Linear Scale Layout for Thermally Stable Machine Tool Positioning
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Solution Overview
Problem
Existing machine tools fail to maintain high precision in position control due to thermal expansion and deformation, particularly affecting the spindle stock and tool rest, which are not adequately considered in existing feedback systems.
Innovation Solution
A machine tool design with a linear scale positioned over the spindle stock and tool rest, allowing for relative movement in the X-axis and Z-axis directions, and a rail system that guides the linear scale to maintain its position close to the tool attachment and work center, reducing the impact of thermal effects on measurement precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the linear scale is placed near the machining origin on the spindle stock side, then the position feedback precision is improved, but the measurement is affected by thermal expansion and deformation of the tool rest
Solution Approach 1:
The linear scale is repositioned from the spindle stock side to the tool rest side, changing the spatial dimension and location of measurement. This dimensional change allows the scale to be positioned closer to the tool tip, reducing the measurement distance and minimizing the impact of thermal expansion and deformation on measurement accuracy.
Solution Approach 2:
The patent replaces the traditional mechanical positioning system with an optical measurement system (linear scale with laser beam). This substitution eliminates mechanical contact and friction, reducing thermal effects and improving measurement precision while maintaining the ability to compensate for thermal expansion through software algorithms.
2Measurement precision
If the linear scale is positioned close to the tool attachment, then the measurement precision is improved, but the scale is exposed to thermal effects from the tool rest
Solution Approach 1:
The patent introduces thermal compensation algorithms as an intermediary between the linear scale measurement and the final position control. The scale measures position, but thermal effects are compensated through software calculations that reference temperature sensors and material expansion coefficients, effectively mediating between the physical measurement and the controlled output.
Solution Approach 2:
The system dynamically changes measurement parameters by adjusting the reference temperature and expansion coefficients based on real-time temperature monitoring. When thermal effects are detected, the system modifies the position calculation parameters to compensate for thermal expansion, maintaining measurement accuracy despite temperature variations.
3Adaptability or versatility
If the tool rest moves away from the scale portion, then the tool positioning flexibility is improved, but the position feedback accuracy deteriorates
Solution Approach 1:
The patent implements a closed-loop feedback system where the linear scale continuously provides position information back to the control system. The scale reads position at all times, and the control system uses this feedback to maintain accurate tool positioning even when the tool rest moves to various locations, ensuring both flexibility and precision.
Solution Approach 2:
The linear scale is designed with universal applicability to measure positions across the entire range of tool rest movement. The scale system serves multiple functions: measuring tool rest position, compensating for thermal expansion, and maintaining accuracy across different machining operations, making it adaptable to various positioning scenarios.
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 configuration enhances precision by minimizing the effect of thermal expansion and deformation on position detection, ensuring stable and accurate measurement of the distance between the tool tip and work center, even during spindle stock and tool rest movement.
Implementation Method 1
thermal expansion and deformation, particularly affecting the spindle stock and tool rest
Implementation Method 2
thermal expansion and deformation, particularly affecting the spindle stock and tool rest
Implementation Method 3
a rail extending in the Z-axis direction to guide movement of the linear scale in the Z-axis direction
Data Source
AI summary
A machine tool with a spindle stock 20 and a tool rest 40 mounted on a bed 11, in which the spindle stock 20 and the tool rest 40 are able to relatively move in an X-axis direction that is a diameter direction of a spindle and a Z-axis direction that is an axial direction of the spindle, includes: a linear scale 50 disposed over the spindle stock 20 and the tool rest 40 on an upper side in the X-axis direction to detect position information in the X-axis direction; and a rail 23 extending in the Z-axis direction, and the linear scale 50 moves in the Z-axis direction while guided by the rail 23 integrally with either the spindle stock 20 or the tool rest 40 when the spindle stock 20 and the tool rest 40 relatively move in the Z-axis direction.