1. The influence of molding process on the shrinkage of plastic products

　　(1) The molding temperature remains unchanged, the injection pressure increases, and the shrinkage decreases;
　　(2) The holding pressure increases and the shrinkage decreases;
　　(3) The melt temperature increases and the shrinkage decreases;
　　(4) The mold temperature is high, and the shrinkage rate increases;
　　(5) The shrinkage rate decreases due to the long holding time, but the shrinkage rate does not affect after the gate is closed;
　　(6) The cooling time in the mold is long, and the shrinkage rate is reduced;
　　(7) The injection speed is high, and the shrinkage rate tends to increase slightly, and the impact is small;
　　(8) The molding shrinkage is large, and the post-shrinkage is small. After the contraction begins two days old and is stable for about a week. Plunger type injection machine molding shrinkage is large

2. The influence of plastic structure on the shrinkage of products

　　(1) The shrinkage rate of thick-walled plastic parts is greater than that of thin-walled plastic parts (but most plastic 1mm thin-walled parts have a larger shrinkage rate than 2mm on the contrary, which is due to the increase of melt resistance in the mold cavity);
　　(2) The shrinkage rate of the plastic part with inserts is smaller than that without inserts;
　　(3) The shrinkage rate of complex shapes is smaller than that of simple shapes;
　　(4) The shrinkage rate of the height direction of the plastic part is generally smaller than that in the horizontal direction;
　　(5) The shrinkage rate of slender plastic parts in the length direction is small;
　　(6) The shrinkage rate of the size in the length direction of the plastic part is smaller than that in the thickness direction;
　　(7) The inner hole shrinkage is large, and the shape shrinkage is small.

3. The influence of mold structure on the shrinkage rate of plastic products

　　(1) The gate size is large, and the shrinkage rate is reduced;
　　(2) The shrinkage rate decreases in the perpendicular gate direction and increases in the parallel gate direction;
　　(3) The shrinkage rate away from the gate is smaller than that near the gate;
　　(4) The shrinkage rate of the plastic parts with mold restrictions is small, and the shrinkage rate of the plastic parts without restrictions is large.

4. The influence of plastic properties on the shrinkage rate of products

　　(1) The shrinkage rate of crystalline plastics is greater than that of amorphous plastics;
　　(2) Plastics with good fluidity, small molding shrinkage;
　　(3) When filler material is added to the plastic, the molding shrinkage rate decreases significantly;
　　(4) Different batches of the same plastic, the molding shrinkage is not the same.