Create safe, efficient barriers for human-machine interaction
Advances in machining and robotics have increased operational efficiency in virtually any manufacturing operation. Production and profits would plunge if manufacturing were done by hand.
While the advantages of machines are undeniable, these automated systems can create potentially dangerous hazards for workers who operate and/or interact with them. Facilities can and should protect workers by implementing safeguards at critical points of interaction. Recent changes in regulations and protocols by national and international governing bodies such as OSHA, British Standard European Norm (BS EN), and the Robotics Industries Association (RIA) reflect a conscious effort to protect employees working these advanced machining technologies.
Facility managers have a number of options to comply with these standards and improve worker safety. The proper safeguard depends on the exact application. Before examining those options, it’s critical to determine risk if a facility is introducing a new automated operation.
Determine potential risk
Even before RIA updated its machine guarding regulation, R15.06, several years ago to make risk assessments mandatory, assessments have always been a good idea. Point-of-operation guarding is perhaps the most involved aspect of this regulation because it represents the intersections of human and machine, and safety and efficiency.
Because most situations require a machine operator to interact by loading or unloading materials (components to be welded or worked) and "running" the machine, installing perimeter guarding is rarely the proper solution. This point-of-operation requires many details to be considered. Some of them include the layout or design of the process, the limits of the system, properly identifying all associated hazards, and devising methods for hazard elimination and risk reduction.
The distance formula in OSHA guidelines can assist in determining the best machine-guarding device. The formula is:
DS = K (T) + DPF.
DS stands for safety distance; K stands for the maximum speed an individual can approach the hazard; T stands for the total time to stop the hazardous motion; and DPF stands for the depth penetration factor of the safeguarding device.
Per this formula, the safeguarding product has a prescribed location based on a number of factors, including secondary hazards that might harm a machine operator. This formula makes a big difference in determining which safeguarding device a facility should implement.
Benefits of presence-sensing devices
The most basic devices used for safeguarding manufacturing operations are presence-sensing devices such as light curtains and laser scanners. Operations from Tier 1 automotive to small machine shops and fabrication facilities commonly use them. Once the infrared beam of these devices is tripped, the automated process ceases.
In many instances, these devices provide acceptable safety. However, they’re not always the best choice. One of their biggest shortcomings is workers must adhere to OSHA’s distance formula to reduce risk of injury. This can lead to larger work cells, which equates to additional time for employees to walk between the non-operational machine and the safety area when the machine is operating. Employees who skirt the system with shortcuts compromise their own safety. Additionally, an employee who enters a work cell can still be at risk of injury from roll inertia as a machine powers down.
From an efficiency standpoint, presence-sensing devices come with another drawback. Because an infrared beam can’t be seen, a worker who has no intention of entering the hazardous area can accidentally trip them. This can result in unintended delays in operations.
Automated barrier doors offer physical protection
In some instances, light curtains are a viable choice. They can limit exposure to the hazard and reduce risk within regulatory guidelines. In many other cases, though, a fast-acting automated barrier door or roll-up curtain is often a better choice because they can eliminate exposure to both the dangerous movement of the machine and secondary hazards produced by the process, potentially eliminating risk and the severity of exposure.
When they are coupled with safety interlocks (up to PLe, Cat. 4 per EN "ISO 13849-1 – Safety of Machinery" when integrated properly), automated barrier doors and roll-up curtains offer an increased level of protection for point-of-operation guarding. Not only do they restrict access to the process, they also contain secondary hazards such as smoke, flash, splash, mist, or flying debris associated with automated welding operations by placing a barrier between machine operators and machine movement. These types of guards are an ideal alternative to light curtains and other presence-sensing devices in many situations.
Making automated processes safer and more efficient
Interlocked automated barrier doors aren’t held up against OSHA’s safety distance formula because there is no depth penetration factor, which allows the safeguard to be placed much closer to the hazardous area. This correlates to less space being dedicated to a "safety zone" and directly results in reducing the manufacturing cell’s footprint.
This space savings is a huge benefit in most facilities and it means workers actually can stand closer to the automated operation than with light scanners. The smaller safety zone may also make for a better ergonomic situation for the machine operator by limiting required motion and help increase productivity, an essential in today’s competitive market.
The elimination of accidental entry into the cell is another benefit of interlocked automated barrier doors. Unlike the invisible infrared beams of presence-sensing devices, barriers provide safeguarding that can be seen. The physical separation they provide is a marked visual indicator the machine operator needs to be on task.
Properly guard machine operations
Any time a new automated machining or robotic process is being considered for a facility, a risk assessment should be performed to guard the operation properly. Once feasible safety options have been narrowed down, consider the safety option that interferes with productivity the least. When it comes to manufacturing facilities, physical barriers generally offer more protection than presence-sensing devices and likely will improve productivity.
Keywords: Machine safety
Automated machines pose potential dangers to workers.
Presence-sensing devices and physical barriers can provide some measure of protection for workers.
Any barriers designed to protect workers should not hamper productivity or efficiency on the plan floor.
What else can companies do to make human-machine interaction safer?