Machine Tool Calibration Using Measurement Probe

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Solution Overview

Problem

Existing methods for calibrating the axis of rotation in machine tools like lathes and mill-turn machines are either time-consuming or prone to errors, particularly when relying on sacrificial cuts or manual measurements.

Innovation Solution

A method using a measurement probe to determine the position of a feature on a rotatable portion, rotating it through an angle, and calculating the axis of rotation based on position measurements, allowing for automated calibration without the need for sacrificial cuts or assumptions about feature equidistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If manual methods like dial test indicators are used to determine the axis of rotation, then measurement capability is achieved, but machine downtime increases and reproducibility decreases

Engineering Contradiction:

Improveaxis of rotation determinationVSAvoidmachine downtime

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces manual mechanical measurement methods (dial test indicators) with an automated measurement probe system that can be integrated into the machine tool's control system. The probe automatically measures feature positions at different rotational orientations, and the controller calculates the axis of rotation, eliminating manual intervention and reducing downtime while maintaining measurement accuracy.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If sacrificial cuts are made to establish the centre line, then the axis of rotation can be determined, but the process becomes time consuming and material is wasted

Engineering Contradiction:

Improvecentre line establishmentVSAvoidcalibration speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent extracts the calibration process from the workpiece itself, eliminating the need for sacrificial cuts. Instead of using the workpiece or dedicated calibration pieces that require cutting, the method uses a measurement probe to measure features on the chuck or machine components directly, calculating the axis of rotation from these measurements without removing any material.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent eliminates the need for expensive or time-consuming sacrificial calibration pieces. By using the measurement probe to directly measure existing features and calculate the axis through mathematical processing, the method replaces physical sacrificial cuts with a virtual calibration process that is both faster and less material-intensive.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Productivity

If automated calibration methods are implemented, then machine downtime is reduced, but complexity of the calibration system increases

Engineering Contradiction:

Improvecalibration speedVSAvoidcalibration system complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent makes the measurement probe multi-functional by enabling it to perform both workpiece measurement and machine calibration functions. The same probe used for measuring part features can also determine the axis of rotation by measuring features at different rotational positions, eliminating the need for separate calibration equipment and reducing overall system complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The calibration system performs self-calibration using its own measurement capabilities. The measurement probe measures features on the machine components, the controller processes these measurements to calculate the axis of rotation, and the system automatically updates its reference frame without requiring external calibration equipment or complex additional hardware.

Inventive Principle:

Principle #25Self-service

4Ease of manufacture

If features are assumed to be equidistant from the centre line, then calibration is simplified, but measurement accuracy is compromised

Engineering Contradiction:

Improvecalibration simplicityVSAvoidaxis of rotation accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

Instead of assuming features are equidistant from the centre line and using that assumption to find the axis, the patent inverts the approach: it measures the actual positions of features at different rotational orientations and calculates the true axis of rotation from these measurements. This mathematical approach determines the centre line based on actual geometry rather than assumptions, significantly improving accuracy.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentEP2287687B1Method of machine tool calibration

Publication Date: 2017.09.27 RENISHAW PLC

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Figure 4a~4e

AI summary

Methods are described for calibrating a machine (30) having a first rotatable portion or chuck (4;32;202) for holding a workpiece. The first rotatable portion (4;32;202) has a first feature (6;34;206) associated therewith. The method comprises the steps of using a measurement probe (10;38;204;236) to determine the position of the first feature (6;34;206), rotating the first rotatable portion (4;32;202) through an angle, and using said measurement probe (10;38;204;236) to determine the new position of the first feature(6;34;206). The method also comprises translating at least one of the measurement probe (10;38;204;236) and the first rotatable portion (4;32;202) along a translational axis and repeating the measurement.