IMAGE: HP Inc.
When HP announced the key features of their new 3D printer ‘Multi Jet Fusion 4200’ in 2014, they promised it would introduce a new kind of additive technology, which would print parts that were more accurate and stronger than those produced by FDM and laser sintering printers – and at ten times the speed. This announcement shook up the entire 3D printing world, with some being extremely excited about the new technology and others being skeptical about whether HP, a newcomer to the arena, could make good on its promises.
One of the hottest topics at that time (and now), was how HP Jet Fusion compares to laser sintering. These technologies are fundamentally different (more details below); however, they use similar materials to create additive manufactured parts. HP Multi Jet Fusion currently works only with one particular plastic, PA12 (Polyamide 12, otherwise known as Nylon 12, see details below). Laser sintering works with a number of different materials; however, PA12 is by far the most common plastic polymer used in laser sintering as well.
Now that the HP Multi Jet Fusion 4200 has been on the market for a few months, it is time to take an in-depth look at the most important characteristics of both technologies and most importantly, at the quality of the 3D printed parts that they are capable of producing.
Manufacturers – the companies behind the technologies
Laser sintering has been on the market for more than 30 years. It was initially developed by Carl R. Deckard in the mid-1980s; he founded the company DTM Corp. (Desktop Manufacturing Corporation), which marketed the world’s first laser sintering machine (‘Sinterstation 2000’) in 1992. That company was finally sold to the industry giant, 3D Systems, in 2001, for 45 million USD. However, today 3D Systems plays only a minor role in laser sintering, whereas the German–based Corporation, EOS, sets the industry standards. EOS initially produced stereolithography machines; later on it switched to the laser sintering technology, and then quickly became world market leader.
Hewlett-Packard (HP) entered the 3D printing market quite late, at the end of 2016. They were known before this for their sophistication in ink jet 2D printing, among other things. Not surprisingly, their first 3D printer, the Multi Jet Fusion 4200, was based on ink jet technology (more details in the technology sections). While HP Inc. (Hewlett-Packard’s hardware arm) might be new to the field of 3D printing, they are not exactly a ‘start up’ – just the R&D budget of HP Inc. alone is larger than the revenues of EOS and 3D-Systems taken together.
Technologies – HP Jet Fusion vs. Laser Sintering
The principle of laser sintering is fairly simple: a layer of powder (metal or plastic) is spread on a build platform. Next, a laser beam ‘sinters’ the powder in defined areas. Sintering means that the powder is heated up to a temperature at which the plastic particles start sticking together –they solidify once they cool down. The platform is then lowered (typically 100 – 120 microns for most machines) and the process is repeated until the model is complete. More about the technology.
Multi jet fusion works completely differently. The only step that both technologies have in common is that a powder is spread onto a build platform. Then, HP Jet Fusion 3D printers eject a liquid called a fusing agent onto the powder. The solidification is achieved by applying a heat source (infrared light) to the entire build platform. The fusing agent is a heat conductive liquid which absorbs more energy, and therefore heats up more readily, than the powder without the fusing agent. The areas with fusing agent heat up to the extent where the powder entirely melts and fuses.
Imagine a white sheet of paper; one area is printed completely black. If the sheet is then placed in sunlight for a while, the black area will become warmer than the white surrounds since the black absorbs more of the sun’s energy. Fundamentally, jet fusion applies the same logic; it uses a black colored fusing agent which absorbs more heat (from the heat source) than the raw, white powder.
Jet fusion uses a detailing agent in addition to the fusing agent. The detailing agent is printed right around the model area. The detailing agent is thermal insulating and ensures that the edges are clearly defined by creating a steep temperature gradient between the model areas and the space around. Without the detailing agent, the edges and details of the model would be rather blurry.
More about HP Jet Fusion.
Source: Youtube.com / HP Inc.
Mechanical Properties of the 3D Printed Parts
Both technologies use the same basic material, in chemical terms, however, the mechanical properties of the 3D printed parts produced in these different ways, differ significantly.
In laser sintering, a small laser beam (typically 100 – 200 microns diameter) heats up the powder to slightly below the melting point. Hence, the parts are ‘sintered’ (as the name suggests) and not fully fused together.
In contrast, jet fusion (again, as the name suggests) fuses the material: i.e., actually melts it. As a result, jet fusion parts are more homogeneous in all directions (X-Y and Z-axis), and have a higher density.
Here are some examples of what this means in practice (black bar, jet fusion; grey bar, laser sintering):
Laser-sintered parts are more porous, while HP Jet Fusion parts have the same density as injection-molded PA12.
In the X-Y-axis, most of the data is comparable. Differences arise in the Z-Axis, where jet fusion performs better in terms of tensile strength and elongation at break. This data indicates that jet fusion parts are more isotropic than laser sinter parts (which display a greater difference between X-Y and Z axes).
Please keep in mind that all these figures are just for guidance; actual values can differ by part, machine, machine settings and part orientation.
Laser sintering and jet fusion parts perform equally in the x-y axis, however, along the z axis (parallel to the printing layers); laser-sintered parts have significantly less strength. This means that jet fusion and SLS parts are equally strong perpendicular to the printing layers, but SLS parts break more easily along the layers.
While jet fusion parts do display differences between their X-Y and their Z-axis, all these values are lightly above those yielded by laser sintering. This means that jet fusion parts are slightly more resilient against deformation.
Elongation at Break
Both technologies perform (almost) equally in the X-Y axis, but jet fusion is more resilient along the Z axis.
Differences in Surface Quality
Since both technologies are powder-based, both types of surface are covered with individual powder grains. The powders used in laser sintering and jet fusion are fairly similar (~60 micron grain size); hence, the surfaces have a similar look and feel. However, measurements unveil a slightly decreased surface roughness of HP’s Multi Jet Fusion System over Laser Sintering. The superior surface quality of the Multi Jet Fusion system most likely results from a more homogeneous melting process of the powder.
Ra and Rz surface roughness for untreated SLS & Jet Fusion prints.
Source: 3Faktur & Ernst-Abbe Hochschule Jena
Ra and Rz surface roughness for bead blasted SLS & Jet Fusion prints.
Source: 3Faktur & Ernst-Abbe Hochschule Jena
Methodology: Ra and Rz values were measured on standardized test parts (20 x 40 x 3 mm). The parts have been printed flat (x-y) on HP’s Multi Jet Fusion 4200 (HP High-reusability PA12) and EOS P 380 (PA2200). Measurements were made by Ernst Abbe Hochschule Jena and 3Faktur.
Dimensional Accuracy of both Systems
Source: Hewlett-Packard, own measurements.
The chart displays the dimensional tolerance in mm for a part not exceeding 100 mm.
The dimensional accuracy of jet fusion is slightly higher. There are a number of reasons for this difference: one of the most important being the heating process. Whereas in laser sintering a laser beam with a small diameter of just 100 – 200 microns heats up very small areas of the powder, in Jet Fusion the entire build platform is heated up at the same time. The effects are that a) the model areas are heated up much more slowly in jet fusion and b) the entire area is heated up simultaneously, so that temperature gradients are less of a problem. Both circumstances minimize the risk of thermal effects (such as shrinking or wearing) compromising dimensional accuracy.
Cycle time Jet Fusion vs. SLS
The printing time of one complete cycle of an HP Multi Jet Fusion 3D Printer (layer height 80 microns) takes about:
- Pre-heat: ~1.5 – 2 h
- Printing: ~12 h
- Cooling: ~12 h
- Total: ~26 h
The build volume is 380 x 284 x 380 mm (~40 l).
For laser sintering, those values vary strongly, since there are tons of machines, settings and materials. A fairly popular machine is an EOS Formiga, which allows high-resolution 3D printing. The build volume is roughly half the size of the Multi Jet Fusion 4200 (~16 l). For a 100 micron layer height print the printing cycle looks about the following
- Pre-heat ~1.5 – 2 h
- Printing ~30 h (strongly dependend on how packed the build space is)
- Cooling: ~10 – 12 h
- Total: ~40 – 45 h
It is recommended to cool the platform 1:1 with the printing time (i.e. 30 h printing = 30 h cooling), however in practice this time is normally shorter. There are larger, high-performance machines by manufacturers like EOS, which match HP’s speed performance by applying large build platforms and dual laser systems.
Advantages and disadvantages of each technology
HP Jet Fusion
- High Accuracy / repeatability
- High Strength
- High through-put
- Large variety of system sizes and materials
- Ease of dyeing
- Established and mature technology
- Only one material & color
- Size limitation – only one machine with one size
- Mechanical performance of parts
- Low dimension accuracy
- More expensive, since less material can be re-used.
Laser sintering has a wider range of applications because this technology is well established and offers a large choice of materials and sizes. Multi jet works (so far) only with PA 12 and the machine comes in only one size (380 x 284 x 280 mm max. space).
Laser sintering is the right choice for:
- Parts larger than 380 mm
- Parts for which color matters (e.g. white architectural models or colorful accessories)
- All materials other than PA12
Applications for HP Jet Fusion include:
- Short-run manufacturing (high-throughput and higher accuracy of the system)
- Parts for which mechanical properties and isotropy matter
- Projects with tough timelines (short printing cycle)
About 3Faktur: 3Faktur is an additive manufacturing service provider for companies across all major industries. We work with multiple 3D printing systems, including the HP Jet Fusion.
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