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PRESENTATION Critical Characteristics Affecting the


Surface Finish of Castings AUTHORS Nathaniel Bryant and Jerry Tiel,


University of Northern Iowa (Cedar Falls, Iowa)


BACKGROUND Surface finish is an integral part of


casting quality specifications. Rough internal surface finishes on castings can cause the loss of efficiency for both fluids and high velocity gasses. Such is the case for turbocharger and intake manifold components. Te University of Northern Iowa has been investigat- ing mold material characteristics that affect surface smoothness for cast- ings. Te research was conducted on aluminum castings but has applications and relevance in ferrous alloys that don’t exhibit defects such as penetra- tion or fused sand defects. Te study investigates the influence of molding media characteristics such as sand fine- ness, material type and refractory coat- ing selection. Te goal of the project was to accomplish investment casting surface finishes in sand cast parts. Te dimensional accuracy at which


sand castings now can be produced has approached that of investment cast- ings. 3-D sand printing technologies have greatly improved the dimensional accuracy of molds and cores but have failed to match the surface smoothness of conventional sand castings let alone investment castings. Investment casting provides very smooth parts with excellent feature resolution and dimensional accuracy. 3-D printed sand molds and cores may provide a cost effective alternative to investment casting if the process can meet both dimensional and surface requirements.


Although many changes and


improvements have been made in the area of foundry consumables, sand is the one material that has stayed somewhat constant. After mining and washing, if


required, foundry sands are classified into individual or two mesh groupings and stored. Tey are combined into normal distributions for shipping to


May 2017 MODERN CASTING | 51 etalƬ hemical orpǤ


Germany: gtuetz@temc.com.tw Taiwan: eric64731@temc.com.tw


This depicts Vingas’ RHR vs. AFS-GFN results.


the foundry customer. Although there are many different mine distributions, sand of similar AFS-GFN is supplied in similar distributions. Te industry


has completed minimal study on the optimization of the sand’s screen dis- tribution. In 1962, Swing and Vingas published their research on surface


THE t/EE Z OF OUTSTANDING AWARD FOR FOUNDRY INDUSTRY IN 2015.


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