Spindle-Mounted Diameter Measurement for Thermal Drift Accuracy
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Solution Overview
Problem
Existing workpiece measurement methods in machine tools face accuracy issues due to unstable positional relationships caused by thermal displacement and interference from cutting chips, leading to measurement errors in workpiece diameter.
Innovation Solution
A machine tool equipped with a displacement sensor mounted inside a guide bush or spindle supporting unit, which measures the workpiece at a short distance and in the same environment, with a temperature sensor to correct measurement values, ensuring accurate diameter calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the measuring instrument is attached to a tool post or bed, then the measurement can be performed, but the positional relationship becomes unstable due to thermal displacement in multiple structures
Solution Approach 1:
The patent divides the measurement system into two independent parts: the workpiece support system (spindle and workpiece) and the measurement system (displacement sensor). By mounting the displacement sensor directly on the spindle, the patent eliminates the need for long transmission paths through multiple structures like tool posts and beds, thereby reducing thermal displacement errors and improving positional stability.
2Ease of operation
If the measuring instrument is placed at a distance from the workpiece, then the measurement can be performed, but measurement errors increase due to thermal displacement in intermediate structures
Solution Approach 1:
The patent uses the spindle as an intermediary carrier to mount the displacement sensor directly near the workpiece. This intermediary approach allows the sensor to be positioned close to the measurement point without requiring long external transmission paths, thereby maintaining measurement accessibility while improving precision by eliminating thermal displacement errors in intermediate structures.
3Measurement 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 patent extracts the measurement function from the workpiece holding mechanism (claws). Instead of using claws that can trap cutting chips, the patent employs a displacement sensor that non-contactively measures the workpiece diameter. This extraction of the measurement function eliminates the harmful effect of cutting chip interference while maintaining measurement precision.
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.
Implementation Method 1
a displacement sensor installed inside of at least one of a guide bush and a supporting unit for the spindle
Implementation Method 2
The machine tool of the invention is further provided with a temperature sensor which measures a temperature around a position where the displacement sensor is mounted
Data Source
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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 predetermiend measurement position in the axial direction to allow the displacement sensor to measure the machined portion.