The spray refers to the thread-like streamline that appears at the pouring gate of the injection moulding product, and it mostly appears at the outside of the pouring gate of the mold. When the plastic melt flows through the narrow areas such as nozzles, runners and pouring gates at high speed, and suddenly enters an open, relatively wide area, the molten material will bend forward like a snake along the direction of the flow, and will quickly cool down after contact with the mold surface.
Since this part of the material cannot be well fused with the resin that enters the cavity afterwards, it will cause an obvious jetting mark on the plastic injection molding products. Under certain conditions, the resin is ejected from the nozzle at a relatively low temperature at the beginning. Before contacting the surface of the cavity, the viscosity of the resin becomes very high, so it generates a serpentine flow. Then as the melt with higher temperature continuously enters the cavity, the initial material is squeezed to a deeper position in the mold, thus leaving the above-mentioned jetting marks.
Feman Tooling, a reliable ABS plastic injection molding manufacturer, will provide much more injection moulding information and useful tips for customers.
1. Improper operation of process conditions.
The causes and treatment methods are as follows: the local temperature at the nozzle is too high. The nozzle temperature should be appropriately lowered. If the temperature of the melt is too high, for example, the barrel temperature should be appropriately lowered or the PVC plastic injection molding cycle should be shortened, and a filter screen should be set in the nozzle. If the residual pressure in the barrel is too high, the injection pressure should be appropriately lowered, the time of residual pressure and injection should be shortened. If the nozzle hole is too large, switch to a nozzle with a small diameter, or use a spring needle valve nozzle or an inverted inclined nozzle.
2. The raw material of the injection moulding product is wet and does not meet the requirements for use.
If the moisture content of the molding material is too high, it will also cause the nozzle to drool. For this, the raw materials should be pre-dried or a hopper dryer should be used.
3. The design of the hot runner mold is unreasonable.
In the hot runner mold, in order to prevent the nozzle from drooling, a device that can release the residual stress in the manifolds should be provided.
There are many types of injection moulding products and they have a wide range of applications, especially in textile equipment and automobile manufacturing industry, where injection moulding products of various shapes are used as accessories. They are also used in medical equipment, cultural and educational supplies, and various containers and turnover boxes that can be seen everywhere in people's daily lives. There are also a variety of complex injection moulding structural parts, functional parts and precision parts for special purposes. Injection moulding products are widely used in all the fields of national economy, such as transportation, packaging, post, telecommunications, communications, construction, home appliances, computers, aerospace and defense cutting-edge industry. Injection moulding products have become an indispensable means of production and consumption.