Tool Holder Thermal Decoupling for Measurement Accuracy
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Solution Overview
Problem
High-speed machining in machine tools leads to heat accumulation, causing tool holders and tools to expand, which can result in inaccurate measurements if not accounted for, as existing cooling systems cannot fully dissipate heat and current materials with low thermal expansion coefficients are not widely used.
Innovation Solution
A tool holder with a material section having a smaller coefficient of linear expansion and thermal conductivity, extending over more than 50% of the cut surface in the axial direction, provides thermal decoupling between the tool holder and spindle, reducing thermal expansion and heat input, allowing for minimal dimensional changes, typically less than 2 µm, thereby maintaining measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional tool holder material is used, then the tool holder can be manufactured easily and cost-effectively, but the tool holder experiences significant thermal expansion when exposed to heat from the spindle, compromising measurement accuracy
Solution Approach 1:
The tool holder is constructed as a composite structure combining two different materials: a conventional tool holder material (e.g., steel) and a material with low thermal expansion coefficient (e.g., Invar, ceramic, or polymer). The first material section provides structural strength and stability, while the second material section extending over more than 50% of the cut surface in the axial direction compensates for thermal expansion effects, thereby maintaining measurement accuracy without significantly complicating manufacturing
Solution Approach 2:
Instead of manufacturing the entire tool holder from expensive low-expansion material, the patent applies the low-expansion material locally in a specific section that extends over more than 50% of the cut surface in the axial direction. This localized application targets the critical area most affected by thermal expansion while keeping other parts made from conventional, easier-to-manufacture materials
2Manufacturing precision
If the tool holder is made entirely from material with low thermal expansion coefficient, then thermal expansion is minimized, but the manufacturing complexity and cost increase significantly
Solution Approach 1:
The tool holder employs a composite material structure where a first material section (conventional material) and a second material section (low thermal expansion material) are combined. The second material extends over more than 50% of the cut surface in the axial direction, providing sufficient dimensional stability to compensate for thermal expansion without requiring the entire tool holder to be made from complex low-expansion material
Solution Approach 2:
The patent changes the material parameter (thermal expansion coefficient) in a specific section of the tool holder. By selecting materials with different thermal expansion coefficients and positioning the low-expansion material in the critical section extending over more than 50% of the cut surface, the overall thermal expansion of the tool holder is reduced to an acceptable level without requiring complete material replacement
3Temperature
If cooling systems are enhanced to dissipate more heat, then less heat is transferred to the tool holder, but the system complexity and energy consumption increase
Solution Approach 1:
Instead of trying to eliminate the harmful heat through more complex cooling systems, the patent converts the thermal challenge into a material selection challenge. By using a composite structure with low thermal expansion material in the critical section extending over more than 50% of the cut surface, the tool holder naturally compensates for thermal effects, turning the heat problem into an opportunity to demonstrate material science solutions rather than requiring additional active cooling complexity
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 minimizes thermal expansion of the tool holder, ensuring high measurement accuracy by reducing heat transfer from the spindle, allowing the tool holder and probe to maintain precise dimensions during machining tasks.
Implementation Method 1
a material section which differs from the usual base material of a tool holder in that it has a smaller coefficient of linear expansion α and/or a smaller thermal conductivity λ
Implementation Method 2
a material section which differs from the usual base material of a tool holder in that it has a smaller coefficient of linear expansion α
Data Source
AI summary
The invention relates to a tool holder (2), particularly for a measuring sensor (3), having an interface (5) to a spindle (1) of a machine tool. The tool holder (2) comprises a material section (6) as viewed from the interface (5) for the spindle (1), said section differing from the common base material of a tool holder (2) by a smaller longitudinal expansion coefficient a and/or lower thermal conductivity ?. According to the invention, the material section (6) forms a thermal decoupling between the section of the tool holder (2) on the tool side and a tool (3) of the tool spindle (1) received therein for reducing a longitudinal change due to a heat input coming from a comparatively hotter tool spindle.