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About Deep Drawn Stampings
Deep drawn stamping is a metal stamping process that
converts flat sheet metal, consisting of copper, aluminum, steel, nickel
or a variety of other metals, into three-dimensional shapes. Examples
of shapes include cylindrical, shell-like, cup-like, rectangular and square.
Deep drawn parts are created using stamping presses. A stamping press
consists of a die and a punch, which are the main shaping components.
The die consists of a cavity, the shape of which reflects the shape of
the end product design. As the flat metal moves over the die, the metal
blank is restrained on either side of the die opening by a blankholder,
a mechanism that ensures the blank does not move during the drawing process.
The punch then pushes the secured blank into the die cavity, creating
the desired shape. In order to create intricate features on the stamped
part, the punch may also be shaped accordingly.
In order for a part to be considered deep drawn, the lengths, or depths,
of these shapes must exceed one-half of the part’s diameter. Parts
with shorter lengths are considered shallow drawn parts. Deep drawn parts
vary greatly in size, ranging from millimeter-size parts to parts measuring
several feet in length. The size and shape of the part depend upon the
design requested. Deep drawn stamping remains useful in numerous industries,
including the automotive, construction, food packaging, hardware and communications
industries. Deep drawn parts include food cans, such as soup cans, thimbles,
oxygen sensors, sprinkler components and air bag components.
Drawn parts may require redrawing to increase height or smooth over possible
imperfections, such as die lines or wrinkles. Parallel features, such
as piercing, flanging bottom forming and slotting, can be imparted with
the motion of the transfer press plungers. Some pieces require rotation,
special surface finishing and distinct feature orientation, which adds
to the complexity and cost of the part. Each secondary process can cost
four times that of a parallel process. The transferring of the pieces
to each machine performing the secondary processes may cause massive damage
to production tooling or can significantly slow down production efficiency.
Drawn parts that are either too thin or too thick require special additions
to the machinery, which also drives up the cost.
Successful deep drawing depends on many factors, including the following:
material type, material thickness, N and R values, blank size and shape,
part geometry, press speed (ram speed), draw radii, draw ratio, die surface
finish, die temperature, lubricant draw bead height and shape, binder
pressure, binder deflection and standoff height. The most important element
is initiating metal flow. Ignoring even one of these factors in designing
a product for deep drawing can prove disastrous. Thicker materials hold
together better and can stretch longer distances, because they are stiffer
and have more volume. The “N” value refers to the ability
of a steel to stretch; the “R” value refers to the ability
of a material to flow or draw. The extent to which a given material will
stretch before it cracks or the walls thin excessively or other undesirable
effects occur must be known by the designer. The sizes and shapes of blanks
and the geometry of the parts may impede metal flow. Die surface finishers
and lubricants reduce friction, allowing materials to slide through tools
more easily; die temperature affects the viscosity of lubricants. Draw
bead height and shape controls metal flow, causing materials to bend and
unbend to create restrictive forces in the tooling process.
Featured
Articles
http://archive.metalformingmagazine.com/2002/10/DeepDrawing.pdf
http://archive.metalformingmagazine.com/2003/11/Simulation.pdf
Types
- (http://electronic.metalstamper.net)
are metal stamped electronic components.
- (http://fourslide.metalstamper.net) is a specialized metal
stamping process that allows fourslides
to produce
complex stamped parts from strips and wires with multiple bends and
twists,
as well as parts requiring bends greater than 90°. During fourslide
forming, sliding tools, regulated by cams, glide into the metal blank
from four directions at right angles to one another, bending the metal
around a vertical mandrel.
- (http://medical.metalstamper.net)
are metal stamped parts created specifically for use in the medical
industry.
- (http://progressive.metalstamper.net)
utilizes several workstations, unlike the usual single workstation,
through which the sheet metal sequentially moves to complete multiple
operations of the stamping process.
- (http://shortrun.metalstamper.net)
produces between five and ten thousand pieces, and the cost of the
dies themselves
is greater than the cost of the parts produced. Labor costs
are higher
per piece, materials are more costly, setup time is greater and
other cost factors are higher in short run stamping than conventional
stamping,
because of the greater number of operations involved.
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