Continuous Flow Impregnation to Treat Individual Castings and Maintain High-Volume Production

In July, the U.S. Patent Office granted Patent No. 6,913,650 B2 to Cleveland, OH-based Godfrey & Wing Inc. for its concept of casting impregnation, and for equipment used to complete this process. G&W employees Christopher D. Gilmore and Christopher B. Barney were recognized as the inventors of the new concept.

Known as Continuous Flow Impregnation (CFi), the G&W concept is based on impregnating castings individually rather than in the traditional batch treatment approach. The objective of impregnation is to eliminate porosity in the castings. Any porosity in a casting can result in a leak path through the casting walls that would prevent it from holding pressure.

G&W began developing the CFi process in 2001 to provide direct-coupled casting impregnation within automotive manufacturing facilities. The basic idea was that treatment of individual parts would enable manufacturers to incorporate casting impregnation in real time while matching upstream production rates.

According to Tom Shantz, sales manager, automotive and heavy truck for G&W, the CFi system evolved in stages. “Before CFi became commercially viable we tested it at various critical points. We wanted to make sure all the variables were accounted for and all the elements worked together.”

The system is based on the dry vacuum and pressure (DVP) process, which has proved to be the most effective impregnation process available.

According to statements by Godfrey & Wing, the process uses the combined effects of vacuum and pressure and focuses impregnation on the individual part, not on the ambient environment. Resin, the most significant production cost after labor, is conserved and recovered, with no waste. Recovering resin also prevents it from entering the plant’s waste stream, an environmental benefit and further cost savings.

Part handling is a key characteristic in eliminating failure modes caused by the impregnation process. In the CFi system, a robot provides automated, repeatable handling of machined castings without damage or contamination. The system requires no operator, significantly reducing labor costs.

As implemented in an operation in Massena, NY, the process begins with an operator visually inspecting the cylinder head castings on a rotating fixture. Then, a robotic arm picks up the cast component and loads it into the impregnation vessel or chamber. This chamber is much smaller than a traditional batch-impregnation chamber, allowing for efficient removal of air from the porosity, which is the key characteristic of the impregnation process. Once the vacuum is drawn, the component is lowered into the impregnating resin, which occupies the lower portion of the ASME impregnation pressure vessel. Once the component is covered with resin, pressure is applied allowing for fast and deep penetration of the resin into the evacuated porosity.

Following the impregnation process, the component is centrifuged to recover the excess resin from the surface and machined features.

The robot then moves the casting to a wash station where any resin left on the metal is removed.

In the final process step, hot water is used to catalyze the resin to turn it into a solid.

When the process is complete, the robot moves the casting to an outbound conveyor, where an operator once again visually inspects it and places it into the shipping containers. The before-and-after visual inspection is not related to the impregnation process.

Except for the inspection requirement, the impregnation cell operates without direct labor involvement.

Today the CFi system is operating in Dayton, OH, as well as in the original implementation in Massena, NY. Cycle times are well under 2.5 min./component. Under the traditional impregnation system, larger batches of components would require 45-60 min. for impregnation with much less control of the process. The Massena CFi system has been delivering impregnated parts for almost three years with zero PPM defects.