Rostock (Germany) based AIM3D, a manufacturer of multi-material 3D printers, developed a new generation of printheads for its proprietary CEM process (composite extrusion modeling). The new CEM-E2 extruder is a multi-material printhead for additive manufacturing that can print metals, plastics and ceramics. AIM3D is currently developing larger pellet 3D printers in order to be able to manufacture larger parts and achieve even higher build rates. The official launch of these products is planned for Formnext 2021 in Frankfurt, Germany.
The new CEM-E2 extruder
The CEM-E2 extruder’s printheads are matched to different material groups. The version “M” (metals) printhead is used for metal-filled materials (MIM pellets), printhead “P” (plastics) is for filled and unfilled plastics and printhead “C” (ceramics) is for higher abrasion ceramic-filled materials (CIM pellets). The new extruders/print heads are characterized by significantly improved accuracy of delivery. This enables a higher surface quality and better mechanical properties of the component. Extrusion speed has been increased by more than 200%, with manufacturing rates of up to 220 cm³/h with a 0.4 mm nozzle now possible. Clemens Lieberwirth, CTO at AIM3D: “The material feed, as well as an optional water cooling system and an improved holder for the quick-change system, are all new developments. The patented CEM-E2 extruder with its parameters tailored to specific materials sets new standards in the CEM processes.”
The appeal of CEM technology lies in the use of an additive manufacturing system for multiple materials. In addition, filaments can often be dispensed with and conventional pellets used, which offers considerable cost savings. However, the most significant benefit is the reduction in component build times through the direct use of pellets.
Schaeffler’s 3D printed PPS GF 40 manifold
With the new CEM-E2 extruder, a component has been successfully developed made of PPS GF 40 for Schaeffler. A polyphenylene sulfide (PPS) from Celanese was used. In addition to good basic properties such as high flame retardancy, there are a large number of possibilities to tailor properties such as conductivity, thermal expansion or friction behavior with this material. The development partnership between AIM3D and Schaeffler set the task of developing a coolant manifold as a 3D printed component. The CEM-E2 extruder was also able to print the identical PPS and, as in the case of injection molding, PPS GF 40 material was chosen for 3D printing. Normally, the alternative for 3D printing this component would have been a PA6 30 GF (polyamide) since glass fiber reinforced PPS in filament or powder form suitable for 3D printing is not available. The PPS material enables higher temperature characteristics and improved mechanical properties as well as the potential for lightweight construction. The extremely high media resistance is also a decisive factor, as PPS absorbs hardly any water.
PPS GF 40 materials, which are chemically identical to the injection molding pellets, are currently not available as filaments form for 3D printing. A cost-based comparison between PPS filaments available on the market and the pellets already shows the great potential of pellet extrusion, even if the materials were available. Clemens Lieberwirth: “A direct comparison between PPS in filament and in pellet form shows there are very significant cost advantages of the pellets as well as considerably higher build rates. The manufacturing costs alone for the component (machine hours + material) are around €70, printing time is around 12 hours. Filament printers would need at least 50 hours with the same layer thickness (50 µm).” According to Lieberwirth, PPS is an interesting material for many challenging environments in the automotive and chemical industries. For example in coolant distribution systems.
Versatile, stable, conductive and media-resistant
PPS offers a number of properties that other plastics, but also metals, cannot achieve. The lightweight material reduces weight and thus fuel consumption and CO2 emissions, and in many areas, the customer can tailor material properties such as conductivity, tribology or stability to suit their needs. Combinations of these properties, which other materials are unable to provide, are also possible. When compared to cheaper polymers, PPS exhibits higher strength and lower thermal expansion. At the same time, PPS is more resistant to water, hydrolysis and solvents as well as having clear advantages in terms of electrical and thermal insulation.
Another relevant benefit of PPS is its “built-in” flame retardancy. PPS is inherently flame retardant, while other polymers require additives. However, these additives sometimes considerably alter mechanical properties and have the undesirable characteristic that they can be washed out by steam or aggressive cleaning agents. In addition to flame retardancy, PPS has other favorable properties without the need for any further optimization. These include a high melting point of around 280°C, very low moisture absorption and very high chemical resistance – at room temperature PPS is impervious to all solvents. Another benefit is its thermal and electrical conductivity. By means of using additives and adjusting the dosage of these additives, electrical conductivity can be increased, making any specific volume resistance between 1 and 1015 ohms possible. Functional characteristics thus range from antistatic to conductive properties and electromagnetic shielding right up to protect against electrical discharges. This makes the material suitable for industrial instruments in environments that require explosion protection or for electronics housings that have to meet electromagnetic compatibility requirements.