By using foreign components, fixturing and machining costs can be significantly reduced, but there are some requirements for what can be used.

Foreign Component Requirements:

• The component needs to be of metallic nature with a melting point which exceeds the melting point of the PIAD alloy.
• The surface of the metallic component must be clean of all organic substances.
• Plating of the foreign component is possible as long as the vapor temperature of the plating material exceeds the pouring temperature of the cast alloy. Therefore, chrome and nickel plated parts can be used without problems, but zinc and cadmium plating are not acceptable.

It is important to know that the bond which is achieved between the casting and the foreign component is strictly mechanical, no metallurgical bond is achieved. With this in mind, it is important to design your foreign component with a flat area or an undercut, this will keep the component from pulling out or spinning when forces are applied.

Security Against Rotation and Shifting

The “foreign component” is placed in the precision machined mold allowing complete closure around the component without flashing. To prevent radial or axial movement of the “foreign component” features such as grooves, flats, undercuts, splines or knuckles are machined to the cast-in components. Consultation between the PIAD casting expert and the design engineer is important to achieve the best technical and economic solutions.

Gears - Special Cases

Spur and worm gears represent special opportunities for cost savings using the composite casting approach. Tin bronze or aluminum bronze is only used in the teeth area where the special properties of these alloys are needed. The center part of the gear, the hub section, is formed by a foreign component made from less expensive gray or ductile iron castings. The iron casting is pre-machined to provide a close fit in the precision machined chill mold and must be preheated. The outside of the iron hub casting is serrated to provide a secure mechanical bond and must be metallic clean.

Parameters of Cast-in Technology

The decision to use “foreign components” as part of a casting design is primarily determined by economic factors; it can be considered as value-added enhancement. Bolts; threaded pins; threaded inserts; cooling tubes; heating elements and bushings can all be used as foreign components as part of a PIAD chill casting. In case pins, bolts, or bushings are cast-in attention must be paid that sufficient casting material surrounds the insert to assure a complete coverage of the insert and provide a sufficiently strong bond. The amount of the surrounding cast material and the depth to which the component is embedded depends mainly on the load to which “foreign component” is exposed. If cast in components are heat treated, such as hardened bolts, attention must be paid to the amount of the surrounding cast material, if the temperature gets too high the hardened bolt will be annealed.