Integration of pure copper to optimize heat dissipation in injection mould inserts using laser metal deposition

Abstract

Conventional infrared lasers (1070 nm) are not ideal for processing materials such as copper or gold. The reason for this is the corresponding high reflectivity of the aforementioned materials for infrared radiation. Since 2017, so-called “green lasers” {wavelengths around 500 nm [Kaliudis, see https://www.trumpf.com/de_DE/magazin/gruene-welle-fuers-kupferschweissen/ for “Grüne Welle fürs Kupferschweißen, TRUMPF Media Relations,” Press Release (2017)]} are available for welding processes and additive manufacturing technologies, viz., laser powder bed fusion (LPBF) and laser metal deposition (LMD). These lasers are specially designed for the processing of highly reflective materials and have been recently used for the fabrication of specimens from pure copper. Due to process reasons, only one alloy is typically used for the manufacturing of components if powder bed based methods (LPBF) are applied. For many components, however, it is the combination of different materials (differences in thermophysical properties) that leads to an improvement in the component performance. The LMD process, in contrast to LPBF, can be adjusted with relative low efforts for the processing of two or more different materials. This offers new possibilities for the functionalization of parts that are already fabricated through a combination of subtractive and additive technologies (hybrid manufacturing). A mould insert for polymer injection molding will be presented in this contribution. It was produced by using a combination of different processes (subtractive, additive) and materials (pure copper, steel 1.2764).2–5 For a conventionally manufactured basic body (1.2764), copper cores were integrated in the corner areas by means of LMD. The cladding of the cores with 1.2764 was carried out with regard to the basic body and guaranteed dimensional accuracy for further processing. In order to improve the flow of coolant to the copper cores in the later application, the upper part of the mould insert with conformal cooling channels was manufactured using LPBF. The entire tool insert demonstrator was then finished and case-hardened. Initial tests under real conditions on the overall component are intended to prove full functionality. Simultaneously, we discuss the added value of the hybrid manufacturing approach that was funded by the Federal Ministry of Education and Research (BMBF) in Germany as part of the AGENT-3D project IMProVe.