Tool Runout Measurement Using Multi-Orientation Edge Sensing
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Solution Overview
Problem
Existing methods for measuring the runout of fluted cutting tools, such as dial test indicators and non-contact break-beam devices, are prone to errors due to the variation in radial position of teeth along the tool length, which complicates the accurate determination of Total Indicated Runout (TIR).
Innovation Solution
A method involving a tool edge sensor mounted to a machine tool that rotates the tool into multiple orientations, measures the tool edge position in each orientation, fits these positions to a function to determine the tool centre point, and calculates runout by comparing this centre point to the spindle centre line, thereby separating the effects of tool runout and circumferential position variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional DTI or non-contact break-beam devices measure tool runout by detecting the radial position of cutting teeth, then the measurement process is simple, but the measurement precision deteriorates due to variation in radial position of teeth along the tool length
Solution Approach 1:
The patent segments the tool edge measurement into multiple discrete points taken at different rotational orientations (at least three orientations). By dividing the circumferential measurement into separate angular positions, the system can fit these points to a circle to determine the tool centre point, thereby separating runout effects from tooth position variations and improving TIR measurement accuracy.
Solution Approach 2:
The patent transitions from measuring only radial position (one dimension) to measuring positional coordinates in multiple dimensions by taking measurements at different rotational orientations. This multi-orientational approach adds the angular dimension to the measurement, enabling the system to distinguish between runout (deviation from spindle centre line) and circumferential tooth position variations through circular fitting.
2Measurement precision
If measurements are taken at multiple rotational orientations to improve accuracy, then measurement precision improves, but the measurement time increases
Solution Approach 1:
The patent uses at least three rotational orientations for measurement, which is the minimum required to perform circular fitting and determine the tool centre point accurately. This partial action approach achieves the necessary measurement precision without taking excessive measurements, thereby balancing accuracy requirements with measurement time efficiency.
Data Source
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AI summary
A method and apparatus are described for determining the runout of a tool (12) retained by a rotatable spindle of a machine tool using a tool edge sensor, such as a non-contact tool setter (2), mounted to the machine tool. The spindle is arranged to rotate the tool, which may be a fluted cutting tool, about a spindle centre line (20). The technique comprises rotating the spindle into three or more rotational orientations and using the tool edge sensor to measure a position of the edge of the tool (12) for each of the three or more rotational orientations. A tool centre point is found by fitting the positions of the tool edge to a function and a difference in position between the tool centre point and the spindle centre line (20) is used to determine a runout of the tool.