Hot to Cold Runner Golf Ball Injection Mold
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Solution Overview
Problem
Conventional retractable pin injection molds face issues with severe shear imbalance, high pressure, and material freezing due to directional changes in cold runner systems, leading to imperfections and defects in golf ball covers, especially when forming thin thermoplastic polyurethane layers.
Innovation Solution
A hot to cold runner system is introduced, featuring a heated manifold with hot runner drops that supply molten material to cold tertiary runners, reducing travel distance and maintaining temperature, thus ensuring uniform flow and balanced shear distribution, eliminating the need for direct injection into mold cavities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a cold runner system is used to transport thermoplastic material to mold cavities, then the system structure is simple and cost-effective, but the material freezes during travel leading to severe shear imbalance and high pressure
Solution Approach 1:
A hot runner drop acts as an intermediary component between the cold runner and the mold cavity. It receives molten material from the cold runner, maintains it in molten state through heating, and then distributes it uniformly to multiple cavities. This intermediary structure resolves the contradiction by eliminating the freezing issue in cold runners while maintaining structural simplicity.
Solution Approach 2:
The invention changes the temperature parameter of the runner system by introducing a heated portion. The hot runner drop is heated to maintain the thermoplastic material in a molten state during distribution, fundamentally changing the thermal parameter from cold to hot in the critical distribution zone, thereby preventing freezing and achieving uniform flow.
2Length of stationary object
If thermoplastic material travels through long cold runners, then the system can reach multiple cavities, but the material freezes leading to high pressure and shear imbalance
Solution Approach 1:
The runner system is segmented into distinct functional zones: a cold runner portion for material transport and a hot runner drop portion for material distribution. This segmentation allows the material to travel through the cold runner without freezing, then transitions to a heated zone where uniform distribution occurs, thereby reducing injection pressure and shear imbalance.
Solution Approach 2:
The hot runner drop serves as a transitional intermediary that receives material from the long cold runner, maintains it in molten state, and distributes it to cavities. This intermediary prevents the freezing that would occur in a purely cold system, reducing the injection pressure required while maintaining the ability to reach multiple cavities.
3Temperature
If hot runner systems directly inject material into mold cavities, then material temperature is maintained, but stresses and vestiges are left on the dimpled cover
Solution Approach 1:
The cold tertiary runner acts as an intermediary cooling zone between the hot runner drop and the mold cavity. Material is heated in the hot runner drop to maintain temperature, then passes through the cold tertiary runner which cools it slightly before entry, reducing thermal stresses and surface vestiges while maintaining sufficient fluidity for filling.
Solution Approach 2:
The invention dynamically changes the temperature parameter by first heating the material in the hot runner drop to maintain molten state, then allowing controlled cooling in the cold tertiary runner before cavity entry. This parameter modulation optimizes both temperature maintenance and surface quality by preventing direct high-temperature injection.
4Ease of manufacture
If cold runners are used with thin thermoplastic polyurethane covers, then the system is simple to manufacture, but 60 percent or more regrind is generated
Solution Approach 1:
The hot runner drop acts as a heated intermediary that prevents material freezing during the distribution phase. By maintaining the material in a molten state through the hot zone, complete cavity filling is achieved without premature solidification, thereby reducing the need for regrind while keeping the overall system simple to manufacture.
Solution Approach 2:
The invention changes the thermal parameter of the distribution zone from cold to hot, preventing material freezing during transit. This temperature parameter change ensures complete filling of thin thermoplastic polyurethane covers without solidification issues, dramatically reducing regrind generation while maintaining manufacturing simplicity.
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 system reduces material cooling, lowers injection pressures, and achieves balanced, uniform flow into each mold cavity, resulting in improved golf ball quality with reduced defects and increased durability, while minimizing regrind generation and cycle time.
Implementation Method 1
a heated manifold having a hot runner drop connected thereto
Implementation Method 2
the hot runner drop is configured to reduce the distance the layer-forming material travels to the cold runner by at least about ten inches
Implementation Method 3
the cold runner maintains the layer-forming material at a temperature within three degrees of the temperature of the manifold
Implementation Method 4
filling the mold cavity with the layer-forming material through one or more gates that extend around a circumference of the mold cavity
Data Source
AI summary
A hot to cold runner system for a golf ball injection mold is disclosed. The hot to cold runner system includes a hot runner for supplying layer-forming material in a molten state, the hot runner including a heated manifold having a hot runner drop connected thereto, and a cold runner operatively connected to the hot runner drop such that the cold runner is in fluid communication with the hot runner. The cold runner injects the material into a mold cavity to form a golf ball layer over a core. Methods of forming a golf ball layer by injection molding using the hot to cold runner system are also disclosed.