By Phil Bodenheimer
What may be seen as a similar casting in size and weight to the buyer may not be viewed the same way by the iron casting producer. There are many variables that can affect seemingly similar gray iron and ductile iron castings in different ways. Here are the six common cost drivers you may not be aware of, but need to know. Spoiler alert: "piece price" isn't one of them.
Yield is the saleable amount of iron in the mold versus the total amount of iron poured into the mold. The extra iron poured forms the gating that is required to properly feed the liquid iron into the casting mold to produce the required casting soundness and quality. The efficiency of the gating used to make gray iron or ductile iron castings will heavily influence the yield and therefore cost.
Parting line is the plane that separates two pattern halves and allows for the optimum placement of gates, risers and core prints that hold the core in the mold when cores are required. The parting line also determines the total number of castings that can be produced in each mold.
Cores (when required) are used to displace iron to create a cavity or passage in the casting that cannot be formed with the pattern. The size of the core and number of cores required will affect both the cost of the casting and tooling required to produce the casting.
Section size in an iron casting helps determine the parting line placement and required cooling time for the iron casting. The thicker the section is, the longer the cooling time. The length of cooling time may affect the speed of molding and the total number of castings produced in a given time period.
Custom alloys (also known as inoculants), when required beyond the typical melting process allows the metalcaster to meet the required material specifications. When used, these added alloys can vary based upon the end use of the iron casting. The cost from one alloy to another can also vary greatly.
Cleaning, finishing and inspection processes are dictated by the parting line, core print areas and the geometry of the casting along with the customers’ requirements. The more time needed to clean, finish and inspect a ductile or gray iron casting will impact the cost.