Stamping machine and method including variable binder gap

A method of stamping a sheet material comprising:

• placing a sheet material in a stamping machine, the stamping machine including:
• a punch fixed to a support surface;
• an upper binder that is movable relative to the punch, and defining a cavity that is shaped to correspond to a shape of the punch;
• a lower binder located about a periphery of the punch, the lower binder being movable relative to the punch;
• a first cylinder positioned between the lower binder and the support surface, the first cylinder supporting the lower binder as it moves relative to the punch;
• a second cylinder positioned between the upper binder and the lower binder;
• a cushion pin positioned at the support surface that is configured to contact and control movement of the lower binder relative to the punch,
• wherein the cushion pin is a cylinder configured to exert a force that is greater than that exerted by both the first cylinder and the second cylinder
• first teeth formed on the upper binder and second teeth formed on the lower binder that are opposed to and correspond to the first teeth;
• wherein each tooth of the first and second teeth includes a material engagement surface, a first side surface that faces the punch, and a second side surface that faces away from the punch,
• a rounded corner is located at an intersection between the material engagement surface and the first side surface that faces the punch, and a sharp corner is located at an intersection between the material engagement surface and the second side surface that faces away from the punch,
• the rounded corners of each of the first teeth are configured to face the sharp corner of an adjacent second tooth when the first and second teeth are engaged with the sheet, and
• a force exerted by the second cylinder is greater than that exerted by the first cylinder, and a force exerted by the cushion pin is greater than that exerted by the second cylinder;
• moving the upper binder in a direction toward the punch such that the lower binder is moved by the second cylinder against the force exerted by the first cylinder to an extent that a gap is maintained between the first teeth and the second teeth that ensures that the first and second teeth do not grip the sheet material and permits the sheet material to be drawn in a direction toward the cavity;
• continuing to move the upper binder toward the punch such that the lower binder is moved by the second cylinder against the force exerted by the first cylinder until the lower binder contacts the cushion pin,
• wherein upon contact by the lower binder with the cushion pin, the gap between the first and second teeth is removed such that the first and second teeth grip and hold the sheet material while permitting the sheet material to undergo final stretching until a final part is formed of the sheet material.