A mechanical die spring has exactly one spring rate. If the stripping force is wrong you change the spring, change the pocket, or shim the plate. A gas spring changes the equation because the force is set, not selected.
The force ladder, from the catalog
The Kaller line spans the range a stamping die actually needs. Published initial force at maximum pressure, with available strokes from 7 to 125 mm depending on series:
| Series | Initial force | Typical mounting |
|---|---|---|
| EP3 16 / EPS3 16 | 420 N (95 lbf) | M16x1.5 / M16x2 cylinder |
| R12 / R15 / R19 | 500 / 700 / 900 N | Ø12 / Ø15 / Ø19 rod-sealed, compact and fully adjustable |
| EP2 24 / EPS2 24 | 1,700 N (382 lbf) | M24x1.5 cylinder |
| M2 / MM2 | 2,000 N (450 lbf) | Ø25 with M28x1.5 threaded cylinder, repairable and fully adjustable |
The EP3/EPS3 16 series is the direct swap for a mechanical spring plunger: color-coded gas ejector pins, interchangeable with mechanical spring plungers, built on a 45 + 2 × stroke envelope. That interchangeability is the reason a die can move from mechanical to gas force without re-machining the pocket.
Force is not constant through the stroke
A gas spring's force rises as it compresses, and the rise is not the same in every application. Kaller publishes both an isothermal model — force as a function of stroke with temperature held constant — and a polytropic model that accounts for what actually happens in a press: stroke length and used stroke, gas volume, press velocity, strokes per minute, operating temperature and internal friction all move the real force curve.
Practical translation: gassing the spring to the number you need at bottom dead center is not the same as gassing it to the number you need at contact. Size on the used stroke, not the nominal stroke.
Mounting rules that decide service life
Use the threaded holes in the base of the cylinder for mounting. Do not use the threaded hole in the top of the piston rod for mounting loads. Thread engagement should be 2 to 4 times the thread diameter in length, with a thread depth of at least 1.5 × the thread diameter in steel and 2 × in cast iron. Rod-sealed series are suited to dirty or wash-down environments; repairable series (M2, MM2, MC3) can be rebuilt rather than replaced.
When to stay mechanical
If the required force is fixed, the stroke is short, and the die will never be re-tuned, a mechanical die spring in the correct ISO class is cheaper and simpler. Gas springs earn their premium when force has to change — prototype and development dies, high-tension stripping, and multi-stage tools where the pressure pad has to be dialed in on the press.
Catalog spotlight: gas springs
Tooling Components stocks the Kaller gas spring line: color-coded gas ejector pins and compact, fully adjustable, repairable gas springs, threaded and non-threaded cylinder styles, plus mounting accessories and charging equipment. Bring us the required force at contact and the envelope you have, and we will return the series, stroke and mounting thread that fits it.