MJF vs FDM 3D Printing: Comparison and Considerations

Since its inception in the 1980s, additive printing or 3D printing technology has evolved into various technologies. Today in this article, we will compare the two most popular and versatile 3D printing methods today: the very popular FDM 3D printing and Multi Jet Fusion technology. The latter, introduced in 2016 by HP, represented the most important breakthrough in additive technology in the last decade.

1. 3D printing with FDM technology

1.1. What is an FDM 3D printer?

A FFF (Fused Filament Fabrication) or FDM (Fused Deposition Modeling) printer is a 3D printer used primarily for concept and prototype development. The material (fused plastic) is deposited by a three-axis system in individual layers and then several layers are fused together to form the 3D model. The low purchase costs - FDM printers can be found on Amazon starting at just over 100 €/$ - and the relative ease of use make this technology the most popular among makers.

In FDM technology, a filament a) of plastic material is fed through a heated moving head b) which melts and extrudes it, depositing it, layer by layer, in the desired shape c). A mobile platform e) lowers after each layer has been deposited. For this type of 3D printing technology additional vertical support structures are required d) to support the protruding parts. Source: Wikipedia by Paolo Cignoni

1.2. How does an FDM printer work?

The 3D file of the model you want to print is processed by a slicing software (the most used and easy to use are Cura, Simplify3D and PrusaSlicer) which literally 'slices' it into layers of the desired thickness. At the same time it generates a G-code file that describes to the printer the axis movements required to create the part itself. The FDM printer then melts the solid plastic filament and extrudes it from a nozzle layer by layer, thus forming the 3D object on the build surface. The layers are generally 0.1 mm to 0.5 mm thick, but can also be outside these values depending on the purpose of the object being created.

Printing process: 1 - Print extruder, 2 - Deposited material, 3 - Construction plan.
Source: Wikipedia by Paolo Cignoni

1.3. What are the most used materials in FDM printers?

The two most commonly used materials in FDM printing are ABS (acrylonitrile butadiene styrene) and PLA (polylactic acid). Both are inexpensive and available in a wide range of colours.

• PLA: offers one of the best surface qualities in FDM printing, is one of the easiest materials to print with and is also biodegradable, but is not resistant to impacts and temperatures above 60/70 degrees Celsius.
• ABS: offers good strength and thermal characteristics, but needs good ventilation as it emits strong odours when printed. It requires a heated build platform to prevent deformation.

FDM printing offers a good range of materials. Source filament to print

FACT: Professional FDM printers priced from 25K € and featuring heated chambers, nozzles that print at over 500 degrees and have adequate mechanics can create functional, high-performance technical parts of which the most popular are Peek, Carbon Peek and other materials suitable for industrial use and metal replacement.

1.4. What are FDM printers typically used for?

In addition to the functional solutions in the previous point, designers and engineers generally use FDM printers in the early concept exploration and medium-fidelity prototyping phases.

• Initial concept exploration phase: FDM printing allows users to easily print multiple concepts to examine the shape and fit of the real part before pursuing detailed features.
• Medium-fidelity prototyping phase: FDM printing is a good compromise for testing or prototypes that resemble real production parts. In these cases, thin layers of 0.1/0.2 mm are generally used. This option is ideal for obtaining feedback on feel and performance.
• Production of print runs: Although it is possible to see images of printing companies with dozens if not hundreds of FDM printers online, this seems to be a niche solution as the poor mechanical versatility of the input materials, the slow production rate (10cm3/h on average per machine compared to approximately 300cm3/h for MJF technology), the need for media, and the fact that the parts are not 100 per cent filled, limit its applications.

FACT: there are printing farms with over 500 FDM printers!

FDM printing farm: the Prusa printing farm has over 300 FDM printers in a single room

1.5.What are the advantages and disadvantages of FDM printers?

• Advantages: The most significant advantage offered by FDM printers is the low purchase and running cost. Due to their popularity in the consumer market, low-end FDM printer models start at EUR 100. FDM printers are easy to use and offer fast turnaround times from idea to prototype.
• Disadvantages: FDM printers do not offer the high quality, dimensional accuracy or reliable operation that other 3D printers offer. Reliability can be an issue with frequent remaking of parts and clogging of nozzles. Ultimately, FDM is not the best choice for printing parts that need to be of high quality.

2. 3D printing with MJF technology

2.1. What is an MJF 3D printer and how does it work?

Multi Jet Fusion is an additive manufacturing method developed by the Hewlett-Packard (HP) company and presented in 2016.
The final parts feature quality surface finishes, excellent resolution and more consistent mechanical properties than processes such as selective laser sintering or FDM.

Multi Jet Fusion uses an inkjet matrix to selectively apply fusing agents and details onto a bed of nylon or other material powder, which are then melted by heating elements into a solid layer. After each layer, the powder is spread over the bed and the process repeats until the part is completed.

At the end of the printing process, the build box is removed from the printer. An operator carefully takes parts out of the build box and removes residual dust with various shot peening systems.

To learn more about this topic, we suggest you read: What is Multi Jet Fusion 3D Printing?

Multi Jet Fusion (MJF) process scheme: (a) stages 1-5 of the fusion process); (b) 3D construction unit; (c) processing station. Source: research gate

2.2. What materials can be used with MJF printers?

MJF printing technology offers a limited range of materials but they are very versatile from a mechanical point of view. Currently there are five materials available. These materials are PA11, PA12, PA12GB, TPU and polypropylene. For an in-depth discussion we recommend you to read: HP Multi Jet Fusion (MJF) 3D Printing Materials and Properties

2.3. What are MJF printers used for?

Being able to produce at low cost 100% filled, functional parts with complicated and detailed designs without the need for any support, this technology offers a wide range of solutions, here we will limit ourselves to the main ones.

• Rapid Prototyping: Although prototypes can be created with any 3D printing technology, MJF can create robust prototypes with excellent mechanical properties to really test function and form.
• Run Production: The scalability of this technology is becoming a real contender to move low-volume production away from other production methods and in particular injection molding (see the article Injection Molding vs. 3D Printing. Which is Better?). This is particularly true for complex parts: in fact, not only with MJF technology obviously there is no need for expensive molds but besides this there are practically no design constraints normally associated with the production of injection parts.

One of 12 HP Multi Jet Fusion printers installed by Weerg. Get an instant quote.

Conclusions

One question that must be asked when asking whether one technology is better than another is: better for what?

Certainly, the arrival of MJF technology marked an enormous leap forward in the simplicity of construction, in the quality of truly functional industrial parts, and in the ability to compete effectively with injection moulding.

But it also has to be said that FDM printers, although with a limited range of professional uses, can provide visually acceptable parts and a considerable range of materials with an investment starting at around 150 euros versus the 500,000 euros needed to set up a single MJF.