Abstract

This Research is aimed to predict the maximum varying blank holder force (VBHF) over the punch stroke in order to eliminate cracks on cup deep drawing product. The constant blank holder force during the process, it's frequently not capable to prevent cracking, effectively. Using the slab method with assuming a constant volume of material, the simple analytical approach of maximum VBHF, has been conducted under the failure deformation and cracking criteria on every stage punch stroke. The cracking criteria are based on the maximum strength of materials. Steel sheet of SPCD grade, thickness 0.2 mm was used in this study. And the diameter of the cylindrical cup-shaped product was 40 mm. The analytic calculation of the maximum VBHF has been compared to FEM simulations, and its effects in the prevention of cracking. Analytical Results of maximum VBHF, not much different with FEM simulation. Compared to the application of the constant blank holder force, VBHF can be quite effective for preventing the occurrence of cracking and increasing the formability of deep drawing.

1. Introduction

Cracking is the most critical defects in deep drawing process, which caused by the radial stress and the drawing load too high. Process parameters that greatly affect the magnitude of the radial stress and drawing load is the blank holder force. In order to maintain that proses condition and to prevent cracking, the blank holder force magnitude should be controlled effectively.

3. Conclusion

Results of the calculation of VBHF maximum, not much different with FEM simulation. Compared to the application of the constant blank holder force, VBHF can be quite effective in preventing the occurrence of cracking and improve the formability. Mathematical modeling of VBHF can be used as a simple approach for estimating the magnitude of blank holder force in every punch stroke. From VBHF modeling indicated a tendency and its similar trend compared to FEM simulation results. Compared constant BHF, the application of maximum VBHF with the lubrication of palm oil (P= 0.18 - 0.2) would increase the formability up to 8 % and increase the cup depth the cup depth up to 17 %.