Shielding workers with
PRESS BRAKE SAFTY
A look at accident prevention
By John W. Russell
Unsafe operation of press brakes causes many serious accidents in the United States every year, according to a study conducted by Liberty Mutual Group on press accidents that were reported to it.
Several types of accidents can occur on press brakes (see Figure 1). Many people believe press brakes cannot be safeguarded without compromising production, efficiency, quality, and cost. Others may believe press brake safety only requires installing a guard, training operators, or repairing equipment when it malfunctions. Some companies have gone out of business, realizing too late that they should have incorporated safety into their daily operations.
Safe press brake operation requires a comprehensive strategy that should include equipment designers, manufacturers, users, and safety consultants.
This article discusses the major components of such a program, including designing, manufacturing, and purchasing of safe equipment; preplanning machinery installation and setup; safeguarding equipment; implementing safe work procedures and training; and ensuring regular maintenance of equipment (see Figure 2).
Manufacturers and users who follow these procedures can experience a range of benefits, including fewer accidents and injuries, reduced medical costs, reduction of downtime, fewer equipment repairs, less material damage, and reductions in labor costs. Productivity, compliance with standards, product quality, and customer satisfaction can increase. Liability claims and legal expenses may also decrease.
Figure 3 lists the most common types of press brakes, and Figure 4 shows a number of different ways they can be operated. Using guards, devices, and other supplementary protective measures may not result in complete protection from all possible hazards. However, improving the margin of safety by 40 or 50 percent is better than doing nothing until 100 percent protection can be attained. Every margin of protection should be implemented as soon as it is available.
Before specifying and installing guards or devices on equipment, manufacturers and users must identify and then eliminate or control hazards while improving ergonomics and minimizing occupational health exposure.
The user's purchasing, engineering, production, and risk management departments together must develop specifications and safety requirements that meet safety standards and regulations. The intended use of the equipment should be reviewed with the manufacturer and distributor, and plans should be discussed with the insurer's loss prevention consultants.
One should not assume that equipment automatically meets the latest safety standards. A company needs to specify exactly what codes, standards, and regulations must be met. Unexpected hazards could exist when the machinery arrives, possibly requiring expensive modifications before it can be used.
These unexpected hazards include machines that do not have lockout/tagout capabilities and therefore have to be rewired. Another example of this type of hazard can arise when two operators need to run the equipment, but the press brake has one set of controls. In this case, a second set of machine controls should be installed.
Obtaining and reviewing safety standards such as American National Standards Institute B11.3-Safety Requirements for Construction, Care and Use of Power Press Brakes; Occupational Safety and Health Administration 1910.212-Machine Guarding; and 1910.147 Control of Hazardous Energy are essential to establish practical safety requirements for power press brakes. ANSI B11.3 is being revised to include new helpful safety information.
Job Safety Analysis (JSA) is a valuable tool that can help reduce accidents and improve productivity. It also can be used for training employees, investigating accidents, and conducting safety surveys. JSAs are not difficult to complete, but manufacturers should take some time and effort to prepare them properly. They can produce immediate paybacks that far outweigh the effort spent preparing them. Other types of risk assessment and system safety techniques can also be used during preplanning stages.
Safety controls must be feasible and appropriate since many accidents have occurred because employees removed guards that proved to be impractical for the job. Patience and cooperation are needed for developing effective guards. Obtaining employee input is important in determining which safeguarding methods may be the most practical, acceptable, and useful by the press brake operators. After installing safeguards, their effectiveness must be monitored to determine if further changes are necessary.
Safeguarding-Point of Operation
Depending on the parts being produced, safeguarding a press brake point of operation can be accomplished by using one of several guards, devices, or methods. These include:
Presence Sensing Device (Light Curtain): The light curtain can be used for short- (fewer than 2,000 parts) and long-run operations and for small, medium, or large workpieces. Proper use provides protection for operators and individuals passing by the equipment and helps minimize operator resistance to their use.
However, operators may be resistant to using light curtains if they have not received training on how to work with them. In addition, the press brake may stop in the middle of a bending cycle.
The light curtain usually is mounted vertically on a press brake and protects individuals from point-of-operation hazards while maintaining visibility and accessibility. It also allows easy setup, tool adjustments, and maintenance. Light curtains allow easier access to the point of operation during setup compared to removing, reinstalling, and adjusting fixed barrier guards.
The height of the transmitter and receiver should be sufficient to protect against accidental access above or below the light plane. The light curtain must be installed at the proper safety distance. Side guards should be included to prevent users from reaching behind the curtain. In some cases, pressure-sensitive mats are installed in front of the press brake to prevent someone from operating the brake while standing between the light curtain and the point of operation.
Many light curtains use a feature that allows them to be muted during the nonhazardous portion of a press brake stroke, generally from 1/4 inch above the workpiece to top dead center. Other options include blanking single beams and using a floating blank.
Success Story: A major manufacturer called its insurance loss prevention consultants about improving the safety of its press brakes after two employees were injured.
The company installed a light curtain on one of its eight press brakes for evaluation. After using the modified machinery for six months, the customer and its employees decided that safety had improved. The other seven press brakes were equipped with light curtains, and during the past three years, there have been no employee injuries.
Press Brake Accident Examples
Listed here are the types of accidents that can occur when using a press brake.
Types of Powered Press Brakes
(May have different types of clutches)
Types of Operations
Manufacture of Safe Equipment
--Preplanning-Equipment Installation and Setup
--Safe Work Procedures and Training
--Equipment Maintenance and Lockout/Tagout
bend angles, channels
Two-Hand Control Device: Two-hand controls used as point-of-operation devices for press brakes work well for short-run operations. Each operator must have an operator station with two protected run/inch palm button assemblies and a red emergency stop button.
The two-hand control provides protection against point-of-operation injuries during the die-closing portion of the stroke. Each operator must depress both palm buttons until the slide reaches 1/4 inch above the workpiece. If a button is released, the slide stops. Both buttons must be released and reinitiated to finish the stroke.
Pullback Device: Pullback devices are usually installed on press brakes for long-run jobs and when small- to medium-size parts are being produced.
A pullback is a mechanical device operated by the motion of the slide or upper die. When two or more operators are working on a press brake, each must have a pullback. The overhead design allows operators to move freely for loading and unloading parts. Pull-backs must be properly adjusted and inspected before each shift or before use by a new operator.
Restraint Device: Restraints usually are installed on press brakes for long-run jobs and when medium-size parts are being produced. Overhead restraints are similar to pullback devices, except they do not include a pull-out mechanism. The restraints must always be adjusted to prevent operators from reaching into the hazardous area at any time.
Restraint devices usually include a mounting bracket, tubular arm, and a strap with a wristlet attached. They allow the operator to load, unload, and hold parts without being able to reach into the point of operation.
In some cases, the restraints slide along a horizontal bar that allows operators to move along the front of the press brake. The restraints must be properly adjusted and inspected before each shift or use by a new operator.
Safe-Distance or Safe-Holding Method: Safeguarding by using safe-distance or safe-holding methods can be applied to short- and long-run jobs for operations that involve large parts. This safeguarding method should only be considered when no other guard or device can be used to protect operators.
When no safeguard or device is used, the operators have to remember to keep their hands away from the point of operation. This may be possible if large parts are being handled. However, smaller parts may require operators to place their fingers and hands very close to the danger area. Physical safeguards or devices are preferable to the use of this administrative control.
Auxiliary Safeguarding: Additional safeguarding equipment can be used with primary safeguarding devices. These can include side and front point-of-operation barrier guards, pressure-sensitive safety mats, cables and warning signs for the rear of press brakes, and hand feeding tools. Hand tools, backgauges, or material positioning gauges and stops can assist in lining up material from the front of the press brake. However, hand tools are not meant to replace guards or devices.
To prevent the unused portions of the die from posing crush/amputation hazards, dies should not be any longer than necessary.
Other Methods: Gates or movable barrier devices are two other alternative safety methods. The type of press brake operation can help determine which guards or devices may be practical or feasible.
These methods can be used in press brake operations in which the operator does not hold the material because a fixture or support is used. The press brake ram does not move unless the gate is closed.
Safeguarding-Other Than Point of Operation: Other potential hazards include rotating flywheels, gears, sheaves, shafts, belts, chains, and unguarded foot controls. Tooling must be kept in good condition. Caution and warning labels/signs should be installed and operating/maintenance manuals should be available to setup personnel, operators, maintenance workers, supervisors, engineers, and others.
Safe Work Procedures and Training: Physically safeguarding equipment is only part of a comprehensive safety approach.
Written safe work procedures must be established, communicated, and enforced. One study showed that approximately 45 percent of serious injuries occurred to employees who had been on the job less than a year. This indicates the necessity of initial and periodic training of employees and supervisors.
Before training sessions are held, appropriate and reasonable training objectives must be clearly defined. Frequently, not enough thought or preparation is given to what training is really needed and what type of follow-up will be done. Managers, supervisors, and employees must understand that training is important and is not being done just to fulfill a legal requirement.
Other factors that can affect safe work conditions include proper layout for machine operation and material handling of stock/parts, lighting, noise, ventilation, personal protective equipment, and scrap removal. Mode selector switches (off, inch, single stroke, continuous) and hand/foot switches must be designed so they can only be operated by authorized individuals.
Equipment Maintenance and Lockout/Tagout: Some companies and individuals may feel that equipment should be maintained or repaired only when it breaks down. Serious injuries, property damage, and lost business can result from this attitude.
No press brake safety program will be successful nor will production be efficient without regular inspections and preventive maintenance of equipment and safeguards.
A checklist based on information and recommendations from the press brake manufacturer should be developed. The purpose of the checklist is to provide a step-by-step inspection of specific components. Depending on the specific equipment, inspections may be necessary on a daily, weekly, monthly, semiannual, or annual basis.
Action to correct serious hazards should be taken immediately.
Lockout/Tagout (LOTO) involves establishing a written program and procedures for isolating equipment from energy sources, for affixing locks and tags to the energy-isolating devices, for training, and for auditing periodically. The purpose of LOTO is to prevent employee injuries caused by the unexpected start-up or release of stored energy during repairs, maintenance, cleaning, and operation. All power sources, including electrical, hydraulic, pneumatic, and gravity, must be included.
Complying with OSHA, ANSI, and other legal requirements can provide many safety benefits. The potential for injuries, violations, and fines can be reduced significantly while a company increases productivity.
John W. Russell is Product Manager of Manufactuting Technology at Liberty Mutual Group, National Technical Center, 114 Turnpike Road, Suite 204, Westborough, MA 01581, 508-870-3333 x254, fax 508-836-4563. Liberty Mutual Group provides workers' cornpensation insurarce prograrns, and services .
Questions about ANSI or OSHA can be directed to the American National Standards Institute, 11 W. 42nd St., 13th Floor, New York, NY 10036, 212-642-4900 or to the Occupational Safety and Health Administration, 20 Constitution Ave. NW, Washington, D.C. 20210,202-219-8151.
THE FABRICATOR August 1998