Precision casting is mainly to perform relatively precise operation of the machine, and the products made afterwards are precision and very high-quality products, but there will be low precision during the operation. Let’s analyze the precision of precision casting. The reason is not high.

1. The influence of the shell-making material: Because of its small expansion coefficient, the use of zircon sand, zircon powder, Shangdian sand, Shangdian powder, etc., can be ignored.

2. The effect of shell baking: Due to the small expansion coefficient of the shell, when the shell temperature is 1150℃, the shell temperature is only 0.053%, so it can be ignored.

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

4. The influence of precision casting materials: a. The higher the carbon content of the material, the smaller the linear shrinkage rate, and the lower the carbon content, the greater the linear shrinkage rate. The casting shrinkage rate of common materials is as follows: (LM-LJ)/LJ=(LM-LJ)/LJ*1, LM is the cavity specification, and LJ is the casting specification. Affect K type: wax mold K1, K2 type castings, K3 type alloy, K4 pouring temperature.

5. The influence of mold making on the linear shrinkage rate of precision castings:

a. The influence of wax injection temperature, wax injection pressure, and pressure holding time on the investment specifications; in addition, the wax injection pressure and pressure holding time have little effect on the final specifications of the investment after the investment is formed.

b. The linear shrinkage rate of wax (mold) material is between 0.9-1.1%. When the investment mold is stored, further shrinkage will produce shrinkage, and the shrinkage value is about 10% of the total shrinkage, but after storage for 12 hours, the specifications of the investment mold are basically stable.

The radial shrinkage rate of the wax mold is only 30-40% of the lengthwise shrinkage rate, and the influence of the wax injection temperature on the free shrinkage rate is much greater than the effect on the closed cell rate.

There are some reasons why the accuracy of the above-mentioned common precision casting methods is not high.