Micro Scale Force Fit Insertion

Several LIGA (Lithography Galvonoforming Abforming) test mechanisms have been designed and fabricated to study tribology and performance attributes of LIGA mechanisms. The LIGA test mechanism studied in this paper is a ratchet drive mechanism consisting primarily of pawls, cams, and springs ranging in size from about one-half millimeter to tens of millimeters of various nickel alloys fabricated using the LIGA process. To assemble the test mechanism, subassemblies are made by inserting force-fit pins into stacks of piece-parts. These pins are cut from 170μm wire and range from 500 to 1000μm in length. Human insertion of these pins is extremely difficult due to their small size and tolerances required to perform the force-fit operation. This paper describes the tooling to permit fabrication, bulk handling, and force-fit insertion of pins with the operator-guided automation required to achieve micron-scale tolerances using hybrid force/position control algorithms.