- October 29, 2014
- SICK, Inc.
By Steve Aamodt, SICK
To help prevent injuries and increase productivity for end users, machine builders are incorporating safety into the design of metal forming and bending machines. The old way of thinking, that safety harms productivity, has changed, in large part due to better safety systems.
By Steve Aamodt, SICK Safety systems should be an integral part of a machine’s initial design to cut costs, increase safety and boost productivity. To help prevent injuries and increase productivity for end users, machine builders are incorporating safety into the design of metal forming and bending machines. Safer machines make operators more confident and faster in their work, and dramatically reduce the number of injuries, which saves companies time and money. The old way of thinking, that safety harms productivity, has changed, in large part due to better safety systems. A simple analogy explains why it is better to procure metal forming machines with the needed safety solutions already installed rather than adding them later. Buying a vehicle with a factory-installed stereo system is cosmetically more appealing, has a consistent best-practice installation process and includes a warranty. Stories of bad installations after purchase run rampant, along with a host of corresponding problems.
Figure 1: A fabrication shop can contain dozensof potentially dangerous metal forming and fabrication machines, but safety sensors can help mitigatehazards. The same is true with metal forming and bending machines. Even if the “update” by various installers and integrators technically works, the aesthetics and safety results may not be as reliable, or fit seamlessly with the existing machine design. By increasing machine safety, compliance with the relevant ANSI norms is improved while achieving risk reduction. During the early phase of the machine-building project, compliance with directives and laws is an integral aspect of project planning. Adding this functionality after the fact often leads to over-dimensioning, minimized effectiveness and competitiveness. Workplace fatalities, injuries, and illnesses cost the U.S. billions of dollars every year. The U.S. Department of Labor and Occupational Safety and Health Administration (OSHA) reports machinery users suffer 18,000 amputations, lacerations, crushing injuries, and abrasions annually; over 800 machinery users are killed per year. For example, OSHA identified hazards associated with power presses (Figure 2). According to the OSHA Safety and Health Information Bulletin, the most common type of injury associated with mechanical power presses is amputation, an extremely serious incident. An integrated safety system can prevent this and other types of incidents. The control and safety sensor components function together as a unit, so if a safety sensor detects a problem, the press will not initiate a successive stroke until the situation is corrected. There is a direct positive correlation between investment in safety, health, and environmental performance and subsequent return on investment, according to the American Society of Safety Engineers. In addition to reducing injuries, employers often find process and other changes made to improve workplace safety and health result in significant improvements to their organization's morale, productivity and profitability.
Figure 2: The most common injury with a power press is amputation, which can be prevented by the correct application of a safety system.
Unless requested by the end user, machine builders may not build safety into the machine. Increasingly, however, there is a case for machine builders to design the safety solution into the machine, producing an integrated solution that’s much less expensive than having the end user add this functionality after the fact. In addition to the benefits of building safety into machines up front, there are also often standards that machine builders must meet. Compliance with Standards Machine builders must ensure machines comply with the latest safety standards and regulations. As safety standards continue to evolve, more machine builders are choosing to incorporate safety into machine designs on the front end. Safety is a way to improve productivity, which can justify an increase in the selling price of the machine to the end user. Safety regulations are getting stricter worldwide. In Europe, machine builders must conform to the Machinery Directive and standards such as IEC 61496 (which governs opto-electronic protective devices) and EN 62061 (which defines safety integrity levels), or they will not receive a CE Mark. Without a CE Mark, they can’t sell the machine in Europe. The U.S. has similar applications and standards, but not the same requirements. The requirement is on the end user to make machines safe for their employees. Safety technology also leads to more satisfied customers, and reduces costs when safety risks are assessed during the design phase, rather than after the machine is placed on the plant floor of the end user. Lean manufacturing principles have had an impact on the technologies developed to safeguard machines and employees. Safety component manufacturers are looking at ways to design their safety offering to better meet the requirements of lean best-practices. Challenges machine builders face when incorporating safety into metal forming and bending machines are significant and include fast speed, dangerous movements and cost concerns. Frequent operator involvement means metal forming machines represent a significant safety risk when proper safeguards are not instituted from the start. U.S. fabricators and metal working manufacturers are increasingly working on an Engineer-to-Order (ETO) basis instead of very long production runs of standard products. Safety systems must therefore accommodate these custom jobs, which require more flexibility and frequent part changeovers, necessitating the need for intelligently designed safety systems. Considerations for Designing a Safe Machine Point-of-operation safeguarding Point-of-operation safeguarding products generate a safety stop signal based on the detection of a finger or hand. These safeguards are used to protect the operator from being exposed to a hazardous motion where material is positioned and a process is performed.
Figure 3: A safety light curtain detects the presence of a finger or hand, and sends a signal to the safety controller to stop the machine.
Applications for point of operation safeguarding include press brakes, welding and assembly lines, and hydraulic and mechanical presses. Presses in the metal, plastic, rubber and brick industries—along with punches in the metal, plastic and textile processing industries—are best designed with these safeguarding products up front. Safety light curtains (Figure 3) are frequently used to provide protection at the point of operation. Perimeter safeguarding Perimeter safeguarding products generate a safety stop signal based on the detection of a body/torso or arm/leg breaking a defined perimeter. Typical solutions include safety light curtains and single beam safety sensors, which are generally used to protect the operator from hazardous motion occurring within an area. Special applications exist, such as muting. Muting is the temporary automatic suspension of the safety function during the non-hazardous portion of the machine or process cycle. This allows material to be fed into a machine without issuing a protective safety stop command. Muting is an excellent example of how a sophisticated safety system can protect workers while maintaining a high level of machine productivity. Muting should not be confused with “bypassing” or “overriding,” which is initiated by an individual who manually suspends the normal function of a safeguard. See ANSI B11.19 for additional information about muting. An assembly cell, for example, can be equipped with safety controllers and components to allow safe and efficient production. During operation, the hazardous area becomes the working area and vice versa due to the movement of the robot, safely increasing productivity. To monitor this assembly cell with changing hazardous areas, a safety laser scanner is used in conjunction with a safety PLC. The SICK S3000 Profinet IO safety laser scanner has an integrated Profinet interface, which facilitates connection to a safety controller with its own Profinet interface. The safety laser scanner is available with three scanning ranges, up to 8 field sets and up to 8 monitoring cases to provide flexible protection of changing hazardous areas. Other applications for perimeter safeguarding include palletizers, conveyors, gantry cranes and automation lines where metal forming equipment is used. Hazardous area protection Hazardous area protection and mobile hazardous protection allows manufacturers of metalworking machinery to evaluate the response time and safety distance required as well as the reliability of the safety functions. This creates a safe working environment without undue impact to efficiency.
Figure 4: This assembly cellwith arobot can alternately be freely accessed by an operator.
Solutions included in these safeguards must have the ability to differentiate between man and material. The maintenance and service life of the solution must also be considered, along with the following factors. Design Concerns Environmental factors that must be taken into account when designing a safe machine include electromagnetic interference, ambient light and human variables. Safety components can be adversely affected by electromagnetic interference, which is often generated during the manufacturing process, and also can occur in other situations. Electromagnetic interference is generated by the normal operation of motors and other devices. It can also be caused by surge voltages, lightning strikes to the grid, high frequency interference, or electrostatic discharge. Care must therefore be taken to protect safety components from interference, and to only select items with a high level of built-in immunity to interference. Vibration and shock are other environmental factors that must be dealt with up front, rather than an after-the-fact consideration. Machines can be designed to minimize vibration and shock, and safety components can be selected with resistance to these factors at a level matching the machine’s operating characteristics. Human variables must also be carefully considered including the qualifications of the operator, the expected number of people in the area, and foreseeable misuse. Maintaining compliance with standards such as ISO 10218, ANSI / RIA R15.06 2011-2012 must be evaluated when designing safety into a metalworking machine, and this can often be done through the intelligent use of safety solutions. Safety Solutions for Metalworking Machines Opto-electronic protective devices include safety laser scanners, perimeter guards, and safety light curtains.
- Safety laser scanners are used for non-contact safeguarding in work cells. These scanners use time-of-flight technology to scan their surroundings and detect intrusions into predefined areas. After manual work in the hazardous area, an operator must manually restart the machine. When used with a safety controller, up to four simultaneous protective fields can monitor four hazardous areas at the same time.
- Safety light curtains and perimeter guards are typically used for hazardous point protection and perimeter guarding. Single-beam safety photoelectric switches can be used in single or multiple beam systems to ensure the necessary distance for safety is observed in front of a machine according to the space available at the site. Multiple light beam devices can be used for providing access protection to machines.
- Safety controllers are used to connect all safety devices. Safety switches, emergency stop pushbuttons and optoelectronic safety devices are connected to safety controllers. When used with safe motion control devices, this enables safe implementation of a speed monitoring system.
- Physical fixed or movable guards or fences provide safety solutions as well as mats. These solutions are generally less expensive initially, but can cost more over time due to a higher rate of replacement, and are less flexible
Figure 5: Safety controllers connect to the safety sensors in a system, and can be programmed to take appropriate action.
Summary Reduced injuries and deaths are the most obvious benefits of designing safety into machinery on the front-end. Metalworking shops, job shops, and fabricating plants are increasingly insisting that safety technology is built in to the machines they buy, and not added as a mere afterthought. In addition, regulations often require safety to be built into the machine before shipment to a customer. The value of building safety into metal forming and other machines far exceeds the liability exposure of just one serious incident. Economically as well as responsibly, it makes sense to get safety right the first time.Learn More
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