The use of ribs, hubs and bosses should be made in such a way that the weight is reduced, the part is strengthened and the general appearance is improved. Thick sections tend to cause the die to run hotter and, therefore, shorten die life.
In addition, cooling of a large lump may cause porosity and give trouble if drilling is required at that point. Wherever change in cross-section is excessive, a gradual transition should be provided to avoid cooling of adjacent areas at varying rates.
Undercuts should be avoided unless their use contributes to a great saving of metal, or is essential for assembly, or adds to the value of the product. Fillets are desirable over sharp edge in all castings to avoid cracking as well as to overcome the danger in handling. Drafts are required on all castings. Ejector pins should be located at the back so that their marks are not clearly visible.
Flash is a necessity on all castings because otherwise it is impossible to maintain absolutely sharp corners and perfect mating, therefore, some flow of metal is expected at the intersections of die parts. It is usually removed easily with a trimming die, however, choice of the location of the parting line will make trimming easier and the appearance better.
