Today's Science Popularization: Plastic Mold

What is a plastic mold?
Plastic mold is a combination mold used for compression molding, extrusion molding, injection molding, blow molding, and low foam molding. The coordinated changes between the convex and concave molds of the mold and the auxiliary forming system can process a series of plastic parts with different shapes and sizes. Plastic molds are the mother of industry, and the release of products involves plastic. It mainly includes a concave mold with a variable cavity composed of a concave mold combination substrate, a concave mold component, and a concave mold combination clamp plate, and a convex mold with a variable core composed of a convex mold combination substrate, a convex mold component, a convex mold combination clamp plate, a cavity cutting component, and a side cutting combination plate.
The production process of plastic molds
1. During injection molding, the mold is clamped onto the injection molding machine, and molten plastic is injected into the mold cavity, where it is cooled and shaped.
2. Separate the upper and lower molds, and use the ejection system to eject the product from the mold cavity and leave the mold.
3. The mold is closed again for the next injection molding, and the entire injection process is cyclic.
Factors affecting the production of plastic molds
1. Parting surface
When the mold is closed, the concave and convex molds are formed by mutual coordination.
2. Structural components
They are slider, inclined top, straight top block, etc. for complex molds.
3. Mold accuracy
Including card avoidance, precise positioning, guide pillars, positioning pins, etc.
4. Pouring system
Located between the injection molding machine nozzle and the mold cavity, it is composed of a main flow channel, a splitter channel, a gate, and a cold material cavity.
5. Product parts condition
The surface quality, Hardness, elongation and other mechanical properties of the processed part materials.
6. Mold working status
When the mold is working again, it needs to undergo frequent processes such as mold closing, locking, injection molding, pressure maintaining, cooling, mold opening, and ejection. This process needs to ensure the flexible operation of each mechanism. Lubrication is required and maintenance is required to keep it in optimal working condition.
Common problems with plastic molds
1. Cracking
Cracking is a common defect in plastic products, mainly caused by stress deformation. There are mainly residual stress, external stress, and stress deformation caused by external environment.
2. Insufficient filling
3. Pitted surface
The reason for this defect is essentially the same as insufficient filling
4. Shrinkage pit
5. Overflow edge
6. Weld marks
The fusion mark is caused by the cooling of the front end of the molten resin from different directions and the incomplete fusion at the junction
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7. Burns
Burns caused by different reasons such as mechanical, mold, or molding conditions
8. Silver wire
The silver wire is mainly caused by the moisture absorption of the material
9. Jet pattern
Jet streaks are traces that bend like snakes along the flow direction from the gate. It is caused by the high injection rate of resin starting from the gate.
10. Warping and deformation
11. Whitening
Caused by poor demolding
12. Bubbles
Precautions for selecting plastic molds
1. Don't just focus on product design and neglect plastic mold manufacturing.
2. Don't just look at the price, consider quality, cycle, and service from all aspects.
3. Avoid multiple collaborations and strive to integrate plastic mold production and product processing as much as possible.