Now that MJF (Multi Jet Fusion) is being used to make parts, everyone is asking how is this different than SLS. In this blog I will try to explain some of the similarities and differences.
SLS has been around for a long time. It was originally patented by Carl Deckard and Dr. Joe Beaman in 1997. The patent expired in 2014.
MJF is a new technology that was developed by HP. It has only been commercially available in 2017.
How are they the same?
Material: Both use a powder material that is fused to form a solid part.
Layering: Both use a layering technique to build the part layer by layer.
Material Type: Both produce parts made from PA 12.
Supports: Both technologies don't require supporting the parts as they are supported by the powder bed.
How are they different?
Material Form: While both technologies use powder material, the powder used with MJF is claimed to be finer, producing a part with a higher density and better surface finish.
Layering: SLS has varying layer thickness from .06 mm to .18 mm. MJF has a fixed layer thickness of .08 mm. Addition layer thicknesses are expected for MJF in the future.
Material Type: SLS can do multiple materials including PA-12, glass filled PA-12, Flexible Material and PEEK. MJP is only doing PA-12 while other materials are in development.
Fusing Method: This is where the two processes differ the most. SLS fuses the material by melting with a laser that scans the surface of the powder fusing it into a solid section. MFJ uses a jet head that deposits a fusing agent on the power bed where the material should be fused and also deposits a detailing agent on the outline on the layer that needs to be fused. A heating lamp heats the fusing agent causing the powder to fuse together. The detail agent prevents the bleeding of the fusing to the untreated powder. This provides a crisper edge than SLS.
Mechanical Properties: Properties below are based upon unfilled PA-12
| Property |
SLS |
MJF |
Unit |
SLS Test Method |
MJP Test Method |
| Tensile Modulus |
1650 |
1700 |
MPa |
ISO 527-1/-2 |
ASTM D638 |
| Tensile Strength |
48 |
48 |
MPa |
ISO 527-1/-2 |
ASTM D638 |
| Strain at break |
18 |
20 |
% |
ISO 527-1/-2 |
ASTM D638 |
| Charpy impact strength (+23° C) |
53 |
-- |
KJ/m2 |
ISO 179/ieU |
-- |
| Charpy notched impact strength (+23°C) |
4.8 |
-- |
KJ/m2 |
ISO179/ieU |
-- |
| Flexural modulus (23°C) |
1500 |
-- |
MPa |
ISO178 |
-- |
| Izod Impact notched (23°C) |
4.4 |
-- |
KJ/m2 |
ISO 180/1A |
-- |
| Shore D hardness |
75 |
|
-- |
ISO 7619-1 |
|
| Melting temperature |
176 |
187 |
degC |
ISO 11357-1/-3 |
ASTM D3418 |
| Vicat softening temperature (50degC/h 50N) |
163 |
|
degC |
ISO 306 |
-- |
| Heat deflection temperature (@0.45 MPa)-Z |
-- |
175 |
|
-- |
ASTM D48 |
Speed: HP claims that it is over 10 times faster than SLS. View the video below to see how...
Part Size: SLS is available in different size machines with the largest with the build volume of 28 inches x 15 inches x 23 inches. MJF is only available in one size machine that has a build volume of 15 inches x 11.2 inches x 13.7 inches.
Accuracy: SLS has an accuracy of +/-.25mm with +/-.1mm for every 100 mm. MJF claims to have an accuracy of +/- .2 mm.
Material efficiency: SLS does have contamination issues of the powder that is left from each run that is not fused. Most reputable service providers use virgin material for each run to prevent problems. HP claims that they can reuse 80% of the material not fused without any degradation of quality.
Versatility: An SLS machine has everything contained in one piece of equipment. MJF separates the printer, build unit and Processing station into separate units. This allows for easier implementation of different materials and simultaneous building and cooling cycles.
What does the future hold for each technology?
SLS has been around for decades, so since the patents have mostly ran out competition will evolve with different designs to lower the cost. You're already seeing it with Formlabs introduction with the Fuse 1. HP is just starting with the MJF and we are expecting more materials soon as well as improvements in the software. In the future HP says that the technology can be used to change the color and property at the voxel level, producing parts that are not possible with any other technology.
For more information on MJF fusion see our blog "Is Multi Jet Fusion just another 3D printer"
For more information on MJF fusion materials see our blog "MJF Material"