Cold runner mold
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Cold-runner mold Developed to provide for injection of thermoset material either directly into the cavity or through a small sub-runner and gate into the cavity. It may be compared to the hot-runner molds with the exception that the manifold section is cooled rather than heated to maintain softened but uncured material. The cavity and core plates are electrically heated to normal molding temperature and insulated from the cooler manifold section.
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Types of Cold Runner Molds
There are two major types of cold runner molds: two plate and three plate.
two plate mold
A two plate cold runner mold is the simplest type of mold. It is called a two plate mold because there is one parting plane, and the mold splits into two halves. The runner system must be located on this parting plane; thus the part can only be gated on its perimeter.
three plate mold
A three plate mold differs from a two plate in that it has two parting planes, and the mold splits into three sections every time the part is ejected. Since the mold has two parting planes, the runner system can be located on one, and the part on the other. Three plate molds are used because of their flexibility in gating location. A part can be gated virtually anywhere along its surface.
Advantages
The mold design is very simple, and much cheaper than a hot runner system. The mold requires less maintenance and less skill to set up and operate. Color changes are also very easy, since all of the plastic in the mold is ejected with each cycle.
Disadvantages
The obvious disadvantage of this system is the waste plastic generated. The runners are either disposed of, or reground and reprocessed with the original material. This adds a step in the manufacturing process. Also, regrind will increase variation in the injection molding process, and could decrease the plastic's mechanical properties.
Process: Injection molding cycle Reaction injection molding, Reinforced reaction injection molding, Liquid injection molding, Gas assist injection molding, Coinjection molding, 2-shot injection molding, Fusible core injection molding, Rapid injection molding, Micro injection molding
Equipment: Injection molding machine(Vertical, Horizontal), Injection molding press, Injection mold (Hot runner, Cold runner), Injection unit (Injection ram, Injection screw), Clamping unit (Toggle , Hydraulic, Hydromechanical), Plunger injection molding, Injection molding machine manufacturers, Types of injection molding machines
Terms: Injection pressure, Injection rate, Clamping pressure
See also: Plastic thermoforming • Blow molding • Plastic welding • Plastic extrusion • Rotational molding
