Piezoelectric Spindle Assembly for Axial Chip-Breaking Oscillation
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Solution Overview
Problem
The use of piezoelectric elements in spindles for generating axial oscillations to break up chips during machining poses challenges such as fragility, limited elongation, risk of buckling, thermal energy dissipation, and power supply reliability, while also requiring a compact design to operate across a wide range of rotational speeds and efficiently evacuate chips.
Innovation Solution
A spindle design incorporating two stages of piezoelectric actuators with axial overlap, where the actuators are arranged to add their effects, and a preload system to maintain compression, along with flexible supports and a compact structure to integrate an electric motor, allowing for efficient generation of non-ultrasonic axial oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If piezoelectric actuators are used to generate axial oscillations for chip fragmentation, then machining efficiency is improved, but the actuators are fragile and require adequate loading systems
Solution Approach 1:
The actuator assembly is segmented into multiple piezoelectric actuators arranged in parallel around the spindle axis. Each actuator is a separate, manageable unit that can be individually loaded and supported, reducing the fragility risk of any single actuator while collectively generating the required axial oscillations for chip evacuation.
Solution Approach 2:
A preload system is implemented that applies compressive force to the piezoelectric actuators before operation. This pre-loading cushions the actuators against tensile stresses and potential buckling during operation, protecting them from damage while enabling them to generate the necessary axial oscillations for improved chip evacuation.
2Productivity
If piezoelectric actuators are used to generate axial oscillations, then chip fragmentation is improved, but the elongation of actuators is limited and buckling risk increases under high axial stress
Solution Approach 1:
Instead of using a single long actuator that would be prone to buckling, the system uses multiple shorter piezoelectric actuators arranged in parallel. Each actuator has sufficient buckling resistance due to its shorter length, while collectively they provide the necessary total elongation for chip fragmentation through their combined axial oscillations.
Solution Approach 2:
The preload system applies compressive force to counteract the tensile stresses that would cause buckling during actuator operation. This pre-cushioning allows the actuators to operate at higher stresses without risking buckling, enabling sufficient elongation for effective chip fragmentation.
3Speed
If piezoelectric actuators operate at high frequencies, then axial oscillations are generated effectively, but thermal energy dissipation increases and must be evacuated
Solution Approach 1:
Multiple piezoelectric actuators are merged into a single functional assembly operating in parallel. The thermal energy dissipation from each actuator is distributed and managed collectively, making it easier to evacuate heat from multiple smaller sources rather than from a single high-power actuator operating at high frequency.
4Adaptability or versatility
If the spindle is designed to be compact for wide rotational speed range, then adaptability is improved, but integrating power supply for piezoelectric elements becomes difficult
Solution Approach 1:
The spindle design integrates multiple functions into a compact structure. The same structural components that provide mechanical support and enable wide rotational speed range also serve as mounting structures and thermal management pathways for the piezoelectric actuators. This multi-functionality reduces the need for separate power supply integration systems, maintaining compactness while supporting the actuators.
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
This design enhances the spindle's ability to generate sufficient axial oscillations for chip fragmentation while maintaining a compact size, reducing energy requirements, and ensuring reliable power supply, enabling efficient machining and chip evacuation across various rotational speeds.
Implementation Method 1
a first exciter stage, comprising at least one piezoelectric actuator, a second exciter stage, comprising at least one piezoelectric actuator
Data Source
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AI summary
Spindle (10) for carrying out machining assisted by non-ultrasonic axial oscillations, comprising: - a tool-bearing shaft (12), and - an exciting portion, for subjecting the shaft to non-ultrasonic axial oscillations, especially during its rotation, this exciting portion comprising: o a first exciting stage, comprising at least one piezoelectric actuator (24), and o a second exciting stage, comprising at least one piezoelectric actuator (22), having a non-zero axial overlap with the first exciting stage, the actuators of the two stages being arranged so that their effects add.