07-10
Gas assisted injection molding is a special injection molding technology developed on the basis of traditional thermoplastic injection molding technology, which is suitable for special performance req...
After the injection of the mold is completed, the mold is opened and the molded plastic parts are removed from the mold. The mechanism that completes the demoulding is called the Ejection System. Its working principle is that after the mold is opened, the hydraulic cylinder on the injection molding machine or the mold is used to push the stripper plate on the mold, and then push the ejector pin and other parts through the stripper plate, and finally push the parts from the mold core.
The Ejection System is composed of ejection mechanism and returning mechanism. The main factors that affect the ejection of plastic parts are: the shape and the performance of plastic parts, and the roughness of the core surface.
1. Keep plastic parts stay in the cavity side
Try to make the plastic parts stay in the cavity side, so that the mold structure is relatively simple.
2. Ensure that the plastic parts are not deformed or damaged
Correctly analyze the size and location of the adhesive force of the plastic parts to the cavity, and choose a reasonable way to push out.
3. Ensure good appearance of the plastic parts
To ensure the good appearance of the plastic parts, the ejection location should be selected inside the plastic parts as far as possible.
4. The Ejection System should be as simple and reliable as possible
The Ejecton System should be as simple and reliable as possible to ensure that the ejection action is flexible, and the parts have sufficient strength, rigidity and hardness.
Ejector pin is a common tool in mold design and it is widely used in the process of mold manufacturing, maintenance and repair.
When arranging the position of the ejector pin, the general principle for deep products (usually bucket shaped) is to place the ejector part on the hardest part of the product. In addition to paying attention to whether the ejecting force is enough, but also to ensure the ejection is convenient and easy to take.
The ejector pin should be arranged at the lowest point of the product, such as the reinforcement rib, wheel ring and convex support.
The ejector pin should be distributed symmetrically and evenly as far as possible, and the ejector pin arrangement should consider the balance of the ejector force.
The setting position of the ejector pin can not affect the cosmetic of the product.
The ejector pin should be located in a position where the venting is difficult. If vacuum is created between the core and the product during ejection, the issue of venting should be considered.
Compared with the Pin Ejection, the Stripper-plate Ejection is more suitable for the Ejection System. The ejection area of the plastic parts is relatively large, and the ejection force is evenly distributed.
In addition, ejection marks are usually not noticeable and do not require a reset mechanism.
Design points of Stripper-plate Ejection:
The separation between the stripper ejector and the core must be smooth.
The stripper ejector and the core must have a 3°~5° cone, which can reduce the friction, and play an auxiliary positioning role. And it is conducive to preventing the stripper ejector eccentricity and overflow, the stripper ejector hole should be 0.20~0.25mm larger than the core forming part to prevent friction, displacement or stuck between them.
