These are some pictures I took when I toured a jewlery factory in Thailand. The process is lost wax (investment) casting. The shaft at the bottom of the ring in the picture is put in the hole in the rectangular cavity so that it is centeralised and then liquid rubber is poured in until the rubber reaches the top of the cavity. When the rubber solidifies it is removed from the cavity and cut appart so the pattern can be removed (the two halves of a finished rubber mold can be seen on the left of the picture).