Article - Machine and Tool Blue Book:
IMPACT PRESS SHOOTS THROUGH MATERIAL
By George M. Meyerle
Presses use High Velocity to fabricate materials from credit cards to cruise missile rotors.
Imagine a punch connected to a bullet. The sharp edges of the punch strike a tough stainless steel workpiece so fast that the metal does not have time to react. High Velocity impact presses, a new breed of machines, fire a punch into the workpiece much like that bullet.
Typical punching operations undergo three phases: elastic, plastic and fracture. Because of the impact press's high speed, impact pressing bypasses the elastic and plastic phases, and rolled edges and burrs do not have time to form. The machines are compact, fit on table tops, use only one moving part, offer "plug and go" operation and deliver up to 100 tons of force when working 0.010-inch-thick material.
A spring assembly, separates the die plates, holding the ram (toolholder) in position. A magnetic force generated by an electrical pulse accelerates the armature and tooling downward. The velocity of the toolholder and its mass determine the kinetic energy available for the cutting operation. The armature with its return spring assembly, is the only moving part (other than the dieset itself).
Impact presses suitable for all metals as well as the new, exotic high-strength space-age materials. Green ceramics, which generally need stress relieving after cutting on a mechanical press, can be fired immediately after fabrication on an impact press. Rubber and cork react well, producing sharp edges. Hard plastics that normally shatter in a mechanical press are candidates for this process. All general-purpose plastics, as well as Mylar's, generally cut without deforming or stringing. The impact press also cuts paper, leather, composites, cardboard and felt.
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