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PROFESSIONAL FACTORY OF PRECISION CASTING PRODUCTS

Factors affecting the dimensional accuracy of precision castings

Issuing time:2020-11-16 08:34Author:Allen Ai

In general, thedimensional accuracy of precision castings is affected by many factors such ascasting structure, casting material, mold making, shell making, baking,pouring, etc. Any setting or unreasonable operation of any link will change theshrinkage of the casting. The dimensional accuracy of the castings deviatesfrom the requirements. The following are the factors that can cause defects inthe dimensional accuracy of precision castings:


(1) The influenceof the casting structure: a. The casting wall is thick and the shrinkage rateis large, and the casting wall is thin and the shrinkage rate is small. b. Thefree shrinkage rate is large, and the hindered shrinkage rate is small.


(2) Influence ofcasting material: a. The higher the carbon content in the material, the smallerthe linear shrinkage rate, and the lower the carbon content, the greater thelinear shrinkage rate. b. The casting shrinkage rate of common materials is asfollows: casting shrinkage rate K=(LM-LJ)/LJ×100%, LM is the size of the cavity, and LJis the size of the casting. K is affected by the following factors: wax mold K1, casting structure K2, alloy type K3, pouring temperature K4.


(3) The influenceof mould making on the linear shrinkage rate of castings: a. The influence ofwax injection temperature, wax injection pressure, and pressure holding time onthe investment size is the most obvious in the wax injection temperature,followed by the wax injection pressure, and the pressure holding time isguaranteed After the investment is formed, it has little effect on the finalsize of the investment. b. The linear shrinkage rate of wax (mold) material isabout 0.9-1.1%. c. When the investment mold is stored, there will be furthershrinkage, and its shrinkage value is about 10% of the total shrinkage, butwhen stored for 12 hours, the investment mold size is basically stable. d. Theradial shrinkage rate of the wax mold is only 30-40% of the lengthwiseshrinkage rate. The wax injection temperature has a far greater influence onthe free shrinkage rate than the hindered shrinkage rate (the best waxinjection temperature is 57-59, The higher the temperature, the greaterthe shrinkage).


(4) The influenceof shell-making materials: zircon sand, zircon powder, Shangdian sand andShangdian powder are used. Because of their small expansion coefficient, only4.6×10-6/, they can be ignored.


(5) The effect ofshell baking: Because the expansion coefficient of the shell is small, when thetemperature of the shell is 1150, it is only 0.053%, so it can be ignored.


(6) The influenceof casting temperature: the higher the casting temperature, the greater theshrinkage rate, and the lower the casting temperature, the smaller theshrinkage rate, so the casting temperature should be appropriate.


Precision casting is also called precision casting, lost wax casting,and its materials include stainless steel, various alloy steels, and carbonsteel.


As a professional precision casting manufacturer, we also have strongmachining capabilities, with various Japanese imported and domesticallyproduced processing equipment to ensure that the product processingrequirements are qualified.

20200311_143942.jpg13.JPG圖2.jpgSolisWorks Design.jpg


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