Radial Compression Die Mechanism for Constant Die Gap Control
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Solution Overview
Problem
Existing radial compression mechanisms for medical devices like stents and catheters suffer from issues such as varying die gaps, positional inaccuracies, and inconsistent compression due to design tradeoffs, leading to potential damage and manufacturing challenges.
Innovation Solution
A radial compression mechanism featuring a circular array of dies with interface surfaces and cam guides that allow for linear motion and controlled die positioning, using rolling elements and low-friction surfaces to maintain a constant die gap and ensure accurate compression, with a rotating cam plate and actuator arm for mechanical advantage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If wedge-shaped dies with hinged connection are used to form cylindrical cavity, then the mechanism size can be reduced, but the die gap varies with cavity diameter causing compression inconsistency
Solution Approach 1:
The mechanism divides the cavity formation into multiple independent wedge-shaped dies (typically 6-12 dies) arranged circumferentially. Each die can be independently positioned and controlled, allowing the gap between dies to be maintained within a specified tolerance (e.g., ±0.05mm) regardless of cavity diameter changes. This segmentation enables consistent compression across varying diameters while keeping each individual die compact.
Solution Approach 2:
The die positioning system incorporates dynamic adjustment capabilities through cam mechanisms that allow real-time modification of die positions and orientations during operation. This dynamic control ensures that as the cavity diameter changes during compression, the dies automatically maintain optimal spacing and alignment, preventing gap variation and ensuring uniform compression force distribution.
2Manufacturing precision
If linear guides with individual die constraints are used, then die gap can be kept constant, but the positional accuracy of dies decreases due to multiple parts influencing roundness
Solution Approach 1:
The cam mechanism integrates multiple functions into a single coordinated system: it simultaneously controls die positioning, orientation, and motion synchronization. The cam profile is precisely engineered to maintain constant die spacing while guiding all dies through identical rotational paths, ensuring both gap constancy and cavity roundness. This merged control eliminates the cumulative errors that would arise from multiple independent linear guides.
Solution Approach 2:
The cam mechanism acts as an intermediary element between the drive system and the individual dies. Rather than directly constraining each die with separate linear guides, the cam translates rotational motion into synchronized radial motion of all dies, maintaining both constant spacing and precise circular paths. This intermediary control mechanism reduces the number of independent constraint elements while improving overall positioning accuracy.
3Manufacturing precision
If more dies are arranged in circular array, then compression uniformity improves, but the mechanism size and complexity increase
Solution Approach 1:
The mechanism is designed with modular die assemblies that can be configured in different numbers (e.g., 6, 8, 10, or 12 dies) depending on the specific application requirements. Each die assembly is identical and interchangeable, allowing the same basic mechanism design to achieve different levels of compression uniformity. This universality enables optimization of compression precision without requiring entirely different mechanism architectures.
Solution Approach 2:
The cam-driven dynamic control system allows the mechanism to adapt to different die configurations. Whether 6 or 12 dies are used, the cam profile can be adjusted or reconfigured to maintain optimal spacing and synchronization. This dynamic adaptability means the mechanism achieves high compression uniformity with fewer dies compared to static systems, reducing overall complexity while maintaining precision.
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 solution provides precise and consistent radial compression with minimal die gap variation, ensuring accurate positional relationship and effective compression of medical devices across varying diameters, enhancing manufacturing accuracy and reducing the risk of device damage.
Implementation Method 1
Rolling elements may be configured between adjacent dies to reduce friction and enable smooth compression
Implementation Method 2
A low friction surface may be configured between compression dies in the interface surface
Data Source
AI summary
A radial compression mechanism incorporates a plurality of compression die assemblies arranged radially about and forming a central cylindrical cavity. The die assemblies are coupled to a cam plate by a cam bearing retained in cam guide slots in the cam plate. The cam plate is configured to rotate about the central axis of the central cylindrical cavity and thereby rotate the plurality of compression dies about the central axis. The plurality of dies are constrained by a stationary guide slot configured in the housing of the radial compression mechanism and this stationary guide slot forces the compression dies to move radially inward to close the cylindrical cavity. Therefore, the compression dies both rotate about the central cylindrical cavity and move radially inward to close the cylindrical cavity. This arrangement and die displacement mechanism reduces the size or area required by the dies. Therefore the mechanism can be made smaller.