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Manufacturing Methods
        Parts May be cast, forged or machined from a solid billet. Cast
parts are made by pouring molten material into a mold, letting it
cool, then pulling it out and machining it. Cheap and easy, the
resulting nonuniform grain structure limits strength.                         

 By contrast, a forged part is molded into shape using costly giant
machines, refining the existing grain structure. A variation on
forging is powdered metal technology, a quasi forging process
where metal powder is poured into a mold and heated (like casting),
then hot struck into final shape (like forging). The end result is
stronger than a casting and more uniform with less weight variation
than a traditional forging. Many late model stock steel rods use
powdered metal technology with good results.                             

    With big, complex parts like a crank, forging's full theoretical
benefits may not be realized because economics dictate
compromising the design to accommodate multiple parts from the
same tooling. Even though it does interrupt the grain flow, today the
trend is to machine high end cranks out of premium billet material;
but forging is still preferred for smaller, less complex structures like
connecting rods.