Machine Tool Workpiece Diameter Sensing Under Thermal Displacement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing workpiece measurement methods in machine tools suffer from measurement errors due to unstable positional relationships between measuring instruments and workpieces, caused by thermal displacement and interference from cutting chips, leading to inaccurate diameter measurements.
Innovation Solution
A machine tool equipped with a displacement sensor mounted on a guide bush or spindle supporting unit, which measures the workpiece at a short distance and in the same environment, allowing for accurate diameter calculation, and includes a temperature sensor to correct measurement values for thermal variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the measuring instrument is mounted on a tool post or bed, then the measurement can be performed, but the positional relationship between the instrument and workpiece becomes unstable due to thermal displacement
Solution Approach 1:
The measuring instrument is merged with the guide bush or spindle supporting unit, which are components that are thermally coupled to both the spindle and the workpiece. This merging ensures that the instrument, guide bush, and workpiece experience the same thermal expansion, maintaining stable relative positions during measurement.
Solution Approach 2:
The guide bush or spindle supporting unit serves as an intermediary structure that provides a stable mounting position for the measuring instrument. These components are positioned such that they are thermally affected by both the spindle and workpiece, acting as a reference that maintains consistent dimensional relationships despite temperature changes.
2Measurement precision
If claws are used to hold the workpiece for measurement, then the workpiece can be gripped, but cutting chips may be caught in the claws reducing measurement accuracy
Solution Approach 1:
The measuring instrument is extracted from contact-based gripping mechanisms like claws and positioned to measure the workpiece through non-contact means (such as optical or capacitive sensors). This extraction eliminates the problem of cutting chips being trapped between gripping surfaces while still enabling accurate diameter measurement.
3Measurement precision
If the displacement sensor is mounted on the guide bush or spindle supporting unit, then the measurement error is minimized, but the device complexity increases
Solution Approach 1:
The guide bush or spindle supporting unit is designed to serve multiple functions: it provides structural support for the workpiece or spindle, guides movement, and simultaneously serves as a mounting platform for the measuring instrument. This multi-functionality reduces the need for separate dedicated measurement structures, thereby limiting the increase in device complexity.
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 setup provides precise workpiece diameter measurements with minimal error, effectively mitigating the impact of thermal displacement and environmental factors, and allows for accurate thermal displacement correction, enhancing machining accuracy.
Implementation Method 1
a displacement sensor mounted on at least one of a guide bush for the workpiece and a supporting unit for the spindle
Implementation Method 2
a temperature sensor which measures a temperature around a position where the displacement sensor is mounted
Data Source
AI summary
A machine tool improving measurement accuracy of a machined workpiece diameter. A machine tool comprises a displacement sensor mounted on at least one of a guide bush and a spindle supporting unit. The machine tool further comprises a calculating unit which calculates a diameter of the machined workpiece based on a measurement value of the machined workpiece by the displacement sensor. The spindle is movable back and forth in an axial direction. The spindle is retracted after machining to bring a machined portion of the workpiece to a predetermined measurement position in the axial direction to allow the displacement sensor to measure the machined portion.