Development of Ultra-Fine Piercing By Using SiC Fiber Punch.

Abstract

A new ultra-fine piercing in which SiC fiber was used for a punch was proposed. In the discussion whether the SiC fiber is suitable for a ultra-fine punch, it was clarified that its strength is sufficient and becomes higher particularly in a small size and its tribological properties is good due to characteristics of ceramics. In addition to these suitability the cross section of a ceramics fiber becomes truly round in a smaller size. Many new techniques had to be developed in order to realize the process. An SiC fiber of 14 μm diameter is fixed firmly among an aluminum bar through a plastic deformation of the aluminum, the end of fiber and aluminum is polished, buffed and lapped and finally only aluminum is removed away by 50 μm depth by an electrolysis. Thus the ultra-fine fiber punch which has a flat end and an acute corner and is an appropriate length-to-diameter ratio can be obtained. This fiber punch making method was referred as BEFP. A die without a die hole is set up in a die-set and a hole is pierced by the fiber punch, so the center of the punch agrees well with that of the die. A new micro press was developed for this process. Three kinds of metals which have various thickness and strengths were pierced. A 17 μm thick aluminum foil is a specimen of high aspect ratio and low strength, a 15 μm thick beryllium copper is a specimen of high strength and a 8 μm stainless steel is hard-to-form material. It was cleared by observations of a scanning electron microscopy that every hole is truly round and sheared surface is smooth.