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The harsh environments of a metalcasting facility, however, calls for part marking that must withstand the rigors of production. Direct part permanent bar codes produced by Perma-Code, Overland, Mo, and Dallas, are cast-in and made to withstand the casting process as well as the part’s life of use. In addition, a machine-readable code, such as a bar code or data matrix code, eliminates the risk of human error typical to keyboard entry.

The permanent codes can be applied in sand, lost foam, investment and permanent mold casting processes. With each method, parts are given a unique code using a pre-encoded stencil or mold, which are made either on-site or by Perma-Code. Stencil materials and sizes are tailored to each individual application. When the code is scanned, information on the part is stored in the metalcasting facility’s database.

In a typical sand casting line, a stencil made of mineral fiber with a clay and latex binder is fastened to the sand after it has been sprayed with hot-melt glue. Workers can print out a paper label of the same code to stick on the outside of the mold after it closes in order to keep track of all the steps in the process because the stencil will be hidden from view within the mold. A code scanner or imager is used to read the code and record information throughout the casting process. When the mold closes and molten metal is poured, the part is made with the permanent code cast-in. The stencil, which is 0.04 in. (0.10 cm) thick, comes off with the rest of the sand during shakeout.

In investment casting, a mold with the code is pressed into the wax pattern, and in lost foam, a foam stencil is attached to the foam pattern. A stencil for permanent mold was most recently developed by Perma-Code for aluminum and gray iron. This stencil is attached to the mold with a continuous heat-activated adhesive.

The 3-D non-invasive cast-in bar codes are designed to last the life of the part, but a new coding system has emerged that improves the longevity of a direct-part marking over the typical bar code. The data matrix coding, which government agencies call UID for unique edientification and are beginning to require for all their components, can be read even after 22% of the data cells are damaged.

Perma-Code's direct-part marking can produce small, yet detailed, codes on castings of all sizes.

This data matrix code, shown here after heavy shot blast, was sand cast in gray iron.

A variety of stencils can be used for direct part marking in sand casting. The stencils are fixed to the mold with an adhesive to form the cast-in data symbol after the metal is poured.