Deep drawing is a manufacturing process in which sheet metal is progressively formed into a three-dimensional shape through the mechanical action of a die forming the metal around a punch. The deep drawn metal stamping process work hardens the metal, resulting in a seamless finished part that is stronger than the base material. Deep drawing can produce precise and intricate parts, including both symmetrical and asymmetrical parts.
When the length of a stamped part is equal to or greater than ½ of its diameter it is generally termed as being "deep drawn."
The deep drawing process contains many components and steps. The items listed below are just a few of these. They include information on the materials used in a deep draw process, characteristics of deep drawn stampings, types of deep draw presses, and information on deep draw station types. All of these deep drawn processes combine to influence the metal stamping industry.
Deep Draw Metal Stamping Materials
Many different metals can be deep drawn. Cold rolled steel, stainless steel, copper, brass, aluminum, HSLA, and others are included in the deep drawn metal stamping process.
Characteristics of Deep Drawn Stampings:
- Wall thickness variation: Deep drawn metal stampings typically exhibit some wall thickness variation. Consistent thickness may require additional or secondary processing.
- Work hardening: As raw material is formed into shapes through the deep drawing process the grain structure is stretched and cold worked generating improved material strength properties. This work hardening results in a finished part exhibiting more strength than the base material used to produce it.
- Radii: In some cases the deep draw metal stamping process does not allow sharp corner radii that can be achieved by other processes. A good general rule of thumb is that inside corner radii should not be less than 1/2X the starting stock thickness.
- Part tolerances: The deep drawing process can produce very precise parts; however, it is not always possible to generate tolerances that can be achieved by machining, grinding, or lapping. Near machining tolerances can be achieved on certain part features while other features require greater tolerance.
Deep Drawing Presses
A variety of deep draw presses, each of which have different capabilities, are used to produce deep drawn metal stampings. Trans-Matic's deep draw presses range in tonnage capacity from 5 to 600 tons, with press bed length of up to 168 inches, or 4.27 meters.
Trans-Matic's deep drawn metal stamping presses are capable of drawing a variety of metal types with draw lengths of up to 8" (200mm), part diameters as small as .100" (2.5mm), and material thicknesses from 0.005" (0.13mm) to 0.150" (3.8mm).
Trans-Matic uses three main types of stamping presses:
- ICOP (Individually Cam Operated Press): Transfer stamping presses where the part is transferred via transfer fingers as the part progresses through the forming process. Die components are installed in the press one station at a time.
- Die-Set Transfer Press: Transfer stamping presses where the part is transferred via transfer fingers as the part progresses through the forming process. Tooling components are attached to die plates so that the die can be installed in the press as one unit.
- Progressive Die Press: Stamping presses where the part is carried on the steel webbing as the part progresses through the forming process.
Deep Drawing Station Types
The deep draw stamping process consists of many smaller individual processes. These can include the following:
- Blanking: Blanking is the process of cutting the initial sheet coil stock into round or shaped flats required for deep drawing. The blanking processes is typically the first station in the press and involves a simple punch and die to cut out an initial metal blank that will then be deep drawn.
- Drawing: Drawing is the process of forming the metal with a punch and die, and is the heart of the deep drawing process. Drawing is often accomplished with a progressively smaller series of dies that reduce the shape and increase depth of the part.
- Piercing: Piercing is the process of punching holes in the metal stock that are required for the finished part.
- Trimming: In the Trimming process, excess metal that is necessary to draw the part is cut away from the finished part.