Deepdrawing

Deep drawing is a sheet metal forming process in which a flat blank is radially drawn into a closed die cavity by a punch, producing a cup-shaped or elongated part with height greater than the blank diameter. A blank holder is often used to constrain the blank and prevent wrinkling as material flows into the die. The process may involve a single draw or multiple draws with intermediate steps or annealing to achieve greater depth.

Materials suitable for deep drawing are ductile metals with high plastic elongation, such as mild and stainless steels, aluminum, and copper. Good formability and favorable anisotropy are important to minimize defects such as earing. Key design and process variables include blank diameter, punch and die dimensions, die clearance, lubrication, blank-holder force, and the draw ratio, defined by the relationship between blank and punch diameters. Draw ratios in single drawing are typically around 1.9 to 2.0 for steel, while multi-draw operations can reach higher effective thickness reductions through sequential steps. Draw beads and intermediate stations help control material flow and thickness distribution.

Common defects in deep drawing include wrinkling in the flange, tearing or necking in the wall, earing due to material anisotropy, thinning beyond allowable limits, and springback after unloading. Process equipment consists of hydraulic or mechanical presses with tailored tooling (punch, die, blank holder rings).

Applications encompass beverage cans, cookware and kitchenware bodies, automotive sheet metal parts, and various containers. Deep drawing remains a fundamental process in metal forming, balancing material properties, tooling design, and process planning to achieve the desired geometry and quality.