Guidelines for improved green sand systems - part 1.

The single most important element in producing a good casting using the green sand process is the sand, itself. In planning a sand molding system, the primary concern will necessarily revolve around the "best" molding equipment for the castings to be produced. Unfortunately, capital investment considerations often lead to compromises in the design of the green sand support system for the new process. In many cases we try to "made do" with existing equipment and work around sand system deficiencies. The usual result is a variety of manufacturing problems and castings that fall far short of expectations.

In the past, molding equipment manufacturers encouraged this approach by emphasizing the "forgiving nature" of their machines. This is seldom the case today. Most major manufacturers now demand strict adherence to sand specifications or they refuse to guarantee equipment performance. Several manufacturers of molding equipment were contacted to obtain their latest sand specifications during the preparation of this report. While these are not discussed in detail, it is important to know that this information is readily available.

Nearly any of the new molding systems available today, regardless of where they are manufactured, will perform well if sand properties match the capabilities of the machine. Too often an "all purpose" sand is utilized which must serve a variety of systems ranging from a simple jolt-squeeze machine to automatic systems employing a blow-fill and hydraulic squeeze. While individual situations may call for compromising the type of sand to be used, whenever possible a dedicated sand system is the best approach in assuring consistent sand and mold quality. Tailoring the sand mix to the molding system is a must for achieving optimum results.

In this two-part report prepared by members of the AFS Plant Engineering Committee current practices in controlling sand and additives, muller selection, sand cooling and sand system controls are examined, Trends in the use of finer sands are also discussed, noting difficulties created for machinery as the AFS grain fineness number increases. Every effort has been made to present the information in a practical way that is easily used by the operating foundryman. Our aim in preparing this report is to reinforce the often-repeated fact that proper sand handling and control is the key to a successful green sand molding system. Even the best molding system cannot overcome the deficiencies created by poor sand practice.

Allen J. Filipic Casting Equipment, Inc Cleveland, OH