SHL Robotic Grinding System: Reliable Process Eliminates Fire Cracks

Focus on surface quality: Johannes Schmidt, Sales Manager of RDW (left) and Heiko Märtens, Sales Manager of SHL.

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GIESSEREI 102 01/2015

BY MAREIKE KIRCHER, BÖTTINGEN

Structural components with some complex geometries

t the foundry of Regensburger Druck-gusswerke Wolf (RDW), casting parts with complex geometries is all in a

day‘s work. The company produces aluminum components such as housings, transmission covers, and most recently structural com-ponents for many customers and industries. In order to effectively remove fire cracks on the component surface that are caused by wear, RDW depends on the expertise of SHL Automatisierungstechnik AG in the Swabian town of Böttingen. A robotic grinding system from SHL removes the fire cracks with a reliable process. This helps RDW meet the extremely high requirements of its customers, while also saving time and ensuring that the components have a repeatable, precise surface finish. RDW traces its roots to the time when zinc die casting was still a promising technology. Starting in the mid-1970s, the much lighter aluminum took more and more of the mar-ket, and the Upper Palatinate company jum-ped on the bandwagon. Today 95% of the die

castings that RDW produces are aluminum, while only 5% are zinc. By the end of the 1980s the company had established an "extended workbench" in Hungary, which started out as a joint venture. After the borders were opened, the Prec-Cast company in the northeast of that country was fully acquired. With over 1.000 of the company‘s 1.400 employees, Hungary is now the largest production location within the corporate group. In addition, a manufacturing plant has been running in China since 2011. The main plant in Regensburg is also the engineering center, focusing on large die-casting cells with 1.300 to 2.800 t of closing force. RDW is 100% family-owned and has an equity ratio of over 67%. The company‘s success has also been due to RDW‘s diverse structure. "Strategically, we concentrate not only on high-volume parts, but on many customers with low volumes", says sales manager Johannes Schmidt. The customer portfolio includes the automotive sector (passenger cars and commercial vehicles) as well as the electrical industry and manu- facturers of agricultural machinery.

Today RDW‘s customer list includes well-known automobile manufacturers who purchase struc-tural components with some complex geomet-ries. In this special application, the components are glued to carbon fiber reinforced plastic parts in the customer‘s body assembly process. This requires a homogeneous surface, and a problem occurred in this context. As pressure die casting tools age, small fire cracks appear in the tools. These cause sharp-edged raised areas on the components, which must be clea-ned up in order to obtain a uniform adhesive gap. The question facing RDW was: Should these fire cracks be removed using an awkward and time-consuming manual process, or should the process be automated? Due to the complex part geometries, manual processing with con-ventional grinders was found to be too impre-cise and not reliable enough, based on the to-lerance requirements. After a short discussion, the Regensburg team decided on one hundred percent automated grinding of all adhesive and functional surfaces. To do so, however, RDW needed to find the right partner. "We asked around and performed a classic Internet search. We finally came across SHL and reached out to them," says Schmidt. Initial discussions began in early 2011, and a short time later SHL experts and RDW decision-makers sat down together to look for solutions. "One great challenge was the complexity of the components. They have difficult geometries with many angles and protrusions," says SHL sales manager Heiko Märtens. "We had to find the right machines and especially the tools to be able to handle the required work steps." Extensive testing followed at SHL in close coordination with RDW. The ground finish was coordinated and defined again and again with the automotive customer. "Very intense" is how Johannes Schmidt described relationships with the automation specialists from Böttingen in this phase. They performed extensive tes-ting in their top-of-the-line technology center. Schmidt: "All of the testing was run in-house at SHL before the results were used for the final design and construction of our line."

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Figure 1: the SHL robotic grinding system in the Regensburger Druckgusswerke Wolf (RDW) building.

Figure 3: A camera scans in a data matrix code prior to the work process. this ensures trace-ability.

Figure 2: the robot removes the

workpiece to be machined from the

pallet table.

Figure 4: the workpiece is

machined using the SHL FKS 250/450.

"Strategically, we concentrate not only on high-volume parts, but also on many customers with low volumes"

Two robots work in parallel

Since 2012, one SHL robotic grinding system (Figure 1) with two Kuka industrial robots has been running at Regensburger Druckguss-werken. The system is closely integrated in the production process. The operator loads the workpiece carrier fixtures. Robot 1 picks the part to be machined out of the fixture (Figure 2) and first carries the component to a scan-ner that reads an individual Data Matrix Code for traceability purposes (Figure 3). The robot carries the workpiece to the SHL-FKS 250/450 (Figure 4) belt and contact roller grinding machine for processing. It then travels to the SHL-P 550 Scotsch unit. There the workpiece is ground more finely using various grain sizes. The robot then places it in the workpiece car-rier fixture. A linear guided camera above the removal fixture measures the component, per-forming a 100% check of tolerance values. The second robot performs the same work steps in parallel on the mirror-image component. If the

workpiece has good values, then the process starts again from the beginning. The SHL solution provides benefits in the process at RDW. "Operators using conventio-nal grinders cannot do this work, due to the complex geometries and high dimensional re-quirements. There is just a risk that too much or too little material will be ground away. This would be fatal, and cannot be controlled ma-nually. The SHL system takes care of this with a reliable process, at the required level of repea-tability," says Johannes Schmidt. RDW will set up the system in the future so that it provides a comprehensive process chain. The parts first come from the casting cell to the blasting system for pre-treatment. From there they head directly into the SHL ro-botic grinding system, and then on to machi-ning. "This allows us to optimize the paths," says Johannes Schmidt. The SHL solution pro-vides the precise grinding result that is needed

for further processing on every component. "We are very satisfied with this result." The working relationship with the automa-tion specialist from Böttingen went smoothly in all phases of the project. "Right from the start, through the fine-tuning of the complex process, we had very intensive contact with SHL," says Schmidt. Because clarification with the automotive manufacturer was required again and again, a high level of flexibility was needed. SHL demonstrated this at all times. Schmidt sees a positive outlook for additional future cooperation. Recently RDW has had extensive experience in manufacturing struc-tural components for automotive and believes it is well positioned to win future orders. The joining and contact surface will again need to be free of fire cracks. "They will also need to be 100% ground. In this sense, it offers great potential."

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GIESSEREI 102 01/2015