The design of the injection mold cooling system is very important. Cooling time covers 70 to 80% of the injection molding cycle, a well-designed cooling system can shorten the molding time and dramatically increase productivity. The poor design of the cooling system will prolong the molding time, increase the production cost and the injection mold temperature will have a great impact on mold shrinkage, dimensional stability, deformation, internal stress and surface quality.
If so, what are the factors effective for cooling?
Plastic wall thickness
The thicker-walled part requires longer cooling time. In general, the cooling time is approximately proportional to the thickness of the plastic parts. If possible, designing the wall thickness in the mold design as a minimum will shorten the cooling time.
In Steel Molds
The higher the thermal conductivity of the injection mold steel, the better the heat transfer, the shorter cooling time. In practice, the injection mold is usually replaced by steel, since the cooling line cannot be made of copper.
Cooling line arrangement
The closer the mold cavity is to the cooling pipes, the larger the diameter of the cooling pipes, the better the cooling effect and the shorter the cooling time. The designer should pay attention to everything possible to achieve maximum cooling efficiency.
The structure of the cooler may be different, usually the cooling oil and water are used. The viscosity and thermal conductivity of the coolant also affect the heat conduction effect of the plastic injection mold. The lower the coolant viscosity, the higher the thermal conductivity and the better the cooling effect.
Cooling system design guidelines:
- Ensure cooling efficiency, while achieving the shortest cooling line while achieving quality parts.
- Provide proper cooling to prevent deformation.
- Ease of production.
Cooling can be viewed as “The purpose of cooling is to advantageously remove heat from the component in order to obtain a low-stress component with the best dimensional and physical properties”. Generally, this is considered a ratio for non-complex parts, whereas the parts produced in practice will be complex. Therefore, it is necessary to have different mold designs to draw heat from difficult areas of the part while cooling. To measure the thermal performance of the injection mold, components involving thermocouples require a more comprehensive engineering approach, requiring water circuits and manifolds to control temperatures and perhaps kit materials with a high thermal conductivity.