SLS (Selective Laser Sintering) or MJF (Multi Jet Fusion)? What technology to choose, what are the differences between them, and what are the benefits? We often receive these questions from our customers.
Neither technique is as well known and widely used as FFF/FDM. The main reasons are the higher space requirements and the purchase price of the printer. However, we can say with certainty that in industrial production, SLS and MJF are popular and well-known, and their popularity is growing exponentially. Traditionally they are used in production and automation, but they are increasingly used in small batches.
what do they have in common
In both cases, it is Powder Bed Fusion (PBF). Small powder particles are melted/sintered by heating (the size of powder particles is 30-60 μm).
What is the difference?
The main difference between the technologies is the source of heat source for sintering powder. This directly affects the mechanical properties of prints.
SLS | MJF | |
Technology | Selective laser sintering was developed in the second half of the 1980s in the USA. Currently, most of the patents expired, this allows the growth of the technology and entering new companies. Print quality may vary from printer to printer. The build volume is heated up close to the melting point of the material and after that is used the laser to sinter powder surface. | Multijet fusion is a patented technology of the company HP and their workhorses are printers 4200 and 5200. Both have a build volume of 380 x 284 x 380 mm and the key difference is the printing speed. Likewise using SLS technology, the entire build volume is heated up close to the melting point of the material. Then the print head jets a fusing agent in one pass onto the powder surface in the shape of the two-dimensional layer. Next, infrared lamps heat and fuse the powder. Then, the next layer of powder material is deposited. |
Materials | As this is an older technology, there are several materials and different manufacturers you can choose from. Materials are either offered by the printer manufacturers themselves or there are companies exclusively focused on the production of materials. The most common material is PA12, but other materials such as PA11, PA6, TPU, PEEK, PP are also available. Various composites such as PA12 with glass, aluminum or carbon particles. | Although HP is the only manufacturer of MJF technology, they are opened to materials from external suppliers and they do not want to develop it by themself. They have cooperation with brands like BASF or Evonik which guarentee the quality. Curently provided materials are PA12, PA11, PA12 glass beads, TPU and PP. |
Printing precision | Z-axes-- 0.1 mm | Z-axes-- 0.08 mm |
Print speed /price | Print speed is dependent on how many parts are printed. A laser has to draw the surface of each model separately. This is an advantage when just only one part is printed. At a bigger volume, it takes a longer time compared to MJF. Due to this factor also the price is higher. | Print speed is the same regardless of how many parts are printed. The time needed to make a layer is constant. This is an advantage when many models are printed at once and the whole build volume is filled. Usually, low-volume production is more cost-effective on HP printers. |
Comparison of mechanical properties of PA12
PA12 is the most widespread material for both SLS and MJF. The final mechanical properties of the prints are very similar and in most cases, there is no difference. However, it can say that PA12 printed by MJF has slightly better durability. In the table, you can find information on mechanical properties declared by the manufacturer. The tests were performed according to two different methods, therefore the results are not comparable
SLS | MJF | |
Brand | EOS | HP |
Build volume | 650 x 320 x 560 mm | 380 x 284 x 380 mm |
Tensile strength | XY: 48 MPa Z: 48 MPa (ISO 527) | XY: 48 MPa Z: 48 MPa (ASTM D638) |
Tensile modulus | XY: 1650 MPa Z: 1650 MPa (ISO 527) | XY: 1700 MPa Z: 1800 MPa (ASTM D638) |
Flexural modulus | XY: 1500 MPa Z: 1500 MPa (ISO 527) | XY: 1730 MPa Z: 1730 MPa (ASTM D638) |
Elongation at brake | XY: 18% Z: 4% (ISO 527) | XY: 20% MPa Z: 15% MPa (ASTM D638) |
In order to compare prints were chosen the most common setting, using fresh material. Using high-quality material and handling it is a very important thing that can affect the final properties of prints.