1, the filling condition is bad, the casting part is irregular condensing metal;
(a) when the pressure is insufficient, not enough, the active front of the metal solidification prematurely, resulting in rotation angle, deep concave, thin wall (even thin in the average wall thickness), cylindrical hole wall and other parts produced by the casting.
b The mold temperature is too low;
c) The alloy poured into the temperature is too low;
d The gate position is not good, forming a large activity resistance.
2, gas obstruction, less than the surface lubrication, but irregular shape
A It is difficult to open the part of the overflow system, gas accumulation;
b When molten metal is active, the turbulence is intense and the volume of gas is wrapped.
3, plastic mold cavity has residue
A the dosage of paint or improper spraying method, resulting in local coating deposition.
b) Forming parts of the mosaic gap is too large, or sliding cooperation clearance is too large, when the filling into the metal, casting out, and failed to be completely brought out and the appearance of the sheet clamp in the gap. When the flake of the metal and convex in the surrounding surface more, it will be in the case of closing the protruding height into the wall thickness of castings, so that the future of the casting at the place to penetrate (to the wall thickness) of the groove. This penetrating groove becomes a special form of the cast. This kind of casting phenomenon is more in the case of the deep cavity composed by the mosaic.