A pattern that replicates the finished part geometry is made using by injecting wax into a die. Die creates a wax replica of the desired part by injecting melted wax under high pressure into the cavity. The die can be made as a simple one cavity manual tool or a complex multi-cavity automatic tool depending on volume requirements.
In case of rapid prototype this wax replica can be replaced by foam or PLA, but with a different shrinkage calculation.