The volumetric principle of solid materials in plastic processing is no longer suitable for non-solid material processing. The volume of cavity and materials itself be contracted due to the cooling of materials itself

solidification as well as the distortion of the mold and the core under high temperature and high pressure in the non-solid forming processing such as liquid or semi-solid

the volume of cavity and materials itself after and before forming are varied apparently

which is called the phenomenon of inequality-volume of non-solid processing. In order to obtain the compact product

it is required that the volume of the materials after forming should be smaller than the volume of material poured into the cavity before processing

whose differential value is the potential compression volume of the materials so as to be compressed during processing. In other words

it is required that the initial volume of the cavity must be bigger than the volume of the metal occupied after forming

whose differential value is the sum of the squeezing volume of the extruded core and the exerted volume of the plunger

which is called the principle of inequality-volume of non-solid processing.