Cope and drag
In
In the simplest sand casting procedure, the drag is placed upside down on a board, around a pattern of the part to be cast. The pattern is a model of the desired casting. Talcum powder is often dusted over the pattern to aid in the removal of the pattern. Sand is sifted over the pattern until the model is covered by a few inches of sand. More sand is then dumped into the drag, and rammed with a wooden wedge, or mechanically vibrated to pack the sand down. The sand is then struck level with the top edge of the drag, using a wooden or metal strake. A board is then placed on top of the drag and the drag is flipped over.
Then, the cope is placed on the drag, and dowels (or pins) are put in the sand to make holes for the
The flask is then put back together, and metal can be poured into the mold. The metal will flow down the sprue, into the mold cavity, and back up the riser (of which there may be several). Once the metal has cooled enough to solidify, the flask can then be separated again, and the sand removed to reveal the rough casting. The rough casting is separated from the sprue and riser(s) either by sawing them off, or just breaking the thin metal of the gates and runners.
In some cases the part design is more complicated, and intermediate flasks and mold sections are needed between the cope and drag. These sections are called
Sources
- Davis, Joseph R., ed. (1996). Cast Irons (Illustrated, 2nd ed.). ASM International. pp. 157–160. ISBN 0871705648.