Precision injection molding, strictly speaking, refers to the dimensional accuracy of plastic products produced by injection molding machine equipment , which can reach less than 0.01mm. It is usually an injection molding production method with dimensions 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.
Definition
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 different sizes and product thicknesses, and represents the overall level of the injection molding machine. Generally, the weight repeatability error of an ordinary injection molding machine is about 1%. , 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 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, mold accuracy also requires high-precision mold processing equipment.
Therefore, good mold processing equipment is a necessary condition for precision injection molding.
Influencing factors
- Consider the shrinkage rate of plastic.
- Product shape and size Shape and size of plastic parts.
- Accuracy of mold parts.
- Mold processing accuracy.
- Injection molding machines have high precision requirements for products.
Specific requirements
First of all, the injection pressure must be greater than 25MPa; the injection speed must be greater than or equal to 300mm/s; product dimensional accuracy is 0.001mm; product quality standard deviation coefficient (change rate) is less than 0.1%; mold opening and closing position accuracy: opening ≤ 0.03mm closing ≤ 0.01; The injection position accuracy (pressure end point) is less than 0.03mm; the tie rod force balance is less than 1%; the pre-molding position accuracy is less than 0.03mm; the balance of the fixed and movable platens A: less than 0.03mm when the clamping force is zero B: lock The mold force is less than 0.005 mm at maximum; the barrel and screw temperature control accuracy is less than ±0.5°C.
Technical focus
Clamping force: In the precision injection molding process, high injection pressure is generally required, otherwise it will be difficult to mold.
Measuring 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 larger injection pressure to improve the density of the plastic parts, reduce shrinkage deformation, and ensure the accuracy of the parts.
Holding pressure: Holding pressure has a great impact on precision plastic parts.
Mold temperature: The temperature change on the surface of the mold cavity should be controlled within ±1°C.
