Deep Drawn Stampings

Deep Drawing Process

metal stamping industry infographic
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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."

Metal Stamping Industry

The metal stamping industry is one of the largest manufacturing industries in the US. The infographic to the right highlights some top facts about the metal stamping industry. Click the image to view it larger.

With metal stamping facilities located throughout every state in the US, metal stamping ships over 11 billion dollars of stamped components every year.

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.

Video of the Deep Drawing Process

The following deep drawing video demonstrates the deep drawing process. A part is formed from a flat disc of sheet metal.

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.

Additional Metal Stamping Processes

In addition to the standard drawing processes, there are a number of additional processes that can be employed within the press to generate additional features on the finished part. These additional processes include:

  • Side Piercing: In the side piercing process holes are pierced in the side wall of the drawn part. The holes may be round or shaped according to specifications.
  • Bottom Piercing: In the bottom piercing process a round or shaped portion of metal is cut from the drawn part.
  • Beading: In the beading process material is displaced to create a larger, or smaller, diameter ring of material beyond the original body diameter of a part.
  • Bulging: In the bulging process a portion of the part's diameter is forced to protrude from the surrounding geometry.
  • Coining: In the coining process material is displaced to form specific shapes in the part. Typically coining should not exceed a depth of 30% of the material thickness.
  • Curling: In the curling process metal is rolled under a curling die to create a rolled edge.
  • Extruding: In the extruding process, after a pilot hole is pierced, a larger diameter punch is pushed through, causing the metal to expand and grow in length.
  • Ironing / Wall Thinning: Ironing is a process to reduce the wall thickness of parts. Typically ironing should not exceed a depth of 30% of the material thickness.
  • Necking: In the necking process a portion of the part is reduced in diameter to less than the major diameter.
  • Notching: In the notching process a notch is cut into the open end of the part. This notch can be round, square, or shaped.
  • Rib Forming: Rib forming involves creating an inward or outward protruding rib during the drawing process.
  • Stamping / Marking: This process is typically used to put identification on a part, such as a part number or supplier identification.
  • Threading: Using a wheel and arbor, threads are formed into a part during this process. In this way threaded parts can be produced within the stamping press.
  • Leak Testing: Finished parts can be tested for leakage using a pressure-decay system.