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NOBAKE MOLDING TIPS Anything that can be cast in a green sand mold can be cast in a no-


bake mold, but the reverse isn’t true. Apart from the number of castings to be produced, the decision between green sand and nobake comes down to the complexity of the casting design. Because unfinished no- bake molded castings (without machining) typically cost 20-30% more than green sand, designers and purchasers sourcing to nobake molding must offset this price difference by taking advantage of what the pro- cess offers. Significant reductions in machining costs can be achieved through its tight tolerances and minimal dimensional variability, and by designing in complex shapes and geometries, thin walls, and reduced draft, radii and machine stock. Tooling cost also plays a factor in this comparison. Green sand molds


require compaction force during the molding process, which means the tooling must be able to withstand this force. Nobake tooling doesn’t have to withstand a strong compaction force (often only light vibra- tions), allowing wood and plastic to be viable tooling materials. In addi- tion, the lack of compaction force in molding allows nobake molders to use loose pattern pieces and other innovative tooling options to increase casting complexity and add design features to the components. 


See www.afsinc.org for more information from the Castingpedia..


in the process of planning additional capacity in its coreroom and fi nishing area that will enable it to hit 300 tons per day in the next two years or so. As a result, the metalcaster has


increased its ductile iron business and refi ned its customer base to target growth and higher volume jobs. Where Benton accommodated quanti- ties of 25 or fewer molds per month, in the past, now it refers those jobs elsewhere. T e metalcaster’s target is 50 to 1,000-mold orders. “What we’ve done is target ac- counts to fi ll up the balance of the capacity,” said Tim Brown, vice presi- dent. “And being in a jobbing situation where we don’t make automotive nor do we want to make automotive, it’s been a good up ramp. For example, the top 40 customers of ours represent about 55% to 60% of our tonnage.” Benton serves a diverse range of in-


dustries, producing hydraulics, marine, electric motor and power transmis- sion components. “We don’t let any


Sept/Oct 2012 | METAL CASTING DESIGN & PURCHASING | 37


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