1, filling conditions are poor, less cast parts were irregular condensed metal;
A) When the pressure is insufficient, not enough, the front of the metal solidification prematurely, resulting in corner, deep, thin wall (even thinner than the average wall thickness), cylindrical hole wall and other parts of less cast.
B) mold temperature is too low;
C) alloy pouring temperature is too low;
D) the gate position is not good, the formation of large activity resistance.
2, gas barrier, under the casting parts of the surface lubrication, but the shape of irregular
A) it is difficult to set up the site of the spill system, gas accumulation;
B) When the molten metal is active, the turbulence is intense and the package is gas.
3, plastic mold cavity with residue
A) the amount of paint or spray method improperly, resulting in local coating deposition.
B) the molding parts of the mosaic gap is too large, or sliding cooperation gap is too large, fill into the metal when the filling, casting out, and can not be completely out and showing the sheet caught in the gap. When the kind of sheet metal and convex in the surrounding surface more, in the case of clamping the protruding height into a wall thickness suitable for the casting, so that the future casting in the place to produce penetration (on the wall Thick) trench. This penetrating groove becomes a special form of undercuts. This kind of under-casting phenomenon occurs in the case of deep cavity composed of mosaic.
C) insufficient pouring (including excess material section too thin).
D) vertical die-casting machine, the injection, the lower punch down to open the nozzle orifice is not enough, resulting in a series of poor filling conditions.