Bending Fundamentals 120

acute lower die

A type of lower die press brake tooling that forms bends that are less than 90 degrees.

acute punch

A type of upper die press brake tooling that forms bends that are less than 90 degrees.

against the grain

Bending with the line of the bend perpendicular to the line of the grain direction. Few workpiece materials are bent against the grain.

air bending

A forming method in which the press brake tooling touches the workpiece tooling at three different points: at the tip of the V-shaped section of the upper die and at the top of each corner of the lower die.

air forming

Another term used to describe air bending.

bend angle

The measurement, in degrees, of the bend a workpiece is bent to form a part. A formed workpiece has both an interior and an exterior bend angle.

bend clearance

The amount of space necessary between the upper and lower die so that the components do not interfere with the bending operation.

bend sequence

The order of operations for a workpiece that requires more than one bend. Bend sequence must be adhered to so defects can be avoided.

bending

The process by which a material, usually sheet metal, is formed into a desired angled shape. The shape of a bend is dictated by the type of tooling used.

bottom bending

A forming method in which the die tooling touches down on all surfaces of the workpiece. Bottom bending is also called bottoming.

bottoming

Another term used to describe bottom bending.

clearance

An intentional amount of space left between two components. To ensure quality, clearance is often required between the workpiece and other components on the press brake die tooling.

coining

A forming method that uses extreme force to displace material, usually by a reduction in workpiece thickness.

compression

A pushing or pressing force that is directed toward the center of an object and attempts to squeeze it.

cracking

The breaking of a workpiece. Cracking occurs when the pressure applied to the material far exceeds its tensile strength.

deform

To change or alter an object. Bending is an example of permanently deforming a workpiece.

force

The push or pull that changes an object's state of motion.

forming

A general category of metalworking processes that bend, separate, or shape sheet metal using punches and dies.

gooseneck punch

A type of upper die press brake tooling that is relieved so that it does not disturb previous bends.

grain direction

The layout, or arrangement of molecules that make up a material. To ensure accuracy and avoid defects, all bending operations must stay consistent with the proper grain direction.

included angle

The angle created by two lines that extend from the same point. For successful bending, the included angle formed by the upper die and lower die must correspond.

inside bend radius

A measurement of the radius of the interior portion of a workpiece that has been formed with bending. Inside bend radius is measured from an imaginary point at the axis of the bend to the tip of the workpiece.

lead-in radii

The points that make the first contact with the workpiece on press brake tooling. The inside radius of a workpiece is often dependent upon the dimensions of the lead-in radii.

lower die

The lower portion of a die set that corresponds with the upper die and serves as a support for the workpiece. The lower die must be cut to an angle that matches the shape of the upper die. The lower die is often referred to simply as the die.

neutral zone

An area on a workpiece that does not experience tension or compression. The object's state of motion is not disturbed in the neutral zone.

outside bend radius

A measurement of the radius of the exterior portion of a workpiece that has been formed with bending. The outside bend radius is measured from an imagniary point at the axis of the bend to the exterior of the workpiece.

overbending

A method of purposely applying more pressure than necessary to a workpiece during bending so that after it experiences springback, the proper bend angle is obtained.

parallel

Two lines that are equidistant from one another and do not intersect.

perpendicular

Two lines or axes that meet at right angles.

personal protective equipment

Any example of various safety equipment that workers wear or use to prevent injury in the workplace. Safety glasses are common personal protective equipment (PPE).

press brake

A type of press with an open frame and very wide bed. Press brakes are often used for bending operations, and they are typically manually operated.

pressure

A force or stress which, when applied, causes changes to the properties of the material.

profound radius

A bend in which the angle of the inside radius is over 10 times the material thickness. Profound radius bends have the greatest amount of springback.

punch radius

The section of the upper die that contacts the workpiece. The dimensions of the punch radius determine the dimensions of the inside bend angle of a workpiece.

radii

The plural form of radius. A radius is a line drawn from the center of a circle to any point on the circle.

radius bend

A bend in which the angle of the inside radius is within the range of 63% of the material thickness and 10 times the material thickness. Radius bends are commonly used because they are less prone to bend defects.

relieved die

A die that has a portion cut away so that other bends that have already taken place on a workpiece are not disturbed. A relieved die is typically used if there is a sequence of bends to be made.

sharp bend

A bend in which the angle of the inside radius is less than 63% of the material thickness. Sharp bends are often at risk for cracking because the inside bend radius is so small.

springback

A material's tendency to return to its original state once its state of motion has been disturbed. Springback is often corrected on bending operations with overbending.

square lower die

A type of lower die press brake tooling that forms U-shaped bends.

standard V lower die

A type of lower die press brake tooling that forms 90° bends.

straight punch

A common shape for upper die press brake tooling that forms 90° bends.

stress fracture

Hair-like cracks that appear on the surface of the workpiece if the tensile strength of the material has been exceeded.

tensile strength

The ability of a metal to resist forces that attempt to pull apart or stretch it. Workpieces formed on the press brake must not exceed their tensile strength or they will crack.

tension

A pulling force that is directed away from the object and attempts to move, stretch, or elongate the object.

tolerance

An unwanted but acceptable variation from a specified dimension.

tonnage

A measurement of a press brake's ability to exert pressure. Press brakes are rated by the amount of tonnage they exert.

upper die

The upper portion of a die set that corresponds with the lower die and moves down onto the workpiece. The upper die must be cut to the same angle and fit into the shape of the lower die. The upper die is often referred to as the punch.

V-shaped tooling

Standard, V-shaped punches and dies used on a press brake that typically form 90° bends. V-shaped tooling is a very common type of press brake tooling.

with the grain

Bending with the line of the bend parallel to the line of the grain direction. Most workpieces are best suited to bend with the grain.

workpiece

A part that is being machined, formed, or generally worked on.

yield point

The point at which a material is permanently deformed. Workpieces formed on the press brake must reach their yield point in order to maintain the desired shape.

yield strength

The amount of tension a material can withstand before it is permanently deformed. Workpieces formed on a press brake must exceed their yield strength, but not tensile strength.