Dimensional accuracy of precision castings not meeting production requirements is a relatively serious type of casting defect. For casting enterprises, minor accuracy non-compliance can be tolerated, but severe cases can directly lead to casting rejection, causing losses to the enterprise. For users, if such defective castings enter the market, more industries will be affected. Therefore, the occurrence of such casting defects should be strictly controlled. Generally, precision casting dimensional accuracy is affected by multiple factors including casting structure, casting material, pattern making, shell making, firing, and pouring. Unreasonable setting or operation in any link will change the shrinkage rate of the casting, leading to deviations between dimensional accuracy and requirements. The following are factors that can cause dimensional accuracy defects in precision castings: (1) Influence of casting structure: a. Thicker casting walls have greater shrinkage, thinner walls have less shrinkage. b. Free shrinkage is greater, hindered shrinkage is less. (2) Influence of casting material: a. Higher carbon content results in lower linear shrinkage rate; lower carbon content results in higher linear shrinkage rate. b. Casting shrinkage rates for common materials are as follows: Casting shrinkage rate K = (LM – LJ) / LJ x 100%, where LM is the cavity dimension and LJ is the casting dimension. K is affected by the following factors: wax pattern K1, casting structure K2, alloy type K3, and pouring temperature K4. (3) Influence of pattern making on linear shrinkage rate: a. Wax injection temperature, injection pressure, and holding time affect pattern dimensions, with wax temperature being most significant, followed by injection pressure, and holding time having minimal effect after the pattern is formed. b. The linear shrinkage rate of wax (pattern) material is approximately 0.9-1.1%. c. During storage, the pattern will further shrink by approximately 10% of the total shrinkage, but after 12 hours, the pattern dimensions are basically stable. d. The radial shrinkage rate of wax patterns is only 30-40% of the longitudinal shrinkage rate. Wax temperature has a much greater effect on free shrinkage than on hindered shrinkage (optimal wax injection temperature is 57-59°C; higher temperatures result in greater shrinkage). (4) Influence of shell making materials: Zircon sand, zircon flour, Shangdian sand, and Shangdian flour are used, and since their expansion coefficient is small, only 4.6×10-6/°C, it can be neglected. (5) Influence of shell firing: Since the shell’s expansion coefficient is small, at 1150°C it is only 0.053%, which can also be neglected. (6) Influence of pouring temperature: Higher pouring temperature results in greater shrinkage; lower temperature results in less shrinkage, so the pouring temperature should be appropriate. Precision casting enterprises must strictly follow requirements during production and strictly control all factors affecting dimensional accuracy, doing their best to improve precision casting accuracy.