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Injection Molding Runners ©

2 Notes ©

2 Patent Abstracts

13 Patent Titles

Patentpedia Index 

5/6/2016 through 10/23/2013

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1 Topics

Injec tion Molding Molds (E)

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0 Subtopics

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2 Notes

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1. Mold Design

2. Runners    

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2. Runners

“Runners or flow channels mainly serves to transfer molten plastics which are emitted from the nozzle to the mold cavity. The quality of the flow channels directly affects the overall plastic properties, product appearance, precision of dimensions, and molding cycle. Since designers often delegate the quality portion of the work to the molding factory, quality control becomes difficult to manage.”

“Typical runners are generally categorized as hot and cold runners. A hot runner provides a channel for plastic materials to enter from the injection molding machine to the mold gate. After the plastic product has been ejected for each injection, the plastic materials remaining in the flow channel, which are not solidified, are not bound to be purged. Specifically, hot runner is suitable for manufacturing thin components and large scale plastic components such as liner board for vehicles, and housing for large size LCD televisions. Hot runner is known best for its small flow resistance and small pressure lost, which facilitates molding.”

“The main difference between hot runner and cold runner is the injection molding process. In general, temperature control is appropriately applied such that plastics in the flow channels or runners remain in a molten state, different from the molten plastics in the mold cavity which will eventually solidify, which prevent the casting system from cold slugging. As a result, no excess materials are generated. Since the plastics in the flow channel are not solidified, the injection flow in the flow channel remains smooth for the next injection. In order to keep a smooth flow, temperature control for the hot runner requires highly sensitive. Conventional runners are equipped with automatic heat adjustment controls as well as insulating means to prevent heat loss, clogging in the hot runner nozzle, and to ensure the flow properties of the plastics.”

Lin et al, US Patent 9,205,588 (12/8/2015).

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1. Mold Design

“The mold consists of two primary components, the injection mold (A plate) and the ejector mold (B plate). Plastic resin enters the mold through a sprue or gate in the injection mold; the sprue bushing is to seal tightly against the nozzle of the injection barrel of the molding machine and to allow molten plastic to flow from the barrel into the mold, also known as the cavity. The sprue bushing directs the molten plastic to the cavity images through channels that are machined into the faces of the A and B plates. These channels allow plastic to run along them, so they are referred to as runners.  The molten plastic flows through the runner and enters one or more specialized gates and into the cavity geometry to form the desired part.”

(Mold Design, Wikipedia, 10/23/2013)

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Copyright 2016 by Roger D. Corneliussen.
No part of this transmission is to be duplicated in any manner or forwarded by electronic mail without the express written permission of Roger D. Corneliussen

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Roger D. Corneliussen, Editor
Professor Emeritus
Materials Engineering
Drexel University, Philadelphia, PA
Editor
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