• Analysis of Common Defects of Zinc Alloy Die Castings

    2019/6/5 16:28:28

    First, the surface of the zinc alloy die-casting part has a pattern, and there are metal flow traces:


     1. The flow path to the entrance of the casting is too shallow.

     2. The injection pressure is too large, causing the metal flow rate to be too high, causing splashing of the molten metal. 


    Adjustment method: 

    1. Deepen the gate flow path. 

    2. Reduce the pressure ratio of injection. 


    Second, zinc alloy die-casting parts have small convex tumors on the surface:

     1, the surface is rough. 

    2. The inner surface of the cavity has scratches or pits and cracks.

     

    Adjustment method: 

    1, polishing the cavity. 

    2. Replace the cavity or repair.


     Third, the surface of the casting has a putt impression, the surface is not smooth,

     the rough causes:

     1, the push rod (top rod) is too long; 

    2, the surface of the cavity is rough, or there are debris.


     Adjustment method:

     1. Adjust the length of the push rod. 

    2. Polish the cavity to remove debris and oil. 


    4. There are cracks or local deformation on the surface of zinc alloy die-casting parts:

     1. The uneven distribution of the top rods is not enough, and the force is not uniform: 

    2. The push rod fixing plate is deflected during work, resulting in a large force on one side. The force is small on one side, causing deformation and cracking of the product. 

    3. The casting wall is too thin and deforms after shrinking. 


    Adjustment method:

     1. Increase the number of ejector rods and adjust the distribution position to balance the casting force. 

    2. Adjust and reinstall the push rod fixing plate. 


    5. There are pores on the surface of zinc alloy die-casting parts. 

    Causes: 

    1. There are too many lubricants.

     2. The vent hole is blocked and the vent hole is not discharged.


     Adjustment method: 

    1, rational use of lubricants. 

    2. Add and repair the venting holes to make the exhaust air unobstructed. 


    Sixth, the surface of the casting has shrinkage holes. 

    Cause: The processability of the die casting is unreasonable, and the thickness of the wall is too large. The temperature of the molten metal is too high. 

    Adjustment method: 

    1. In the wall thickness, increase the process hole to make it thin and even.

     2. Reduce the temperature of the molten metal. 


    7. The outer contour of the casting is not clear, and the shape is not formed. The local material is not expected. 

    The cause is: 

    1. The pressure of the die casting machine is not enough, and the pressure is too low.

     2, the thickness of the feed port is too large; 

    3, the gate position is not correct, so that the metal has a frontal impact. 


    Adjustment method:

     1. Replace the die casting machine with larger pressure than die casting; 

    2. Reduce the thickness of the feed port;

     3. Change the gate position to prevent the front impact of the casting. 


    8. The part of the casting is not formed, and the cavity is not full.

     The cause is: 

    1. The temperature of the die-casting mold is too low;

     2. The temperature of the molten metal is low; 

    3. The pressure of the press is too small, 

    4. The molten metal is insufficient, and the injection speed is too high; The air can't be discharged.


     Adjustment method:

     1. Improve the temperature of the die-casting mold and the molten metal; 

    2. Replace the large-pressure die-casting machine.

     3. Add enough metal liquid to reduce the injection speed and increase the thickness of the feed port. 


    Nine, the filling of the castings at the acute angle is not full. 

    Causes: 

    1, the inlet of the ingate is too large; 

    2, the pressure of the die casting machine is too small; 

    3, the ventilation at the acute angle is not good, there is no air discharge. 


    Adjustment method: 

    1. Reduce the ingate.

     2. Change the pressure casting machine with high pressure. 

    3. Improve the exhaust system. 


    10. The structure of the casting is loose and the strength is not high. 

    Causes:

     1. The pressure of the die casting machine is not enough;

     2. The inner gate is too small;

     3. The vent hole is blocked.


     Adjustment method: 

    1. Change the press. 

    2. Increase the ingate. 

    3. Check the venting holes and apply ventilation.


     11. Porosity in the castings

     Causes:

     1. The flow direction of the molten metal is not correct. The cavity of the die-casting part has a frontal impact, which generates eddy currents, envelops the air and generates bubbles. 

    2. The ingate is too small, the flow rate of the molten metal is too large, and the vent hole is blocked prematurely before the air is discharged, so that the gas remains in the casting. 

    3. The dynamic model cavity is too deep, and ventilation and exhaust are difficult. 

    4. The design of the exhaust system is unreasonable and the exhaust is difficult. 


    Adjustment method: 

    1. Correct the shunt cone to be too small and shape to prevent the frontal impact with the metal flow on the cavity.

     2. Appropriately increase the ingate.

     3. Improve mold design.

     4. Reasonably design the vent hole and increase the air hole.


     12. Impurities in the castings

     Causes: 

    1. The molten metal is not clean and has impurities.

     2. The alloy composition is not pure. 

    3. The mold cavity is not clean. 


    Adjustment method:

    1. Pouring in and removing impurities and slag. 

    2. Replace the alloy. 

    3. Clean the mold cavity to make it clean.


     13. In the process of die casting, the metal liquid is splashed. 

    The causes are: 

    1. The tightness between the moving and fixed molds is not tight, and the gap is large. 

    2, the clamping force is enough. 

    3, the pressure maneuver, the fixed template is not parallel.


     Adjustment method: 

    1. Reinstall the mold. 

    2. Increase the clamping force. 

    3. Adjust the die casting machine so that the moving and fixed modes are parallel to each other.

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