A press brake is a frequently used metalworking machine that bends metal sheets into desired shapes. The key to high-quality bending lies in correctly setting up the upper and lower dies. This article explores the structure of the press brake's upper and lower dies, provides methods for setting them up, and explains the principles behind their operation.
Basic Structure of Upper and Lower Dies
The upper and lower dies are crucial components of a press brake, responsible for the bending process. They are typically composed of:
- Upper Die: Consists of a horizontal beam with a protrusion (punch) and a corresponding groove. The punch presses the metal sheet into the groove of the lower die.
- Lower Die: Generally V-shaped, its inner surfaces can rotate. The angle of the lower die determines the bend angle of the metal sheet.
Methods for Setting Up the Upper and Lower Dies
Proper setup of the dies is essential for different materials and thicknesses. Here are three common methods for setting up the dies.
1. Setting the Punch Height
1. Position the Upper Die: Pause the upper die at any position.
2. Insert Spacer: Place a 10mm thick spacer between the upper and lower dies, gradually reducing the gap until the dies clamp the spacer without applying pressure.
3. Adjust Punch Height: Adjust the height of the punch to ensure it clamps the spacer correctly without affecting the processing quality.
This method is suitable for processing thinner metal sheets.
2. Setting the Lower Die Angle
1. Rotate the Lower Die: Adjust the lower die to the desired angle, maintaining a small angle to ensure bending accuracy.
2. Calibrate Before Each Use: Verify the angle of the lower die before each operation to ensure accuracy.
3. Setting the Distance Between Dies
1. Consider Material Thickness: Adjust the distance between the upper and lower dies based on the material's thickness and strength. The goal is to ensure the dies clamp the metal sheet without applying excessive pressure.
2. Adjust Based on Sheet Properties: The larger the distance, the smaller the bend angle, and vice versa. Adjust the distance according to the specific requirements of the metal sheet.
Measuring the Height of the Upper and Lower Dies
1. Use a Ruler: Position the ruler against the central axis and extend it to the worktable.
2. Mark the Measurement: Subtract the total thickness of the layers to get an accurate measurement.
Selecting the Right Dies
The selection of upper and lower dies depends on the material thickness and the final shape of the bent workpiece.
Lower Die Slot Width
- 1mm Sheet Thickness: Requires an 8mm lower die slot width.
- 2mm Sheet Thickness: Requires a 16mm slot.
- 3mm Sheet Thickness: Requires a 24mm slot.
- For Thick Sheets: Slot width can be selected based on a ratio of 1:10 or 1:12.
Upper Die Selection
The choice between straight blades and bend blades depends on the final shape of the workpiece. For example:
- Straight Blades: Suitable for larger opening distances in C-shaped workpieces.
- Bend Blades: Required for smaller opening distances to avoid collision.
Operating Principle of a Hydraulic Press Brake
The hydraulic press brake consists of a frame, a worktable, and a clamping plate. The worktable is positioned on the frame and comprises a base and a press plate, connected by hinges. The base includes a housing, a coil, and a cover plate.
Working Process
1. Electrify the Coil: During operation, an electric current passes through the coil.
2. Generate Electromagnetic Force: The current creates an electromagnetic force that attracts the press plate.
3. Clamp the Metal Sheet: The press plate clamps the sheet metal against the base, enabling precise bending.
The use of electromagnetic clamping allows the press plate to be adapted to various workpiece requirements, including those with side walls.
Safety Considerations for Operating a Press Brake
1. Operator Training: Ensure operators are well-trained and capable of positioning the bending flange accurately.
2. Material Support: Operators must support the material properly during bending to prevent injury.
3. Collaborative Work: For large workpieces, multiple operators may be needed to ensure safety and efficiency.
4. Correct Setup: Verify the alignment and security of the upper and lower dies before starting operations.
Conclusion
Proper setup and adjustment of the upper and lower dies on a CNC press brake are essential for achieving high-quality bends and reducing processing difficulty. The specific settings depend on the material type and thickness, as well as the desired bend characteristics. By following the guidelines outlined in this article, operators can ensure optimal performance and safety during bending operations.
