Chapter 14, Problem 1P

Although cores increase the cost of castings, they also provide a number of distinct advantages. The most significant is the ability to produce complex internal passages. They can also enable the production of difficult external features, such as undercuts, or allow the production of zero draft walls. Cores can reduce or eliminate additional machining, reduce the weight of a casting, and reduce or eliminate the need for multipiece assembly. Answer the following questions about cores.

1. The cores themselves must be produced, and generally have to be removed from coreboxes or molds. What geometric limitations might this impose? How might these limitations be overcome?
2. Cores must be positioned and supported within a mold. Discuss some of the limitations associated with core positioning and orientation. Consider the weight of a core, prevention of core fracture, minimization of core deflection, and possible buoyancy.
3. Because cores are internal to the casting, adequate venting is necessary to eliminate or minimize porosity problems. Discuss possible features to aid in venting.
4. How might core behavior vary with different materials being cast—steel versus aluminum, for example?
5. Discuss several of the reasons why cores may be made from a different material than the molding material used in the primary mold.
6. Core removal is another design concern. Discuss how several different core-making processes might perform in the area of removal. What are some ways to assist or facilitate core removal?