Machine Tool Spindle Bearing Sensing for Diameter Change Tracking
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Solution Overview
Problem
Current methods for measuring the load on a machine tool's spindle axis and detecting bearing abnormalities are limited, as they struggle to accurately account for changes in spindle rigidity due to centrifugal and thermal deformations, and cannot handle cases where the diameter of the measurement target changes simultaneously with axial displacement.
Innovation Solution
A calculation method and device that uses sensors at multiple positions on a plane orthogonal to the spindle axis to measure radial displacement and diameter changes, incorporating compressed gas to detect pressure changes and calculate these measurements, allowing for precise monitoring of bearing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a non-contact displacement sensor is used to measure axial displacement, then the cutting load can be converted from axial displacement, but the measurement accuracy deteriorates when the diameter of the measurement target changes simultaneously
Solution Approach 1:
The patent transitions from measuring only axial displacement (one dimension) to measuring both axial displacement and radial displacement (adding another dimension). By placing sensors at multiple positions around the spindle and measuring radial displacements in addition to axial displacement, the system can detect changes in spindle diameter and accurately calculate cutting loads even when the measurement target diameter changes during operation.
2Measurement precision
If the rigidity of the bearing is considered to convert axial displacement to cutting load, then the cutting load measurement accuracy is improved, but the complexity of the system increases due to the need to account for thermal deformation and centrifugal deformation
Solution Approach 1:
The patent replaces the complex mechanical approach of directly measuring and accounting for bearing rigidity changes, thermal deformation, and centrifugal deformation with a sensor-based measurement system. By using non-contact displacement sensors to directly measure radial and axial displacements, the system indirectly captures the effects of bearing rigidity changes without requiring separate sensors or complex calculations for each deformation component, thus reducing overall system complexity while maintaining measurement accuracy.
Solution Approach 2:
The patent introduces radial displacement measurement as an intermediary parameter that connects axial displacement to cutting load. Instead of directly measuring bearing rigidity or thermal deformation, the system uses radial displacement at multiple sensor positions as an intermediate indicator that reflects the combined effects of centrifugal deformation, thermal expansion, and bearing rigidity changes, simplifying the measurement chain.
3Ease of operation
If three measurement points are used to calculate center deviation, then the calculation of axial displacement vector and diameter change is enabled, but the measurement of radial displacement and diameter change simultaneously becomes insufficient
Solution Approach 1:
The patent divides the measurement system into multiple independent sensor units positioned around the spindle, with each sensor measuring displacement at its specific location. By segmenting the measurement into multiple radial positions and combining these measurements, the system can calculate both radial displacement and diameter changes with higher precision than a single three-point measurement system, while maintaining ease of calculation through standardized processing of each sensor's data.
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 accurate measurement of radial displacement and diameter changes, effectively prolonging bearing life by detecting abnormalities and adjusting operating conditions, while maintaining high-speed and high-accuracy operation of the spindle device.
Implementation Method 1
measuring an axial displacement using a non-contact displacement sensor such as an eddy current displacement sensor
Implementation Method 2
supplying compressed gas to a measurement target gap between a rotating member and a housing from at least three directions around a bearing to detect pressure change of the compressed gas
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
Provided is a calculation method used for a bearing device including a rotating member, a bearing which supports the rotating member so that the rotating member can rotate, a housing which holds the bearing, and sensors which are installed in the housing or a non-rotating part of the bearing to measure a distance to a surface that rotates with the rotating member, where an amount of change in a diameter of the rotating member is calculated based on measurement results by the sensors provided at three or more positions on a plane orthogonal to a rotation axis of the rotating member.