Liquid CO₂ Capillary Cooling for Thin-Core Plastic Molds
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Solution Overview
Problem
The production of plastic parts through molding is hindered by long cooling times, especially for small or thin cores, due to clogging of water channels and risks in weld failure, and inefficient cooling methods that do not effectively address temperature reduction during resin injection and holding phases.
Innovation Solution
A method involving the use of liquid carbon dioxide fed through capillaries to channels in molds, where the channel dimensions increase to accommodate expansion into larger areas, allowing phase transition from liquid to gas for targeted cooling in small or thin cores, slides, and lifters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If water channels are used for cooling small or thin cores, then cooling effectiveness is improved, but channel clogging occurs due to mineral and organic compound content in water
Solution Approach 1:
The patent changes the physical and chemical parameters of the cooling medium from water to carbon dioxide. Carbon dioxide is introduced in liquid form through capillaries and expands to gas phase in the channels, providing cooling without the mineral and organic compound content that causes water-based channel clogging.
Solution Approach 2:
The patent utilizes phase transition of carbon dioxide from liquid to gas as the core cooling mechanism. Liquid CO2 is fed through capillaries into the mold channels where it expands and vaporizes, absorbing heat from the mold and providing effective cooling while preventing clogging issues associated with liquid water.
2Temperature
If two piece laminated cores with welded channels are used, then cooling coverage is improved, but weld failure risk increases causing water leakage
Solution Approach 1:
The patent segments the cooling system into separate capillary feed lines that deliver CO2 to different channel locations. This eliminates the need for welded joints between core halves, as each capillary is independently inserted and sealed, removing the weld failure risk while maintaining comprehensive cooling coverage.
Solution Approach 2:
The patent introduces capillaries as intermediary elements that bridge the cooling system to the mold channels. These capillaries serve as sealed conduits for CO2 delivery, replacing the welded joint configuration and eliminating the reliability issues associated with weld failures and water leakage.
3Temperature
If cooled air is blown on cores between shots, then some cooling is achieved, but cooling during resin injection and pack hold phase is not provided
Solution Approach 1:
The patent enables continuous cooling action throughout the entire injection molding cycle. By delivering liquid CO2 through capillaries directly to the mold channels, cooling occurs continuously during resin injection, pack, and hold phases, as well as between shots, eliminating idle cooling time and maximizing productivity.
4Temperature
If capillaries are placed adjacent to slides or lifters, then cooling of moving components is improved, but channel size must be larger allowing CO2 expansion
Solution Approach 1:
The patent applies local quality by delivering CO2 through capillaries to specific locations adjacent to slides and lifters where cooling is most needed. The channel dimensions are locally increased at these positions to accommodate CO2 expansion, providing targeted cooling to moving components without requiring complex channel configurations throughout the entire mold.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces production cycle times, prevents clogging, and ensures effective cooling where traditional methods fail, exemplified by reducing cycle times from over 22 seconds to below 15 seconds for 0.060 inch cores.
Implementation Method 1
The expansion of the liquid into its gas phase provides the cooling due to the phase transition of the liquid to a gas at the appropriate location
Data Source
AI summary
A method for cooling a mold used in the production of plastic parts is described. A capillary feeds liquid carbon dioxide to a channel present in the mold typically used in making plastic parts having thin gaps or thin open sections in the plastic part. The channel will be approximately the same size as the inner diameter of the capillary but will increase in size either stepwise or progressively as it passes through the mold, particularly at the location where cooling is desired therefore providing more effective cooling to the mold and slides and lifters present therein.