Castability geometry, and in
particular junction design, infl uences solidifi cation, Gwyn said. Designing thermally neutral junctions, therefore, is necessary for solidifi cation integrity, reduction of defl ection and stress con- centration. According to Gwyn, cast- ability geometry must be considered in the context of the casting process you are using, the eventual fi nishing pro- cesses that will be employed, and how the component will perform structur- ally in the fi nal application.
Optimization of Conversion to Castings From Fabrications and Weldments
David Laude, G & W Electric
Co., Blue Island, Ill., Dwight Barn- hard, Superior Aluminum Castings Inc., Independence, Mo., and Chris Witt, Dotson Iron Castings, Manka- to, Minn., led a panel discussing the best practices for performing casting conversions. T e presenters highlighted 10 things engineers should know when designing castings: 1. A great casting design is not an exact duplicate of the weldment or fabrication it replaces.
2. Uniform, consistent material thickness is best.
3. Pockets deeper than their width are not achievable without a core.
4. Draft is necessary. 5. Machine material allowance is generally 0.125 in. (3 mm).
6. Webs or ribs of a wheel confi gura- tion should be an odd number.
7. X-rays of castings are not the most reliable predictor of future shrink.
8. Off set parting lines create thin sections on pattern plates.
9. Part numbers must be on the top or bottom of the casting to draw.
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Metalcasting Congress buyer and designer papers. May/Jun 2012 | METAL CASTING DESIGN & PURCHASING | 47
10. Four or more pieces welded together makes for a good conversion candidate.
The panelists also discussed how
simulation software can further optimize casting quality.
Simulation software allows designers to create solutions for potential defect areas, repeat the design process until defects are minimized and add a gating system, among other things.
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