18 Partners & projects <strong>AHEAD</strong> Issue 01.20<strong>12</strong> Partners & projects A wInDow foR tHE wAsHIng mAcHInE with a fully automated manufacturing cell, miele is making doors for automatic washing machines in the warendorf, germany plastics plant. The doors are in premium quality and correct plastics design, without visible bolts. while doing so, the company relies on the process consistency and reliability of the cX series from Kraussmaffei. TeXT: marKus BeTsche Precision The finished, installed washing machine door from miele
KraussMaffei Partners & projects miele has over 40 years of experience in the manufacturing of plastic parts in their own production, which since 1974 has been located at the plant in Warendorf, Germany with a production area of approximately 10,000 square meters. Here, about three million parts are built per month by 220 employees; this corresponds to about 70 percent of the company’s total demand. Of the 44 total injection molding machines in the clamping force range of 800 to 10,000 kN, over two thirds are from KraussMaffei. All machines are equipped with robots that simultaneously do tasks like imprinting, packing and buffering. From the final device assembly comes the demand to get more finished function components delivered, which leads to a trend of further assembly directly at the injection molding machine. With function groups such as dryer floor assembly modules, the filter, cover, and other metal and plastic parts are, in some cases, assembled automatically and delivered to the final assembly as a complete module. High-gloss finish in one piece The “Sophia” washing machine door, which is available in various appliance series, is an example of how appealing plastic parts with a good design can be. High-gloss finish with depth effect and closed surfaces without visible bolts are the outstanding features of the entire line. In addition, the door is superior in strength to its predecessors, which were made of metal. The complete door consists altogether of 11 parts made of plastic, metal, glass, and rubber and is easily assembled in a complex but very compact manufacturing cell made of three injection molding machines with automation based on modular manufacturing sections. “The high surface demands on the visible parts and the very low intermediate buffer with 10 to 14 parts in the system require the injection molding machine to be highly reliable with high article quality. In this respect, KraussMaffei machines have performed outstandingly through the whole line,” said Dr. Jürgen Jahn, Plant Manager at Miele. Reliable and precise Everything begins with the injection molding of the front panel ring on a SpinForm CX 650-2700/2700 reversing plate machine, which is later visible on the outside of the washing machine. This consists of an approximately 3 mm thick polycarbonate part which is over-molded with gray ABS after opening and rotating the middle plate. This results in a scratchresistant component with an enormous depth effect that has an impressive design. The electric-powered sliding and turning unit makes fast and precise movements for short cycle times and a pronounced high positioning accuracy, which has a positive effect on the access point. After a short cooling/conveyor section, the sprue is removed automatically by milling, the edges are rounded with hot air in order to eliminate the possibility of injuries, and subsequently a film is applied to protect against scratching. In the meantime, a CX 420-3000 injects what is called the basic carrier made of glass-fiberreinforced polypropylene, which is responsible for mechanical stability and fixes the fastening elements and the inspection glass. After the injection molding process is done, it is followed by installation of hinges, bushing and axes and the fitting of the inspection glass, which is fixed and bonded with a clamping ring, also in an automatic process. On the third machine, the high-gloss ABS inner trim panels are finished and are also routed to the final installation step. Three become one In the central assembly cell, the pre-assembled parts from the three injection molding machines come together. The basic carrier and front panel ring are glued with polyurethane and locked additionally. For quality control and traceability, a designation is applied and at the end, the inner trim is equipped with a closure and closing piston. A complete washing machine door is finished. This peak achievement with regard to design engineering, production engineering and using the correct plastics for the job was recognized by the Verband Technische Kunststoff- Produkte e.V with the TecPart Innovation prize in 2010. At Miele, they are particularly proud, as the entire assembly concept and the higher-level control system were devised in-house. This demonstrates the Warendorf plastics specialists' extensive automation expertise and longtime experience in factory automation. Simple solutions with large effects All three injection molding machines are equipped with cylinder and pipe insulation in order to prevent unnecessary heat emission where logical and feasible in terms of process technology. The BluePower set of electric drives for selected functions, such as an electric plasticizing unit drive, increase the precision and energy efficiency of the machines even more. Flexibility as a challenge Another core business in Warendorf is manufacturing premium quality vacuum cleaner housings. For this, the surface quality in particular is the focus. Additionally, various variants and colors are needed for the housings. Each day, approximately 18 mold and material changes take place in addition to the color changes for similar components. A fast flushing of the plasticizing unit is mandatory in these processes. Therefore, the newer KraussMaffei HPS-AT machine screws without mixing and shearing parts are used to allow fast material change, and they simultaneously ensure an excellent coloring and material homogeneity in production. KraussmaFFei services • SpinForm reversing plate injection molding machine CX 650-2700/2700 • Injection molding machine CX 420-3000 • Linear robot LR 300 in cantilever arm version • BluePower cylinder isolation 19
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