The sand casting process employs techniques that produce shaped parts of nearly any design, including very big parts and those with internal passageways. There will be more optimal casting or metalworking processes for any specific product, based on needed tolerances, design intricacy, volume, tooling availability, or lead time. Fanovo is capable to make a casting in the needed configuration using the sand process
Sand is used as the mould material. Sand is compacted round a pattern, into a two part mould, to form a cavity in the shape of the component to be cast.
In Fanovo foundries, molds of small and medium sizes are prepared by machines. For mass-production, match-plate patterns are used with the cope pattern attached to an aluminium plate and the drag pattern on the other side of the plate. The plate fits between cope and drag. Ramming of sand can be done by machine. Holes are produced by the use of cores.
Hand-ramming of sand depends on operator skill. Accuracy is usually poor, and this is usually countered by generous machining allowances. Repeatability and surface finish are poor.
1.The size and shape of the pattern must take into account the relative amount of shrinkage and the change in shape that can occur on solidification.
Approximate shrinkages for some casting alloy.
2.The shape of the casting should allow for progressive solidification, from the remotest parts backwards. When wall-thickness variations are essential, the transition is improved by applying generous radii, Figure (a). Small radii or sharp corners act as stress raisers in the finished casting, and may also prevent proper feeding during solidification. Localized heavy cross-sections, Figure (b), create hot spots where the molten metal only solidifies after adjacent zones have frozen, creating shrinkage cavities. Applying a radius to the outer surface, or offsetting the ribs, Figure (c), alleviates this problem. Low melting point constituents cause hot tears, Figure (d), so S-shaped spokes are used. The pattern must be shaped as in Figure (e), to give a casting of the required shape, Figure (f).