Sheet-gripper post formed by edm

Claim 1

A gripper post for cooperating with a gripper finger to grip a sheet therebetween, said gripper post comprising a body and a plurality of bosses distributed throughout a surface of said body, said bosses having substantially coplanar contact surfaces for contacting the sheet when gripped and being defined by valleys surrounding said bosses, said post being made from a member constructed of metal by a process comprising the steps of hardening the surface of the member before forming said valleys, positioning an electrode having raised portions corresponding to the valleys and apertures extending therethrough and corresponding to said bosses of the gripper post adjacent to the hardened surface of the member, said apertures being configured and spaced apart from each other by a distance respectively corresponding with the desired configuration of and desired spacing of said bosses on said gripper post, providing a dielectric fluid between the electrode and the hardened surface of the member, inducing opposite electrical charges between the electrode and the member so that the dielectric fluid between the electrode and the member is ionized to erode the member to produce said valleys and bosses while simultaneously surface hardening said valleys, pressurizing said dielectric fluid to flow through said apertures of said electrode to wash away the metal removed from said member when opposite electrical charges are induced between the electrode and the member and finally finishing the surfaces of said bosses.