Fine-Gauge SMA Wire Crimping with Soft Tooling
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Solution Overview
Problem
There is a significant difficulty in effectively crimping shaped memory alloy (SMA) filament wire of finer gauge sizes due to existing techniques either distorting or damaging the filament, altering its mechanical characteristics, and no suitable solution exists for maintaining constant and uniform tensile stress during crimping, which is critical for length-critical applications.
Innovation Solution
A crimp apparatus and method using a carrier assembly with a novel crimp geometry that 'kinks' the filament without intrusion or over-compression, employing a softer material than the SMA to prevent damage, and maintaining tension during the crimping process to preserve mechanical properties, along with automated manufacturing equipment to produce precision crimp and wire assemblies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional crimping techniques are used on fine-gauge SMA wire, then the wire can be secured to the terminal, but the filament is distorted or damaged, altering its mechanical characteristics
Solution Approach 1:
The patent changes the material parameter of the crimping tool by using a softer material (durometer 20-40 Shore A) compared to conventional hard crimping tools. This parameter change allows the crimping tool to deform without damaging the fine-gauge SMA filament, securing the connection while preserving the filament's mechanical characteristics and strength.
2Reliability
If existing crimping methods are applied to fine-gauge SMA wire, then connection is achieved, but tensile stress is not maintained uniformly, affecting length-critical applications
Solution Approach 1:
The patent applies preliminary tensioning to the SMA filament before crimping, maintaining constant and uniform tensile stress throughout the crimping process. This preliminary action ensures that the filament is properly positioned and stressed uniformly, which is critical for length-critical applications such as artificial muscle actuators, before the crimping operation secures the connection.
3Reliability
If standard crimping pressure is used, then the filament is secured to the terminal, but the filament undergoes over-compression and damage
Solution Approach 1:
The patent changes the pressure parameter by using a softer crimping tool material (durometer 20-40 Shore A) that applies lower compression force compared to conventional hard crimping tools. This parameter change prevents over-compression and damage to the fine-gauge SMA filament while still achieving reliable mechanical and electrical connection to the terminal.
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
The solution effectively crimps fine-gauge SMA wire without damaging it, maintaining the desired mechanical properties and length relationships, ensuring the crimped wire's strength and reliability, particularly in precision applications like medical device actuators.
Implementation Method 1
The actuator comprises a biasing means which is normally biased in a first position and a shape memory alloy actuator element cooperatively engaged with the biasing means. The shape memory alloy actuator element in a first unactivated condition is biased in the first position by the biasing means.
Implementation Method 2
In a second unactivated condition, the actuator element biases and retains the biasing means in a second position. The actuator element in an activated condition biases the biasing means in the second position.
Data Source
Figure 1
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AI summary
Apparatus and methods for filament crimping. In one embodiment, the apparatus comprises a body and a filament crimp element. The filament crimp element comprises a first set of cavities disposed at a spacing which creates a first set of features and a second set of cavities disposed at a spacing which creates a second set of features. The first and second set cavities are substantially opposite one another. The first set of features are adapted to be placed at least partially within the second set of cavities and the second set of features are adapted to be placed at least partially within the first set of cavities. Methods and apparatus for the manufacture of the device are also disclosed. In addition, methods for automated placement and manufacture of assemblies using the crimp elements are also disclosed.