Increasing throughput on injection molding machines can be a tricky balancing act. If you fill and cool molds too quickly, you will likely have a high level of quality assurance rejects. If you fill and cool too slowly, you are increasing your costs. The key here is to maximize throughput – careful consideration of the proper injection molding process chiller is vital.

The Molding Cycle

In injection molding there are typically three stages to the molding process:

1. Injection – When the plastic material is injected into the mold.
2. Mold Cooling – When the part material is solidifying
3. Mold Opening and Ejection – When the solid part is done cooling and ready to be ejected from the mold.

Why is cooling important in molding cycles?

Cooling is necessary in molding cycles because the material that the part is made out of must solidify in the mold prior to being ejected. Without proper cooling times in the manufacturing process there will likely be a large number of part defects such as warping and distortion. This is primarily because the thermoplastics or other material that makes up the part must be allowed to cool properly to ensure structural integrity.

Cooling, in most cases, is the part of the injection molding process that takes the largest amount of time, but cutting the time too short can cause a significant number of product defects. In order to maximize throughput, the best solution is find an acceptable cooling time for the part being made and ensure you have proper cooling to remove the necessary amount of heat.

Over many injections the mold accumulates heat. Working with process chiller experts that have experience working with injection molding applications allows you to prevent this heat accumulation and consistently achieve uniform cooling times.

Ways to reduce cooling time in the Injection Molding Process

There are two points of heat transfer in the molding process: 1) between the plastic and the mold and 2) between the mold and the coolant. Properly designing the process at these points allows you to minimize cooling time and provide efficient cooling.

To ensure maximum heat removal at point one (1) [between the plastic and the mold] designing efficient mold channels is of extreme importance.

To ensure proper cooling at point (2) the coolant must be sufficiently cold to prevent heat accumulation in the mold as well as remove heat added during each cycle. It is at this point that chiller selection is critical. A properly sized chiller will be able to provide enough heat removal to prevent heat buildup in the mold.

Considerations when selecting Injection Molding Process Chillers

To properly size a chiller for an injection molding application consider the following:

• Constant cycle time is extremely important to maximize system throughput. In order to consistently deliver the proper cooling you should have sufficient data on your process.
  • Do you have your heat removal requirements?
  • Do you have information on flow rates?
  • Do you have information on temperature drops? (Delta T)
• Do you have multiple molding machines?
  • Load-Matching or Variable drive chillers will allow you to provide ample cooling for multiple units. As the head load increase the chiller will react accordingly to ensure proper coolant temperature is maintained.