Press Brake Operation Basics

A press brake is a machine pressing tool for bending sheet and plate material, most commonly sheet metal.[1] It forms predetermined bends by clamping the workpiece between a matching punch and die. (From Wikipedia)

Bending process analysis

Bending process helps to produces a V-shape, U-shape, or channel shape along a straight axis in ductile materials, most commonly sheet metal. Typical products that are made like this are boxes such as electrical enclosures and rectangular ductwork.

The bending process is the last and most important process in the forming of most parts (apart from the welding process) and the bending process directly affects the final size and appearance of the product.

The bending process

In press brake forming, a work piece is positioned over the die block and the die block presses the sheet to form a shape.

Bending force calculation and corresponding value table

The drawing of common dies

Press brake metal forming tips

Take the springback into consideration

Springback is the change in geometry and size when the sheet metal has been released from the forces of the forming tool. Springbacke of the workpieces depends on many factors, such as the mechanical properties of the material itself, the shape of the workpiece, the mould gap, the bend radius and the bending pressure. The harder the grade, the more springback you should expect. If you use softer material, you will experience far less springback as that material conforms much easier to the angle of the die it is being forced into.

Watch out for cracking or spreading

If cracking and spreading occur, especially with sharp bends, the workpiece will be out of use.  Bottom bending provides an accurate bend but makes the material easier to get fractured. In this case, the nearer you get to a 1-1 radius between the material thickness and the inside bend, the less likely fracture occurs at the outside of the bend.

Don’t compensate for springback by bottom bending

Bottom bending is not a good choice for you to compensate for springback, you’d better refer to appropriate toolings. However when you’re bottom bending, you need to work with the 88-degree punch. If you use an 85-degree punch, the bend will extend too much achieve enough spring to get the bend back to a 90-degree angle.

Bending machine structure drawing and introduction

Take the common twisted shaft bending machine on the market as an example.

In a twisted shaft bending machine: the internal twisted shaft drives the swing arm and assists the work of the upper die. The main accessories include the frame, the slider, the hydraulic system, the motor, the synchronous rod, the mould (clamp), the backstop, etc.

1. Motor

2.Timing pulley

3. Belt

4. Ball screw

5. Track

6. Crossbeam

7. Finger

System

The mainstream bending machine controllers on the market today are the ESTUN system from Nanjing, China, the DELEM system from the Netherlands, the CYBELEC system from Switzerland and the ESA system from Italy. For more details, please see CNC Press Brake Controller.

The manufacturing process and introduction of bending machine parts

1. Large steel plates are cut off using flame or plasma

2. The gears and chains are machined by hobbing machines or machining centres.

3. The housing is cut by laser, then bented by a bending machine.

4. Cylinders, motors, proportional valves are purchased.