Core and Core print

Castings are often required to have holes, recesses, etc. of various sizes and shapes. Theseimpressions can be obtained by using cores. So where coring is requ ired, provisionshould be made to support the core inside the mold cavity. Core prints are used to servethis purpose. The core print is an added projection on the pattern and it forms a seat in themold on which the sand core rests during pouring of the m old. The core print must be of adequate size and shape so that it can support the weight of the core during the castingoperation. Depending upon the requirement a core can be placed horizontal, vertical andcan be hanged inside the mold cavity. A typical job, its pattern and the mold cavity withcore and core print is shown in Figure 1.Fig.

Core print design requires various considerations. They are :

• To hold the core in place during the mold assembly process, the print design is required to maintain a balance in the body.
• The print must be strong enough to resist the buoyancy force of the molten metal during casting process.
• The print should be stable enough during the process of filling the mold.
• The deflection of the core must be minimized.
• The transfer of the heat from the core to the mold should be maximized.
• There should be a provision for escaping the internal gases within the core.
• To avoid inaccurate assembly structure, unsymmetrical holes should have infallible prints.
• Combining the prints of adjacent cores to form single structure.

Furthermore, design of the core print depends on the type of core classified as:

• Horizontal simply supported core
• Horizontal overhanging core
• Vertical doubly supported core
• vertical hanging core
• Vertical bottom core