DEEP DRAWING

6.1 Introduction

6.2 Mechanics of Deep Drawing

6.3 Forces

6.4 Blank Calculations for Symmetrical Shells

6.5 Determining Shape of Blank for Nonsymmetrical Shells

6.6 Drawing Practice

6.1 INTRODUCTION

The drawing of metal or “deep drawing” is the process by which a punch is used to force sheet metal to flow between the surfaces of a punch a die. A flat sheet is formed into a cylindrical-, conic-, or boxshaped part. With this process, it is possible to produce a final workpiece—using minimal operations and generating minimal scrap—that can be assembled without further operations. The development of specific methods for the deep drawing process has paralleled general technological development, especially in the automotive and aircraft industries. However, this process has a broad application for the production of parts of different shapes and different dimensions for other products, ranging from very small pieces in the electrical and electronic industries to dimensions of several meters in other branches of industry.

Deep drawing is popular because of its rapid press cycle times. Complex axisymmetric geometries, and certain non-axisymmetric geometries, can be produced with a few operations, using relatively nontechnical labor.

From the functional standpoint, the deep drawing metal-forming process produces high-strength and lightweight parts as well as geometries unattainable with some other manufacturing processes.

There are two deep drawing processes:

• deep drawing without a reduction in the thickness of the workpiece material (pure drawing) and

• deep drawing with a reduction in the thickness of the workpiece material (ironing).

Fig. 6.1 Schematic illustration of deep drawing process: pure drawing, b) ironing.

A schematic illustration of these deep drawing processes is shown in Fig. 6.1. From the illustration of the deep drawing process without a reduction in the thickness of the workpiece material (Fig.6.1a), it is clear that the basic tools for deep drawing are the punch, the drawing die ring, and the blank holder. Deep drawing is one of the most widely used sheet metal working process and is used to produce cupshaped components at a very high rate. Cup drawing, besides its importance as a forming process, also serves as a basic test for sheet metal formability. Typical products are pots and pans, containers of all shapes, sinks, beverage cans, and automobile and aircraft panels.