Effect of back pressure of injection molding machine on the quality of modified plastic products

The adjustment of injection back pressure shall depend on the performance, drying condition, product structure and quality of raw materials. The back pressure is generally adjusted at 3-15kg / cm3. When the surface of the product has a little airiness, color mixing, shrinkage, and the size and weight of the product change greatly, the back pressure can be increased appropriately. In case of glue leakage, salivation, overheated decomposition of molten material, product discoloration and too slow material return at the nozzle, it can be considered to reduce the back pressure appropriately.

Proper back pressure can compact the modified plastic melt in the barrel, increase the density, improve the glue injection amount, and ensure the stability of the weight and size of the modified plastic products;

Proper back pressure can “extrude” the gas in the melt, reduce the air spray on the surface and internal bubbles of the modified plastic products, and improve the gloss uniformity;

Properly raising the back pressure can improve the shrinkage of the product surface and the glue walking around the product;

Proper back pressure can improve the humidity of melt, improve the plasticization quality of melt, improve the fluidity of melt during mold filling, and there is no cold glue on the surface of modified plastic products.

The influence of high back pressure on modified plastic products: low plasticizing efficiency, reduced production efficiency, easy to salivate melt glue, glue leakage from the nozzle, waste of raw materials, burn out of the heating ring near the nozzle, and increase the mechanical wear of the pre molding mechanism and screw barrel.

Impact of low back pressure on modified plastic products: it will lead to poor plasticization quality, unstable glue injection, large changes in product weight and product size, shrinkage, air flower, cold material grain, uneven gloss and other adverse phenomena on the product surface, bubbles in the product, and insufficient glue around the product and bone position.

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