF and FDM have their own advantages and disadvantages, and choosing the right technology depends on the specific needs of the project.

For those looking for multiple high-quality and precise parts, MJF is a better option due to its ability to create parts with fine details. Nylon PA 12 is suitable for a huge range of applications and is especially good for tactile parts and rugged prototypes.

On the other hand, those looking to produce parts with simple geometries and do not require high precision can use a wider range of materials through FDM. The process is slower and suited to one-off parts or very short runs.

Accessing both MJF and FDM 3D printing through a service provider allows access to the technology that best meets the project requirements without the cost of ownership of the system — and a project today might have very different requirements to the next!

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