A press brake is a machine used for bending sheet metal, capable of performing various processes such as bending edges, stretching, rounding, and punching through the use of different molds. It finds extensive application in industries like light manufacturing, aviation, and shipbuilding. This article explores the structure, operation, and safety measures for using both hydraulic and CNC press brakes.
Structure of a Press Brake
The basic components of a press brake include:
- Frame: The main support structure of the machine.
- Worktable: Positioned on the frame, it consists of a base and a clamping plate.
- Clamping Plate: Connected to the base via hinges, responsible for holding the sheet metal in place during bending.
- Base: Made up of a housing, coil, and cover plate, with the coil placed in a recess within the housing.
During operation, an electric current is supplied to the coil via wires, generating an electromagnetic force that attracts the clamping plate. This mechanism allows the clamping plate to hold the sheet metal securely, enabling the machine to handle various workpieces, including those with side walls, with ease.
Operating a Hydraulic Press Brake
To illustrate the basic steps of operating a hydraulic press brake, let's consider the example of processing Q235 sheet metal:
1. Power On
- Connect the Power Supply: Ensure the machine is properly connected to a stable power source.
- Turn on the Key Switch: Activate the key switch on the control panel.
- Start the Oil Pump: Press the oil pump start button. You should hear the pump running, indicating it is operational.
2. Stroke Adjustment
- Adjust the Stroke: Ensure proper stroke adjustment to avoid damaging the molds and the machine.
- Test Before Bending: Perform a test run to verify the stroke settings.
- Maintain a Gap: When the upper die descends to its lowest point, there should be a gap equivalent to the thickness of the sheet metal.
3. Select Bending Slot Width
- Choose Appropriate Slot: The slot width should be about eight times the thickness of the sheet metal.
- Example: For a 4mm thick sheet, select a slot width of approximately 32mm.
4. Adjust the Back Gauge
- Electric or Manual Adjustment: Use electric controls for quick adjustments and manual controls for fine-tuning.
5. Start Bending
- Foot Pedal Operation: Press the foot pedal to initiate the bending process. Release the pedal to stop, and press it again to continue the downward movement.
Operating a CNC Press Brake
Operating a CNC press brake involves similar steps to a hydraulic press brake but requires the use of a CNC system for programming. Here are the basic steps:
1. Power On
- Connect the Power Supply: Ensure the machine is connected to a stable power source.
- Turn on the Key Switch: Activate the key switch on the control panel.
- Start the Oil Pump: Press the oil pump start button to begin operation.
2. Establish Coordinate System
- Use G92 Command: Use the G92 command to set up the coordinate system program.
3. Set System Axis Parameters
- Select Programming Method: Choose between diameter programming or radius programming based on the requirements.
4. Tool Setup
- Z-Axis Tool Setting: Conduct a trial cut on the workpiece end face at a low feed rate and record the Z-axis coordinate value Z2 in the machine coordinate system. The Z-axis coordinate value Z1 in the workpiece coordinate system should be 0.
- X-Axis Tool Setting: Conduct a trial cut on the workpiece’s outer circle at a low feed rate and record the X-axis coordinate value X2 in the machine coordinate system. Measure the workpiece diameter D. The X-axis coordinate value in the workpiece coordinate system is D (or the radius value if using radius programming).
Safety Operating Procedures
Proper safety measures are crucial to prevent accidents and ensure smooth operation.
General Safety Procedures
- Follow Safety Regulations: Adhere strictly to safety operating procedures and wear appropriate protective gear.
- Pre-Start Checks: Inspect the motor, switches, wiring, and grounding to ensure they are in good condition.
- Check Molds and Positioning Devices: Verify the alignment and firmness of the upper and lower molds, and ensure the positioning device meets the requirements.
- Initial Run: Allow the machine to run idle for 1-2 minutes and operate the upper slide 2-3 times to ensure normal operation.
During Operation
- Unified Command: One person should be in charge of directing operations, ensuring all personnel are in safe positions before issuing bending commands.
- Secure Sheet Metal: Ensure the sheet metal is firmly pressed to prevent it from lifting and causing injury.
- Power Off for Adjustments: When adjusting the sheet metal press die, turn off the power and stop the machine before proceeding.
- Avoid Contact with Lower Die: Do not touch the lower die while changing its opening.
- No Standing Behind the Machine: No one should stand behind the machine during operation.
- No Solo Bending at One End: Do not bend sheet metal at one end only.
- Stop for Corrections: If the workpiece or mold is misaligned, stop the machine to correct it. Do not attempt manual corrections while the machine is running.
- Avoid Bending Thick or Hard Materials: Do not bend materials that are overly thick or of high hardness beyond the machine’s capacity.
- Regular Inspections: Frequently check the alignment of the upper and lower molds and the pressure gauge to ensure they meet specifications.
- Stop for Abnormalities: Immediately stop the machine if any abnormalities are detected, and troubleshoot the issue.
- Shut Down Properly: Before shutting down, place a wooden block on the lower die and lower the upper slide onto it. Exit the control system program and then turn off the power.
Daily Maintenance of CNC Press Brakes
Regular maintenance ensures the safe and efficient operation of the press brake.
Routine Inspections
- Check Protective Components: Inspect all protective panels, covers, and doors to ensure they are in proper condition.
- Smooth Operation: Run all axes and observe if the movement is smooth.
- Limit Switches: Ensure that all limit switches are functioning correctly.
- Inspect Rails: Check the guide rails for any scratches or excessive wear.
- Check Rail Cleaners: Ensure the rail cleaners are intact and not damaged.
- Lubrication: Verify that the guide rails are properly lubricated.
Conclusion
By adhering to these operational and safety procedures, you can ensure the safe and effective operation of a press brake, thereby avoiding accidents and injuries. Regular maintenance and proper handling of the machine are crucial for its longevity and optimal performance. Following the detailed steps for operating hydraulic and CNC press brakes, as well as understanding the necessary safety measures, will help operators achieve precise bends and maintain the machine in excellent working condition.
