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The blank is then stamped into shape with embossments to help increase release efficiency. 
The ACT diaphragm spring on the right is thicker and has more clamp load than the OEM part on the left.
After stamping the springs, they are sent to the heat treating oven to get proper heat treatment. This ensures a long life. ACT heat treats the springs in house to maintain quality control over the process. Here batches of springs await heat treatment. The numbered parts that look older are approved first articles. These are used as a visual reference standard to compare against the new production parts to make sure they are made correctly.
Here is a completed cut, formed and heat treated diaphragm spring ready for assembly into a pressure plate.
On many clutches when needed, ACT uses their own pressure plate cover stamping. The pressure plate cover is what contains all of the pressure plate components. A stiffer cover helps improve release efficiency which allows ACT to do more aggressive tuning without the clutch feeling like a snappy full race clutch. A stiff clutch cover also helps give the clutch a consistent pedal feel and engagement/disengagement characteristics. The stock part on the left is thinner than the ACT part on the right.
Here is another view where you can see the thicker ACT cover plate on top vs the thinner OEM part on the bottom. 
