Method of integrating wear plates into a spray formed rapid tooling

Method of integrating wear plates into a spray formed rapid tool includes the steps of making a model of a desired tool and constructing a ceramic pattern as the inverse of the model. The method also includes the steps of locating at least one wear plate on the ceramic pattern and thermally spraying a metal material against the wear plate and ceramic pattern to form the desired tool and embedding the wear plate into the desired tool.

It is known to make a spray formed rapid tool. In spray forming, a master model of a desired tool is produced using a free form fabrication technique. This master model is then used to create a ceramic pattern which is the reverse of the desired tool to be produced. The resulting ceramic pattern is the receptor onto which metal is sprayed to form a deposit in the shape of the desired tool.

Typically, the spray forming process uses a wire-arc spraying. In wire-arc spraying, electric current is carried by two electrically conductive, consumable wires with an electric arc forming between the wire tips. A high-velocity gas jet blowing from behind the consumable wires strips away the molten metal which continuously forms as the wires are melted by the electric arc. The high-velocity gas jet breaks up or atomizes the molten metal into finer particles in order to create a fine distribution of molten metal droplets. The atomizing gas then accelerates the droplets away from the wire tips to the ceramic pattern where the molten metal droplets impact the ceramic pattern to incrementally form a deposit in the shape of the desired tool. The completed desired tool is then mounted and used to produce parts in conventional stamping, die casting, or molding processes.

Molds may be used for injection molding parts. The mold may include one or more slides for forming a particular feature of the molded part. Mold slides are common features in complex injection mold or die cast tools where undercuts are designed into the molded part. Mold slides are used to allow the molded part to be ejected from the mold without interfering or being trapped by the molding features which create the undercut in the molded parts.

Wear plates are typically provided in conventional molds to provide a hard, but machinable smooth bearing surface for the slides to run or ride on. The wear plate is positioned to guide the slide where it needs to go in the mold. Wear plates ease repairability of a mold and increase its life.

The spray formed rapid tool may be used in molds for injection molding parts. The spray formed rapid tool may be used with mold slides. Currently, wear plates for spray formed rapid tools are machined into the spray formed rapid tool after the spray process is completed. Although the wear plates machined into the spray formed rapid tool have worked well, they suffer from the disadvantage that the machining process is both laborious and time consuming. Another disadvantage is the thermal spray coatings are heavily oxidized and the wear plates can only be ground or electro discharge machined (EDM) into the spray formed rapid tool which is costly. Yet another disadvantage is that the high oxide content does not allow for weld repair or traditional machining processes on the wear plates of the spray formed rapid tool.

Accordingly, the present invention is a method of integrating wear plates into a spray formed rapid tool. The method includes the steps of making a model of a desired tool and constructing a ceramic pattern as the inverse of the model. The method also includes the steps of locating at least one wear plate on the ceramic pattern. The method further includes the steps of thermally spraying a metal material against the wear plate and ceramic pattern to form the desired tool and embedding the wear plate into the desired tool.

One advantage of the present invention is that a method is provided of integrating prefabricated cast or wrought wear plates into a spray formed rapid tool at the same time the spray material is being deposited. Another advantage of the present invention is that the integration of wear plates in a spray formed rapid tool shortens product development cycle time. Yet another advantage of the present invention is that the wear plate can be machined or modified after the spray formed deposit is completed.

Still another advantage of the present invention is that the wear plate can be conventionally machined to make it parallel to the surface of the slide. A further advantage of the present invention is that the wear plate can be conventionally machined instead of using the EDM process, thereby saving time and cost. Yet, a further advantage of the present invention is that the method eliminates secondary machining of the thermal spray material. Still a further advantage of the present invention is that the method reduces material loss. Another advantage of the present invention is that the method improves yield, quality and repeatability.

Once the spray formed rapid tool is formed, the ceramic pattern is removed by chipping, grit blasting, or using a water jet. The slide contact surface can be machined "true" to the rest of the spray formed rapid tool after the spray process is complete if the wear plate 16 was not in the exact location during the spray deposition.