A press brake machine bends sheet metal and plates into angles, channels, boxes and other profiles. It presses a top tool (the punch) into a bottom tool (the die) along the length of the sheet. The bend angle depends on how far the punch goes into the die. Press brakes are among the most important machines in sheet metal fabrication, because almost every enclosure, bracket, cabinet and panel needs accurate bends.

A hydraulic press brake uses hydraulic cylinders to move the ram. The operator sets the bend depth and backgauge manually or with a simple digital display. A CNC press brake adds a computer control that sets the ram depth, backgauge position and bending sequence automatically from a stored program. CNC press brakes are faster to set up, more accurate and better for repeat or multi-bend parts. Hydraulic press brakes are more economical for simpler, low volume bending.

A torsion bar press brake uses a steel torsion bar to keep the two ends of the ram moving together. It is simple, robust and economical. An electro hydraulic synchronous press brake uses proportional valves and linear encoders to control each cylinder separately (the Y1 and Y2 axes). That gives higher accuracy, better repeatability and the ability to correct the ram for off-centre or uneven bending. Synchronous press brakes are preferred for high precision and complex work.

Yash Machine Tools, based in Ahmedabad, supplies three types of press brakes:

• Hydraulic press brakes, with an optional E10-D digital display.
• CNC torsion bar press brakes, with the E200 CNC control.
• CNC electro hydraulic synchronous press brakes, with Delem CNC control.

The range covers capacities from about 40 to 300 ton and bending lengths up to 5 metres. A wide choice of press brake controllers is also available, from simple E10 displays to 3D graphical DA69We controls.

A press brake controller is the CNC or NC unit that controls the ram depth, backgauge position and bending program. Basic controllers such as the E10 and E200 handle backgauge positioning and multi-step programs. They suit simpler bending at a lower cost. Advanced controllers such as the DA56, DA66We and DA69We offer 2D or 3D graphical programming, automatic bend sequence and pressure calculation, and crowning control. They suit complex parts and frequent job changes. The right choice depends on part complexity, batch sizes and operator skill.

Under heavy load, the ram and table of a press brake bend slightly. The bend angle then comes out different in the middle of the sheet than at the ends. Crowning compensates for this deflection by raising the centre of the table slightly, either with manual wedges or automatically through CNC control. This keeps the bend angle consistent along the full length, which is especially important for long and thick parts.

Press brake capacity is chosen from three things: the maximum sheet thickness, the material and the bending length you need. Thicker plates, stronger materials such as stainless steel, and longer bends all need more tonnage. Also check the throat depth, the stroke, the opening height for deep boxes and the number of CNC axes you need. A supplier can calculate the required tonnage from your thickest and longest bend to avoid buying a machine that is undersized or oversized.

The backgauge is the adjustable stop behind the tooling that positions the sheet for each bend, so every bend lands at the correct distance from the edge. Basic machines have an X axis backgauge (front to back). Advanced CNC press brakes also have R (height) and Z (side to side) axes for complex parts. A servo-driven backgauge with ball screws and linear guides gives fast, accurate positioning.

A press brake is designed mainly for bending long sheets and plates along a straight line, using long punch and die tooling. A power press, such as a C type precision press, is designed for punching, blanking, stamping and forming smaller parts at high speed with dedicated dies. Fabrication shops use press brakes for bending panels and enclosures. Stamping units use power presses for high volume pressed components.

Press brake machines are used in sheet metal fabrication, electrical panels and enclosures, HVAC ducting, automobile and body building, elevators, kitchen equipment, furniture, agricultural machinery, railway coaches, and steel structure and construction products. Any business that bends metal sheets or plates into finished shapes relies on a press brake.