MoldMaking Technology

SEP 2018

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moldmakingtechnology.com 29 Four EDM machines from OPS Ingersoll are connected via a robot. Hofmann started its first automation efforts in its EDM department. Because electrode milling and EDM are time-consuming processes, they are ideally suited for automation. they ideally are suited for automation. The implementation is relatively straightforward. It is a good opportunity to learn when you are just beginning with automation, because if something goes wrong at the beginning, throwing away an electrode is not a big deal. But, with a finished workpiece, it would not be that simple. Of course, you need to control the entire process and to do so, you should never start with the most complicated process. Today, we are milling around 25,000 electrodes per year—even the Chinese cannot work any more efficiently!" To control the process, Hofmann works with transponder chips based on RFID in its automated EDM line that CERTA makes. CERTA is a medium-sized software and process consulting company and a 100-percent subsidiary of Erowa Group in Büron, Switzerland. The system assigns electrodes to workpiece holders and makes them available in the CERTA central process control system, preventing errors during the insertion of the parts into the machine. When machin- ists insert the workpiece (or in this case, electrode) into a magazine, the system immediately recognizes it in the cor- responding magazine position. The system also provides the data centrally. Machinists therefore can change workpieces correctly and flexibly. NC programs for processing, offset data for tools, tool positions in magazines as well as pallet and loading informa- tion are provided centrally in the CERTA process control system based on the order. All of the required information is on the chip. "We insert the tools via barcode, and the system does the rest automatically. Thus, clamping errors and the like are practically eliminated. But of course the whole pro- cess has to be simulated before going into production." The process for determining the offset data of the elec- trodes is fully automated at the presetting station. The necessary geometry data, dimensions and tolerances are automatically transferred from all popular CAD systems to the measuring machine. The required measuring points are defined in the CAD plug-in. If deviations occur in the tar- get or actual comparison during the measuring process, the required process steps are automatically initiated. This may involve remanufacturing or reworking, for example. After successfully automating its EDM department, the company also largely automated its milling lines. Hofmann runs two fully automated lines, a smaller line with two Hermle C50U units and a robot and a larger line with four Hermle C42U machines, a washing and measuring station, 60 pallets and space for 400 tools. According to Hofmann, the latter is as efficient as 10 stand-alone machines. "Even though automation makes up half the investment, it is still worth it," Hofmann says. Automating the milling lines was not the easiest task, Hofmann says, because fully automated milling of hardened mold inserts involves much more tool wear and requires even higher accuracy than EDM die-sinking and electrode milling. As a result, the process has to be highly standardized and needs more than machines, pallets and robots. Standardization Is the Prerequisite for Automation "You need to organize the material flow properly, be trans- parent about planning and control operations and identify standardization and modularization potentials throughout the entire order-fulfillment process, from costing to design and programming to production." To ensure data consistency throughout the streamlined production process, Hofmann uses Siemens NX. "Apart from designing and using our own standard components to build our molds, we count on standardized design," Hofmann says. "You need standard elements that are always designed exactly the same. That is one key aspect of it, but you must also standardize the process itself. Reduction is key here. Take, for example, reducing the number of tools. When you have 500 tools, it is unrealistic to think you could operate an automated line. Fifty would be a good number, because your tool library remains manageable, and you can reduce potential sources for error. And these 50 tools will have to do, no mat- ter what." Hofmann explains that you must also standardize programming through libraries, configurations and attributes to execute the process in a secure and uniform manner. "An automated workflow from design to NC code helps reduce programming time and eliminates errors. Since we never man- ufacture the same workpieces, standardization and process reliability are crucial for us," he says.

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