What is low pressure injection molding
The low pressure injection molding process is a packing process that uses a very low injection pressure
(0.15-4MPa) to inject hot melt materials into the mold and quickly solidify.
The excellent sealing properties of the hot melt materials and excellent physical and chemical properties are used to achieve insulation and resistance.
It has the functions of temperature, impact resistance, vibration reduction, moisture resistance, water resistance, dust resistance, chemical corrosion resistance, etc., and it has a good protective effect on electronic components.
1. Molding process and application
Put the skin in the mold in advance, and then by the thrust of the screw to inject the plasticized molten plastic into the closed mold cavity, and then solidify and shape the product to obtain the product. The material used for the low-pressure injection molded skin can be cloth or PVC fabric. At present, this process has been widely used in the production of automobile door guards, column guards, and parcel shelf guards.
2. Advantages of low-pressure traditional technology
1) The low pressure may be the integration of the plastic skin material and the plastic base, and there is no falling off.
2) Since there is no gluing process required by the coating process, the process is used as little as possible and is more environmentally friendly.
3) The internal structure of the low-pressure free and brighter modeling features can be designed arbitrarily, the degree of the surface modeling is planned to be long in the coating process, and the modeling features are fresh and hard.
4) No additional low-pressure secondary coating is required, which improves production efficiency.
5) The product has a good feel and appearance.
6) Low-pressure troubleshooting products have low perceived pressure, which can effectively protect the internal parts of the product, and the rejection rate is low.
3. Factors to consider in low pressure injection molding process
1) The ductility and tension of the fabric
At present, the fabrics used for low-pressure injection molding are all bottom non-woven fabric + foam layer + surface fabric layer. Due to the compression of the mold and the extrusion of the molten plastic, the longitudinal and transverse extensibility of the fabric are different, and the phenomenon reflected on the product is also different. . Among the most prominent problems are: seepage, breakdown, and damage. That is to say, when the mold state is constant and the process conditions are constant, the characteristics of the fabric have a great influence on the quality of the product. Similarly, the longitudinal and transverse elongation have different adaptability to different molds. Some molds may require high longitudinal elongation due to design constraints, and some molds may require high transverse elongation. Therefore, it is necessary to comprehensively consider this issue when trying to produce new products and new molds.
2) The fluidity of plastics
The index for evaluating plastic fluidity is: melt index MI value. Everyone knows that the flow of plastic on the fabric must be much slower than that on a smooth mold cavity. This is why the low pressure injection mold for the fabric has more gates than ordinary molds. The slow flow rate will inevitably affect other appearance problems of the product, such as bond marks, lack of material, etc.