MOLDING METHOD FOR GREEN COMPACT HAVING STEPPED SHAPE AND MOLDING DEVICE THEREFOR

摘要

PURPOSE:To prevent the generation of cracks in a green compact by simultane ously parting an upper punch and a lower punch from the green compact after ending of the compression of powder. CONSTITUTION:The upper punch is retreated and simultaneously, the lower punch is retreated as well after the compression stage for compressing the powder packed into the hole in a die by the upper and lower punches and molding the green compact varying in thickness in the compression direction. A stress releasing stage for releasing the pressurizing force of the lower punch acting on the end face of the green compact is executed. A green compact extracting stage for extracting the green compact from the hole in the die by advancing the lower punch relatively with the die is thereafter executed. The application of bending stresses and shearing stresses on the green compact is obviated in this way and the generation of the cracks in the green compact is prevented.