Negative pressure chemical foaming injection molding method

Abstract

The invention discloses a negative pressure chemical foaming injection molding method which comprises an injection molding machine. The injection molding machine is provided with a sealing mold with an air flue; a mold cavity is connected with a vacuum tank through the mold air flue and two external pipelines; a negative pressure valve with the large-size valve element diameter is arranged on oneexternal pipeline; a pressure-stabilizing valve with the small-size valve element diameter is arranged on the other external pipeline; the mold cavity is connected with outside atmosphere through themold air flue and one external pipeline, and an atmosphere valve is arranged on the pipeline; the vacuum tank is connected with a vacuum pump through the pipelines; gas pressure sensors are arranged on an air flue of the mold cavity and the position of the vacuum tank; the negative pressure valve, the pressure-stabilizing valve, the atmosphere valve, the vacuum pump and the gas pressure sensors are connected with a control and monitoring unit; and the control and monitoring unit is in communication with a control unit of an injection molding machine. According to the negative pressure chemicalfoaming injection molding method provided by the invention, on the premise of improving the foaming ratio of a chemical foaming injection molding piece, the surface gas trace defects of the injectionmolding piece are eliminated, and the green production of chemical foaming injection molding appearance products is realized.

Description

technical field [0001] The invention relates to a foaming injection molding method, in particular to a negative pressure chemical foaming injection molding method. Background technique [0002] With the diversified development of injection molding products and the increasing market demand, people put forward higher requirements for the quality of injection molding products. In order to achieve the purpose of improving product size accuracy, reducing product quality, shortening molding cycle and saving energy, some new injection molding methods, such as foam injection molding method, multi-component injection molding method, reaction injection molding method, exhaust injection molding Methods, gas-assisted injection molding methods, vibration injection molding methods, micro-injection molding methods, etc. have been proposed and realized market applications. [0003] Plastic parts formed by conventional injection molding methods often have defects such as surface shrinkage, ...

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Problems solved by technology

In order to solve the surface quality problem of chemical foaming injection molding products, people have successively proposed gas back pressure chemical foaming injection molding method, rapid thermal cycle injection molding method and mold cavity surface coating molding method, etc. Although the above methods can eliminate chemical foaming Surface defects of foam injection molded parts, but the cell structure inside the product still needs to be improved

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