Machine Tool Thermal Displacement Compensation Using Position Sensor Feedback
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Solution Overview
Problem
Existing thermal displacement compensation methods for machine tools fail to accurately account for variations in thermal displacement across different positions of the feed axis, particularly due to changes in ambient temperatures, leading to inaccuracies in precision machining.
Innovation Solution
A method and device that utilize a position sensor to detect the feed axis position, calculate compensation errors, and modify thermal displacement compensation amounts based on these errors, allowing for precise compensation of thermal displacements without relying on sensor measurements for ambient temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal displacement compensation is performed based on feed shaft position and speed without considering ambient temperature changes, then compensation accuracy at measured positions is improved, but compensation accuracy at other positions deteriorates and ambient temperature variations are not accounted for
Solution Approach 1:
The invention modifies the thermal displacement compensation amount by introducing a compensation error derived from position sensor measurements. The system changes the compensation parameter (compensation amount) based on the detected deviation between initial and actual positions, thereby adapting to ambient temperature variations and improving overall compensation accuracy across all positions.
2Manufacturing precision
If the entire stroke of feed shaft is divided into multiple sections with position detection at each section, then thermal displacement can be estimated for each section, but device complexity and cost increase
Solution Approach 1:
The invention extracts only the essential information needed for compensation by using a single position sensor to detect the feed shaft position at specific points. Instead of installing sensors at every section, the system takes out the minimum necessary measurement (position at initial point and current point) to calculate compensation error, thereby reducing device complexity while maintaining compensation accuracy.
3Device complexity
If thermal displacement compensation is performed without using position sensors, then device complexity is reduced, but compensation accuracy deteriorates due to inability to detect actual position deviations
Solution Approach 1:
The invention implements a feedback mechanism where the position sensor detects the actual feed shaft position, compares it with the initial position, and uses the detected deviation (compensation error) to modify the thermal displacement compensation amount. This feedback loop enables the system to continuously adjust compensation based on actual position deviations, significantly improving compensation accuracy while maintaining relatively simple device structure.
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 high-precision thermal displacement compensation by adjusting compensation amounts in real-time based on detected positions, effectively addressing thermal variations independent of machine operation, such as ambient temperature changes, without affecting machining time or requiring special position detection operations.
Implementation Method 1
setting a position sensor in a detectable position where the position of a movable part of the machine tool is detectable such that the position sensor outputs a signal when the detectable position is reached by the movable part
Implementation Method 2
a feed screw and spindle are driven by a motor, so that they are expanded by heat from the motor, frictional heat from rotating bearings, frictional heat from an engaging portion between a ball screw and nut of the feed screw, thereby causing a shift in machine position
Data Source
AI summary
In a thermal displacement compensation method for a machine tool, in which a feed shaft thermal displacement amount is obtained and an amount which cancels the obtained feed shaft thermal displacement amount is added as a thermal displacement compensation amount to a position command for a feed axis, a position where a signal is first output by a position sensor for detecting the position of a movable part of the machine tool is first stored as an initial position. Then, the position where the signal is output by the position sensor is detected, and the thermal displacement compensation amount is modified according to a compensation error, which is the difference between the detected position (actual position) and the initial position.