Hydraulic press brakes are vital machines in the metalworking industry, designed to bend and shape metal sheets with precision. This article explores the working principles, hydraulic systems, operation procedures, and maintenance tips for hydraulic press brakes.
Working Principle of a Hydraulic Press Brake
Basic Structure
A hydraulic press brake consists of three main components: the frame, workbench, and clamping plate. Here’s how these components are configured:
1. Frame: The main support structure.
2. Workbench: Positioned on the frame, comprising a base and a pressure plate.
3. Clamping Plate: Connected to the base via hinges and includes a housing, coil, and cover. The coil sits within a recess in the housing, covered by the top plate.
Operation
1. Electromagnetic Clamping: When the coil is energized via electrical wires, it generates an electromagnetic force.
2. Metal Sheet Clamping: This force clamps the metal sheet between the pressure plate and the base, allowing for precise bending.
3. Versatility: The electromagnetic clamping system enables the press brake to handle various workpiece shapes, including those with side walls.
Die Replacement
Hydraulic press brakes can be equipped with different dies to meet various bending requirements, such as:
1. Punch Dies: For precise bends.
2. V-Dies: Common for various bending operations.
3. Embossing Dies: For creating embossed shapes.
Hydraulic System Principles
Directional Valve
The hydraulic system's directional valve controls the movement of the hydraulic cylinder:
1. Cylinder Upward Movement: Two two-way valves open, and a high-position oil tank valve is activated. The oil from the cylinder's rodless cavity partly returns to the high-position oil tank and partly to the main oil tank through a three-way, four-position valve.
2. Cylinder Downward Movement: The oil from the cylinder’s rod cavity returns through a relief valve, providing slight back pressure.
Relief Valve
A solenoid relief valve with remote pressure adjustment ensures system pressure:
1. Pressure Regulation: The solenoid activates to create pressure in the system; deactivation releases the oil pump.
2. Main Pressure Adjustment: The lowest relief valve on the control panel can adjust the main relief valve’s maximum pressure.
Operational Procedures for Hydraulic Press Brakes
Safety and Preparation
1. Safety Gear: Adhere to safety operation regulations and wear appropriate protective gear.
2. Initial Checks: Inspect the front material support, rear stop, and slide for any foreign objects. Remove any obstructions to avoid safety hazards.
3. Die Alignment and Security: Ensure upper and lower die alignment and secure attachment. Verify that positioning devices meet processing requirements.
4. Clean Dies: Before starting, thoroughly clean the upper and lower dies to remove any debris that could damage the dies or affect precision.
5. Electrical Inspection: Check motors, switches, wiring, and grounding for stability and proper operation. Ensure control components are in the correct positions.
6. Return to Origin: If the slide and positioning axes are not at their origins, run the return-to-origin program.
Startup and Operation
1. Dry Run: After starting the machine, run it empty for 1-2 minutes, moving the slide through its full range 2-3 times.
2. Listen for Issues: Stop the machine immediately if abnormal sounds or malfunctions are detected, and resolve the issues before continuing.
3. Operate Machine: Use the foot pedal to begin bending. Releasing the pedal stops the process; pressing it again resumes bending.
Maintenance of Hydraulic Press Brakes
Routine Maintenance
1. Shutdown for Maintenance: Before performing any maintenance or cleaning, align the upper die with the lower die and turn off the machine.
2. Manual Mode for Adjustments: Set the machine to manual mode for any necessary adjustments, ensuring safety.
Hydraulic System Maintenance
1. Oil Level Checks: Check the oil tank level weekly and after any hydraulic system repairs. Add hydraulic oil if the level is below the oil window.
2. Hydraulic Oil Requirements: Use ISO HM46 or Mobil DTE 25 hydraulic oil. Change the oil after the first 2000 hours of operation, then every 4000-6000 hours. Clean the oil tank with each oil change.
3. Temperature Control: Maintain the oil temperature between 35℃ and 60℃. Do not exceed 70℃ to prevent oil degradation and component damage.
Filter Maintenance
1. Filter Replacement: Replace or clean filters with each oil change. If the machine issues an oil quality alarm or other filter-related alerts, replace the affected filters.
2. Air Filter Maintenance: Inspect and clean the oil tank’s air filter every three months and replace it annually.
Conclusion
Understanding the working principles, proper operation, and maintenance of a hydraulic press brake is essential for ensuring precision and safety in metalworking processes. By following the detailed guidelines outlined in this article, operators can maintain optimal performance and longevity of their hydraulic press brakes.
FAQs
How does a hydraulic press brake work?
- It uses electromagnetic clamping to hold metal sheets between a pressure plate and base, allowing precise bending when the coil is energized.
What are the key components of a hydraulic press brake?
- The key components include the frame, workbench, clamping plate, housing, coil, and cover.
How do you maintain a hydraulic press brake?
- Regularly check the hydraulic oil level, replace filters, clean components, and ensure proper operation and safety protocols.
What should you do if a hydraulic press brake has no pressure?
- Check and replace the hydraulic control valve spring, inspect cylinder seals, clean and adjust the relief valve, and check the solenoid valve and electrical contacts.
What types of dies are used in hydraulic press brakes?
- Common dies include punch dies, V-dies, and embossing dies for various bending operations.
