Differences between MJF and FDM Printing

MJF vs FDM Tecnologie di Stampa 3D a Confronto

MJF and FDM printing: what are the differences? The comparison

Additive printing (3D printing) originated in the 1980s and has since evolved into many different technologies. Today, the most popular 3D printing methods are FDM wire printing and Multi Jet Fusion (MJF) technology, which HP introduced to the market in 2016 and remains the most innovative additive technology. Knowing which printing technology best suits one’s needs is not always easy. This article compares the two 3D printing technologies. It reveals their functionality, the most commonly used materials, and their intended use to make choosing a printing service easier.

What is FDM (fused deposition modelling) printing?

FDM printing involves loading a thermoplastic filament (PLA or ABS) spool into the printer. The presence of the nozzle is crucial because once it reaches the set temperature, it melts the filament with an extrusion head.

The extrusion head is attached to a system that moves it along three axes. The printer transforms the melted material into thin strands and deposits them layer by layer along a path determined by the design. At each step, the material cools and solidifies. Fans are sometimes attached to the extrusion head to speed up the process.

Several passes are essential to complete an area. When the printer finishes a layer, the build platform descends, and the machine starts working on the next layer. In some printer configurations, the extrusion head moves upwards. This process is repeated until the part is completed. This type of printing is acceptable if we need to print a single object, but it is unsuitable with mass-produced parts, as the production time is too long.

What materials are commonly used in FDM printers?

The materials commonly used in FDM printing are PLA and ABS, known as ‘polylactic acid’ and ‘acrylonitrile butadiene styrene’. Both are inexpensive and available in a wide range of colours.

  • PLA: is not impact resistant or resistant to temperatures above 60°C. However, it is a biodegradable material and very easy to print with the best surface quality for FDM printing.
  • ABS: ABS offers excellent strength properties but requires good ventilation due to the strong smell emitted during printing. A heated build platform is needed to avoid deformation.

For which applications are FDM prints typically required?

FDM prints are fine if we need to print a single object but not mass-produced parts, as the lead time for a single product is too long. This type of print is used to evaluate the initial stages of a project and perform tests.

  • Early concept analysis phase: with FDM printing, different concepts can be conveniently printed, and the shape and fit of the actual part can be analysed before pursuing detailed functionality.
  • Prototyping phase: FDM printing is a good expedient for testing and prototyping, similar to genuine production parts. In this case, thin layers are typically 0.1/0.2 mm. This alternative is suitable for obtaining feedback on feel and performance.

What is 3D printing with MJF technology?

Multi Jet Fusion is an additive manufacturing system designed and produced by Hewlett-Packard (HP), introduced to the market in 2016. The end products have a higher-quality surface finish, better resolution, and more consistent mechanical properties than other processes such as Selective Laser Sintering (SLA) or FDM.

MDF printing is performed on a bed of nylon powder using patented inkjet printing technology. The printer starts by colouring the dots in black to create the object. Subsequently, halogen lamps raise the temperature to 180 degrees, melting the various dots. The parts that have not been coloured are not printed but discarded.

The process is supervised by heat-sensitive cameras, which ensure that the temperature inside the booth remains homogeneous at all times. This printing technique has many merits: it guarantees excellent precision, has a remarkable printing time, and is the best choice for industrial production.

What materials can be used with MJF prints?

Although the materials available for MJF printers are limited, they are very adaptable mechanically and are currently available in different materials, such as PA11, PA12, PA12GF, and polypropylene.

  • PA12

This nylon material is very versatile and, in terms of cost and quality, holds its own against injection moulding. It is ideal for sealed applications, complex assemblies, housings and enclosures.

  • PA12-GF

This nylon material is reinforced with 40% glass fibre. MJF printing offers better detail and high quality on this material. It greatly reduces alteration problems on parts with large planar surfaces.

  • Nylon PA11

It provides more excellent extension at break and, therefore, better impact resistance and elasticity, making it perfect for automotive interiors, sporting goods, snap fasteners, prostheses, insoles, and living hinges.

  • Polypropylene

This material has very high chemical resistance and weldability. It also absorbs little moisture for prototypes and functional parts. It has many applications, particularly in the automotive, industrial, medical and consumer sectors.

What are MJF prints used for?

MJF prints are robust, complex, accurate, and 100% functional. They are required in rapid prototyping and low-volume production.

  • Rapid Prototyping: MJF prints create robust prototypes with brilliant mechanical properties to verify form, efficiency and functionality.
  • Short-run production: With MJF technology, other production methods, such as injection moulding, can be dispensed with. Where complex parts have to be produced, there is no need for expensive moulds or design constraints, usually required for injection moulding.

When we ask ourselves whether one technology is better than another, we always have to ask the question: what is better? Indeed, the advent of MJF represented a quantum leap in terms of ease of production, quality of truly functional industrial parts and competitiveness compared to injection moulding.

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