The following factors may cause dimensional accuracy defects in precision casting:

1. The structural effect of castings. The billet has a large wall thickness, a large shrinkage rate, a thin wall, a small shrinkage rate, a large free shrinkage rate, and a small shrinkage resistance.

2. The influence of casting materials. The higher the carbon content of the material, the smaller the linear shrinkage, and the lower the carbon content, the greater the linear shrinkage rate; the casting shrinkage rate of general materials is the casting shrinkage rate K=(LM-LJ)/LJ×1, LM is the cavity size, LJ is the size of the casting, and K is affected by factors such as wax mold K1, casting K2, alloy type K3, and pouring temperature K4.

3. The influence of forming dies on casting shrinkage. The investment temperature, wax injection pressure, and pressure holding time have obvious effects on the investment size, followed by the wax injection pressure to ensure that after the investment is formed, the impact on the final size of the investment is small; the linear shrinkage rate of the wax (mold) material It is only 30-40% in the length direction, and the influence of wax spraying temperature on free shrinkage is much greater than that on shrinkage (waxing temperature is 57-59°C, the higher the temperature, the greater the shrinkage).

4. The influence of the shell material is zircon sand, zircon powder, Shangdian sand, and Shangdian powder. The expansion coefficient is small and can be ignored. The effect of shell baking is due to the small expansion coefficient of the shell. When the temperature of the shell is 1150℃, the temperature of the shell is only 0.053%, so it can be ignored.

5. The influence of casting temperature, the higher the casting temperature, the greater the shrinkage rate, the lower the casting temperature, the smaller the shrinkage rate, and the more suitable the casting temperature.