Development of Ultrafine Piercing By SiC Fiber Punch

An integrated micropress was developed for ultrafine piercing of metallic foils by a SiC fiber punch. The fiber punch was produced by a series of processes that use buffing and electrolysis operations. The technology incorporates unique tooling and fixturing techniques to handle delicate pinholes, apertures, collimators, and air slits to allow a repeatable manufacturing process with minimal part handling. Since the diagnostic pinholes may be very thin or small in size, it is critical that there is minimal human intervention from the start to the final process of the piercing operation. Selection of materials, design of the integrated micropress, and performance of the system are discussed in detail. The performance of the technique was tested on three kinds of metal foils that have various thickness and strength. A 17-μm-thick aluminum foil was tested as an example of a high aspect ratio and low strength, a 15-μm-thick beryllium copper for a high strength, and an 8 μm stainless steel for a hard-to-form materials. Observations of the scanning electron microscope show that every hole was truly round with the sheared surface being smooth and burr free. Based on the measurements of the punch force and punch stroke, the material behavior in the ultrafine piercing process resembled that of the normal punching process, with a strong dependence on the material properties and the aspect ratio. The SiC fiber was found to be a secure ultrafine punch, with sufficient strength that can produce truly round holes particularly in smaller sizes.