CEM process
The ExAM systems make use of the CEM process (composite extrusion modeling), which is mainly related to FDM/FFF as well as to the EBM and SLS/SLM processes. It further combines these processes with an additional manufacturing step: the MIM (metal injection molding) process.
The result is a simple process based on cost-efficient and widely available pellets, which were originally designed for injection molding, with all of the liberties of additive manufacturing and without the need of casting molds. Thus, the CEM process drastically reduces not only the material costs, but also the machine costs, as no lasers, electron beams, real-time controlling or vacuum pumps are needed.
Furthermore, the process eliminates some common problems of additive metal manufacturing, such as internal stresses or the complicated adaptation of the system to new materials.
The internal stresses are considerably reduced by the CEM process, as the debinding and sintering of the metal part does not occur while it is being printed layer by layer, but during a subsequent step in a sinter oven, where it is subjected to a constant temperature field. Due to the fact that these two steps are separated, it is also possible to add an intermediate step for the processing of the unsintered green compact. This can subsequently further reduce the machine and tool costs for the post-processing steps. At this stage, it is worth pointing out that the process of debinding and sintering of the material has not changed due to the 3D printing process. Hence, all available systems and ovens can still be maintained.
The reason that the adaptation to a new material is so simple in the context of the CEM process is because the ExAM system does not need to be tuned to a new metal, but usually only to the matrix material, i.e. the plastic carrier. This matrix material is usually very similar for most MIM pellets, thus enabling fast and cost-efficient material adjustments.
