Brake forming metal fabricating is a manufacturing
process that produces a V-shape, U-shape, or channel shape along a straight axis in ductile materials, most commonly
metal fabrication. Commonly used equipment include box and pan brakes, brake presses, and other specialized
fabricating machine presses.
Ameco uses many different metals that can be made into metal fabricated products, such as aluminum, brass, copper,
steel, tin, nickel and titanium. For decorative uses, important sheet metal fabrication include silver, gold, and
platinum.
In press brake metal fabricating, a work piece is positioned over the die block and the die block presses the sheet
to form a shape. Usually bending has to overcome both tensile stresses as well as compressive stresses. When bending
is completed, the residual stresses cause the metal to spring back towards its original position, so the sheet must
be over-bent to achieve the proper bend angle. The amount of spring back is dependent on the metal, and the type of
fabrication being formed. When metal fabricating is performed, it stretches in length. The bend deduction is the
amount the metal will stretch when bent as measured from the outside edges of the bend. The bend radius refers to the inside radius. The formed bend radius is dependent upon the dies used, the metal properties, and the
material thickness.
There are three basic types of press brake metal fabricating, each is defined by the relationship of the end tool
position to the thickness of the metal. These three are Air Bending, Bottoming and Coining. The configuration of the
tools for these three types of bending are nearly identical. A die with a long rail form tool with a radiused tip
that locates the inside profile of the bend is called a punch. Metal fabrication punches are usually attached to the
ram of the machine by clamps and move to produce the bending force. A die with a long rail form tool that has
concave or V shaped lengthwise channel that locate the outside profile of the form is called a die. Dies are usually stationary and located under the material on the bed of the machine. Note that some locations do not differentiate
between the two different kinds of metal fabrication dies (punches and dies.) The other types of bending listed use
specially designed tools or machines to perform the work.
Press brake metal fabricating is a form of bending, used for long and thin sheet metal parts. The machine that bends the metal is called a press brake. The lower part of the press contains a V shaped groove. This is called the die.
The upper part of the press contains a punch that will press the metal down into the v shaped die, causing it to
bend. There are several techniques of Press brake metal fabricating, but the most common modern method is "air
bending". Here, the die has a sharper angle than the required bend (typically 85 degrees for a 90 degree bend) and
the upper tool is precisely controlled in its stroke to push the metal down the required amount to bend it through
90 degrees. Typically, a general purpose Press brake metal fabricating machine has a bending force available of
around 25 tonnes per metre of length. The opening width of the lower die is typically 8 to 10 times the thickness of
the metal to be bent (for example, 5mm material could be bent in a 40mm die) the inner radius of the bend formed in
the metal is determined not by the radius of the upper tool, but by the lower die width. Typically, the inner radius
is equal to 1/6 of the V width used in the forming process.
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