In addition to selective laser melting (SLS), two other inkjet-based 3D printing processes have now become firmly established in additive manufacturing technology “powder bed fusion”. One is Multi Jet Fusion technology and the other is High Speed Sintering technology (HSS). But what exactly are the differences between the two processes? Where can the technologies be used economically? And what makes HSS an attractive alternative to Multi Jet Fusion?
Both binder jetting technologies demonstrate unique advantages, for example in terms of printing speeds, installation space volumes and the associated part costs. A serious difference, however, lies in the adaptability of the process technologies and the variety of materials that can be processed. But one thing is clear, both processes can be used to realize a wide range of applications – quickly and economically.
With a wealth of experience in inkjet technology, it is little wonder that the company decided to enter the 3D printing business in 2017 with its Multi Jet Fusion (MJF) technology. Today, 3D printed Multi Jet Fusion parts (printed in PA 12) find application in a wide range of fields thanks to their good heat resistance and mechanical strength. These include automotive engineering, mechanical engineering and the sports and leisure industry.
In the Multi Jet Fusion process, a radiation-absorbing ink is applied to a white powder bed, e.g. of polyamide 12 (PA12), by means of a print head. Areas not to be printed, on the other hand, are cooled with a second printing fluid, a detailing agent. The printer works layer-based according to a digital CAD data set. After the powder bed has been printed, an infrared lamp is used to inject energy into it after each layer. The black colored parts of the powder bed absorb more energy and fuse, while the white powder, thanks to the detailing agent, remains unfused. This process sequence is repeated until the entire build volume of the job box is filled and the required components within the powder bed are printed.
The Polymer High Speed Sintering (HSS) technology differs only slightly from the Multi Jet Fusion process. In HSS, too, an energy absorber is used to introduce a white powder bed into which IR energy is also introduced via a print head.
Just as with the MJF process, the colored sections of the powder bed fuse together, while the unprinted powder remains loose. A second cooling fluid is not necessary with HSS, because the temperature of the printed and unprinted powder material can be controlled independently of each other by means of two different IR emitters of different wavelengths with absorbers. The unprinted powder can be recycled, reprocessed and fed back into the process cycle, just as with MJF.
In terms of part quality and also application possibilities, the HSS technology is in no way inferior to the Multi Jet Fusion. However, the size of the VX1000 HSS makes it more suitable for industrial use and cheaper in terms of consumption costs than current printers, which significantly reduces the cost per part. In addition, the process allows customers to use their own materials without restriction and gives end users full access to print parameters to optimize production for the specific material and application. This is an advantage that is particularly useful for large-volume components or batch sizes for series production. This means that HSS printed components can also be used in a wide range of industries such as architecture, automotive and sports.
|Application areas||Material development & research, prototyping, production applications, service centers, manufacturing, injection molding companies||Prototyping, Service centers and production applications|
|Building volume||VX200 HSS: 290 x 140 x 180 mm|
VX1000 HSS: 1,000 x 540 x 400* mm
|MJF 540/580: 322 x 190 x 248 mm|
MJF 4200: 380 x 285 x 380 mm
MJF 5200: 380 x 294 x 380 mm
|Speed||VX200 HSS: 580 cm³/h|
VX1000 HSS: 6,500 cm³/h
|MJF 540/580: 1,817 cm³/h|
MJF 4200: 4115 cm³/h
MJF 5200: 5058 cm³/h
|Resultion||360 dpi||1200 dpi|
|Materials||PA12, TPU, PP, PEBA, EVA||PA12, PA11, TPA, TPU|
|Accuracy||±0.3% (with a lower limit on ± 0.3 mm)||±0.3% (with a lower limit on ± 0.3 mm)|
|Minimum layer thickness||80 µm||80 µm|
|Strengths (PA12)||VX200 HSS|
Method: ISO 527 – 2:93 – 1A
modulus of elasticity (XY): 1716 MPa
modulus of elasticity (Z): 1725 MPa
Tensile strength (XY): 52 MPa
Tensile strength (Z): 46 MPa
Elongation at break (XY): 10
Elongation at break (Z): 5
Method: ASTM D3418
E-modulus (XY): 1700 MPa
Young’s modulus (Z): 1800 MPa
Tensile strength (XY): 48 MPa
Tensile strength (Z): 48 MPa
Elongation at break (XY): 20
Elongation at break (Z): 15
|Cooling times||Without fast cooling: 14h***||Without fast cooling: 48 h*|
With fast cooling: n. A.
|Post-processing||Compatible with most available post-processing solutions||Automatic mixing, sieving and filling, semi-manual unloading, fast cooling, external storage tank|
* depending on material and grain size
** voxeljet allows the customer to use any material at his own risk and can offer advice on material selection.
*** depending on the construction height
The Multi Jet Fusion process uses two types of fluids to print the components. The energy absorber, also called Fusion Agent, is a water-based, radiation-absorbing ink that colors the corresponding areas of the powder bed black. To achieve precise edge definition, a second liquid, known as Detailing Agent, is also added to the outer edge areas of the component to be printed in order to cool the edges of the components prior to the sintering process and thus ensure increased precision. In addition, bubble jet print head technology is characterized by a high, theoretical resolution of 1200 dpi.
With a higher build volume and faster shift times compared to HSS technology and a “plug and play” solution, MJF is well suited for use in prototyping, service centers and production applications. Materials already available for the Multi Jet Fusion include several PA12 variants, as well as TPA, TPU, PP and PA11.
Unlike the Multi Jet Fusion, the HSS technology uses a piezo print head and only one energy absorber. The energy absorber is an oil-based ink that is used to color the powder bed. Through particularly precise light wave control and wavelength definition, the IR energy can be selectively introduced into the powder bed, and only where components are to be formed. This precise control results in extremely sharp edge details.
The print head works with a resolution of 360 dpi. However, since the grain size of the powder to be printed is the decisive variable for the resolution with Powder Bed Fusion technology, a higher printhead resolution is also not necessary, but rather the interaction with the thermal management is decisive for the detail accuracy. The industrial inkjet printhead is optimally matched to the ink, resulting in increased printhead durability. In addition to oil-based fluids, the inkjet printheads can also process water- and solvent-based fluids.
Another difference to Multi Jet Fusion is the open-source approach of HSS technology. With HSS 3D printing systems, users have an open 3D printer at their disposal in which all process parameters can be freely accessed and individually adapted to their own materials. This makes HSS technology ideal for the individual development of new 3D printing polymers for optimum part properties. The developed process parameters can be scaled up for use on a larger 3D printing system, such as the VX1000 HSS, in order to print even larger production volumes and quantities economically. The advantages of the open-source approach, as well as the use of a single absorber, are also reflected in the running costs. While the systems are in a similar price range when considering initial costs, HSS systems can also be operated with customer’s own powders, while the consumption of a single absorber further reduces running costs.
There are further differences in the choice of materials. For example, HSS can be used to process polymers such as PA12, PA6, PP, PEBA, EVA and TPU, due to the ability to flexibly adapt the system to the desired material, as well as the use of only one oil-based ink. So far, powder particle sizes from 30 µm to 1 mm have already been successfully processed.