For the Brazilian faucet and shower specialist Docol, sustainability is an integral part of their corporate policy. Their measures aim at reducing raw material and energy consumption, as well as minimizing environmental impact. To actively contribute to environmental protection in this area, the company decided to use numerical simulation with MAGMASOFT®.
The following example shows how virtual simulation enabled Docol to reduce the scrap rate in the production of a one-handle faucet. Figure 1a shows the “Lift” mixer, whose body is cast from a copper-zinc alloy asa low-pressure die casting. The cast part systematically showed hot tears in the rear area, which affected the surface of the part (Fig. 1c). Hot tears occur at the end of solidification, usually run along grain boundaries, and the fracture surface is intercrystalline. This formation mechanism can often be recognized from the shape of the crack, which is “jagged” in the finished part (Fig. 1d).
In order to find a solution as quickly as possible, Docol contacted MAGMA with the question: What is the optimal way to detect the factors influencing the tendency for hot tears? The objective was to reduce scrap by 50 % and thus reduce material consumption. At the same time, the lead time in production should be shortened systematically.
Fig. 2 shows the initial situation: There is still partially solidified melt in the rear area of the component, while the material outside is already completely solidified. This means that even low stresses are sufficient to form plastic deformations or cracks. The entire height of the one-handle faucet shows increased strain rates in areas that have not yet solidified (Figs. 2a and b). This causes a high hot tear tendency (Fig. 2c).
Based on this analysis, Docol set up a virtual design of experiments with MAGMASOFT® to investigate the influence of geometry variations on the tendency for hot tears. The geometry was parameterized at the gate (thickness and radius) and within the casting (wall thickness). However, it was important to ensure that the changes in casting and process parameters did not lead to an increased shrinkage porosity in the critical area. The evaluation of the 25 different designs calculated by MAGMASOFT® showed that, with regard to hot tears, design 20 was the optimal variant: lower strain rates (represented by the result 'Max Principal Strain Rate') as well as reduced fraction liquid ('Fraction Liquid') in the investigated area. Fig. 3 compares the results of the original and the optimized version of the project. The hot tear tendency decreased significantly and the shrinkage porosity remained stable at a low level. Mission accomplished!
The change of geometry reduced scrap by 70 % and weight by 8 %. In addition to the robust production as well as meeting the desired quality requirements, there were further advantages with regard to sustainability: The consumption and the disposal of sand and resins were minimized. Moreover, the consumption of water, electrical energy, abrasives and liquid gas was reduced. As it turns out, protecting nature and being environmentally conscious can be so easy when you have the right tools.
Docol is a Brazilian company manufacturing faucets and valves. They are a pioneer in solutions that help save water and the first Brazilian company in this segment that operates in the international market. Docol can look back on a 60-year history. Meanwhile, the company sells its products on five continents.