Investigation of Hot Stamping with Cooled and Textured Tools Manufactured by Directed Energy Deposition

Additive manufacturing of hot forming tools provides increased flexibility regarding geometry and proximity of the cooling channels to the tools’ surface. In this field, the application of Directed Energy Deposition has not been investigated extensively. The conventional manufacturing route of cooling channels in hot stamping tools comprises the segmentation of the tool and hole drilling. This leads to the disadvantages of possible leakages and low flexibility regarding the channels’ size and location. Thus, a novel combination of Directed Energy Deposition and ball burnishing for leveling the additively manufactured surfaces is established to manufacture hot stamping tools for the forming of hat profiles. In the additively manufactured punch, near-surface cooling channels are integrated after a load-adapted definition of channel geometry and path, both based on numerical and experimental analysis. On the blank holder side, an additively manufactured texture, targeting the control of the heat balance and material flow, is applied. With these tools, hot stamping tests with a hat profile (22MnB5) are conducted and compared with conventionally manufactured tools with drilled cooling channels. It is demonstrated that the near-surface cooling channels are able to decrease the punch temperature in the hot stamping process by up to 50% in the investigated configuration. The textured blank holder creates a more homogeneous temperature distribution over the hat profile during forming. As a result, part properties can be enhanced by a lowered sheet thickness reduction and a higher and evenly distributed hardness. Numerical simulations can be used to depict those effects during process planning.