Controllable Nitrogen Cylinders for Deep Drawing Dies

A gas spring is a cylinder charged with nitrogen gas at a pressure up to 150 bars. The gas pressure acts on the piston of the spring and provides a permanent force. In the field of metal forming, nitrogen gas springs are used for bringing up high closing or clamping forces, replacing conventional springs or even hydraulic or pneumatic cushion systems in the table of single acting presses.

State of the art is a nitrogen spring with a more or less progressive force over the stroke. But for deep drawing applications a decreasing force over the stroke is often needed. Furthermore it would be a great advantage to control the force of the gas spring over the stroke.

Controllable nitrogen springs have been investigated at the Institute for Metal Forming Technology (IFU) of the University of Stuttgart.

This paper gives an overview about the basics of the nitrogen spring technology and discusses the newly developed technology that makes it possible to control the gas spring force over the stroke.