Precision injection molding process-a big analysis of the process!
One, the characteristics of precision injection molding
(1) The dimensional accuracy of the part is high and the tolerance is small, that is, there is a high-precision dimensional limit;
(2) The weight repeatability of the product is high, and the dimensional stability of the day, month and year is required;
(3) The material of the mold is good, the rigidity is sufficient, the dimensional accuracy of the cavity, the smoothness and the positioning accuracy between the templates are high;
(4) Replace the conventional injection machine with a precision injection machine;
(5) Using precision injection molding technology;
(6) Choose materials suitable for precision injection molding.
The most important technical index for evaluating products is the accuracy of injection molded products (dimensional tolerances, geometric tolerances and surface finish of the products). The standard used in our country is SJ1372-78, which is very close to the accuracy of Japanese plastic products and mold accuracy.
In order to inject precision plastic products, it is necessary to strictly control four factors including material selection, mold design, injection molding process, and the technical level of the operator.
Precision injection molding machines require product dimensional accuracy within 0.01～0.001mm. Many precision injection molding machines also require injection molding machines with high injection pressure and high injection speed;
The clamping system is required to have sufficient rigidity and high enough clamping accuracy. The so-called clamping accuracy refers to the uniformity, adjustment, stability and repeatability of the clamping force, and high accuracy of the opening and closing positions;
It is required that the pressure, flow, temperature, measurement, etc. can be accurately controlled to the corresponding accuracy, and multi-stage or stepless injection is used to ensure the reproduction conditions of the molding process and the repeat accuracy of the product size.
1.2 Factors affecting the dimensional accuracy of products
(1) Mold accuracy;
(2) Molding shrinkage rate;
(3) The temperature, humidity and fluctuation range of the environment in which the product is used.
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