The Handtmann Group is a portfolio of manufacturing businesses, one of which operates several light-metal diecasting plants in Germany, Slovakia, and China. At its headquarters plant in Biberach, Germany, a total of 44 Westomat dosing furnaces are in use, and recently updated with a flanged riser design that the diecaster along with system developer StrikoWestofen credit with improving the availability and process stability of the dosing process.
Handtmann emphasizes three strategies for its manufacturing efforts: adopting best available technology, innovating new production methods, and maintaining high quality standards for finished products. All of these points were checked during the recent modernization project, according to the furnace supplier. Over 24 months, StrikoWestofen carried out a comprehensive upgrade of the 44 Westomat dosing furnaces at Handtmann. Switching to flanged riser tubes with pneumatic measurement of liquid metal levels — the PneuCo system — and installing ProDos3 process-control systems means the furnaces now are equipped to perform reliably, consistently, and effectively.
To optimize dosing system availability and process stability, and to minimize the scrap rates, all 44 dosing furnaces were outfitted with flanged riser tubes that offer replicable conditions and straightforward handling. However, Handtmann insisted that its positive experience with the previous PneuCo system cast riser designs should be upheld following the switch to flanged riser tubes.
The PneuCo system is a way of evaluating the liquid metal level at the pouring edge of the riser tube. Usually, measurement is done with electrodes, or a top-stop position. The advantage of the PneuCo system is that it is not subject to wear: the pressure change at the scanning point is measured to determine the level of the liquid metal in the riser tube. A small flow of air from the output of the pneumatic control is directed to the scanning point in the riser tube. As soon as the rising level of the liquid metal in the riser tube covers the air outlet, pressure suddenly increases in the PneuCo system. This rise is detected by a pressure switch and transmitted to the dosing control.
This pressure switch process corresponds to the dosing contact used in classical electrode scanning. Light metal foundries and diecasters benefit in two ways: the dosing contact has no parts to wear out and need replacement, and the scrap rate is minimized by eliminating any possible interference with molten metal.
Handtmann chose to adopt the PneuCo system with flanged riser tubes, which is currently being tested during production, and according to the developer the diecaster has been pleased with the results.
In addition to the PneuCo upgrade, Handtmann decided to improve furnace control with the ProDos3 high-precision control system for high-pressure diecasting. "Our ProDos3 with integrated biscuit correction increases the dosing accuracy of the Westomat (furnaces)," according to Holger Stephan, manager for the furnace developer’s Service and Spare Parts division.
“In addition, pressure fluctuations can be compensated, and reproducibility improved using a number of different correction factors," he added. Another new feature, an optional web server makes it possible to integrate the ProDos3 control with the diecaster’s local network. This means that all relevant information, (e.g., the furnace pressure and performance data) can be accessed conveniently by the operators and management team.
The Handtmann modernization program also included joint testing of new refractory replacement parts for Westomat furnaces. A notable reduction in downtime during refractory repairs to the furnace, with similar quality results, supports Handtmann's three principles. As a result, the product will be used again when repairing or relining the dosing furnaces.
Lastly, a new StrikoWestofen heating station was installed to improve occupational safety when handling hot ceramic components, and a special assembly bench simplifies the process of fitting PneuCo with the flanged riser tubes. "We are extremely happy with the successful modernization program and are proud that we were able to meet the specific requirements of our customer in such a flexible and cooperative way," Stephan concluded.