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Simulation Key to Production of Large, Complex Die Casting Druckguss-Systeme AG

(DGS), St. Gallen, Swit- zerland, faced a significant challenge when a customer approached the aluminum and magnesium diecaster with a potential conversion project. The goal was to convert large frames used for solar panels from welded extrusion components to one-piece high pressure die castings. Measuring 80.7 x 48.4

x 2 in. (2,050 x 1,230 x 55 mm), the frames are subject to substantial temperature changes, which often lead to tears along the welded seams. Tese cracks allow for moisture to penetrate the frame and damage the panel. In investigating whether a high pressure diecast alternative could improve performance in the field, the customer hoped to improve longev- ity and performance. Te components must meet a number of demands such as 20-year corrosion resistance, high dimensional accuracy and stability, minimal weight and tightly controlled production costs. Weighing just 13.9 lbs. (6.3 kg) with a wall thickness of 0.2 in. (5 mm), the frames required extensive property analysis and optimization. When first approaching the project, the DGS team had plenty of ques- tions that needed to be answered. “Can this casting, with flow lengths

of several meters, be completely filled at all?” asked Axel Schmidt, project manager, DGS. “Which filling time is necessary for a complete filling? What happens if filling fronts meet after two to three meters of melt flow? How big are the length variations and how much does the massive gating pull the frame apart? We had to answer these questions very early to work in a cost and resource efficient manner.” DGS selected a primary A360 alloy

because of its strength and castability. Te project engineers then decided on a one-piece braceless frame that featured a Z-shaped frame profile. But with such a large, thin design, the component pre- sented a number of significant challenges.

Simulation with the final gating design allowed engineers to see the temperature distribution at the end of filling.

Initially, the DGS team designed

a gating system with two major lines. Te engineers then used the simulation software MAGMA5 to evaluate criteria such as flow length, fill temperature and material trace by means of virtual experimentation and optimization. Te initial simulation results showed that frame distortion was a primary concern. Areas of the frame reached distortion values as high as 0.35 in. (9 mm), far exceeding customer specifications. Te DGS engineers subsequently decided to completely redesign the gating system

and check the effect of these modifications. Te final design for the gating area called for a total of 20 ingates spread mainly across the four corner sections, successfully avoiding the critical distortion. “To develop the design with minimized frame distor- tion, the software played a crucial role,” Schmidt said. “Te possibility to quickly test different variations was essential, allowing us to create the gating system in a way

that it exercises as little force on

the casting as possible.” Once the design was finalized, it had

to be made in reality. Te design and placement of the die inserts and cooling lines were significant challenges. Again, DGS used the software to predict the cooling of the 10-fold divided die halves, which weighed 14.1 and 20.3 tons. “Today, in spite of the 52.9-lb. (24- kg) shot weight and only 13.9-lb. (6.3- kg) component weight and a form filling time of just 40 milliseconds, the frames are produced without critical distortion,” Schmidt said.

The final frame is a single high pressure die casting, weighing just 13.9 lbs. with 0.2-in. walls. April 2016 MODERN CASTING | 45

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