plastic injection molding using cold runner molds, an economical process to produce plastic parts of simple design, or when more than one color part is needed to be manufactured quickly.
Efficient and Economical
Significant advantages to using a cold runner system include:
Simple mold design
Considerably less expensive than hot runner system
Less skill required to set up and operate
Mold requires less maintenance
Color changes are easy – all plastic in the mold is ejected with each cycle
With a cold runner mold, the runner (excess material retained in the feed channels) is cooled and ejected with the part. Every cycle, a part and a runner are produced.
A Few Disadvantages to Consider
While it is a less expensive process than hot runner systems, there are a few disadvantages to cold runner systems to consider, including:
Waste plastic generated
Runner material must be either disposed of or reground and reprocessed
Additional steps in the manufacturing process
Regrind will increase variations in the injection molding process
Regrinding could decrease the plastic’s strength and mechanical properties
Get the Right Mold for Your Project
Cold runner molds are the least expensive to build for parts of simple design. Depending on part complexity, one of two types of cold runner molds may be used:
A two plate cold runner mold is the easiest and least expensive type of mold to produce.
Two plate molds have a single parting plane, and the mold splits into two halves at the plane
Because the runner system must be in line with the parting plane, the part can only be gated on its perimeter
A three plate cold runner mold differs from a two plate in that it has two parting planes, and the mold splits into three sections each time a part is ejected
This feature provides greater flexibility of design, which allows gating to be placed in the most efficient locations
Since the mold has two parting planes, the runner system can be located on one, and the part on the other, which allows for easier plate separation
In a cold runner system, the runners and the molds are maintained at the same temperature. Within this system, two or three plates are contained within the mold. The two plate system is easier to use, but requires an injection system to remove the part from the mold. Within a three-plate system, the runner functions on a separate plate. Therefore, it can be ejected separately from the runner. A three-plate cold runner mold allows for flexibility in design. To ensure the mold is not under filled in that the material fills the part properly, the runner dimension must be larger than the part within this system.
How does a cold runner system work?
Cold runners consist of an unheated channel that is used to convey molten plastic into a mold cavity after it is dispensed from the nozzle. As a result, the channel of cold runners must be larger, necessitating a greater flow of plastic through each cycle. As a result, you could run up the cost higher than a hot runner assembly process if you need to shoot a large number of parts while running through several iterations to arrive at the correct design.
If the cold runners are not recycled, they can create waste. However, this system is easier and less expensive to maintain than a hot runner system. Another advantage of the cold runner systems is the ability to handle a wide-array of polymers, particularly specialty polymers. This system can also accommodate quick color changes.
thank you for your introduction, we still need cold runner system in many moulds
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