innovations CASTING
Graphite Permanent Mold Process Cuts Lead Times, Costs
D
uring a redesign project, the hardware engi- neering manager of a company that builds cameras for quality-
control applications faced a challenge when the camera’s optics and circuitry were ready weeks before their hous- ings. T e company needed the cases, which measure 4.5 x 2.5 x 1.25 in., to be ready quickly. “T e product introduction sched- ule was the number one driver,” said the engineering manager. “We had started down a path with a diecasting company and were running into some scheduling problems. It was going to take 14 weeks to get aluminum cast- ings for the housing.” T e engineer then consulted sev-
eral machine shops, but cost quickly became a prohibitive factor. T e estimated cost for each half o f the case was $250. Searching for alternatives, the engineering manager eventually contacted Graphicast, Jaff rey, N.H., which casts zinc-aluminum alloy parts in graphite permanent molds. Graphi- cast agreed to provide the fi rst samples ready in six weeks, less than half the lead time for diecast parts. T e camera required a durable
housing. Additionally, the camera’s circuitry could generate signifi cant heat, so the case needed to conduct and disperse heat more eff ectively than the earlier model’s extruded aluminum housing. T e case needed
The castings were produced in graphite permanent molds.
to be hardened and sealed tightly to withstand higher ambient tempera- tures and diffi cult working conditions. T e team developed a two-part design with wedge-shaped halves joined along a line that did not transect the holes for the camera’s lens, connector ports or status indicators. T e team then collaborated with Graphicast’s design department to optimize the design for casting. “Being able to discuss the design with the engineers at Graphicast
was very helpful,” said the end-user’s engineering manager. “T ere was a lot of give and take, and we were able to really leverage their design expertise.” Graphicast delivered fi rst-article
samples four weeks after receiving the purchase order. T e machining, chromating and painting took an ad- ditional 10 days, meaning the samples were completed within the initial six- week deadline. T e collaboration resulted in a case that seals out dust and withstands operating temperatures between 32 and 122F (0 and 50C). For the camera’s production run of 1,000 housings annually, Graphicast’s non-recurring tooling costs were roughly one-fourth the cost of tooling for diecast alu- minum parts. T e cost per housing was approximately one-tenth of parts machined from stock. The camera manufacturer used the samples to assemble prototypes, which were subjected to four months of rigorous testing. The housings performed well, without modifica- tions to the mold and only slight tweaks to painting protocols. “We’ve been very happy with the
quality of the housings,” says the en- gineering manager. “Graphicast really helped us achieve our goal of meeting our production schedule and budgets. T ey helped us through the whole process, listened carefully to our needs, and were very responsive every step of the way.”
The case consists of two wedge-shaped castings (left) that included holes for the camera’s lens, ports and status indicators (right). Jan/Feb 2015 | METAL CASTING DESIGN & PURCHASING | 45
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