Tire Mold Pin Design for Cracking Prevention
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Solution Overview
Problem
Cracking occurs around insertion holes in studded tires due to the removal of mold pins during the tire vulcanization process, leading to a decrease in the holding force of stud pins, tire appearance, and performance.
Innovation Solution
A tire mold design featuring sector molds with end and middle mold pins of varying diameters and lengths, where the end mold pins have a larger trunk diameter and smaller tip diameter, and middle mold pins have a smaller trunk diameter and larger tip diameter, reducing stress on the rubber during removal and preventing cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If mold pins are removed from insertion holes after vulcanization, then the tire can be released from the mold, but cracking occurs around the insertion holes causing decreased holding force and performance
Solution Approach 1:
The mold pin is designed with non-uniform diameter along its length, creating different local qualities: a larger diameter at the base portion for stable formation of the first hole portion, and a smaller diameter at the tip portion for easier removal. This local variation in diameter allows the pin to perform both formation and removal functions effectively without causing cracking.
Solution Approach 2:
The invention changes the geometric parameter of the mold pin by varying its diameter along the length. The base portion has a first diameter while the tip portion has a second diameter that is smaller, creating a tapered or stepped profile. This parameter change enables the pin to form holes accurately while reducing stress during removal, preventing cracking around insertion holes.
2Ease of manufacture
If uniform diameter mold pins are used, then manufacturing is simpler, but cracking occurs during removal due to stress concentration
Solution Approach 1:
The mold pin incorporates local quality variation through its non-uniform diameter profile. The base portion maintains a larger diameter for structural stability during hole formation, while the tip portion has a reduced diameter that minimizes stress concentration during removal. This local differentiation eliminates cracking while remaining manufacturable through standard machining processes.
Solution Approach 2:
The reduced diameter at the tip portion acts as a beforehand cushioning feature that anticipates the removal stress. By designing the pin with a smaller tip diameter, the invention pre-compensates for the stress that will occur during mold release, preventing cracking before it can happen during the removal process.
3Reliability
If end mold pins have larger trunk diameter, then cracking is suppressed during removal, but device complexity increases due to multiple pin types
Solution Approach 1:
The mold pin design incorporates local quality variation with a larger base portion diameter and a smaller tip portion diameter. This non-uniform diameter profile is applied consistently across all mold pins, allowing them to function effectively at different positions (end or middle) in the mold without requiring completely different pin designs, thus limiting complexity while maintaining reliability.
Solution Approach 2:
The non-uniform diameter mold pin design serves as a universal solution that can be applied to all mold pins regardless of their position in the mold. The same base-to-tip diameter reduction principle works for both end mold pins and middle mold pins, creating a multi-functional design that suppresses cracking throughout the entire tire mold system without requiring entirely different pin types for different locations.
Data Source
AI summary
A tire mold comprises sector molds for forming a tread portion of a tire and mold pins provided on the sector molds for forming insertion holes in the tread portion. The insertion holes each comprise a first hole portion with a first inner diameter where a body portion of a stud pin is disposed and a second hole portion with a second inner diameter greater than the first inner diameter where a bottom flange portion of the stud pin is disposed. The mold pins each comprise a trunk portion with a first outer diameter for forming the first hole portion and a tip portion with a second outer diameter greater than the first outer diameter for forming the second hole portion.