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Author:Syrjälä, Tommi
Title:Tolerance Design and Coordinate Measurement in Product Development
Toleranssisuunnittelu ja koordinaattimittaus osana tuotekehitystä
Publication type:Master's thesis
Publication year:2004
Pages:130      Language:   eng
Department/School:Konetekniikan osasto
Main subject:Koneensuunnitteluoppi   (Kon-41)
Supervisor:Ekman, Kalevi
Instructor:Makkonen, Petri
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  5905   | Archive
Keywords:tolerance design
computer-aided tolerancing (CAT)
coordinate measurement
measurement uncertainty
repeatability and reproducibility
Abstract (eng):The main purpose of the work was to compare the coordinate measurement results of a particle detector support structure to a computer-aided tolerance analysis and simulation.
Another aim was to ensure and improve the long-term reliability and repeatability of the coordinate measurement process of the product.
To support the objectives of the thesis, the theories of tolerance design and coordinate measurement were extensively reviewed.

The first manufacturing batches, comprising tens of support structures, were measured with a computer-controlled coordinate-measuring machine equipped with a touch-trigger probe.
Instead of just measuring each support structure once, an extensive set of repetitive measurements of a single structure was made to estimate measurement repeatability and reproducibility that describe the measurement uncertainty.
Moreover, the measurement process was documented in detail.
Simultaneously, the product was analysed with a high-end computer-aided tolerancing software package by creating a digital virtual model, which simulates the assembly of the components by taking into account the 3D-geometry, geometric tolerances, functional feature relationships, assembly sequence and methods.

The results of the measured variables were illustrated with histograms.
The form and range of the distributions were very similar in the actual measurement and in the simulation results.
However, clear mean shifts existed in the actual measurement results, which could not be estimated with the simulation.
This is probably mainly due to the accuracy of the assembly jig and partly due to measurement uncertainty.
In any case, computer-aided tolerancing seemed to estimate 3-dimensional variation realistically.
Yet, great emphasis has to be laid on deep understanding of geometrical tolerances and co-operation between design and manufacture in order to get reliable simulation results.

The repeatability and reproducibility estimates gave important information about the measurement capability.
Yet, they do not include all the systematic errors.
The documentation of the measurement process along with the uncertainty estimates improved the reliability of the measurement process and will help maintain it in the course of the whole manufacturing period.
All the objectives of the thesis were met.
ED:2004-03-05
INSSI record number: 21288
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