Mold temperature Management

In injection molding process, cooling molten plastic inside the mold simultaneously is crucial for cycle time and part quality.

Temperature should be uniform throughout the cavity surface to reach a uniform part temperature.

In order to reach the uniform temperature, heat transfer of the mold has to be managed well.

Normally, the heat from molten plastic is mainly removed by coolant medium such as water or oil.

The coolant medium flows through a hole inside the mold to take out heat from the cavity wall and maintain the mold temperature.

The task of mold designers is to layout cooling channel and choose the proper channel size, distance between cooling channel and cavity, as well as select mold materials to achieve a uniform part temperature.

In general, the distance of cooling channel to cooling channel and to cavity is approximately 2.5 times the channel diameter.

However, there may be limitations from part and mold designs such as variations of thickness, complex geometry, cores, sliders, and ejector pins.

An option to manage temperature at a critical area is to use material with high thermal conductivity to compensate poor heat transfer along the distance from the cooling channel to the cavity wall.

Injection mold simulation is a tool that helps mold designers making the right decision in parallel to their design work.

For example, instead of moving cooling channel close to mold cavity, the designers can alternatively place a mold insert with high thermal conductivity at critical area to reach temperature uniformity.

This can be seen from the images below.

Image 1 show a mold with the standard cooling design. Here we can see a high variation of temperature near the mold cavity.

Image 2 and Image 3, show a more uniform temperature reached with two different modifications.

Image 2 show the temperature when an approach is used with shorter distance of cooling channel to mold cavity.

Image 3 display the temperature distribution if a copper insert is used.

With the help of simulation, the designers can evaluate different approaches and safely choose the best one to deal with heat transfer of the mold. Thus, the mold can produce parts with shorter cycle time and less warpage.

You can learn more about mold cooling from the eLearning course:

https://www.plexpert.ca/product/cooling-system-very-important-yet-ignored-course/

Besides, please feel free to contact PLEXPERT any time in order to discuss your current project.