Endmill Tooth and Frequency Design for Chatter-Stable Machining
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Solution Overview
Problem
Existing endmill processing methods face challenges with regenerative chatter vibrations, especially at high speeds, leading to defective surfaces and prolonged processing times.
Innovation Solution
The method involves setting the natural frequency ω1 and/or the number of teeth N of the endmill to satisfy specific conditions related to the radial depth of cut, allowing for stable high-speed machining by optimizing spindle speed and reducing chatter vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a protruding long tool (L/D≥5) is used to process complicated aircraft structural components, then the product height and integration are improved, but regenerative chatter vibration occurs causing defective surfaces and lengthened processing time
Solution Approach 1:
The invention utilizes controlled mechanical vibration by superimposing a vibration signal on the spindle rotation. The vibration frequency is set to match the natural frequency of the tool-workpiece system, creating a beneficial resonance that prevents harmful regenerative chatter vibration. This allows the long protruding tool to maintain stability and produce high-quality surfaces despite its length.
Solution Approach 2:
The invention applies periodic vibration action to the spindle rotation through a vibration generator. By introducing periodic vibrations at specific frequencies (matching natural frequencies of the system), the cutting process experiences controlled oscillations that prevent the buildup of regenerative chatter vibrations, enabling stable high-speed machining with long tools.
2Reliability
If a stable pocket (low rotation speed region) is used to avoid regenerative chatter vibration, then surface quality is improved, but processing time is extremely lengthened
Solution Approach 1:
The invention introduces periodic vibration to the cutting process, enabling stable machining at high rotation speeds rather than being confined to low-speed stable pockets. The periodic vibration disrupts the regenerative chatter mechanism, allowing the use of higher spindle speeds that significantly reduce processing time while maintaining surface quality.
Solution Approach 2:
The invention changes the vibration parameters (frequency and amplitude) to match the natural frequency of the tool-workpiece system. By setting the vibration frequency equal to the natural frequency, the system enters a beneficial resonance state that prevents chatter vibration, allowing operation in high-speed regions rather than low-speed stable pockets.
3Productivity
If single finishing is used to finish a side surface in one step, then processing time is reduced, but large vibration is generated due to large axial cutting
Solution Approach 1:
The invention applies mechanical vibration to the spindle during single finishing operations. The vibration frequency is set to match the natural frequency of the system, creating a controlled resonance that prevents large vibrations despite the large axial cutting depths used in single finishing. This enables one-step finishing without excessive vibration.
Solution Approach 2:
The invention introduces periodic vibration action during single finishing to counteract the large vibrations caused by deep axial cutting. The periodic vibrations at natural frequency create a stabilizing effect that allows aggressive single-pass finishing while maintaining vibration stability and surface quality.
4Length of moving object
If a tool with long overhang length is used, then accessibility to deep pockets is improved, but damping performance is reduced making the stable region narrow and unstable
Solution Approach 1:
The invention uses controlled mechanical vibration at the natural frequency of the long-overhang tool system to prevent harmful vibrations. By matching the vibration frequency to the natural frequency, the system enters a beneficial resonance state that stabilizes the cutting process, compensating for the reduced damping performance inherent in long-overhang tools.
Solution Approach 2:
The invention changes the vibration parameters (frequency and amplitude) to optimize performance for long-overhang tools. By setting the vibration frequency equal to the natural frequency of the specific tool configuration, the system achieves maximum stability in the cutting zone, expanding the effective stable region despite the long overhang length.
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 approach enables stable and efficient high-speed machining, expanding the stable machining region and reducing the likelihood of regenerative chatter vibrations, thus improving surface quality and processing efficiency.
Implementation Method 1
PTL 1 discloses a method of using an effect (process damping) in which a tool and a workpiece are damped by coming into contact with each other during processing in a case of low-speed cutting.
Implementation Method 2
the protruding long tool has a problem of a regenerative chatter vibration generated on the tool side, thereby causing a problem in that a processed surface may be defective
Data Source
AI summary
Provided is an endmill. The maximum spindle speed, per one minute, of a main spindle to which the endmill is attached is Smax. The number of teeth of the endmill is N. The outer shape of the endmill is Da. The natural frequency at which vibrations at the end of the endmill reach a maximum level is ω1. ω1 and/or N are set so that when the diameter-direction infeed amount of the endmill is set to Rd: i) ω1×60/N×6<Smax, if Rd is at least 4% of Da; and ii) ω1×60/N×3<Smax, if Rd is less than 4% of Da.