Introduction to N.C.M., a Non Contact Measurement Tool

By Dennis R. Branch

This book is designed for the quality professional and student. It explains what a non contact measurement tool is, what it does, how it takes a measurement, why it would be used, how to utilize the data, what the benefit of using it is, how the measurement is made within a coordinate measurement grid and compares it to other coordinate measurement tools. With examples and visual aids throughout, under standing what is read is simplified.

Examples include algorithms, measurement data, comparing measurements, root causing dimensional problems based on the data, data comparisons to other measurement tools, and correlation to other measurement tools.

With a better understanding of the source of the data and how is it derived, the quality professional will have an improved ability to be proactive in preventing a quality issue from becoming another scrap part.

• Language: English
• Publisher: Trafford Publishing
• Release date: Dec 22, 2005
• ISBN: 9781466957381

Dennis R. Branch

The author has accumulated over twenty years of hands on experience working with laser measurement systems. He has obtained, technical training from two different manufactures of this type of measurement equipment and is recognized as one of the most proficient users of this measuring tool by Perceptron Inc., a manufacturer of the equipment. It had become apparent there was a lack of basic knowledge concerning the use of this type of measurement tool, and the ability to trust the measurement data it generated. Most of this misunderstanding stemmed from the attitude " If I cannot see it measure, then I cannot trust the data" and some mistrust of the data, came from the lack of not understanding how it performs the measurement within a coordinate grid measurement system. He has also noted the interest of this type of measuring tool from a local collage in his home state and other companies that came to tour his place of employment were referred to him for assistance in answering questions about the equipment. Over the years, he has transformed the use of the equipment at his employer from being used as a source of reference only measurement data to the intended decision making data. The need to educate others on the basics of this type of measuring tool became apparent with every lost opportunity of product quality improvement, improper usage and misunderstood expectations of the equipment. By increasing the awareness, understanding, and confidence in the equipments ability to provide the much-needed measurements, he has been able to improve his quality departments' response to preventing minor issues from becoming major ones and solving major quality issues in far less time than is required with a manual measurement method. Improved utilization of the equipment has also been realized. By continuously providing familiar statistical data, proving the equipments capability, and reliability, he continues to educate others that the data provided by a Non-Contact-Measurement system, is very reliable and highly beneficial to the company.

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© Copyright 2005 Dennis R. Branch

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ISBN 1-4120-6910-6

ISBN 978-1-4669-5738-1 (e)

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Table of Contents

Preface

CMM-NCM comparison

Introduction

Acknowledgements

Terms and Concepts

Theory Of Sensor Operation

Types of Sensors

Using a Dimensional NCM system Over View

What to Measure

Selecting a sensor for the measurement

Selecting the fixture method

Sensor / Algorithm Basics

Algorithm Measurement Results

Relationship measurements

Data Analysis; Utilizing and comparing the data

Dimensional Correlation Verification

Calibration / Correlation to Other Measurement Tools Theodolite Calibration

Correlating to a C.M.M

Using a master part for measurement verification

Correlating to a manual measurement

Trouble Shooting Measurement Errors

Evaluating Correlation Measurement Data

Evaluating Manual Correlation data

Evaluating Measurement Results of the Product

Setting the limits

Replacing a sensor

Relocating / adding a new sensor

List Of Examples

Test Questions

Answer Guide

PREFACE

By combining personal experience with technical information in this manual, the reader will have a comprehensive understanding of what Non Contact Measurement is, how it can best be utilized, understand the measurement data to make a sound quality decision and be able to establish a regular quality data monitoring system that will be of greatest benefit.

Over the years, the utilization of N.C.M. equipment has been altered from a reference measurement only tool to a decision making measurement tool. In some cases replacing the use of C.M.M. equipment as the decision making tool.

This is largely due to the accuracy and the speed at which the information can be obtained and provided by N.C.M. over C.M.M.

N.C.M. is a computerized measurement tool that has been developed for use in a production facility that fabricates their products at a high rate of production per hour. It was developed in the early 1980s.

As the name indicates the actual measurement does not require that the product be in physical contact with the measuring tool as you would with a height gauge, micrometer or other mechanical means.

In order to maintain a high quality level of the product being fabricated it is required to measure the product on a regular basis. The data must also be reviewed, stored, readily accessible for future reference and monitored.

With productivity increasing every year it is no longer enough to simply measure a single product one day then respond to the data the next or even several days later. By that time, it would be possible to have built several thousand defective products.

The N.C.M. tool can measure a product on a moving production line equipped with a stop station, within seconds without interrupting the flow of production. There is no need to remove the product from production and reinsert it later as is required with a mechanical measurement method. It can be utilized with parts designed on a coordinate grid or the more standard isometric design system.

Before this measurement tool was available, the measurements were taken by a mechanical means and required that the product be removed from a certain stage of production, set up for measurements, then measured and the data accumulated over a period and then evaluated. In the case of an automobile, this may have taken up to five days to complete the entire process, from acquiring the products to evaluating the measurement results, and then implementing a corrective action to a dimensional problem. All based on a maximum sample size of 10 units, sometimes less.

With the use of statistical reporting requiring several units to be measured before we see a measurement trend that indicates a possibleproblem, there is no way to effectively prevent the problem from occurring with manual measurement data in a high volume production facility.

With mechanical measurements we could be reacting to a dimensional problem that may have already occurred, and previously fixed. The data being reviewed may lead to an improper decision to again make a fix, thereby compounding the problem.

With a computerized method of measurement, we would have the statistical data required (100% of production) to prevent the problem from exceeding the control limits in a matter of seconds. The storage and retrieval of the data from the computer makes monitoring and follow up of the quality level of the product easier and faster.

To keep up with customer demand, N.C.M. equipment and its’ computing ability is always improving over time. It is important that the equipment manufacturers’ manuals are followed and that all equipment specific questions, are referred to their respective service departments.

Each improvement to the system, such as changing from analog to a