(3) the influence of the molding shrinkage of casting line: a. wax wax temperature, pressure, the influence of the holding time of molten mould size to wax mould temperature is the most obvious, followed by radiation pressure of wax, the holding time in melt after mould for casting the influence of the final size is very small.B. wax (die) line of the shrinkage rate of about 0.9 to 1.1%.C. deposit moudle, will further produce contraction, the shrinkage value is about 10% of the total shrinkage, after 12 hours, but when stored moudle size basically stable.D. wax models of radial shrinkage rate was only about the length direction shrinkage rate of 30-40%, shooting wax temperature effect on the free shrinkage rate is much greater than stuck to the influence of shrinkage (optimum temperature for 57 ℃, 59 - the higher the temperature the greater the shrinkage).(4) the influence of shell making materials: zircon sand, zircon powder, sand, powder, because of its small expansion coefficient, only 4.6 x 10-6 / ℃, thus can be neglected.