Metrological Apparatus Stylus Data Processor for Surface Measurement

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Solution Overview

Problem

Measuring surface characteristics, particularly for steep-sided aspheric lenses and moulds, is challenging due to high contact angles and access issues, leading to potential stylus slipping, dragging, or collisions, which can result in inaccurate measurements and damage.

Innovation Solution

A metrological apparatus with a pivotally mounted stylus arm and a data processor that adjusts measurement data values to ensure a balanced gauge measurement, simulating surface profiles to determine optimal measurement start conditions, and assists operators in setting up the instrument to avoid out-of-range contact angles and collisions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the stylus arm is inclined to the support surface to reduce contact angle, then measurement accuracy improves, but instrument setup complexity increases

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidinstrument setup complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The data processor performs preliminary calculations to determine optimal measurement start conditions (initial gauge reading and traverse position) before the actual measurement begins. This pre-computation allows the instrument to be set up in a conventional position while automatically compensating for the inclined measurement geometry, thereby maintaining measurement accuracy without increasing physical setup complexity

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system creates a computational model (copy) of the workpiece surface based on nominal surface data and uses this model to simulate measurements and determine optimal measurement conditions. This virtual copy allows the system to pre-determine the best measurement approach without requiring physical adjustment of the stylus arm inclination

Inventive Principle:

Principle #26Copying

2Reliability

If the stylus contact angle is reduced to prevent slipping and dragging, then measurement reliability improves, but the measurement path length increases

Engineering Contradiction:

Improvemeasurement reliabilityVSAvoidmeasurement path length

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The system changes the measurement parameters by calculating optimal initial gauge readings and traverse positions based on the workpiece geometry and stylus configuration. By adjusting these parameters computationally, the system ensures the stylus maintains an optimal contact angle throughout the measurement, preventing slipping and dragging while minimizing the actual measurement path length

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If manual setup procedures are used to adjust stylus orientation, then measurement precision can be achieved, but setup time increases

Engineering Contradiction:

Improvemeasurement precisionVSAvoidsetup time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The data processor automatically performs the function of manual setup by computing optimal measurement start conditions based on input parameters (workpiece geometry, stylus characteristics, measurement path). The system serves itself by eliminating the need for operator intervention in the complex calculations and adjustments, thereby achieving measurement precision without the time cost of manual setup procedures

Inventive Principle:

Principle #25Self-service

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

Facilitates rapid and accurate surface measurements by reducing the risk of stylus slipping and collisions, improving measurement precision and speed, and simplifying the setup process for operators.

Implementation Method 1

detecting, using a transducer, the deflection of the stylus arm as a tip of a stylus carried by the stylus arm follows variation in the form of the surface

Methodology Applied

Scientific EffectTransducer detection:

Data Source

PatentEP2820377B1Data processor for a metrological apparatus for measuring a surface characteristic of a workpiece and corresponding measuring method

Publication Date: 2020.04.01 TAYLOR-HOBSON

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AI summary

In a metrological apparatus a stylus (11) is deflected as a stylus tip of the stylus follows surface variations along a measurement path on a surface of a workpiece and a transducer (39) provides measurement data in a measurement coordinate system. A data processor is configured to: determine a relationship between the measurement data in the measurement coordinate system and nominal surface data representing the expected surface characteristic of the workpiece in a workpiece coordinate system; simulate a measurement data set for the nominal surface using the nominal surface data and the determined relationship, the simulation providing a simulated measurement data set having a simulated range of simulated measurement values; if the simulated range does not meet a given criterion, adjust a selected measurement data value for a selected measurement point and repeat the simulation to determine an adjusted measurement data value for which the simulated range meets the given criterion; and determine measurement start conditions required for a measurement procedure to provide the adjusted measurement data value for the selected measurement point.