Case Study 3
Part name: M73 rotor blade
Material: Aluminum or copper
Thickness: .032 or .064
Challenge: To produce two parts in two different materials with the same profile, with a minimum of tooling expense, in large quantities, producing a finished part with no edge burr, consistent finish, and excellent flatness
Solution: The .032 thick aluminum and the .064 thick copper required completely different clearances between details, so we made one precision die with two sets of details. Both sets were wired from CPM.
Even CPM will dull, and to maintain minimal burr, sharpness of the details was maintained by regular conditioning on a precision surface grinder with liquid coolant, preventing buildup on the wheel and maximizing surface finish, flatness, and cutting-edge integrity. A very small amount of very-low viscosity evaporative coolant was wicked onto the coil just before it entered the die, and the blanked parts were blown through a padded chute. Adjustable precision rollers enabled us to compensate for the die's tendency to affect flatness, resulting in an overall maximum non-flatness of .0005 in the finished part.
After blanking, the copper blades were buffed to a mirror finish and rack silver-plated; the aluminum blades were tumbled in walnut shell chips, achieving a clean, burr-free part with an even finish.