Foam filtration of aluminum alloy castings is well known and well documented. The benefits are easily calculated in financial terms, if the filter is simply used to improve scrap due to inclusions or if the filter is used to improve the yield by simplifying the rigging system. Recent advances in the understanding of the mechanism and effect of flow smoothing in the gating system, coupled with developments in the filter composition and manufacturing methods, have led to greater value being attained from the filter. When these developments are combined with improved scientific application engineering techniques, then foam filter technology is optimized, and hit-and-miss methods of gating are eliminated. This paper explains the requirement for further developments and describes the advances made in both filter technology and application engineering techniques. The basis for an assessment of novel gating arrangements, in terms of cost-effectiveness, is discussed, and examples are given as to how foundries have justified such modifications. Detailed case studies from production foundries around the world, where these advances are now part of the normal casting program, are given, and the thinking behind the decisions is explained.
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