Gate witness removal is a necessary task in the investment casting process. All of the work involved with designing and placing the gate on the casting is ground away before the finished part can be shipped to the customer. Hundreds of thousands of dollars are annually spent in the smallest investment casting houses on the abrasives and labor involved in grinding operations. Grinding and finishing expenses can easily extend into the millions of dollars in some of the largest casting houses. This paper will discuss the benefits of pressure assisted grinding operations over manual methods and recommend optimal grinding parameters to help reduce gate removal costs. Manual grinding methods using coated abrasive belts on backstand grinders are the most common methods of gate removal. These methods rely on the operator's effort to remove the gates. Although a person can easily adapt to changes in parts and complex part designs, manual degating is quite slow, requires the greatest amount of labor and consumes the most abrasives. Plunge grinders adapted with air cylinders to force the part into the abrasive are an improvement over manual methods, but the compressibility of air in pressure assisted grinding operations limits the grinding speed and belt life. High pressure -Rapid Grinding (RG) operations utilize hydraulics or motorized feed methods to remove gates in the most efficient manner. Rapid grinding methods have proven to reduce abrasive costs while improving throughput of gate removal operations.
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