The Chair of Microfluidics at the University of Rostock in Germany is working with Stenzel MIM Technik on a project to print a 3D metal injection molding (MIM) tool. The basis of the development is using AIM3D’s CEM technology with an ExAM 255 system. The ExAM 255 system combines a high precision of 3D components with high build speeds for additive manufacturing (AM). Compared to a conventional machining approach, using an AM process to produce a MIM tool reduces the total production time from around eight weeks to approximately five days.
As part of a project funded by the German Federal Ministry for Economic Affairs and Energy (BMWi), the 3D-printed MIM tool is a cooperative development between the Chair of Microfluidics (LFM) at the University of Rostock and Stenzel MIM Technik. The duration of the project is from April 2021 to October 2023. The basis for the process and application is using the CEM technology from AIM3D, implemented on an ExAM 255 system. The project represents the current state of the art in 3D metal printing.
A 3D tool with near-contour cooling for metal injection molding
The goal of the joint project between the University of Rostock and Stenzel MIM Technik was to use 3D printing to manufacture a tool for metal injection molding with near-contour cooling. In 3D printing, near-contour cooling can be incorporated as a so-called functional integration with helical channels directly in the tool. In other words, it is not embedded as inlets as with larger tools. The goal of any near-contour cooling of injection molds made out of metals or polymers is to reduce the cycle time significantly. The principle of near-contour cooling is to guide coolant fluids through near-contour cooling channels with low cross-sections. They cool the component already during the cycle. This leads to a faster demolding process, which significantly shortens the cycle. The complex geometry of the helical cooling channels is created with the help of CAD technology using simulation models based on the “needs” of the component. Long-term experience shows a reduction in cycle time by around 20%, depending on wall thickness and size.
As an integrated component solution, 3D printing offers the advantage of a “one-shot technique” as a functional integration compared to mold-bound processes. The application example, therefore, demonstrates an opportunity to reduce the “time-to-market” drastically. The cooperative project aims to develop a new process chain for the cost-efficient and rapid production of MIM tools. Up until now, up to eight weeks have been needed to produce a conventional metal injection mold. With 3D metal printing, the provision time of a MIM tool can be reduced to about five days.
Details of tool development at the University of Rostock
As part of the cooperation, an optimized 3D model of the tool was initially developed using CAD and simulation tools. This data was then transferred to the ExAM 255 CEM system, together with the necessary process parameters. A so-called “green part” is then 3D printed. Afterward, the part is sintered in a multi-stage process to produce the final material properties. With this process, complex metallic components can be rapidly produced after the necessary de-binding and sintering steps. At the same time, the CEM process allows for the control of the volumetric shrinkage associated with sintering. The resulting mold has a cavity. The component consists of a thick-walled part with thin fins. These fins cannot be produced without near-contour cooling, as they are difficult to de-mold. Stenzel MIM Technik hopes to significantly reduce cycle time for this component by up to 70 to 80%. However, injection molding trials for testing are still pending.
Material diversity with the AIM3D ExAM 255
The multi-material 3D printer ExAM 255 can use various materials (metals, plastics, ceramics) and multiple processes (hybrid components). Compared to powder bed processes or even other 3D printing processes that use filaments, systems using the CEM process achieve tensile strengths close to classic thermoplastic, mold-bound injection molding. The price advantage of 3D printing is particularly striking when commercially available granulates are used instead of filaments. When granulates are used, the CEM process leads to cost savings of up to a factor of 10.