Shape Memory Workpiece Forming with Multi-Step Thermal Expansion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for shaping shape memory workpieces, such as stents and heart valve frames, face challenges including damage during deformation, complex process control, and inefficient energy use due to large diameter ratios and excessive stretching, which hinder precise imprinting of temperature-related and superelastic properties.
Innovation Solution
A method involving multiple expansion steps with temperature changes to an intermediate temperature below or above the shaping temperature, followed by reheating to the original shaping temperature, allows for gentle expansion and precise control of shape memory properties, reducing damage and energy consumption by allowing the shape memory workpiece to be cooled independently, thereby enabling precise adjustment of diameter and material properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a shape memory workpiece is expanded in a single step with a large diameter ratio, then productivity is improved, but damage occurs during deformation due to locally excessive strain
Solution Approach 1:
The expansion process is divided into multiple sequential expansion steps with intermediate temperature changes. Between each expansion step, the workpiece is cooled to an intermediate temperature below the forming temperature or heated to an intermediate temperature above the forming temperature, then reheated to the forming temperature before the next expansion step. This segmentation reduces locally excessive strain in each individual step while achieving the overall large diameter ratio expansion, preventing damage and ensuring reliable imprinting of shape memory properties.
2Reliability
If progressive expansion with multiple steps is used to avoid damage, then reliability is improved, but process complexity and energy consumption increase
Solution Approach 1:
The process utilizes controlled changes in temperature parameters between expansion steps. By cooling to intermediate temperatures below the forming temperature or heating to intermediate temperatures above the forming temperature, and then reheating to the forming temperature, the material properties are temporarily modified to facilitate controlled expansion. This parameter-based control simplifies the overall process management compared to purely mechanical control, enabling reliable multi-step expansion with manageable complexity.
3Manufacturing precision
If the workpiece is cooled together with the forming tool after expansion, then manufacturing precision is improved, but energy consumption increases significantly
Solution Approach 1:
The workpiece is ejected from the forming tool after expansion to a separate cooling station. This extraction allows the workpiece to be cooled independently without cooling the entire forming tool. The forming tool retains its heat and can be reused for the next workpiece, significantly reducing energy consumption. The separate cooling station cools only the individual workpiece to the cooling temperature below the intermediate temperature, maintaining manufacturing precision while minimizing energy waste.
4Manufacturing precision
If intermediate temperature changes are implemented between expansion steps, then manufacturing precision is improved, but process time increases
Solution Approach 1:
The intermediate temperature changes and reheating steps are integrated into a continuous expansion process. The cooling to intermediate temperatures and subsequent reheating to forming temperatures are performed sequentially without interrupting the overall expansion workflow. This continuous approach minimizes idle time and ensures that each temperature change directly contributes to the next expansion step, maintaining manufacturing precision while reducing unnecessary process delays.
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 method enables the shaping of shape memory workpieces with reduced damage and improved precision in imprinting shape memory properties, particularly suitable for high-demand applications like medical devices, while being energy and time-efficient.
Implementation Method 1
Shape memory workpieces exhibit different states depending on environmental conditions and are characterized by the fact that even slight changes in these conditions can cause significant changes in the shape or geometry of the workpiece
Implementation Method 2
heating the shape memory workpiece to the forming temperature
Implementation Method 3
cooling the shape memory workpiece to a cooling temperature below the intermediate temperature
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present invention relates to a method for forming a shape memory workpiece and a forming tool for forming a shape memory workpiece, wherein the method particularly comprises the following steps: - providing a shape memory workpiece having a first diameter and a predetermined forming temperature; - arranging the shape memory workpiece on a forming tool; - heating the shape memory workpiece to the forming temperature; - first expanding the shape memory workpiece to a second diameter larger than the first diameter; - first changing the temperature of the shape memory workpiece to an intermediate temperature below or above the forming temperature; - reheating the shape memory workpiece to the forming temperature; - second expanding the shape memory workpiece to a third diameter larger than the second diameter;- Ejection of the shape memory workpiece from the forming tool; and - final cooling of the shape memory workpiece to a cooling temperature below the intermediate temperature. Furthermore, a forming tool is provided for forming a shape memory workpiece.