Scanning Probe Compensation Table for Measurement Error Correction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing surface scan measuring devices face challenges in accurately measuring workpiece profiles due to detection errors caused by stylus flexure and sphericity of the contact portion, leading to measurement inaccuracies and difficulties in correcting these errors using compensation coefficients alone.

Innovation Solution

A surface scan measuring device with a scanning probe that uses a compensation table to correct detected values based on specific measurement directions, incorporating compensation coefficients and offset values to accurately determine the relative position between the measuring piece and the workpiece surface, thereby improving measurement accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If compensation coefficients are used to correct detection errors, then measurement accuracy is improved, but measurement precision deteriorates due to insufficient correction of stylus flexure and sphericity effects

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidcorrection precision

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent divides the compensation into two independent parts: compensation coefficients for detection errors and offset values for geometric errors (stylus flexure and sphericity). This segmentation allows each compensation mechanism to address specific error sources independently, improving overall correction precision.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary calculation process that determines the offset value based on the relationship between the contact portion and workpiece surface. This intermediary step bridges the gap between detection data and actual measurement, enabling more precise correction of geometric errors.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the contact portion is pressed to the workpiece surface by a reference displacement amount, then measurement reliability is improved, but measurement precision deteriorates due to stylus flexure and sphericity effects

Engineering Contradiction:

Improvemeasurement reliabilityVSAvoidprofile measurement accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent converts the harmful effects of stylus flexure and contact portion sphericity into correctable parameters. By measuring the actual displacement during pressing and comparing it with the reference displacement amount, the system calculates offset values that compensate for these geometric deviations, turning them from sources of error into correctable variations.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the measurement approach by introducing a new parameter (offset value) that accounts for the relationship between the contact portion and workpiece surface. This parameter change allows the system to maintain the reliable pressing contact while correcting the resulting geometric measurement errors.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If detection errors are corrected using compensation coefficients, then ease of operation is improved, but measurement precision worsens due to inability to fully correct directional errors

Engineering Contradiction:

Improveerror correction easeVSAvoidcoordinate value accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent segments the error correction process into two distinct components: compensation coefficients for detection errors and offset values for geometric errors. This segmentation makes the correction process more systematic and complete, addressing both detection and geometric error sources independently.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent adds a new dimension to the error correction by introducing offset values that account for the spatial relationship between the contact portion and workpiece surface. This dimensional addition enables correction of errors that were previously uncorrectable, improving coordinate value accuracy.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS7376261B2Surface scan measuring device and method of forming compensation table for scanning probe

Publication Date: 2008.05.20 MITUTOYO CORP

AI summary

A measuring system includes a coordinate measuring machine for driving a scanning probe and a host computer. The host computer includes a compensation table (53) and a profile analysis unit (54). The compensation table stores, as compensation data, compensation coefficients to correct counter values of a probe counter (415), and compensation radiuses “r” to the workpiece surface concerning central coordinate values of a contact portion, for respective contact directions. The profile analysis unit has a contact direction calculation unit (542), a compensation data selection unit (543), a compensation calculation unit (544). The contact direction calculation unit calculates the contact direction along which the scanning probe comes into contact with a workpiece W, and the compensation data selection unit selects compensation data set up in the compensation table based on thus calculated contact direction.