Single-Ball Vibratory Spindle for High-Speed Chip Breaking
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Solution Overview
Problem
Existing vibration drilling technologies face limitations in achieving high rotational speeds without generating excessive mechanical loads, particularly when producing small-diameter holes, and are economically unviable with electromechanical or piezoelectric solutions.
Innovation Solution
A spindle design with a single ball interposed between fixed and movable rolling bearing rings, utilizing an inclined rolling bearing surface to induce axial oscillations, allowing high rotational speeds up to 10,000 rpm and reducing mechanical wear and imbalance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional vibration drilling with rolling bearings having undulating surfaces is used, then axial oscillations are generated to break up chips and improve drilling performance, but the rotational speed is limited to around 10,000 rpm due to excessive mechanical loads from inertia of moving parts
Solution Approach 1:
The invention extracts the oscillation-generating function from the complex undulating surface mechanism and concentrates it into a single ball rolling on an inclined surface. This simplification removes the cage and multiple rolling elements, reducing the inertia of moving parts and allowing operation at rotational speeds above 10,000 rpm while maintaining axial oscillations for chip breaking
Solution Approach 2:
The invention changes the fundamental parameter of oscillation generation from undulating surface geometry to inclined surface geometry with a single ball. This parameter change transforms the system from one limited by multi-part inertia to one dominated by single-ball inertia, enabling higher rotational speeds while preserving the beneficial axial oscillation effect
2Productivity
If small-diameter drill bits are driven at high rotational speeds (around 20,000 rpm) in conventional non-vibration drilling to maintain cutting speed, then productivity is improved, but chip evacuation becomes difficult due to longer chip formation
Solution Approach 1:
The invention applies mechanical vibration in the form of axial oscillations generated by the single ball rolling on the inclined surface. This vibration superimposes on the rotational motion, creating a reciprocating axial movement that continuously breaks up chips during cutting, preventing long chip formation even at high rotational speeds of 20,000 rpm or above
Solution Approach 2:
The single ball rolling on the inclined surface generates periodic axial oscillations that occur continuously during rotation. This periodic action ensures regular chip breaking intervals, maintaining short chip length and effective chip evacuation throughout the drilling process at high speeds
3Speed
If electromechanical or piezoelectric elements are used to decouple oscillation frequency from rotational speed, then high-frequency oscillations can be achieved, but the solution becomes much more expensive and complex
Solution Approach 1:
The invention replaces complex electromechanical or piezoelectric oscillation generation systems with a purely mechanical single-ball-on-inclined-surface mechanism. This substitution achieves decoupling of oscillation frequency from rotational speed through mechanical geometry alone, avoiding the high cost and complexity of electronic control systems while enabling oscillation frequencies above 300 Hz
Solution Approach 2:
The invention changes the mechanism of frequency control from electronic/piezoelectric actuation to mechanical geometry of the inclined surface and ball radius. This parameter change allows oscillation frequency to be determined by rotational speed and geometric parameters, achieving high frequencies without complex control systems
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
Enables high-frequency axial oscillations compatible with high rotational speeds, effectively reducing chip length and maintaining productivity without significant mechanical wear or complexity, suitable for replacing conventional spindles without modification.
Implementation Method 1
one of these rings defining an inclined rolling bearing surface that is not perpendicular to the axis of rotation of the shaft, such that the rotation of the ball brings about an axial oscillation of the shaft
Data Source
AI summary
A spindle for a machine tool, including a housing, a shaft for driving a cutting tool, rotatably mounted inside the housing with a possibility of axial movement relative to the housing, a single ball, axially interposed between a bearing ring fixed relative to the housing and a bearing ring movable with the shaft, one of these rolling rings defining an inclined bearing surface that is not perpendicular to the axis of rotation of the shaft, so that the rotation of the ball generates an axial oscillation of the shaft.