Safety molded to perfection
Plastic processing machines are simultaneously becoming more complex and more modular. Both of these qualities increase the demand for control systems with intelligent safety functions and fast response times. The ideal medium for exchanging safety-relevant data is the most prevalent fast system bus in use on the machine. openSAFETY is the only safety protocol that meets the requirements of these challenging applications.
Machines that mass-produce plastic items are fully automated and run non-stop. Because the complex tools involved are expensive to design and build, the machines need to be able to produce large quantities of high-quality products in extremely short production cycles. Manufacturers of plastic processing machines have been driving innovation for years now in an effort to reach these goals. Viewed as a pioneer in many areas, new developments in this sector generally find their way into automation engineering.
The electric servo drive is one such example. The motion axes in these machines exert enormous amounts of force, which is why hydraulic solutions are used for the drives. At the same time, media pressure is not held constant, but varies according to requirements in order to improve efficiency. This is where servo motors come into play. These days, most machines with lower force requirements are already being built with fully electric drive technology. This increases energy efficiency and precision while also making them much more responsive.
The number of motion axes found in plastic processing machines is already high and continues to rise. This is particularly true in injection molding machines, where tools are becoming increasingly complex and feature countless core pullers. These machines generally operate at such high speeds that the human eye is incapable of following the individual processes they perform. At the same time, with clamping forces measured in tons, it is vital that sufficient measures are taken to protect employees on the plant floor.
The basic prerequisites for bus-integrated safety technology are already in place. In order to synchronize their numerous drives, the vast majority of plastic processing machines are equipped with high-speed Ethernet-based fieldbus systems. As a result, hardwired safety circuits are becoming rare. The magnitude and speed of the masses being moved demand especially short stopping distances, making it imperative that safety functions are triggered without delay and take effect quickly.
With extremely short response times, openSAFETY guarantees minimum stopping distances, even for very fast movements. This open-source safety protocol also allows drives to perform intelligent, safe reactions that provide controlled emergency operation and rapid restarts while providing complete safety for plant employees.
The openSAFETY protocol uses the "black channel" principle to communicate safety-relevant messages over the system bus to ensure extraordinarily short stopping distances and rapid restarts. With safety technology integrated directly in servo drives and motors, openSAFETY can reduce a system's response times to a few milliseconds.
"This improves workplace safety while simultaneously boosting the productivity of the machine," says Stefan Schönegger, managing director of the Ethernet POWERLINK Standardization Group (EPSG). "Shorter stopping distances allow for reduced safety clearances, which in turn shrinks the machine's footprint or makes it possible to increase the speed at which it can run with Safely Limited Speed."
Safely Limited Speed is just one of many intelligent reactions made possible by openSAFETY drives with integrated safety logic. Intelligent drives are frequently the better alternative to simple E-stop functionality since they facilitate safe human-machine interaction, allow faster restarts and thus considerably increases the productivity of the machine.
The trend toward the complete automation of entire processes can be observed in every industry, and machinery for processing plastic is certainly no exception. In this pioneering industry, handling equipment for both raw materials and finished products has long been flexibly integrated into the overall automation solution. These devices are docked onto the primary machine as optional modules, as are the saws used to trim pipes or extruded profiles in sync with the feed rate.
openSAFETY facilitates modular machine designs by providing virtual wiring over the network. Ready-to-go machine components – including safe drives – can be easily connected without having to resort to the complicated wiring required by E-stop chains. Up to 200 safe I/O channels and drives can be addressed flexibly from a single safety controller.
openSAFETY is the only completely open safety protocol available, with its open philosophy expressed in two key ways. First, as open-source software, openSAFETY is available to device and system manufacturers with no licensing costs. This technology does not require the purchase of any specific hardware and can be implemented quickly, easily and inexpensively with no legal obstacles.
Above all, however, openSAFETY can exchange safety-related data across any fieldbus system. This allows modules and peripheral machines to be integrated into an overall safety solution even if they use a different brand of controller with a different bus system than the primary machine.
"Machines used in the plastics industry need to be absolutely flexible while also maintaining maximum production speed and eliminating every bit of downtime," "openSAFETY supports these goals by combining vendor independence with high performance, which is why it is the preferred standard for safe communication."
"openSAFETY is the preferred standard for safe communication in the plastics industry." Stefan Schönegger, Managing Director of the Ethernet POWERLINK Standardization Group