Rail-Guided Linear Scale Layout for Thermally Stable Machine Tools
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Solution Overview
Problem
Existing machine tools fail to accurately account for thermal expansion and deformation in both spindle stocks and tool rests, leading to precision issues in position measurement, particularly when the linear scale is not optimally positioned to detect the distance between the tool tip and the work center.
Innovation Solution
A machine tool design where a linear scale is positioned over the spindle stock and tool rest, allowing it to move in the Z-axis direction, maintaining its position relative to the tool tip and work center, and is supported by a rail that extends along the spindle's central axis, ensuring precise detection of position changes due to thermal expansion or deformation.
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 measurement is less affected by ball screw abrasion and thermal expansion, but the measurement does not account for spindle stock inclination or tool rest displacement
Solution Approach 1:
The linear scale is made movable in the Z-axis direction through a rail-guided mechanism, allowing it to dynamically adjust its position and maintain alignment with the workpiece center despite thermal expansion or inclination of the spindle stock. This dynamic adjustment capability enables the scale to continuously provide accurate position measurements under varying thermal conditions.
Solution Approach 2:
The linear scale acts as an intermediary measurement device positioned between the spindle stock and tool rest, reading position information from a scale portion attached to the spindle stock while being mechanically independent through the rail guidance system. This intermediary positioning allows it to measure the actual distance between tool tip and work center without being directly affected by thermal deformation of either component.
2Stability of the object's composition
If the linear scale is fixed on the spindle stock, then the measurement is stable against ball screw issues, but the measurement becomes inaccurate when the spindle stock inclines or thermally expands
Solution Approach 1:
The linear scale transitions from a fixed mounting to a dynamically adjustable position through the rail guidance mechanism. This allows the scale to move in the Z-axis direction and maintain proper alignment with the workpiece center even when the spindle stock undergoes thermal expansion or inclination, thereby preserving measurement precision while maintaining system stability.
Solution Approach 2:
The positional parameter of the linear scale is changed from fixed to variable, enabling it to adjust its Z-axis position in response to thermal deformation of the spindle stock. This parameter change allows the measurement system to compensate for thermal effects while maintaining stable operation.
3Ease of manufacture
If the linear scale is positioned away from the tool to simplify mounting, then the scale installation is easier, but the measurement is more affected by thermal expansion and geometric precision issues
Solution Approach 1:
The linear scale serves as an intermediary measurement device that reads position information from the spindle stock side while being mechanically independent through rail guidance. This intermediary positioning allows the scale to be mounted on the spindle stock (maintaining ease of installation) while still providing accurate measurements of the tool-workpiece distance by compensating for thermal expansion and geometric deviations through its movable design.
4Measurement precision
If the linear scale is made movable in the Z-axis direction, then the measurement accounts for thermal deformation, but the device complexity increases
Solution Approach 1:
The movable linear scale provides continuous feedback on the actual position of the tool relative to the workpiece center by reading the scale portion on the spindle stock. This feedback mechanism enables the control system to compensate for thermal deformation and maintain measurement precision without requiring complex active compensation systems, as the scale's position automatically reflects the current thermal state of the machine.
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 impact of thermal effects on position detection, maintaining stable measurement values regardless of spindle stock and tool rest movements, and preventing measurement errors caused by heat transmission or foreign matter adherence.
Implementation Method 1
a linear scale disposed over the spindle stock and the tool rest on an upper side in the X-axis direction to detect position information in the X-axis direction
Implementation Method 2
a rail extending in the Z-axis direction to guide movement of the linear scale in the Z-axis direction
Data Source
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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.