Sheet-Metal Forming Processes and Equipment

FIGURE 1 Examples of sheet-metal parts.

(a) Stamped parts.

(b) Parts produced by spinning.

Forming Process：Characteristics

Drawing：Shallow or deep parts with relatively simple shapes, high production rates, high toolling and equipment costs

Explosive：Large sheets with relatively simple shapes, low tooling cost but high labor cost, low-quantity production, long cycle times

Incremental： Simple to moderately complex shapes with good surface finish;low production rates, but no dedicated tooling required; limited materials

Magnetic-pulse：Shallow forming, bulging, and embossing operations on relatively low strength sheets, requires special tooling

Peen：Shallow contours on large sheets, flexibility of operation, generally high equipment costs, process also used for straightening formed parts

Roll：Long parts with constant simple or complex cross sections, good surface finish, high production rates, high tooling costs

Rubber：Drawing and embossing of simple or relatively complex shapes, sheet surface protected by rubber membranes, flexibility of operation, low tooling costs

Spinning：Small or large axisymmetric parts; good surface finish; low tooling costs, but labor costs can be high unless operations are automated

Stamping：Includes a wide variety of operations, such as punching, blanking, embossing, bending, flanging, and coining; simple or complex shapes formed at high production rates; tooling and equipment costs can be high, but labor cost is low

Stretch：Large parts with shallow contours, low-quantity production, high labor costs, tooling and equipment costs increase with part size

Superplastic：Complex shapes, fine detail and close dimensional tolerances, long forming times (hence production rates are low), parts not suitable for high-temperature use

 FIGURE 2

(a) Schematic illustration of shearing with a punch and die, indicating some of the process variables.

Characteristic features of

(b) a punched hole and

(c) the slug.

(Note that the scales of (b) and (c) are different.)

FIGURE 3

(a) Effect of the clearance, c, between punch and die on the deformation zone in shearing. As the clearance increases, the material tends to be pulled into the die rather than be sheared. In practice, clearances usually range between 2 and 10% of the thickness of the sheet.

(b) Microhardness (HV) contours for a 6.4-mm (0.25-in.) thick AISI 1020 hot-rolled steel in the sheared region.

FIGURE 4

(a) Punching (piercing) and blanking.

(b) Examples of various die-cutting operations on sheet metal.

Lancing involves slitting the sheet to form a tab.