Outside-of-the-box casting techniques

New ways of doing things usually pose potential risks and rewards. Simulation lets engineers take more risks because they can predict the results of changes they make. Engineers are free to make unusual design changes and see what will happen virtually without waiting until multiple different castings are poured.

For example, one company detected a shrinkage defect in its complex ductile-iron carriers late in the machining process. Simulation showed the root cause: The pass feeding molten metal to the critical area was getting cut off prematurely. Engineers changed the riser layout to eliminate the defect.

They also took design chances by making unusual changes to the gating system. This slashed the pouring weight by 13 kg, a savings of 13 metric tons of melt and 12,272 kW-hr energy used to melt the raw material per year. The redesign also reduced the riser neck cross section by 25%, resulting in lower riser-removal costs. The modified layout shortened pouring time by 2.5 sec and slashed solidification time by 11 min, increasing productivity by 15%. The original job was to eliminate the defect. The final design, based on simulation, resulted in significantly lower production costs.

In another example, simulation results encouraged pump manufacturer Otto Junker in Germany to cast a steel pump housing that had direct-pour top risers instead of the typical side risers. This lowered the amount of liquid metal needed by 81%, reduced molding time by 79%, and minimized the time needed to burn-off the risers by 87%. The company reduced its total production costs for the part by 12%.

Additionally, a South American iron foundry increased the casting yield for a ductile-iron differential-case housing from 62 to 67% by using simulation to develop a nontraditional gating system. The design lowered the overall scrap rate from 17 to 7%, saved 700,000 kW-hr/yr to produce 24,000 parts and slashed total costs by $500,000.

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