Precision injection molding, strictly speaking, refers to the dimensional accuracy of plastic products produced by injection molding equipment, which can reach less than 0.01mm, usually a kind of injection molding production method with a size between 0.01 and 0.001mm. Precision injection molding is mainly used in industrial and civilian products such as aerospace, automotive parts, precision instruments, sports equipment, and testing tools.

Generally, there are two indicators for precision injection molding: one is equipment accuracy, and the other is mold error. The former is difficult to compare due to the size and thickness of the product, which represents the comprehensive level of the injection molding machine. The weight repetition error of ordinary injection molding machines is about 1%, and the better machines can reach 0.8%. Less than 0.5% is a precision machine, and less than 0.3% is an ultra-precision machine. According to relevant data reports, the highest international level is less than 0.15%. The other is mold accuracy. In addition to the experience of engineering and technical personnel, the accuracy of the mold also needs to be completed by high-precision mold processing equipment.

Therefore, first-class mold processing equipment is a necessary condition for precision injection molding.

Influencing factors

(1) Consider the shrinkage rate of plastic.

(2) Product shape and size: the shape and size of the plastic part.

(3) The precision of the mold plastic part.

(4) Mold processing accuracy.

(5) The injection molding machine has high precision requirements for the product.

Specific requirements

First, the injection pressure should be greater than 25MPa; the injection speed should be greater than or equal to 300mm/s; the product size accuracy should be 0.001mm; the product quality standard deviation coefficient (rate of change) should be less than 0.1%; the opening and closing mold position accuracy: opening ¡Ü0.03mm closing ¡Ü0.01; the injection position accuracy (pressure holding end point) should be less than 0.03mm; the tie rod force balance should be less than 1%; the pre-plastic position accuracy should be less than 0.03mm; the fixed and movable template balance A: less than 0.03mm when the clamping force is zero B: less than 0.005 mm when the clamping force is maximum; the barrel and screw temperature control accuracy should be less than ¡À0.5¡æ.

Technical highlights

Clamping force: In the process of precision injection molding, a very high injection pressure is generally required, otherwise it is difficult to mold.

Metering accuracy: To keep the plastic products stable, the 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 density of plastic parts, reduce shrinkage deformation, and ensure the accuracy of parts.

Pressure holding: Pressure holding has a great impact on precision plastic parts.

Mold temperature: The temperature change of the mold cavity surface should be controlled within ¡À1¡æ.

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