Punch

Abstract

A punch for use in molding a workpiece with lubricating oil interposed between the punch and the workpiece includes a straight portion at its end and a diameter-increasing portion. The straight portion includes an end face at its end and a side face. The straight portion extends in an axial direction. The end surface extends in a radial direction perpendicular to the axial direction. The side surface is connected to the end surface. The diameter-increasing portion is connected to the straight portion. The diameter-increasing portion includes a width in the radial direction, which is identical to that of the straight portion, at a junction between the straight portion and the diameter-increasing portion. The width of the diameter-increasing portion in the radial direction increases with distance from the straight portion. At least one of the end surface and the side surface of the straight portion is formed with a pit.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2005-94691 filed on Mar. 29, 2005, the entire contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The invention relates to a punch for use in molding a workpiece. [0004] 2. Description of the Related Art [0005] Various molds and molding methods using the molds have been proposed in order to mold a workpiece. For example, JP Sho. 57-208250 A has disclosed a method of producing an inkjet nozzle from an orifice back sheet and an orifice sheet and a punch used in the method. This method of producing the inkjet nozzle is carried out as follows. A tip end portion of a conical punch is pressed against a sheet placed on a die to thereby form concave portions shaped in accordance with the shape of the tip end of the punch in the sheet. Then, convex portions formed on a surf...

AI Technical Summary

Benefits of technology

[0008] The invention provides a punch in which lubricant retention capacity is made high enough to suppress the punch from being broken or worn away.

[0010] According to this configuration, when the end of the straight portion is pressed against the workpiece to perform molding, a part of lubricant supplied to the straight portion or to the workpiece remains in the pit to thereby keep the lubricity between the straight portion and the workpiece high. For this reason, the punch is prevented from being broken or worn away, so that the life of the punch is elongated.

[0012] According to this configuration, when the end of the diameter-increasing portion is pressed against the workpiece to perform molding, a part of lubricant supplied to the diameter-increasing portion or to the workpiece remains in the pit to thereby keep the lubricity between the diameter-increasing portion and the workpiece high. For this reason, the punch is prevented from being broken or worn away, so that the life of the punch is elongated.

Problems solved by technology

In the technique disclosed in JP Sho. 57-208250 A, there is however a problem that the punch, especially a portion of the punch being in contact with the sheet, is broken or worn away so severely that the life of the punch is short.

Particularly, when fine holes in a range of from the order of microns to the order of tens of microns such as nozzle holes of an inkjet nozzle are formed by molding, the life of the punch becomes very short due to breaking, frictional wear, etc. because the tip end portion of the punch must be as narrow as each fine hole.

There is however a limit to elongate the life of the die because the surface of the die is so smooth that the lubricant flows out immediately even if the lubricant is supplied in this manner.

Therefore, a method for always supplying lubricant may be conceived but there is another problem that the method is uneconomic to bring increase in production cost.

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