Process Encyclopaedia

Sheet forming

Overview

Sheet metal forming (also called pressworking) is among the most important metalworking processes. It is used in the manufacture of a wide range products as there are many different forming operations including blanking, drawing, pressing and bending. Sheet metal is produced by rolling and is generally coiled prior to forming. Parts made this way and subsequently mechanically fastened are said to be fabricated.

Materials and shapes

Sheets are usually less than 6 mm thick. Dominant material used is mild steel. Blanking (shearing) is used to cut parts for subsequent processing, sheet is shaped with bending (1-D) and drawing (2-D), pressing contains elements of all three. Surface finish is usually good, but this is dependent on good die design and quality. A wide variety of shapes can be made, but die design must account for the elastic 'springback' of the sheet after forming. Some scrap is always produced and cannot be directly recycled.

Economics

Primarily used when near-net-shape processes are impractical in terms of time or materials e.g. for car body panels. Simple manual equipment can cost only a few thousand pounds, but is only used for prototyping and small batches as the production rates are low. Automated tooling (which can be expensive) is usually dedicated to individual components, so is normally only used for long production runs in order to be cost-effective. Production rates with automated equipment can be very high (drinks cans can be produced at almost a 1000 a minute).

Typical products

Cans, washing machine cases, car body panels, kitchen utensils, hubcaps, metal desks.