Today's Question: What Does Cope and Drag Mean in the Sand Casting Process?
Cope and Drag refer to the two halves (top and bottom, respectively) of a Pattern or Mold that is used in the Green Sand Casting Method. So let's get down to the basic of how a casting is made and figure out how all the steps work together. The first step is that a pattern must first be planned and created.
The Pattern Maker, such as our Journeyman Pattern Makers at CPM Industries, will use a solid model (or print) in this phase to create the pattern. Considerations must be made into which alloy is being poured for shrinkage rates and draft to be added in order to remove the pattern from the sand. During this phase, another decision will be made into where the Parting Line on the casting will be placed. The Parting Line will separate the top and bottom of the Pattern. The top half is known as the Cope and it's compliment on the bottom is known as the Drag.
The line separating the two halves is known as the Parting Line. A quick visualization would liken itself to a hamburger bun cut in half (the lateral cut representing the Parting Line). The top bun piece would be the Cope and the bottom bun piece would be the Drag.
But How Does This Make a Casting?
Each half of the pattern is put into a flask (metal frame) or wood box frame for sand containment.
In the next step, a sand/silica mixture (varies on type of casting method) is poured and packed onto the pattern in the flask to create the mold. The sand will then harden and it is time to remove the pattern from the sand-filled flask. Visualize the negative imprint has been created in the sand box after pattern is removed. Also, this is when core boxes (sand cores used to make the casting hollow) will be inserted when applicable to the casting project. The two halves are then joined together and locked into position. This is where the metal alloy will be poured to collect, shape, and solidify.
The last step is to pour the metal into the sand. After the metal solidifies and cools, then it is ready to be shaken and cleaned of excess sand. After the casting is clean, then the casting is off for inspections, tests, treatments, and machining if needed to complete project goals.
Want to learn more about castings and other projects?
Download our buying guide