plastic molding for in china

Plastic Molding in China 4 Injection Molding Defects and Causes

Plastic Molding in China 4 Injection Molding Defects and Causes

Dec 13, 2020
By hqt

 Plastic Molding for in China -- Defects and Causes

Plastic molding for in China gets fame in the international plastic market as the majority of our daily use items or their parts are made using injection molding

Chinese Plastic Molding revolutionizes the plastic industry across the globe. We now surround the majority of the items in our daily usage that are injection molding products. The best example of injection molding products is the one we usually hold in our hands. Laptops and our mobile devices make the most of it. Furthermore, injection molding in China comprises storage boxes, toys, bags, plastic utensils, cutlery items, and food containers. Many stationary items make the major section of injection molding parts. Indeed, plastic becomes the most popular method and product.

You May Also Read: Plastic Molding Processing: Industries and Applications

This is because plastic production revolutionizes its methods of production in the past few years. Since the device offers durability and reliability much more than metal, therefore users like it. Additionally, we can mold injection plastic into any shape and design. This customized nature of injection plastic is famous to create any item of choice.

plastic molding for in china

Benefits of Using Plastic Molding for in China

There are many advantages and feasibilities of using plastic injection molding parts and products. plastic molding in China offers a variety of benefits that include:

  • State of the art Molding machinery: The injection molding in china guarantees innovation with quality products. It makes the heart of the injection molding in China. The industry uses plastic molding products, mold, and die casting which are world-class and highly competitive products. 3D tool design technology ensures efficiency and reduces mistakes.
  • Assurance of Quality Products: Plastic molding for in China offers a wide range of products with a full quality guarantee. The whole process of production is under constant monitoring to assess any possible error. The mold and molding material are checked under constant monitoring to mitigate any mistake and to ensure high-quality deliverance to customers.

4 Injection Molding Defects and Causes:

Despite the number of benefits that Plastic molding in China offers, there are several common defects. There are 4 manor defects and we discuss them from here:

Many defects are common in plastic molding in China. This happens due to many technical reasons. However, most of the defects and their causes are due to the defects in the injection mold process. Therefore, here are the 4 major defects and their causes.

Flow Marks and Flow Line

One of the most common defects in plastic molding for in China is flow marks or flow lines.  Flow marks and flow lines are the most common defects that we find in the injection molding process. Flow lines mean there are some lines or waves that are apparent on the surface. Consequently, these marks make a streak of line. Thus, this usually discolors the defected section in comparison with the rest. Therefore, the surrounding area hence becomes more distinguishable because of the color difference.

This defect is common on the gate point of the mold. These gate points or gate locations are the places where molten plastic enters the mold. However, these marks or lines do not affect the final finished product. Furthermore, the lines do not affect the functionality of the final product. The problem persists with the visual appearance of the product. It looks unpleasant and makes the product look least attractive which requires it to be aesthetically pleasing.


Plastic molding parts go through many phases and changes in the process. The last step is the cooling rate process, where the product goes through the cooling process. Hence, it passes the heated barrel and thus molds and solidifies itself in the end.

These defects usually happen when the thickness of the walls of the mold is not uniform. The variant thickness thus allows the molten material to cool at different speeds. Furthermore, another cause of the flow line is the slow injection process and low-pressure injection. This happens when the molding plastic cools down so quickly that its leaves pattern marks and lines.

Burns Marks in Plastic Molding in China:

Burn marks in plastic molding in China are the black colored marks on the edge of the final product. The marks however can also appear on the edge in the form of rust color. The marks furthermore may appear on the surface of the molded parts.

These marks are therefore not the actual part of the final product. The marks hence are harmless for the final material; However, the damage may occur if the marks burn the actual product. The burn to the final material therefore degrades the plastic.


 The most common cause of these defects is overheating. The burn marks appear when the trapped air bubbles in the molds get overheat. Furthermore, the molten risen in the molds also get overheating and thus cause burn marks. All this happens in the mold cavity during the processing time. The main cause of these issues is thus the overheating of the molded parts. It also happens when a process involves high injection speed.

Warping Defects in Plastic Molding in China:

Warping is an uneven distribution of mass or shape of the final product. In the plastic injection molding process, warping occurs when the final product cools down and solidifies unevenly. During the process of plastic production, this uneven cooling and solidification make the process defective. This makes the final product a disfigured one. The final compression product contains bends and twists.


There are many reasons for the final product to be defective in shape and form. The most common cause is the premature cooling of the raw material. Furthermore, the uneven cooling rate process causes the uneven distribution of mass and material. However, this also when there is an overheating in the process. Also, when the walls of the molds are uneven this causes the product to have warps.  

Air Pockets and Vacuum Voids:

Air Pockets in plastic molding in China are the plastic bubbles. This bubble hence usually gets trapped in the final product. The finished product thus remains unfinished. But this defect is not the major default in the final product. However, the presence of this defect in the product may cause the weakening of the final items. This happens during the product development phase.


The happens when there is a low volume production in injection molding. The vacuum voids appear in the final product when there is insufficient pressure in the mold. Low pressure happens due to low production. Therefore, in the final product, the air bubbles remain. The presence of the vacuum voids thus appears when the plastic cools down and solidifies having an air bubble in it.

You May Also Read: The Role of Thermoplastics in Custom Plastic Molding

Final Thoughts:

As we see there are many defects in plastic molding for in China. This happens due to the faults in the initial process of the molding machines. This also happens when the tool used is defective. Furthermore, the defects appear when the raw material used in the process is defectives. To avoid this, the design of the mold should be proper and it should properly finish the final product.

plastic molding for in china

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