Press brake

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A press brake bending a sheet of steel

A press brake is a machine used for bending sheet metal and metal plate, most commonly sheet metal.[1] It forms predetermined bends by clamping the workpiece between a matching top tool and bottom die.[2]

Bending process A high-tonnage hydraulic press brake

Typically, two C-frames form the sides of the press brake, connected to a table at the bottom and on a movable beam at the top. The bottom tool is mounted on the table, with the top tool mounted on the upper beam.

Types

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A brake can be described by basic parameters, such as the force or tonnage and the working length.[1] Additional parameters include the stroke length, the distance between the frame uprights or side housings, distance to the back gauge, and work height. The upper beam usually operates at a speed ranging from 1 to 15 mm/s.

There are several types of press brakes including nut-stop hydraulic, synchro hydraulic, electric and hybrid.

Hydraulic presses operate by means of two synchronized hydraulic cylinders on the C-frames moving the upper beam.[3] Servo-electric brakes use a servo-motor to drive a ballscrew or belt drive to exert tonnage on the ram.

Historically, a mechanical press entailed with energy that was added to a flywheel with an electric motor. A clutch engages the flywheel to power a crank mechanism that moves the ram vertically. Accuracy and speed are two advantages of the mechanical press.[3]

Until the 1950s, mechanical brakes dominated the world market. The advent of better hydraulics and computer controls have led to hydraulic machines being the most popular.

Today's press brakes are controlled by two types of controls, NC (Numeric Controlled) or CNC (Computer Numeric Controlled). NC is a basic controller where the CNC is the high-end controller, although the initial outlay might be more than a NC, a CNC controller can be more effective, keeping cost down in the long run.

Pneumatic and servo-electric machines are typically used in lower tonnage applications. Hydraulic brakes produce accurate high quality products, are reliable, use little energy and are safer because, unlike flywheel-driven presses, the motion of the ram can be easily stopped at any time in response to a safety device, e.g. a light curtain or other presence sensing device.

Back gauge

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Recent improvements are mainly in the control and a device called a back gauge. A back gauge is a device that can be used to accurately position a piece of metal so that the brake puts the bend in the correct place. Furthermore, the back gauge can be programmed to move between bends to repeatedly make complex parts. Early brakes relied on the tooling to determine the bend angle of the bend. The animation to the right shows the operation of the back gauge, setting the distance from the edge of the material or previous bend to the center of the die.

Press brakes often include multi-axis computer-controlled back gauges. They allow operators to position material correctly and sequence the bends step-by-step until completed. Optical sensors allow operators to make adjustments during the bending process. These sensors send real-time data about the bending angle in the bend cycle to machine controls that adjust process parameters.

Dies

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Press brakes can be used for many different forming jobs with the right die design. Types of dies include:[3]

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• V-dies—the most common type of die. The bottom dies can be made with different-sized die openings to handle a variety of materials and bend angles.
• Rotary bending dies—a cylindrical shape with an 88-degree V-notch cut along its axis is seated in the "saddle" of the punch. The die is an anvil over which the rocker bends the sheet.
• 90 degree dies—largely used for bottoming operations. The die opening dimension depends on material thickness.
• Acute angle (air-bending) dies—used in air bending, these can actually be used to produce acute, 90 degree, and obtuse angles by varying how deeply the punch enters the die by adjusting the ram.
• Gooseneck (return-flanging) dies—The punch is designed to allow for clearance of already formed flanges
• Offset dies—a combination punch and die set that bends two angles in one stroke to produce a Z shape.
• Hemming dies—two-stage dies combining an acute angle die with a flattening tool.
• Seaming dies—There are a number of ways to build dies to produce seams in sheets and tubes.
• Radius dies—A radiussed bend can be produced by a rounded punch. The bottom die may be a V-die or may include a spring pad or rubber pad to form the bottom of the die.
• Beading dies—A bead or a "stopped rib" may be a feature that stiffens the resulting part. The punch has a rounded head with flat shoulders on each side of the bead. The bottom die is the inverse of the punch.
• Curling dies—The die forms a curled or coiled edge on the sheet.
• Tube- and pipe-forming dies—a first operation bends the edges of the sheet to make the piece roll up. Then a die similar to a curling die causes the tube to be formed. Larger tubes are formed over a mandrel.
• Four-way die blocks—A single die block may have a V machined into each of four sides for ease of changeover of small jobs.
• Channel-forming dies—A punch can be pressed into a die to form two angles at the bottom of the sheet, forming an angular channel.
• U-bend dies—Similar to channel forming, but with a rounded bottom. Spring back may be a problem and a means may need to be provided for countering it.
• Box-forming dies—While a box may be formed by simple angle bends on each side, the different side lengths of a rectangular box must be accommodated by building the punch in sections. The punch also needs to be high enough to accommodate the height of the resulting box's sides.
• Corrugating dies—Such dies have a wavy surface and may involve spring-loaded punch elements.
• Multiple-bend dies—A die set may be built in the shape of the desired profile and form several bends on a single stroke of the press.
• Rocker-type dies—A rocker insert in the punch may allow for some side-to-side motion, in addition to the up-and-down motion of the press.

See also

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References

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Further reading

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• Benson, Steve D. Press Brake Technology: A Guide to Precision Sheet Metal Bending. Society of Manufacturing Engineers, 1997. ISBN 978-0-87263-483-1

Modern metal fabricators use machines called press brakes all the time. But, if you don’t work in the industry, you probably couldn’t guess all the things the machine does by name alone. So where does the press brake get its name?

The term “press brake” is a combination of two words that describe the basic action of this machine. But the history of how the meaning of those words developed helps us understand why these modern machines are called press breaks.

“Press” Referred to Crushing or Squeezing

The original meaning of “press” can be traced back to the 15th century when we used it to describe the act of crushing or squeezing something. This is still the same basic action that press brakes perform but with more precision and control than was available in centuries past.

In the 14th century, “press” described a machine that squeezed juice or oil from fruit like grapes or olives.

The phrase “press brake” first appeared to describe a range of machines that use pressure to crush, flatten, and form metal. It is believed to have originated in the late 19th century when machine engineers began experimenting with ways to make metalworking more efficient.

Why Does It Include the Word “Brake”?

The word “brake” is derived from an Old English term meaning “to break” or “broken.” As time passed, the meaning of “brake” evolved to refer to tools that could be used for crushing or pounding. It eventually came to refer to machines that execute these functions.

Modern Use of “Press Brake”

Today, the press brake is one of the most used machines in metal fabrication shops. These machines have rams and apply powerful force to tools and dies to bend, form, and shape sheet metal. But its name still reflects its origin—a combination of two words for machines that crush, squeeze, and bend.

Before, you may have just known “press brake” as the name of the workhorse of any metal fabrication shop. But now you know where the press brake got its name.

Press brakes come in many sizes and configurations, from small benchtop models to large machines that weigh several tons. They can be manually operated or powered by a motor. Most modern press brakes use an electric motor and hydraulics for power and precision control of the bending force. A press brake also typically includes dies of varying shapes and sizes that can be used to bend materials into different shapes and angles.

Mac-Tech sells new and pre-owned electric and hydraulic CNC press brakes and also provides maintenance service and repairs. Metal fabrication shops look to Mac-Tech for quality metalworking machines.

For more information, please visit Cnc Hydraulic Press Brake Bending Machine Manufacturer.