The Impact of Incorrect Injection Mold Temperature on Plastic Parts

The Impact of Incorrect Injection Mold Temperature on Plastic Parts


Injection molding is a widely used manufacturing process for producing plastic parts with high precision and efficiency. One critical factor that significantly affects the quality and performance of the final products is the mold temperature. Maintaining the appropriate mold temperature is essential for achieving consistent and defect-free plastic parts. In this blog post, we will explore the consequences of incorrect injection mold temperature on various aspects of the molded parts.

1. The Influence of Mold Temperature on Appearance

The mold temperature has a profound effect on the surface finish and appearance of the plastic parts. When the mold temperature is too high, it can cause surface defects such as burns, splay marks, and discoloration. On the other hand, if the mold temperature is too low, it may result in uneven cooling and cause flow marks or surface roughness. Achieving the right mold temperature is crucial to ensure smooth and aesthetically pleasing plastic parts.

2. Impact on Product Size

Mold temperature plays a vital role in controlling the dimensions of the plastic parts. The cooling rate of the molten plastic affects the shrinkage of the material as it solidifies within the mold. Incorrect mold temperature can lead to dimensional inconsistencies, warping, and variations in the size of the parts. This can be especially problematic for products with strict dimensional requirements or when assembling multiple components.

3. Influence of Mold Temperature on Deformation

Proper mold temperature is essential for minimizing the risk of part deformation during the cooling process. Rapid cooling due to a low mold temperature can cause differential shrinkage, leading to warping or twisting of the parts. On the other hand, insufficient cooling caused by a high mold temperature can result in prolonged cooling time and potential overpacking of the material. Properly controlling the mold temperature helps prevent deformations and ensures the dimensional stability of the parts.

The Impact of Incorrect Injection Mold Temperature on Plastic Parts

4. Influence of Mold Temperature on Mechanical Properties (Internal Stress)

The mechanical properties of plastic parts, including their strength, flexibility, and impact resistance, can be affected by the internal stress within the material. Incorrect mold temperature can induce internal stress during the cooling process. High mold temperatures may lead to lower mechanical strength due to reduced molecular orientation, while low mold temperatures can result in increased internal stress and reduced impact resistance. Controlling the mold temperature within the recommended range is vital for achieving desired mechanical properties in the final products.

Mold temperature is one of the key factors that affect the mechanical properties of injection-molded parts. The internal stress of a part is related to the thermal history and the cooling rate during the molding process. A higher mold temperature can reduce the internal stress by allowing more time for the polymer chains to relax and achieve a more uniform distribution of molecular orientation. However, a higher mold temperature also increases the cycle time and the energy consumption, which may affect the productivity and the cost of the part. Therefore, it is important to optimize the mold temperature for different materials and applications to achieve the desired balance between mechanical performance and production efficiency.

5. Influence the Thermal Deformation Temperature of the Product

The thermal deformation temperature, also known as the heat distortion temperature (HDT), is a critical property of plastic parts. It represents the temperature at which the material begins to deform under load. The mold temperature can significantly impact the HDT of the finished products. Higher mold temperatures tend to increase the HDT, making the parts more heat-resistant, while lower mold temperatures can lead to lower HDT values. Properly adjusting the mold temperature can help achieve the desired thermal deformation temperature for specific applications.


Correctly controlling the mold temperature is essential for achieving high-quality, dimensionally accurate, and mechanically sound plastic parts. Improper mold temperature can lead to various issues, including poor surface finish, inconsistent dimensions, part deformations, altered mechanical properties, and improper thermal deformation temperatures. Therefore, it is crucial for injection molding professionals to carefully monitor and adjust the mold temperature during the production process to ensure the best possible outcomes for the final products.

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