Variable Temperature Injection Mold for Elastomer-Metal Adhesion
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Solution Overview
Problem
The conventional manufacturing process for elastomer timepiece components with metal inserts faces challenges in achieving reliable adhesion due to temperature constraints, particularly when using primers with limited maximum allowable temperatures, leading to potential primer degradation and adhesion issues with metal inserts having high surface area to volume ratios, restricting the process's applicability to diverse shapes and mechanical properties.
Innovation Solution
A variable temperature injection mold process is implemented, where the temperature is initially kept below the primer's degradation point during injection and gradually increased to the vulcanization temperature, ensuring the primer remains intact and allowing for controlled adhesion and vulcanization, thereby preventing premature primer degradation and ensuring strong bonding between the elastomer and metal insert.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the injection mold temperature is maintained at high level throughout the process, then vulcanization efficiency is improved, but the primer degrades due to excessive temperature
Solution Approach 1:
The mold temperature is preliminarily set to a lower level during the injection phase to protect the primer from degradation, then adjusted to a higher level during the vulcanization phase to ensure proper curing. This preliminary temperature control prevents primer degradation before it occurs.
Solution Approach 2:
The mold temperature is made dynamic rather than static, varying at different stages of the manufacturing process. The temperature profile changes from a lower initial temperature during injection to a higher temperature during vulcanization, adapting to the different requirements of each phase.
2Manufacturing precision
If the mold temperature is increased to ensure vulcanization, then elastomer curing is improved, but primer adhesion deteriorates due to thermal degradation
Solution Approach 1:
The temperature application is divided into periodic stages: a first period with lower temperature during injection to preserve the primer, followed by a second period with higher temperature during vulcanization to cure the elastomer. This periodic temperature control ensures both primer integrity and elastomer curing.
3Device complexity
If conventional constant temperature process is used, then process simplicity is maintained, but adhesion reliability deteriorates for metal inserts with high surface area to volume ratio
Solution Approach 1:
The temperature parameter is changed at different stages of the process rather than maintaining a constant value. The mold temperature profile is optimized to be lower during injection and higher during vulcanization, improving adhesion reliability for challenging geometries like thin metal strips with high surface area to volume ratios.
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 ensures reliable adhesion of the elastomer to the metal insert across various configurations, including those with high surface area to volume ratios, enabling the production of timepiece components with improved mechanical properties and compatibility with diverse materials, such as thin metal strips and high thermal conductivity materials.
Implementation Method 1
a third step of vulcanizing the elastomer material, wherein the temperature of the injection mold is variable, the process comprising a step of increasing the temperature of the injection mold between a first temperature at a first instant during the injection second step, and a second temperature higher than the first temperature at a second instant, during the vulcanization third step
Data Source
AI summary
A process for manufacturing a timepiece component having a first step (E1) consisting in arranging a metal insert in an injection mold, one surface of said metal insert being at least partially coated with a primer, a second step (E2) of injecting an elastomer material into the injection mold in order to overmold the elastomer material over the metal insert, a third step (E3) of vulcanizing the elastomer material, wherein the temperature of the injection mold is variable, and a step (E31) of increasing the temperature of the injection mold between a first temperature at a first instant during the injection second step (E2), and a second temperature higher than the first temperature at a second instant, during the vulcanization third step (E3).