CNC Press brakes are widely used in the sheet metal and manufacturing industries, but they also pose a significant threat to operators’ safety.
Every year, there are numerous accidents related to the use of press brakes.
Unfortunately, many employers or users often neglect safety training for press brake operators, and many press brake manufacturers do not provide adequate safety protection devices.
The main hazard of using press brakes is that operators may bypass the safety guards and enter the machine’s bending area.
Additionally, the clamps and the rapid movement of the backgauge also pose a risk to operators.
Whenever a new press brake is installed, upgraded, or renovated, the risk factors associated with the press brake must be re-evaluated.
The dwell time of mechanical and flywheel press brakes is relatively long, which cannot be reduced without the use of modern light curtain protection technology.
On the other hand, the stop time of hydraulic press brakes is shorter, allowing for the implementation of more protective measures.
Potential Hazards of CNC Press Brake Usage
The common injuries that occur during CNC press brake usage include crushing injuries and contact with the machine’s operating points.
These hazards can occur during various activities such as setting and adjusting the machine, bending with the press brake, cleaning machine blockages, lubricating the machine, and performing maintenance.
Other common hazards include touching the foot switch during operation, being crushed during bending, and injuries resulting from not properly closing relevant parts.
Additionally, individuals may be pinched by the backgauge or injured while changing the punch and die.
Basic Safety Precautions
Before operating the bending machine, employees must undergo proper training to ensure their safety.
The training should cover safe operating procedures, knowledge of the equipment and its protective devices, hazard identification, and emergency control measures.
Operators should be strictly supervised to ensure they follow established rules.
It is important to wear appropriate personal protective equipment, such as gloves and goggles, before starting the bending operation.
The area around the machine should be kept clean and free of any obstructions that may interfere with the operation of the bending machine.
It is also important to properly commission the machine to avoid malfunctions and contamination.
During bending, operators should remain alert and never leave the bending machine unattended.
Infrared Light Curtain Protection for Press Brakes
Infrared light curtain protection is a common safety device used in press brakes.
The light curtain, initially designed as a product testing equipment, has since been adapted for machine protection.
The light curtain is a photoelectric induction device that prevents human contact with dangerous areas.
It can be installed near the toolings of a hydraulic press brake and consists of an emitter and a receiver.
The light curtain system must be connected to the safety monitoring relay and the magneto starter as it is part of the machine’s control circuit.
By creating a sealed protective area through an infrared beam, the light curtain protects both the operator and those nearby.
If an object, such as an operator’s hand, passes through the work area, the press brake will stop bending or will not continue working until the object is removed.
The LED emitter and receiver of the light curtain detect the object and send an output signal upon interruption of the light plane.
However, the safe distance between the light curtain and the press brake is uncertain and may vary based on the installation, type, and emergency braking function of the light curtain.
There is also a possibility of receiving incorrect signals during the bending process.
The light curtain is a common protective device used with press brakes and is a type of photoelectric induction equipment designed to prevent human contact with hazardous areas.
It works by creating a sealed protective area near the toolings through an infrared beam.
If an operator’s hand enters the work area, the press brake will stop bending or not continue working until the hand is removed.
The light curtain provides protection not only to those in the working area but also to those near it.
The light curtain system is connected to the safety monitoring relay and the magneto starter, and it is part of the machine control circuit.
It starts the output signal when it senses an object, such as a worker or another object, interrupting the light plane.
Additionally, the light curtain has a function of automatically closing the system before the punch bends the workpiece.
It also has a floating blank function that allows the bending stroke to continue without stopping.
On both sides of the press brake, the infrared beams emitted by the light curtain are synchronous and parallel.
The light curtain can be programmed or non-programmable.
Programmable light curtains can input the flange of the workpiece into the program, which cancels the light beam blocked by the workpiece and allows the ram to reach the up dead point without stopping.
Non-programmable light curtains cannot cancel the interference light beam and may require the operator to close the light curtain, creating a danger.
Finally, when bending very small workpieces, the operator may need to manually adjust them, which means the light curtain will not work when the operator is in front of the working area.
Two-Handed Control Device
A two-handed control device is an effective tool for protecting hands from injury.
It consists of a vertical control device with two manual control buttons.
For the machine to start, the operator must press both control buttons simultaneously.
If the buttons are not pressed, the machine will cease operation.
Once both buttons have been manually pressed and held, the machine stops when the mold reaches a certain position.
At this point, the operator can then feed the workpiece and use the foot switch instead of the manual control buttons to initiate the bending of the workpiece.
The two-handed control device allows the operator to feed the workpiece from a safe distance away from the operating point between the punch and die, thereby protecting the operator’s hands from being hurt by the punch and die.
The purpose of this device is to prevent the operator’s hands from coming into contact with the operating point while the machine is in operation.
Barrier Guards
The side guards of the press brake are movable barriers located on either side of the machine.
These guards prevent the operator from entering the work area or reaching the rear gauge from either side, thereby protecting their hands from injury.
The rear guard blocks access to the machine from the rear, preventing the operator from coming into contact with the rear gauge.
The press brake’s housing and interlocking press barrier can also be positioned at a safe distance to prevent damage to the machine and injury to the operator from personnel or objects.
Installation Tools
There are potential hazards to the operator during the installation of tools, such as the tools unexpectedly falling and striking the operator’s hand or the sudden movement of the machine ram.
Before installing the toolings or any other tools, it is necessary to lock the ram at the closed height position and raise it to the highest position.
Before turning off the relevant switch, it is also necessary to adjust the position during the installation of other tools.
Conclusion
Regular maintenance is necessary for the press brake, and protective equipment must be worn while operating it.
The press brake must be equipped with the appropriate safety devices and clear warning signs.
The manufacturer of the press brake should provide operational training materials for their customers.
Employers must provide professional pre-operation training for their operators and establish strict rules for operating the press brake.
Using a press brake is a complex task, and special attention must be paid to safety considerations.
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