The products are provided with uneven surface glossiness and are even covered with shades. The causes whereof comprise:

1 Insufficient drying of plastic raw materials, excessively strong volatility of raw materials,

foreign matters existing therein, poor intrinsical glossiness of resin, bad influence of additives on glossiness;

2 Poor quality of plastication, overlow melt temperature, insufficient quantity of injection, overlow mold temperature, and excessive dosage of mold release agent;

3 Oversmall section of gate and runner, improper gate position, and unsteady flow of melt in the mold;

4 No cold-slug well provided for the molds, inadequate exhausting, moistures attached to the surface wall of cavity, and rough cavity surface.