Stress-Rod Tool Holder for Stronger Shrink-Fit Tool Retention
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Solution Overview
Problem
Conventional shrink-fit tool holders face issues with insufficient gripping strength and tool extraction due to inadequate thermal expansion coefficient differences between the tool-holding section and the tool shank, leading to potential failures in retaining the tool.
Innovation Solution
The introduction of stress fit rods around the circumference of the tool holder's bore, made from materials with a lower thermal expansion rate than the tool holder, which form bulges on the bore surface to mechanically lock the tool shank in place by adjusting their relative diameters through temperature changes or insertion by pressing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional shrink-fit tool holders use thermal expansion differences between tool-holding sections and tool shanks, then tool retention is achieved, but gripping strength is insufficient and tool extraction fails
Solution Approach 1:
The tool holder is segmented by introducing multiple stress rods distributed around the circumference of the bore. These rods divide the tool-holding section into distinct zones, each contributing to gripping strength. The segmentation allows localized stress application points that collectively enhance overall tool retention and gripping capability.
Solution Approach 2:
Stress rods are strategically positioned at specific locations around the bore circumference rather than uniformly distributed. This local quality approach places higher stress concentration points where they most effectively improve gripping strength, while maintaining appropriate clearance in other areas for tool insertion and thermal expansion.
2Reliability
If stress rods are added to enhance gripping strength, then tool retention improves, but device complexity increases
Solution Approach 1:
The stress rods are designed with specific dimensional parameters including diameter, length, and material properties that can be adjusted to optimize gripping strength. By carefully selecting these parameters, the system achieves enhanced tool retention without requiring an excessive number of rods or overly complex structural modifications to the holder.
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 enhances the gripping strength and extractability of the tool, allowing for a wider range of tool sizes and reducing the risk of overheating damage, while maintaining or improving the tool holder's structural integrity and efficiency in machining operations.
Implementation Method 1
a plurality of stress rods positioned around the bore and comprising a thermal rate of expansion less than a thermal rate of expansion of the tool holding section, wherein the plurality of stress rods form corresponding bulges on the surface of the bore
Implementation Method 2
The plurality of stress rods can be placed in the corresponding plurality of holes by changing the relative temperature of the plurality of stress rods and the tool holding section
Data Source
AI summary
A tool holding section opposite the first section with a bore formed in the tool holding section adapted for receiving the shank of the tool. A plurality of stress rods positioned around the bore and comprising a thermal rate of expansion less than a thermal rate of expansion of the tool holding section. The plurality of stress rods form corresponding bulges on the surface of the bore to decrease the inner diameter of the bore to mechanically lock the shank of the tool in the bore.