3.3.1 Materials Cost

Material cost is the cost to purchase and process enough material to ship the product. The amount of material purchased must include the amount in the end product plus "engineered" scrap. The raw material for forging is bars, billets, blooms or ingots. Forging alloys purchased in these forms are equivalent in cost to similar alloys used for castings, bar or plate stock.

Purchased raw material must include allowances for punch-outs, flash, other discards and machining allowances. The amount varies with the forging process and part design. The material loss is generally much lower for forging than for "hog-outs" (machined from plate or bar) and stampings, but higher than for powder metallurgy parts making processes. Forging usually produces a higher yield (ratio of product to material consumed) than casting, but the processes do not lend to direct comparison.

There are five primary sources of engineered scrap in forging: punch-outs, flash, other discards, material losses from furnace heating and machining allowance.

• Open die forgings generally have the greatest amount of machining allowance of the forging processes. The process does not produce flash, but there are generally discards from either or both ends of the forging.
• Impression die and upset processes require less finish allowance, but usually generate flash. Net, or near-net impression die forgings eliminate most or all finish allowance, and are sometimes flashless. Near-net forgings also have lower draft angles, and thus embody less material in the end product.
• Ring rolling uses preforms, which are disks with the centers pierced out. The process produces no flash and requires few, if any, finish machining operations.
• Cold forging generally produces no flash and very close dimensional tolerances