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detailset DESIGN


Casting Cuts Lead Time, Cost JITEN SHAH, PRODUCT DEVELOPMENT & ANALYSIS, NAPERVILLE, ILLINOIS


CASTING PROFILE


Cast Component: Right extension arm.


Process: Nobake sand casting.


Material: Cast steel A148 135-125 grade. Weight: 450 lbs. Dimensions: 51 x 20 x 12 in.


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ompanies making the investment in time and tooling to change a manufacturing process to metalcasting are doing so to fi nd a return through better lead times, improved quality and/or improved effi cien- cy. Such was the case for an extension arm for the military produced by May Foundry & Machine Co., Salt Lake City. Originally produced


as a casting welded to plate stock, the arm was redesigned as a single component cast in A148 135-125 grade steel. By casting in one piece, the customer realized quicker lead times and increased quality, plus it gained simplicity by purchasing the arm, which serves as a boom extension on a bomb loader, as a complete machined part. T e new single-piece cast component saved the customer an estimated $500 per part, which amounted to about $80,000 on the production run.


Mounting holes were machined instead of cast-in due to their small size.


• Cores are required to produce unaccessible interior features in the sand casting process and typically are placed manually into the mold.


• T e optimum core size (diameter or thickness) depends upon adjacent casting section thick- ness. T e location with reference to the parting plane and the ease of the placement into the mold also are considered when deciding be- tween as-cast and machined cored holes.


Smooth transitions lead to better fatigue life.


• Smooth transitions at the in- tersection, as shown here, help avoid localized stress concen- tration for better fatigue life.


• In properly designed steel cast- ings, features are placed where they will benefi t from direc- tional solidifi cation.


18 | METAL CASTING DESIGN & PURCHASING | May/Jun 2015


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