Lost Wax Casting Processes By Keith Farley

Did you ever wonder or even consider just how an article of jewelry is made? Some are fabricated from metal sheet and wire or a combination of such components, adhering to purely metals processes. There are, however, forms so complex that one would be better served to approach using an alternative process. What will be discussed here are those procedures involved in taking the preliminary wax model and transforming it to a metal replica of the piece of jewelry to be. What follows will provide a brief description of the lost wax casting process as well as different approaches to it.

lost wax casting

Working With Waxes

There are many varieties of wax, each developed with particular applications in mind. Some waxes may be carved while others may be shaped by hand, some cut from flat sheets, others twisted, melted, heated, engraved, textured, or fashioned by any number of methods to define shapes and details in the wax. This area is quite broad and merits its own pages which will be developed at a later point in time. For now, let us assume we already have one or more finished waxes that represent exactly the form of the object or objects we have envisioned and are trying to achieve.

Spruing

lost wax casting

The term "sprue" generally refers to a wax rod or series of these rods that secure the wax model to a specifically configured rubber or plastic base that is called a sprue base. In the center of the base is a wax insert to which is attached one or more waxes that are to be cast. On the outside is a lip that is used to secure a stainless steel cylinder into which the investment will be poured. The term, "to sprue" refers to the development of a spruing strategy as well as the act of physically attaching the sprues to the waxes and these to the sprue bases. This process must be approached with care and considerable thoughtfulness.

Once the waxes have been securely attached to the sprue base using sprue rods, a stainless steel flask is carefully inserted inside the outer lip of the sprue base, so as to surround the waxes while still leaving, minimally, a quater inch space between the wax and the inside of the flask. The flask pictured here is the perforated variety, intended for vacuum casting which will be described shortly. In this case, a sleeve must be placed around the outside of the flask to prevent investment from spilling out as it hardens before moving on to our next step. A flask used for centrifugal casting is straight sided with no perforations, simplifying the process of investing the waxes.

lost wax casting



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