have been avoided. T e associated costs were far greater than the upfront investment for the simulation software and training to perform the analysis. T e pattern was revised to refl ect a
single feeder, shown in Figures 5a-b. T e feeder in this case is not con- nected to an area of high modulus. In iron castings, the location of the feeder
DESIGN WITH IRON IN MIND
A 463-lb. (210kg) circular bearing connector offers another example of complications with feeders in iron castings. It was designed using a system of fi ve feeders, but after machining, many castings showed areas of porosity.
In response to the defective cast- ings, engineers added a sixth feeder to the design, as shown in Fig. A. As discussed in the case of the control arm, this apparent solution is a typical approach to problems with steel cast- ings but an incorrect way to handle feeder systems in iron castings. As a result, the problem worsened, and this casting became the facility’s most costly scrap.
casting consisted of a single feeder zone, meaning only a single feeder was necessary. The revised design, shown in Fig. B, remedied the defect and resulted in a quality casting.
The defective areas were found at the location of the feeders on the top of the casting, a telling sign that the issue was related to non-piping risers. During additional analysis, including a simulation that calculated the transfer modulus (MTR
), it became clear the
is not as critical as with steel castings because of the expansion pressure’s eff ects throughout the casting after graphite precipitation begins. No porosity was discovered at the
casting’s contact area with the single feeder, shown in Figure 6, or elsewhere. A simple, quick analysis of the casting produced the correct feeder design that
resulted in a sound casting. Computer simulation off ers engineers an eff ective tool to design a production process, thereby avoiding potential costs involved with defective castings.
T is article is based on a paper (13-1261) from the AFS Metalcasting Congress Proceedings 2013.
Fig. A
Fig. B October 2013 MODERN CASTING | 37
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