The size accuracy of precision castings, generally speaking, the tension is the influence by casting layout, material, tooling, shell making, baking, casting, in particular to:
(1) the layout of the casting
Tension is the casting wall thickness, compression rate, which is proportional to the relationship, that is, the wall thickness of casting large enough, then the contraction rate is high, and vice versa.
Stress refers to the carbon content of master, generally speaking, the higher carbon content is line contraction rate is smaller, and vice versa.
In this regard, we stress the following points to understand, for:
A. injection temperature, the free shrinkage influence to macro tightening is greater than the impact on the rate of obstruction.
The B. pattern in the storage process, will be further tightening, as usual 10%. But after stored for 12 hours, its size was never changed.
C. injection pressure, holding pressure time will also affect pregnant, but did not affect the injection temperature.