What are the common causes of burns in injection molding?

Injection molding is a common plastic processing technology, but during the production process, you may encounter some problems, one of the common problems is burns.
Burn occurs when the plastic melts at high temperatures and adheres to the mold, causing black or yellow streaks or spots to appear on the surface of the product. This problem not only affects the aesthetics of the product, but may also affect its performance and service life.
So, why do burns occur? Generally speaking, burns are caused by plastic being left in the heat for too long or being too hot. When the plastic melts, if the mold cavity is not filled or cooled in time, an adhesive layer will form on the surface of the mold. As the temperature further increases, the adhesive layer becomes harder and tighter, eventually forming burns.
To solve the burn problem, you can start from the following aspects:

Control the mold temperature: During the production process, the mold temperature should be controlled within an appropriate range to avoid excessively high or low temperatures. At the same time, it is necessary to regularly check whether the cooling system of the mold is working properly.

Control plastic temperature: Plastic that is too hot can cause burns. Therefore, the plastic temperature should be controlled within an appropriate range and adjusted accordingly according to the characteristics of different plastics.

Optimize the injection process: Optimization of the injection process parameters can reduce the residence time of the plastic in the mold, thereby reducing the risk of burns. For example, the injection speed and injection pressure can be appropriately increased to speed up the filling speed.

Clean the mold regularly: Dirt and residue on the surface of the mold can cause burns. Therefore, the mold should be cleaned regularly and residues on the cavity surface should be cleaned at any time during the production process.

Check the quality of the plastic: Using poor quality plastic can lead to burns. Therefore, the purchased plastic should be checked to see if it meets quality standards.
Through the implementation of the above measures, the burn problem during the injection molding process can be effectively reduced and the quality and performance of the product can be improved.

Increase the use of release agent: During the production process, an appropriate amount of release agent can be sprayed on the surface of the mold cavity to reduce the adhesion between the plastic and the mold, thereby reducing the risk of burns.

Adjust the mold structure: An unreasonable mold structure may cause the plastic to stay in the mold for too long, causing burns. Therefore, the mold structure can be adjusted, such as increasing the length of the flow channel, changing the feed point, etc., to optimize the flow of plastic in the mold.

Adjust the plastic's formula: By adjusting the plastic's formula, the plastic's flow and thermal stability can be improved, thereby reducing the risk of burns. For example, the content of fillers or additives can be increased to improve the properties of the plastic.

Control the production environment: The temperature and humidity of the production environment may affect the temperature and viscosity of the plastic, thereby affecting the risk of burns. Therefore, the temperature and humidity of the production environment should be controlled to ensure that they are within the appropriate range.