Machining Method Suppressing Chatter Vibration via Variable Spindle Speed
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Solution Overview
Problem
Conventional machining methods, such as varying spindle rotational speed in triangular or sinusoidal waves, fail to sufficiently suppress self-excited chatter vibration due to limited variation rates near peak and minimum values, leading to incomplete disruption of the regeneration effect between cutting resistance and thickness variation.
Innovation Solution
A machining method where the spindle rotational speed is varied in a periodic or non-periodic waveform with a predetermined amplitude, and the relative moving speed between the tool and workpiece is synchronized to maintain a non-constant ratio, especially around maximal and minimal rotational speed points, effectively breaking the periodicity of cutting resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the spindle rotational speed is varied in a triangular wave or sinusoidal wave, then the periodicity of cutting resistance is broken to some extent, but self-excited chatter vibration cannot be sufficiently suppressed near peak and minimum values
Solution Approach 1:
The patent applies dynamics by making the spindle rotational speed variable rather than constant. The rotational speed is varied in a periodic manner (triangular wave, sinusoidal wave, or other periodic waves) to dynamically change the cutting conditions and break the regeneration effect that causes self-excited chatter vibration. This dynamic variation prevents the system from settling into a stable vibrational state.
Solution Approach 2:
The patent changes the parameter of rotational speed from a constant value to a periodically varying value. By modifying the rotational speed parameter according to a predetermined periodic waveform, the cutting speed varies periodically, which disrupts the periodic variation in cutting resistance and thickness of cut that sustains self-excited chatter vibration.
2Object-affected harmful factors
If the rotational speed variation amplitude is increased to improve chatter suppression, then the regeneration effect is disrupted more effectively, but the complexity of speed control increases
Solution Approach 1:
The patent employs periodic action by varying the rotational speed according to a periodic waveform (such as triangular wave, sinusoidal wave, or other periodic waves). This periodic variation in rotational speed creates a corresponding periodic variation in cutting speed, which disrupts the periodic nature of the regeneration effect and prevents self-excited chatter vibration from being sustained.
Solution Approach 2:
The patent implements feedback control where the actual rotational speed is monitored and compared with the target rotational speed, and the spindle motor is controlled based on this comparison to achieve accurate speed variation. This feedback mechanism ensures that the rotational speed follows the desired periodic waveform while maintaining stability and precision.
Data Source
AI summary
A machine tool includes a spindle retaining a tool, a spindle motor, a feed device relatively moving a workpiece and a tool with a feed motor, a spindle motor control unit, and a feed motor control unit. In a method of machining a workpiece with the machine tool, the spindle motor control unit continuously varies a rotational speed of the spindle in a periodic or non-periodic manner with a predetermined amplitude with respect to a target rotational speed. The feed motor control unit continuously varies a relative moving speed between the tool and the workpiece in synchronization with the spindle motor such that a ratio of the rotational speed of the spindle to the moving speed does not become constant at least in a predetermined time zone in which a spindle speed reaches a maximal value and a predetermined time zone in which the spindle speed reaches a minimal value.