Tool Holder Bore Embedding Compound for Grip Strength
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Solution Overview
Problem
Conventional shrink-fit tool holders fail to achieve sufficient gripping strength due to insufficient differences in thermal expansion coefficients between the tool-holding members and tool shanks, leading to inadequate retention of tools during machining operations.
Innovation Solution
Embedding a joining compound with a higher Young's modulus than the tool holder material into the bore of the tool holder, using a hard applicator to apply the compound under controlled temperature expansion, which increases the coefficient of static friction and mechanically locks the tool shank, employing materials like diamond, aluminum oxide, or tungsten carbide for enhanced grip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional shrink-fit tool holders are used with standard thermal expansion materials, then the tool holder structure is simple and manufacturing is easy, but the gripping strength is insufficient due to inadequate difference in thermal expansion coefficients
Solution Approach 1:
The tool holder is constructed using composite materials: the main body is made of high-expansion material (hot work tool steel or nickel-chromium steel) while the insert is made of low-expansion material (sintered carbide or high-speed steel). This composite structure creates sufficient difference in thermal expansion coefficients between the tool holder and tool shank, enabling strong gripping force during shrink-fit operations without requiring complex overall design changes
Solution Approach 2:
Instead of making the entire tool holder complex, the invention applies local quality enhancement by inserting a specific material component (low-expansion insert) only in the critical gripping region (bore area). This localized material substitution provides the necessary thermal expansion difference exactly where needed for strong tool retention, while keeping the rest of the tool holder structure relatively simple
2Strength
If the thermal expansion coefficient difference is increased to improve gripping strength, then the holding power increases, but the risk of material structure change and strength loss due to excessive heating increases
Solution Approach 1:
The invention changes the material parameter (thermal expansion coefficient) by selecting specific materials with appropriate properties: high-expansion material for the tool holder body and low-expansion material for the insert. This parameter selection enables effective shrink-fit gripping at moderate temperatures, avoiding the need for excessive heating that would cause material degradation
Solution Approach 2:
The invention utilizes thermal expansion principles by employing materials with different expansion coefficients. The high-expansion tool holder material expands more than the low-expansion insert and tool shank during controlled heating, creating the shrink-fit gripping force. The process is designed to operate within temperature ranges that achieve sufficient expansion without causing material structure changes or strength loss
3Ease of operation
If the tool shank and aperture sizes are precisely controlled for detachability, then the tool can be easily removed and reinstalled, but the heating required for shrinkage fitting must be minimized to prevent material degradation
Solution Approach 1:
The composite material structure with different thermal expansion coefficients allows for effective shrink-fit gripping at lower temperatures compared to conventional single-material designs. The high-expansion tool holder and low-expansion insert create sufficient gripping force with moderate heating, enabling tool detachment and reinstallation without subjecting the materials to degradation temperatures
Solution Approach 2:
By changing the material parameters (thermal expansion coefficients) of the tool holder components, the invention achieves effective tool retention at optimized temperature levels. The precise size control of tool shank and aperture is maintained while the heating temperature is kept within safe limits due to the enhanced efficiency of the composite material system
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 method significantly improves the gripping strength of the tool holder, providing a 400% increase in holding power and reducing the risk of tool slippage and damage to workpieces, while maintaining concentricity and resisting abrasion, thus enhancing the durability and extractability of tools.
Implementation Method 1
The joining compound is partially embedded into the surface of the bore by plastic deformation of the surface of the bore
Implementation Method 2
The applicator is fixed temporarily in the bore of the tool holder with the surface of the bore in a state of stress from heating the tool holder to expand the bore and allowing the bore to cool onto the applicator
Data Source
AI summary
Tool holder has a first section adapted to be connected to a machining center and a tool holding section comprising a bore with a surface defining an inner diameter of the bore. Dispersed around the surface of the bore and at least partially embedded in the surface of the bore is a joining compound having a Young's modulus greater than a Young's modulus of the surface of the bore.