[IndustryNews] What is precision injection molding?

Precision injection molding, strictly speaking, refers to the dimensional accuracy of plastic products produced through injection molding machine equipment, which can reach below 0.01mm, usually between 0.01-0.001mm in size. Precision injection molding is mainly used in industrial and civilian products such as aerospace, automotive components, precision instruments, sports equipment, testing tools, etc.

Generally, precision injection molding has two indicators: one is equipment accuracy, and the other is mold error. The former is difficult to compare due to differences in size and product thickness, representing the comprehensive level of injection molding machines. Generally, the weight repetition error of ordinary injection molding machines is around 1%, and better machines can reach 0.8%. Machines below 0.5% are precision machines, and those below 0.3% are ultra precision machines. According to relevant data reports, the international highest level is less than 0.15%. Another aspect is mold accuracy, which requires high-precision mold processing equipment in addition to the experience of engineering and technical personnel. So, first-class mold processing equipment is a necessary condition for precision injection molding.

Influencing factors:

(1) Consider the shrinkage rate of plastic.

(2) The shape and size of a plastic part.

(3) The accuracy of mold components.

(4) Mold processing accuracy.

(5) Injection molding machines have high precision requirements for products.

Specific requirements:

Firstly, the injection pressure should be greater than 25MPa; Injection speed greater than or equal to 300mm/s; The dimensional accuracy of the product is 0.001mm; The coefficient of standard deviation (rate of change) of product quality is less than 0.1%; Precision of opening and closing positions: opening ≤ 0.03mm, closing ≤ 0.01; The injection position accuracy (pressure maintaining end point) is less than 0.03mm; The force balance of the pull rod is less than 1%; The precision of the pre molded position is less than 0.03mm; Balance degree A of fixed and dynamic templates: less than 0.03mm when the locking force is zero; B: less than 0.005mm when the locking force is maximum; The temperature control accuracy of the barrel and screw is less than ± 0.5 ℃.

Technical focus:

Locking force: In the process of precision injection molding, high injection pressure is generally required, otherwise it is difficult to form.

Measurement accuracy: To maintain high stability of plastic products, the amount of hot melt plastic injected into the mold cavity must be equal each time.

Injection speed: Injection speed is an important indicator of precision injection molding machines.

Injection pressure: Precision injection molding requires a larger injection pressure to improve the compactness of the plastic part, reduce shrinkage deformation, and ensure the accuracy of the product.

Pressure maintaining: Pressure maintaining has a significant impact on precision plastic parts.

Mold temperature: The temperature change on the surface of the mold cavity should be controlled within ± 1 ℃.