Tool Holder Tensioning Arrangement Thermal Expansion Centring
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Solution Overview
Problem
Existing tool holders are susceptible to vibrations during machining, leading to precision and reproducibility issues due to thermal expansion mismatches between materials, which can cause changes in tensioning force and centring problems, potentially damaging the assembly.
Innovation Solution
A tool holder with a tensioning arrangement that includes both axial and radial tensioning components, utilizing materials with lower thermal expansion coefficients, such as ceramics or hard metals, to maintain centring and prevent damage through flexible sliding surfaces, and incorporating modular design for easy adaptation and replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a tensioning arrangement with axial tensioning force is used to dampen vibrations, then vibration damping is improved, but thermal expansion mismatch causes changes in tensioning force and centring problems
Solution Approach 1:
The patent applies parameter changes by modifying the physical state of the tensioning arrangement through thermal tensioning. The tensioning arrangement is heated to expand it radially outward, creating permanent radial tensioning forces that compensate for thermal expansion mismatches during operation. This parameter change (thermal expansion of the tensioning arrangement) directly addresses the reliability issue by pre-compensating for dimensional changes that would otherwise cause centring problems.
Solution Approach 2:
The patent directly utilizes thermal expansion as the core mechanism. The tensioning arrangement is made of a material with higher thermal expansion coefficient than the tool holder base body. By heating the tensioning arrangement during assembly, it expands radially outward to contact and tension against the base body. Upon cooling, it contracts but maintains permanent radial tensioning, creating a pre-compressed state that stabilizes the assembly against further thermal expansion variations during machining operations.
2Reliability
If radial tensioning force component is added to maintain centring, then centring accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into a single integrated tensioning arrangement. The same component provides both axial tensioning (through its positioning between bearing surfaces) and radial tensioning (through thermally-induced radial expansion). This merging eliminates the need for separate axial and radial tensioning mechanisms, reducing overall device complexity while achieving both tensioning directions simultaneously.
Solution Approach 2:
The patent replaces complex mechanical centring and tensioning mechanisms with a thermally-actuated system. Instead of using multiple mechanical adjustment devices, bearings, or elastic elements to achieve radial tensioning, the invention uses controlled thermal expansion of the tensioning arrangement to generate the necessary radial forces. This substitution simplifies the mechanical structure while achieving the desired centring accuracy.
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 tool holder effectively dampens vibrations, maintains centring accuracy during thermal expansion, and allows for easy adaptation to different tools, ensuring high precision and reproducibility in machining operations.
Implementation Method 1
When the material used for the tensioning arrangement has a lower thermal expansion than the material of the rest of the tool holder, there is a risk that, in the event of thermal expansion, for example due to workpiece machining or thermal clamping or unclamping of a tool shaft, the tensioning force and thus the vibration damping changes, the centring of the tensioning arrangement with respect to the tool holder changes
Implementation Method 2
The axial tensioning introduced into the tool holder by the tensioning arrangement changes the spring properties of the tool holder, especially its spring rate in the tensioned axial section and thus of the tool holder overall relative to a mechanically untensioned state, as a result of which, given a suitable setting of the spring properties of the tool holder, excitable vibration properties and their associated resonance frequencies of the tool holder can be selectively altered
Implementation Method 3
Between the tool holder base body and tensioning arrangement are preferably arranged one or more damping elements, which damp axial and/or radial vibration of the tool holder or the tool holder base body with respect to the tensioning arrangement and vice versa
Data Source
AI summary
The present invention relates to a low-vibration tool holder (1) with a tool holder base body (2, 3, 4, 6) and a tensioning arrangement (5) which provides axial tensioning of the tool holder base body (2, 3, 4, 6) and which is simultaneously tensioned in a radially flexible way with respect to the tool holder base body (2, 3, 4, 6). This tool holder (1) is less susceptible to vibration than previously known tool holders, which ensures better true running even during operation and in particular when heat-induced expansion of materials occurs, since the clamping arrangement (5) which is integrated in the tool holder (1) is continuously centered with respect to the tool holder base body (2, 3, 4, 6). Furthermore, such a tool holder (1), in particular within a modular design, can be adapted very flexibly to different types of tools and workpiece machining processes.