A die separator cylinder for use in separating first and second portions of a metal forming die set comprises a housing including a bore. A piston is adapted to reciprocate in the bore between an extended position and a depressed position. The die separator cylinder further includes gas flow paths leading to and from the bore that define asymmetrical gas flow rates relative to each other so that said when the bore is charged with an inert gas, the inert gas biases the piston to the extended position with a force that varies depending upon a time interval elapsed since the piston moved from the depressed position to the extended position. As such, the cylinder is configured so that during opening and closing of the press for metal-forming operations, the piston moves inward and outward with reduced force, while during periods of inactivity, the piston is biased outward with maximum force sufficient to separate the die halves of the die set to protect the die surfaces and to facilitate stacking of the die set for storage. The die separator cylinder can be configured as a stand-alone self-contained cylinder or can be configured as part of a hosed system or the like.