In practice, however, optimizing performance in this manner has been prohibitively expensive. Tooling costs, especially for large impellers like those that Tech Cast manufacturers, can be very high and lead times long. The tools often require cores, either soluble or ceramic, to create the internal flowpaths, requiring that two tools be built. It simply isn’t practical to repetitively modify or rebuild tooling to evaluate design changes. As a result, pump manufacturers only iterate until they achieve acceptable performance. They can’t afford either the time or cost required for the extra iterations to achieve optimum performance. Tech Cast has pioneered a process that drastically reduces both the cost and time required per iteration so that pump manufacturers can go through several versions in less time than they previously could go through a single casting in the past, and spend less money in the process. Tech Cast uses SLA QuickCast 3D printed patterns to eliminate the need to create or modify tooling for each iteration. QuickCast patterns were the first direct pattern (patterns created via a 3D printing process) and are by far the most popular direct pattern technology in North America. With Quickcast patterns, castings can be created without the time-consuming process of creating tooling to produce wax patterns, allowing the design to be evaluated in days instead of months. The cost of QuickCast patterns is typically a small fraction of what tooling costs and they are available in less than a week, so fully machined impellers are available within three weeks.
The resin-based patterns from Quickcast are hollow with a unique internal honeycomb structure that allows the pattern to collapse internally as it expands with temperature. It also minimizes the material in the pattern, resulting in an almost ash-less burn that enables a cast to be created quickly and without a lot of additional steps. Tech Cast and 3D Systems worked together on a study to quantify the advantages of their process. A double suction impeller about 15 inches in diameter (pictured right) was chosen for the study. Castings were created both with molded wax patterns and with SLA QuickCast patterns supplied by 3D Systems.Ĭosts and timing were recorded at each step of the casting process so that an accurate comparison could be made. The customer can go through at least two iterations in the time it would take to get the first casting from the conventional process.Īssume that when the first casting is tested, the performance is not acceptable. The manufacturer will make an engineering change to improve the performance and request a second impeller to test. The foundry will then create the casting model of the modified design.
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