CNC Spindle Tool Mount Detection Under Ball Screw Thermal Expansion
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Solution Overview
Problem
The expansion and contraction of the feed shaft due to temperature changes affect the accuracy of determining the mounted state of a tool on the main shaft, making it difficult to distinguish between variations caused by thermal expansion and the actual tool mounting state.
Innovation Solution
A numerical control device that estimates the expansion and contraction amount of the feed shaft, acquires torque and rotation speed of the motor, and corrects the peak angle based on this estimation to accurately determine the tool's mounted state, using statistical processing to eliminate variations and ensure precise determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the peak position of the torque differential value is used to determine tool mounting state, then the determination method is simple, but thermal expansion and contraction of the feed shaft causes inaccurate determination
Solution Approach 1:
The patent replaces the direct mechanical measurement approach (using torque differential peak position) with a computational approach (calculating correction values based on motor temperature and rotation speed). This substitution allows the system to compensate for thermal expansion effects through calculation rather than relying solely on raw mechanical signals, thereby maintaining determination simplicity while improving accuracy.
Solution Approach 2:
The patent introduces new parameters (motor temperature, rotation speed, and correction values) to adjust the determination criteria. By changing the parameters used for determination from just peak position to peak position plus correction values derived from temperature and speed data, the system adapts to thermal conditions and maintains accurate tool mounting state detection despite feed shaft expansion and contraction.
2Measurement precision
If thermal expansion effects are compensated for using additional measurements and calculations, then determination accuracy is improved, but device complexity increases
Solution Approach 1:
The patent makes the motor serve multiple functions: it not only drives the feed shaft but also acts as a temperature sensor and speed sensor. By utilizing the motor's existing operational parameters (temperature and rotation speed) for dual purposes (driving and measurement), the system avoids adding separate sensing devices, thus improving determination accuracy without significantly increasing device complexity.
Solution Approach 2:
The motor's own operational parameters (temperature and rotation speed) are used to generate correction values for its own performance measurement. The system essentially uses the motor's self-generated data to compensate for the thermal effects it causes, eliminating the need for external correction mechanisms and reducing overall system complexity.
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 device accurately determines the tool's mounted state by accounting for thermal expansion and contraction, reducing errors in tool mounting detection and maintaining cutting accuracy.
Implementation Method 1
The feed shaft expands and contracts in the up-down direction due to a temperature change thereof
Data Source
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AI summary
The present invention provides a numerical control device and a determination method in which it is possible to accurately determine the mounting state of a tool on a main shaft. A numerical control device according to the present invention estimates the amount of expansion and contraction of a ball screw. The numerical control device acquires a rotation angle and disturbance force of a Z-axis motor. The numerical control device acquires the torque of the Z-axis motor to acquire the disturbance force included in the torque. The numerical control device determines the mounting state of a tool on a main shaft on the basis of the amount of expansion and contraction of the ball screw, and a peak angle determined by fluctuation of a derivative value, which is the time derivative of the disturbance force (S101).