Punch Force Behavior during Micro V-Bending Process of the Copper Foil

Sheet metal bending is defined as a straining process of flat strip material around a linear axis. The micro V-bending process was conducted to investigate its punch force behavior with 0.1 mm thick copper foil. The V-shaped configuration of the punch and die provides a simplicity of tools and an ability to produce different bending angles with a single tool. During the straining of material, a unique force profile, which is related to punch trajectory, occurs. The process was performed with the punch speeds 0.5 mm/s, 1.0 mm/s, 5.0 mm/s and 10.0 mm/s. The results showed that the punch force profile consists of the free-bending stage and the coin-bending stage. In the free-bending stage, the force magnitude was not influenced by the punch speed for the same geometrical and mechanical properties of the sheet material. Furthermore, during the coin-bending stage, the force magnitude increased significantly since the material needed to be bottomed.

Copper foil; Micro V-bending process; Punch force behavior; Punch speed

The results showed that the punch force profile in the micro V-bending process consists of the free-bending force and the bottoming force. Based on the formula of the free-bending force, the factors that can influence the force are the mechanical properties and geometry of the material to be bent. From the experimental results, it was proven that the punch speed did not affect the magnitude of the free-bending force at this stage.

The initiation of the bottoming process occurred very close to the end of the free-bending stage. The force increased significantly after the bending force was obtained at a certain point. At this stage, the force magnitude was clearly affected by the punch speed. The bottoming force increased with increasing punch speed due to the inertia effects of the punch.

For further works, more investigation is required to observe the influence of the punch force on the occurrence of spring back in the bent-part.

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