Collet Workholding Mechanism for Damage-Free Gripping
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Solution Overview
Problem
Existing work-holding solutions in manufacturing often damage workpieces, are incompatible with various operations, and interfere with machining processes, particularly due to the use of swinging clamps and serrated mandrels that can scratch or scar the workpiece, and are limited in versatility across different workpiece orientations and configurations.
Innovation Solution
A work-holding mechanism utilizing a threaded adaptor and arbor with conical surfaces, a draw cylinder, and a collet with radially expanding fingers, actuated by a servo screw drive, which securely grips the workpiece without damaging it and is compatible with multiple orientations and configurations, allowing precise control and high torque loads without biting or scarring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If swinging clamps or serrated mandrels are used to hold the workpiece, then gripping force is improved, but the workpiece surface is damaged (scratched or scarred)
Solution Approach 1:
The patent changes the fundamental parameter of gripping mechanism from mechanical biting (serrated mandrels) or leveraged clamping (swinging clamps) to hydraulic expansion. The collet is actuated by a draw bar that applies axial force, causing the collet to expand radially and grip the workpiece through distributed pressure rather than concentrated biting forces, thereby maintaining high grip force while preventing surface damage
Solution Approach 2:
The patent replaces the mechanical swinging clamp system with a hydraulic actuation system. The draw bar, when actuated hydraulically, pushes the collet to expand and grip the workpiece. This substitution eliminates the need for mechanical leverage and swinging motion, providing more controlled and uniform gripping force that avoids workpiece damage
2Measurement precision
If locating work stops are used to prevent workpiece pulling, then positioning accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent merges the positioning and gripping functions into a single integrated collet assembly. The collet, when expanded, simultaneously grips the workpiece and maintains its position through the hydraulic actuation system, eliminating the need for separate locating work stops. The draw bar mechanism provides both the gripping force and the positioning reference in one system
Solution Approach 2:
The collet assembly serves multiple functions: it provides gripping force, maintains positioning accuracy, and prevents workpiece pulling all through a single mechanism. The hydraulic actuation system enables the collet to perform these multiple functions without requiring additional separate components like traditional locating stops
3Extent of automation
If hydraulic or pneumatic actuation is used to drive the draw bar, then automation is improved, but control precision deteriorates
Solution Approach 1:
The patent incorporates a feedback mechanism where the expanded collet's grip on the workpiece provides tactile feedback to the hydraulic system. The draw bar's axial movement is directly coupled to the collet's radial expansion, creating a self-regulating system that automatically adjusts the gripping force based on the workpiece's presence and resistance, thereby maintaining precision control while fully automated
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 provides a secure, damage-free, and versatile work-holding mechanism that ensures accurate positioning and high gripping forces, reducing the risk of workpiece damage and interference with machining processes, while being adaptable to various workpiece configurations and orientations.
Implementation Method 1
The collet can include axially extending channels that define fingers therebetween and interior coaxial surfaces that are configured to communicate with the exterior coaxial surfaces of the shaft portion of the arbor, such that axially downward movement of the collet moves the fingers in a radially outward direction
Implementation Method 2
a threaded adaptor that is configured to be rotated by the actuator, and an arbor including a flange portion and a shaft portion... A draw cylinder can be disposed in communication with the threaded adaptor, such that rotation of the threaded adaptor moves the draw cylinder in axially upward and downward directions
Data Source
AI summary
Some embodiments are directed to a fixing apparatus that includes a threaded adaptor, an arbor having a flange portion and a shaft portion, and a draw cylinder disposed such that rotation of the threaded adaptor moves the draw cylinder in axially upward and downward directions. A collet can be disposed around a periphery of the arbor so as to be coaxial with the draw cylinder, such that movement of the draw cylinder in the axially downward direction causes the draw cylinder to contact the collet and thereby cause the collet to also move in the axially downward direction. The collet can include axially extending channels that define fingers therebetween and interior coaxial surfaces that are configured to communicate with exterior coaxial surfaces of the arbor such that axially downward movement of the collet moves the fingers in a radially outward direction to thereby increase an exterior diameter of the collet.