Design for additive manufacturing of hot stamping tools

Abstract

Hot stamping is a widely used process in the automotive industry for forming advanced steel grades and aluminium alloys into complex geometries. In this process, a blank is heated, formed while hot, and quenched in the die to achieve desired mechanical properties. These properties depend on the quenching rate, achieved through fluid circulation, typically water, via a complex system of cooling channels. Designing these channels is a sophisticated process, involving iterative design to meet quenching requirements. Hot stamping tools usually feature straight channels as conventional manufacturing processes limit the creation of advanced cooling systems like conformal channels. Other manufacturing approaches with higher flexibility, such as casting or segmentation, are used but at significantly higher cost and quality drawbacks. Additive Manufacturing (AM) has gained significant interest for its design freedom, facilitating complex shapes without increasing costs. This work proposes a novel AM-based design for hot stamping tools, integrating lattice structures to enhance quenching performance and reduce raw material use. A comprehensive literature review highlights the intersection of AM and hot stamping tool design, identifying key design variables. The integration method of lattice structures is detailed, with experimental proof from testing four dies with varying lattice integration in a multi-cycle hot stamping scenario. Subsequently, a multi-cycle thermo-mechanical 2D model was developed and the proposed hot stamping tool design underwent an optimisation routine. The results show that proposed novel design method for hot stamping tools can reduce the quenching step by 17% and requires 13.8% less material than a conventional hot stamping die.