Reducing robot risk: how to design a safe industrial environment
A laser scanner allows design flexibility in area protection In the last couple of decades, laser technology has also begun to help improve safety on the factory floor. A safety laser scanner can provide three-dimensional protection of an area, and offers the designer increased flexibility to tailor the system response by specifying different warning and safety bands, also known as zones, around the hazard (Figure 5).
false trigger. A human operator, however, can still interrupt one of the active channels and cause an alarm. When the muting system detects that the product has passed, it reenables the muted channels. Additionally, a blanking function can disable channels (Figure 4b) that are always blocked, by a piece of equipment, for example. The SF4D series of light curtains from Panasonic Industrial Automation includes multiple products optimized for different applications. The “H” series devices are intended to detect hand-sized objects, with a vertical spacing between beams of 20 mm (0.8”). For example, the SF4D-H28 has 28 transmit/receive channels that form a curtain 550 millimeters (mm), or 21.7 inches (“) high. This product has an operating range from 0.2 meters (m) to 9 m. With a 20 mm (0.787”) spacing, “F” series products protect against smaller objects such as fingers. The SF4D-F79 features 79 transmit/receive pairs for a protective height of 790 mm (31.1”) and has a range of 0.2 m to 12 m. The SICK C4C-SA03030A10000 transmitter and its matching C4C- EA03030A10000 receiver combine to form a 300 mm (11.8”) light curtain with a maximum range of 15 m (49 feet). The company also offers a range of transmitter/ receiver pairs with protective heights up to 900 mm (35.4”).
Safety laser scanners use time-of- flight technology. The transmitter emits a pulsed laser beam that is reflected by an intruding object and detected by the receiver. The time between transmission and reception is proportional to the distance between the scanner and the object. An integrated rotating mirror deflects the pulsed laser beam and enables the unit to perform a fan shaped scan of the surrounding area. The real-time measurement data can be transmitted over a networked interface for further analysis if needed. SICK’s S32B-2011BA safety laser scanner, for example, uses a laser diode to produce a near-infrared pulse with a wavelength of 905 nanometers (nm). This device is part of SICK’s S300 family and features a protective range of 2 m and a warning range of 8 m. Another S300 device, the S32B- 3011BA , features an expanded protective range of 3 m. The OS32C Area Scanner from Omron Automation and Safety features a monitoring field of up to 270˚ and includes two separate warning zones, plus a safety zone (Figure 6). The OS32C can communicate via the industrial EtherNet/IP protocol: it can be monitored by ODVA EtherNet/ IP-compliant products such as programmable logic controllers (PLCs) or industrial human- machine interface (HMI) modules.
Figure 6: Omron’s OS32C family of area scanners features multiple programmable zones (Image source: Omron Automation)
A variety of data including system status, zone status, and measurement details can be transmitted. Until recently, laser scanners have been considerably more expensive than safety mats. But lower cost laser safety scanners are becoming available, and the return on investment (ROI) for safety scanners compares well to older technologies from a total-cost-of- ownership (TCO) perspective. The TCO analysis particularly favors a laser scanner in a high traffic area where a safety mat might have to be periodically replaced.
Other safety components help to “connect the dots”. The main safety devices discussed above are used in conjunction with other safety components that might not be as technologically sophisticated, but play a vital role in plant safety. Among these are items such as emergency switches, door interlocks, light towers, and cable-pull actuators. Designers can find out more about these products on DigiKey’s Safety Components page.
Conclusion
Designing a safe industrial environment requires a multi- layer approach which employs multiple strategies to guard against unwanted human-machine interactions. The key is to first prevent personnel and equipment from entering potentially dangerous areas. Safety mats, light curtains, and safety laser scanners play an important role in detecting intrusions and shutting down machines automatically without the necessity of human interaction.
Figure 5: A laser scanner allows the designer to set up multiple safety zones with different response levels. (Image source: SICK)
Once an object or person is detected in the outer warning zone, the scanner sends a warning signal to an audible or visible indicator that notifies them of a potential hazard. When the person or object enters the inner safety field, the laser scanner sends a signal to stop the hazardous motion of the robot or machine. The zones are programmable and can be changed dynamically by an input to the safety scanner.
we get technical
52
53
Powered by FlippingBook