Answer for the deep drawing practice?
deep drawing is a sheet metal forming process that involves complex material flow and force distributions. As mentioned, the punch and die setup is somewhat similar to a sheet metal cutting operation, such as punching or blanking. Two main factors will cause the punch in deep drawing to draw the metal into the die cavity, rather than shearing it.
One major factor in deep drawing is the die corner radius and the punch corner radius. When cutting sheet metal, the punch and die edges do not have a radius. Sharp corners on the punch and die cause it to cut. A radius on an edge will change the force distribution and cause the metal to flow over the radius and into the die cavity. The other major factor causing the punch to draw the sheet metal and not cut it, is the amount of clearance. Clearance in cutting operations is relatively small, usually 3% to 8% of sheet metal thickness. In deep drawing manufacture, if the clearance is too small the sheet may be cut or pierced, (not well), despite the radius. Clearance in deep drawing manufacture is greater than sheet thickness, usually clearance values are 107% to 115% of sheet thickness.
For many calculations the sheet metal thickness is assumed to remain constant. However, there are changes in thickness in certain areas, due to the forces involved. In order to form the side walls of the part, material must flow from the blank’s peripheral over the die corner radius, then straight in the direction of the punch. Material forming the straight wall is under tensile stress that will naturally cause it to thin. deep drawing process factors are controlled to mitigate thinning, but some thinning of the sheet metal is unavoidable. Maximum thinning will most likely occur on the side wall, near the base of the part. A correctly drawn part may have up to 25% reduction in thickness in some areas.