CASTING INNOVATIONS
Impeller Cast Using SLA-Printed Patterns Needing to replace two double
suction impellers with 30-in. diame- ters, SPX, Charlotte, North Carolina, decided to explore alternative casting processes to improve performance and limit lead times. It contacted Tech Cast LLC, Myerstown, Pa., a producer of large (up to 500 lbs.), precision engineered investment castings using stereolithographic (SLA) rapid prototype technology, an additive manufacturing process that produces objects from CAD models by printing successive layers of curable resin that are hardened via ultraviolet light. Because an older wood pattern
was the only model for the 500-lb. impeller, Tech Cast needed to gener- ate a 3-D drawing for production of the mold. (Te 3-D printing was handled by a third party.) Despite having to generate a 3-D model from scratch, Tech Cast produced two impellers in corrosion-resistant martensitic stainless steel at nearly equal cost in half the time as the traditional method. “It took us about two weeks to
produce an SLA prototype,” said Shawn McKinney, general manager, Tech Cast. “Actual manufacturing time, from receipt of the prototype to
SPX’s BB2 is a horizontal, single-stage pump used in a variety of heavy duty applications.
delivery of the casting, was four weeks.” Cast nearly to net shape, the
components required significantly less machining and avoided the time con- suming welding/grinding loops that typically were necessary with green sand casting. In all, the lead time dropped to six weeks from the previ- ous 12 weeks. Additionally, no defects were discovered on the impellers.
Te order was relatively small,
but Tech Cast’s ability to produce the castings quickly and cost ef- fectively has resulted in additional opportunities with SPX. “Tat was the biggest, toughest
impeller we could find, and not only did the process work, but it came out better than anything we’d ever seen for that size,” said Dan Crum- rine, buyer, SPX. “We took a huge chance and it paid off beautifully.” While Tech Cast plans to
continue to receive its 3-D molds from an outside vendor, additive manufacturing can reduce tool- ing costs and lead times, which can make investment casting more competitive by reducing lead times for short-run components. “Traditional investment cast
tooling can take 8-12 weeks to build and may require significant capital investment, both of which can pres- ent barriers to entry into this manu- facturing process,” McKinney said. “Te use of additive manufacturing technology to produce quality in- vestment castings represents an area of organic growth opportunities for investment casting manufacturers to
The stainless steel impellers measure 30 in. in diameter and weigh 500 lbs.
expand their businesses.” Visit
www.techcastllc.com for more information.
February 2014 MODERN CASTING | 67
Photo courtesy of SPX.
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