BENDING DIES

10.1 Introduction

10.2 Simple Dies

10.3 Complex Dies

10.1 INTRODUCTION

Bending dies may be conveniently classified according to their design, whether simple or complex, and according to their universality of application, whether universal or specific. The design of bending dies depends on the complexity of the workpiece shape, its dimensions, the type of material, the tolerances, etc.

10.2 SIMPLE DIE DESIGNS

Some die sets are designed to perform a single bending operation, which may include V, L, U, or Z, bends and other profiles. Such dies are called single-operation dies or simple dies. One operation is accomplished with each stroke of the press.

10.2.1 U-Profile Bend Dies

Fig. 10.1 illustrates a simple die for bending a U-profile. In this example, the blank of length L , width b , and thickness T , is positioned on the die (1) between stop pins (11). The die (1) is mounted on the lower plate (3) in the conventional position. The punch (2) is attached to the punch holder (4), which is fitted a shank (6) for that purpose, to the ram of the press. The pressure pad (10) applies pressure to the blank so that as the punch pushes the blank into the die, the workpiece is formed by a single stroke of the press. The bent workpiece is ejected from the die by the pressure pad mechanism (a) when the press ram retracts. For bending workpieces of small dimensions and thin material, the punches and dies are made from a single block of metal.

Fig. 10.1 .Simple bending die.

For bending a larger workpiece, using a heavier die set (see Fig. 10.2), the die is made up of segments which in turn are generally made from alloy tool steel. The advantages of this design are the same as with punching and blanking dies, as described in Chapter 9.

The segments (4) are fixed to the die shoe with screws and dowels. The stop pin (7) is fixed to a pressure pad plate (6), which holds the blank in position while it is being worked on. The pressure plate also

Fig. 10.2 Simple bending die with segments.

provides resistance to the bending operation, which is needed to perform the operation. An air cushion or hydraulic cylinders are used to generate the force necessary for this resistance. If the width of the workpiece is large, it is necessary for the die to have a stripper. In the following description of a die set console, the stripper (1) is fixed to the die shoe, and the punch holder has a slot so that the upper set of the tool can move up and down without obstruction when the press ram cycles.