Shaping things up
From EDM and handling systems to shop floor software – Zimmer & Kreim offer everything from a single source. When the company sought to expand its Chameleon handling system, the heightened safety requirements of the EU's new machinery directive presented a complex challenge. With a combination of integrated safety technology from B&R and the open, real-time POWERLINK fieldbus protocol, they found exactly the solution they were looking for.
"People laughed back in 1985 when we were the first to use an electrode changer for die sinking," recalls managing partner Klaus Kreim. The laughter stopped quickly, however. Since EDM is such a slow process compared to other machining techniques, the fully automated electrode changer offered a clear advantage: by allowing production to continue through the nighttime hours, it significantly increased output.
The universal Chameleon handling system provides a reliable supply of workpieces, electrodes and milling tools for a wide variety of machines.
Shaping things up
EDM stands for electric discharge machining – a manufacturing process that uses electrical discharges, or sparks, from an electrode tool to gradually remove material from a conductive workpiece. These machines may use one of several different methods, including wire-cut EDM, small hole drilling EDM or die sinking EDM. The latter involves sinking the electrode, whose shape is the negative of the desired result, into the workpiece.
Zimmer & Kreim is a market leader when it comes to die sinking EDM machines. Chameleon, the company's fully-automated, universal handling system, supplies machines and magazines with workpieces, electrodes and milling tools – even during operation – both horizontally and vertically. True to its name, the Chameleon adapts to all different technologies, able to easily integrate a wide range of production machines such as milling or wire-cut EDM machines. It provides a seamless flow of materials throughout the entire processing chain in the tool and mold-making industry – even including the final step of cleaning and drying to prepare for the next use. The clear advantage: shorter processing times for substantially increased output.
During EDM processing, the electrodes generate sparks between the tool-electrode and the workpiece being shaped. The shape of the tool-electrode is the negative of the desired final shape of the workpiece – which could be virtually anything from a Lego block to a car dashboard to a shampoo bottle. The areas of application are virtually limitless: From toys to automotive to packaging – there is hardly an industry where EDM processing isn't involved at some step along the way. "Some of the simplest everyday commodities are made this way," Kreim points out. "Very few people stop to think about the complex technology behind it." Once an electrode-tool has been milled, the handling system takes it to the measurement machine, which measures it, determines its zero point and verifies its quality.
The goal: Faster and better than the competition
By now, the EDM process has been optimized to its mechanical limits. Any competitive advantage that remains to be gained must come from fine-tuning details such as computing performance. In the worst case scenario, a computer failure could turn the EDM process into a welding process, with material being added to the workpiece rather than eroded away. The potential damage to the workpiece surface through such an error makes it extremely important that the pulses of voltage to the electrodes are constantly monitored.
This is done using an analog-to-digital converter, which – with a sampling rate ten times faster than the pulse width – monitors one thousand measurement points every microsecond. The focus of this monitoring is on the amplitude of the voltage pulse. If there is a delay in the pulse, it must be re-triggered to achieve the desired duration, which determines the quality of the workpiece surface. A voltage that is too low (below 5 volts) is equivalent to a short circuit, while voltage that is too high (over 24 volts) is referred to as open-circuit voltage. This is measured using an oscilloscope, which first takes a base reading and then monitors the surface.
Shorter voltage pulses (around 1 µs each) produce a smoother surface, but also make processing take longer.
Developing a distributed system with B&R
"Our Chameleon handling system has been around since 2007, but back then, all the safety technology – the E-stop circuits, light curtains and other equipment – was an entirely discrete system," notes Volkmar Marquardt, head of development at Zimmer & Kreim.
"Our handling system was already scalable at the time, but only for up to two machines. The system expanded quickly after that, and has now reached 23 meters in length with 9 machines and 12 magazines. With the increasingly stringent safety requirements and the new machinery directive, we had to look at how to move toward a distributed solution, and who would be the best partner to help us get there," Marquardt continues.
For Zimmer & Kreim, it was clear from the beginning that the distributed system would be built together with its longstanding technology partner, and now primary shareholder, Indel.
More safety – with POWERLINK and openSAFETY
With a number of suppliers in the running, it was B&R who got the green light. "The decision fell quickly in B&R's favor," says Marquardt, "particularly because of how easy it would be for Indel to implement POWERLINK, and also because the solution provided all the required safety features."
B&R's safety solution also facilitates a modular design of the overall line, where communication between all of the subsystems takes place over openSAFETY and POWERLINK. All of the hardware is configured using the Automation Studio development tool, and the safety application for the SafeLOGIC safety controller is created in the visual SafeDESIGNER editor. As an integral component of the Automation Studio engineering environment, SafeDESIGNER ensures safety and reliability when programming sensitive functions for the protection of equipment and personnel.
All modifications to safety systems are completely protected by a restrictive change process. The basic elements of the safety application only have to be developed once, after which they can simply be selected and enabled according to the actual requirements of any given line – without having to make any other changes to the safety application itself.
Prior to POWERLINK, Zimmer & Kreim used a fiber optic bus. The electrical network was laid out in a star topology, while the fiber optic bus was a ring, which made troubleshooting a nightmare. With POWERLINK they can now mix star and ring topologies as needed and are free to make changes as requirements dictate. "There were other bus systems that we could theoretically have integrated, but it would have been rudimentary and lacked safety functionality. That wouldn't have been any help," says Marquardt.
The new solution also uses B&R's SafeLOGIC controller to handle the safety application. The various functional and safety I/Os used can be combined flexibly to adapt optimally to the topology of the machine. Valve terminals are also directly integrated in the I/O network. This results in fewer I/O modules and less wiring, which also reduces the production cost of a machine.
"The decision fell quickly in B&R's favor, particularly because of how easy it would be to implement POWERLINK." "There were other bus systems that we could theoretically have integrated, but it would have been rudimentary and lacked safety functionality. That wouldn't have been any help." Volkmar Marquardt, Head of Development, Zimmer & Kreim
Consistent quality, worldwide
Zimmer & Kreim have few competitors in their field – most of them located in Germany, Austria and Switzerland, with Japan quickly gaining ground as well.
"Time and again, we've seen German manufacturers try moving production to China in order to cut costs," says Kreim. "When precision is critical, however, the products fail to live up to the necessary quality standards and end up coming back. The problems with the technology, and ultimately with quality, are the result of an insufficiently trained workforce."
Recently, a well-known electronics manufacturer placed an order with Zimmer & Kreim, and within six months, four completely automated manufacturing systems were on their way to Asia. This substantial order was a big win for the Hessian company and its 80 employees.
openSAFETY is the first open and only bus-independent safety standard available for all industrial Ethernet and fieldbus solutions. This technology makes it easier to implement safety solutions in compliance with current 2006/42/EC machine guidelines as well as other applicable standards. Using the "Black Channel" principle, openSAFETY is the only safety protocol in the world that can transfer secure data via any fieldbus system. openSAFETY is a step ahead of the rest with regard to response times as well. The additional integration of POWERLINK further reduces the response times and drastically improves the availability of machines and production lines.