Thermal Expansion Collet Tool Holder for High-Force Small Tools
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Solution Overview
Problem
Conventional collet systems face challenges in achieving high, reproducible, and automated clamping forces with high concentricity, particularly with smaller diameters, and are not suitable for automated operation.
Innovation Solution
A device and method utilizing a tool holder with a conical collet and an axially movable tensioner, where thermal expansion of the tool holder combined with friction-based clamping induces high clamping forces through a combination of shrink-fit and friction-based mechanisms, enabled by an inductive heating unit and rotary actuator, allowing for precise control and automation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional collets are used with smaller diameters, then the clamping force is naturally limited, but reducing the diameter is necessary for smaller tools
Solution Approach 1:
The patent changes the temperature parameter of the tool holder, heating it to cause thermal expansion. This expansion increases the internal diameter temporarily, allowing the collet to be inserted and clamped with much higher forces than would be possible at room temperature, thereby achieving high clamping force on small diameter tools
Solution Approach 2:
The tool holder is heated to expand thermally, creating a larger internal cavity that can accommodate the collet and tool shank. When the tool holder cools down, it contracts and generates enormous clamping forces on the collet, solving the limitation of conventional collets on small diameter applications
2Force
If the clamping nut is heated and tightened with higher torque, then higher clamping force is achieved, but the process becomes complex and automation is hardly possible
Solution Approach 1:
The patent extracts the heating function from the clamping mechanism itself and places it on the tool holder. This separation allows the clamping nut to remain simple and mechanical, while the thermal expansion of the tool holder provides the force multiplication, greatly simplifying the overall system and enabling automation
Solution Approach 2:
The patent replaces the complex mechanical system of heated clamping nuts with a simpler system where thermal expansion of the tool holder provides the expanding force. The clamping mechanism becomes purely mechanical with a simple nut and collet, while the force generation is achieved through thermal effects
3Force
If the collet is heated together with the clamping nut, then the heating unit must be removed before clamping, but this reduces productivity and increases cycle time
Solution Approach 1:
The patent extracts the heating function from the collet assembly and applies it only to the tool holder. This allows the collet and clamping nut to remain at room temperature throughout the process, eliminating the need to remove heating units and enabling continuous automated operation
Solution Approach 2:
The tool holder is heated in advance before the collet is inserted. This preliminary thermal expansion creates the necessary space for insertion, and the clamping can then proceed immediately as the holder begins to cool, optimizing the cycle time and enabling automation
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 achieves clamping forces 2 to 4 times higher than conventional shrink-fit chucks, ensures high reproducibility, and enables automated operation with improved concentricity and damping properties, independent of tool shank tolerances.
Implementation Method 1
heating unit for heating the tool holder in the region of the collet
Implementation Method 2
when the tool holder is thermally expanded
Implementation Method 3
friction-based clamping induced by the axial movement of the collet
Data Source
AI summary
A device for clamping and unclamping tools in a collet comprises a tool holder, a collet and a movable tensioner. The tool holder has a machine side and a tool side that is configured to accommodate a tool shank of a tool. The collet is arranged for clamping the tool shank inside the collet, the collet having a conical outer surface, which rests against a correspondingly shaped inner surface of the tool holder. The tensioner is configured to effect an axial movement of the collet with respect to the tool holder when the tool holder is thermally expanded, for clamping and unclamping the collet with the tool shank therein. The tensioner is arranged inside the tool holder on the machine side of the collet. A method is used to clamp tools in a collet of a tool holder.