TABLE OF CONTENTS Well-functioning springs are one of the most important prerequisites of a good die function. After all, what good is the drawing operation if the part cannot be stripped off the punch because there is not enough spring power behind the pressure pad? Or what kind of parts will emerge from a die where the spring stripper is not spring-loaded adequately?
If ample pressure is the absolute basic of a good die operation, then springs are the most vital parts of every die.
Springs are elements designed to withstand great amounts of deflection and return to their original shape and size on its release. To be capable of such cyclical loading, spring materials must possess very high elastic limits.
Often materials not specifically made for the spring application are utilized for that purpose because their elastic limits are within the above requirements. Steels of medium-carbon and high-carbon content are considered good spring materials. Where a copperbase alloy is required, beryllium copper and phosphor bronze are utilized.
The surface quality of the spring material has a considerable influence on the function of a spring, namely, on its strength and fatigue. Where possible, the surface finish has to be of the highest grade, preferably polished. This is especially important with closely wound springs, where friction between single coils may create minute defects in their surface, which subsequently will cause the spring to crack. Music wire, the highest-quality spring material, is polished, and its surface is almost...
