Contact Us
Five Reasons for the Shrinkage of the Plastic Injection Mold Tooling

Five Reasons for the Shrinkage of the Plastic Injection Mold Tooling

Ⅰ. Injection molding products are inseparable from plastic injection mold tooling


No matter what injection molding products, they are inseparable from plastic injection mold tooling. But sometimes the plastic injection mold tooling will shrink. So what are the reasons for the shrinkage of plastic injection mold tooling?


Ⅱ. Five reasons for the shrinkage of the plastic injection mold tooling


1. Thermal expansion and cold contraction of plastics

When the plastic mold is formed, it is necessary to melt the plastic raw materials. At this time, the melting temperature reaches 200 ~ 300 degrees, and the plastic raw materials are heated and expanded. During the cooling process of the injection mold, the temperature decreases, and its volume potential must shrink.


2. Changes in the chemical structure of plastics

For example, in the molding process of thermosetting plastics, resin molecules change from linear structure to body structure. The volume mass of body structure is larger than that of linear structure, and its total volume becomes smaller, so it shrinks.


3. Residual stress change

During the plastic injection mold tooling, it is affected by the shear force of molding pressure, anisotropy, uneven mixing of additives and mold temperature.


There is residual stress in the injection mold after molding. This residual stress will gradually decrease and redistribute. As a result, the injection mold will shrink again. This shrinkage is generally called post shrinkage.


4. Gate section size

Different injection molds have different cross-section sizes. Large gate helps to improve cavity pressure and prolong gate closure time, so as to facilitate more melt to flow into the cavity.


5. Plastic variety

Generally speaking, crystalline plastics such as PP and PA have larger shrinkage after demoulding and wider shrinkage range than non crystalline plastics such as PC, PS and ABS.


The reasons for the large shrinkage of crystalline plastics are the influence of the coefficient of thermal expansion of plastics and the condensation of melt during the formation of crystalline structure.


The above five points are the reasons for the shrinkage of injection molds. Therefore, for injection molding plants, the quality of injection molds must be checked frequently when producing injection products.

Related News
  • Pretreatment of Plastic Injection Molding Raw Materials

    Pretreatment of Plastic Injection Molding Raw Materials

    April 20, 2022Due to the different supply methods (powder or pellets) and properties of plastics, the structure of the parts (with or without inserts) and the use requirements are different. The preparations for va...view
  • How to Use Die Casting Mould Correctly?

    How to Use Die Casting Mould Correctly?

    July 19, 2021For die casting, the three elements of die casting materials, die casting machines and moulds are indispensable. In the production process, the correct use of die-casting molds is very important due t...view
  • What's the Difference Between Molding and Casting?

    What's the Difference Between Molding and Casting?

    August 30, 20211. What's the difference between molding and casting?Casting is the manufacturing process of introducing molten material into a solid mold and curing it. The term usually refers to metals, but it ...view
  • The Advantages of 3D Printing Prototype

    The Advantages of 3D Printing Prototype

    November 18, 2021Prototyping is the first and key step of all design. It can not only ensure the correctness of design, but also ensure the applicability of parts assembly, and even ensure the stability in extreme env...view
  • How to Realize the Thin Wall of Automobile Plastic Bumper?

    How to Realize the Thin Wall of Automobile Plastic Bumper?

    September 27, 2021I. The thin-walled bumper will have the problem of difficult demouldingBecause the wall thickness gauge is small and has small shrinkage, the injection molded automobile parts are tightly adhered to t...view
  • The Quality of Die-casting Molds Needs to Be Stable

    The Quality of Die-casting Molds Needs to Be Stable

    June 29, 20211. The quality stability of the die-casting mold is very importantThe quality stability of the die-casting mold is very important. If the quality of the die-casting mold is unstable, it is easy to cau...view