Machine Tool Thermal Displacement Correction After High-Speed Spindle Stop
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Solution Overview
Problem
Existing methods for correcting thermal displacement in machine tools, such as those using touch trigger probes and reference tools, are inadequate when the spindle is rotated at high speed, leading to measurement accuracy deterioration due to thermal distortion, especially when measurements are taken after the spindle has stopped and cooled.
Innovation Solution
A thermal displacement correction method and apparatus that sets an initial tool temperature using historical data, spindle temperature, and ambient conditions, estimates tool temperature based on these parameters, and applies a thermal displacement correction formula to accurately account for temperature changes in the tool-mounted portion, regardless of mounting timing, using different formulas depending on spindle rotation status and tool exchange events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the spindle is rotated at high speed for machining and then measurement is performed immediately after stopping, then productivity is improved by eliminating waiting time, but measurement precision deteriorates due to thermal distortion from heat transmission to the tool or sensor
Solution Approach 1:
The system performs preliminary actions by recording the spindle rotation history and tool mounting timing before measurement occurs. This allows the correction amount calculation unit to predict and compensate for thermal distortion in advance, enabling accurate measurements without waiting for the spindle to cool down completely.
Solution Approach 2:
The system implements feedback by continuously monitoring spindle rotation status, tool mounting timing, and temperature changes. The correction amount is calculated based on this feedback information and applied to adjust measurement values, creating a closed-loop system that maintains measurement accuracy despite thermal conditions.
2Device complexity
If the tool temperature is assumed to instantaneously match the spindle temperature upon mounting, then device complexity is reduced by simplifying the estimation model, but measurement precision deteriorates due to large estimation errors in the transient state
Solution Approach 1:
The system transitions from a static assumption (instantaneous temperature matching) to a dynamic model that accounts for the time-dependent thermal response. By incorporating the elapsed time since tool mounting and using exponential decay functions, the system accurately captures the transient thermal state without excessive complexity.
Solution Approach 2:
The system changes the estimation parameters based on the thermal state. Different correction models are applied depending on whether the spindle is rotating or stopped, and the correction amount varies continuously based on the elapsed time since tool mounting, allowing accurate temperature estimation across different operational phases.
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 allows for high-accuracy thermal displacement correction of tools and position measurement sensors, improving processing and measurement accuracy by accurately estimating temperature changes and thermal displacement, even when tools are mounted after the spindle has stopped and cooled.
Implementation Method 1
transmission of heat of the spindle to the touch trigger probe generates the thermal distortion
Data Source
AI summary
A thermal displacement correction method is provided, including a first step of setting an initial tool temperature, a second step of estimating a temperature of a tool or a position measurement sensor based on the initial tool temperature and a temperature of a spindle, a third step of estimating an amount of thermal displacement of the tool or the position measurement sensor with a preliminarily set tool thermal displacement estimation formula based on the estimated temperature, and a fourth step of moving a feed shaft of the machine tool based on the estimated amount of thermal displacement to perform a correction. In the second step, the temperature of the spindle is measured, then a tool-mounted portion temperature of the spindle is estimated from the measured temperature.