Why do injection molds need an exhaust system?
Injection mold exhaust system is an important part of injection mold design, why do injection mold need exhaust systems?
Sources of gases in injection molds
There are several sources of gases in injection molds, including:
1. Air in the runner system and mold cavity.
2. Water vapor is formed by the evaporation of moisture in the raw material that has not been sufficiently dried.
3. Gases are produced by the decomposition of the raw material at high temperatures.
4. Gases are produced by the evaporation of additives in the raw material.
Harms of poor mold exhaust system
Poor mold exhaust system design can have several negative impacts on the quality of plastic parts, including:
1. If gases cannot be removed in time during injection molding, the molten plastic will be difficult to fill, resulting in a short shot.
2. If gases are not removed in time, they can build up pressure in the mold cavity, under a certain amount of compression, seep into the product, causing defects such as air bubbles.
3. Due to the high compression of the gases, the temperature in the mold cavity can rise rapidly, leading to the decomposition and combustion of the surrounding molted plastic, causing local carbonization of the plastic parts.
4. If gases are not removed in time, the speed at which the molten plastic enters the cavity can be different, making it easy to form weld marks, which can reduce the mechanical properties of the product.
5. The presence of a large amount of gas in the cavity can reduce the filling speed, affecting the molding cycle and reducing production efficiency.
