Shunei Mekaru

Improvement of shearing tool life by bevelled punches with high slenderness ratio

Abstract In the present investigation the cutting edge of a slender punch was bevelled in an attempt to prevent bending or breakage in use. Tests with Kovar sheet showed that use of a bevelled punch significantly reduces the risk of bending or breakage, a particular problem when clearance on both sides of the punch is unbalanced. This is because the punch guides itself in the later stage of the stroke. Tool life tests shearing Kovar sheet with the bevelled punch produced a smaller burr on the product than with the conventional punch. The application of such punches is found to be most suitable for thin materials such as are used in the manufacture of IC and LSI parts.

Analysis of single-side shearing by using punch with high slenderness ratio

Abstract Shearing; of thin sheet metal has often relied on the photo etching method [Thin Film Microelectronics, p. 95, 252, Chapman and Hall (1965); Appl. Phys. 27(9), 1 (1975); Metals Handbook, p. 240, ASME (1967)] [1–3]. This is because electronic parts are generally extremely small in size and highly precise in form. The lead frame for IC and LSI integrated circuits is an example of the products obtained by this method. Shearing of such small and delicate parts in commercial quantities requires a carefully designed and manufactured shearing tool and die [J. Jap. Soc. Technol. Plastic. 33(379), 971 (1992); J. Mater. Process Technol. 32(3), 571 (1995)] [4, 5]. The tool must be slender enough to produce narrow slots and small holes; therefore, the tool lacks rigidity and may malfunction, damaging the tool surfaces as the tool buckles and binds, or if the buckling is excessive, breaking completely. This paper reports and discusses the theoretical analysis and experiments concerning several kinds of punch bending caused by the shearing force and side force. The knowledge of the side force acting on the shearing tool is necessary for the analysis of shearing phenomena and the design of shearing tools.