BASIC INSPECTION AND PROCEDURES

CHAPTER 2

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BASIC INSPECTION AND PROCEDURESLearning Objectives

Define and differentiate measuring and gaugingList the advantages of measuring & gaugingList the disadvantages of measuring & gaugingIdentify various types of gaugesDescribe direct, indirect and comparative measurementsExplain factors of consideration in selecting testing appratusDefine the term calibration, traceability & measurement

errorIdentify the sources of measurement errorIdentify the root cause of the problemsExplain the needs for calibration, inventory and care of

apparatus

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BASIC INSPECTION AND PROCEDURESTesting and Inspection Procedures

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• A method of inspection by means of comparing the dimensional characteristics of products against the scale of a measuring instrument.

• Measured value is read off directly from these instruments

Measuring

• A method of inspection by means of comparing the dimensional characteristics of products against a gauge

• True dimensional value cannot be obtain

• This method only determine whether the product is within the allowable limits

Gauging

BASIC INSPECTION AND PROCEDURESMeasuring

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Measured value is read off directly from the measuring instrument

BASIC INSPECTION AND PROCEDURESGauging

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True value is unknown, only determine ‘good’ or ‘bad’ parts only

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Measuring Characteristics

Gauging

more Information lessdifficult Ease of use easy

Slow Time fastExpensive Cost/process CheapHigh skill Operator Less skill

Measuring vs Gauging

BASIC INSPECTION AND PROCEDURESTypes of Measurement

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Direct Measurement

• Compared directly against the line of measuring instruments

Indirect Measurement

• Obtained by using an intermediary (transfer) measuring device

Comparative Measurement

• Comparison between standards blocks or products

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Types of Measurement (cont)

Indirect MeasurementMeasure value obtain using intermediaryMeasurement directly use instrument,

value determine by math (density, volume)

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Types of Measurement (cont)

Comparative measurementComparison between standard/either

known value.

Measure workpiece

Dial gauge

Gauge block

BASIC INSPECTION AND PROCEDURESFactors in selecting Testing Instrument

1. The Rule of 102. Repeat accuracy3. Stability4. Magnification5. Resolution(sensitivity)6. Inspection Cost – maintaining & installing

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BASIC INSPECTION AND PROCEDURES

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BASIC INSPECTION AND PROCEDURESCalibration

Definition : a periodical act of checking/comparing

two measuring instruments, one of which is traceable to national standards

Purpose : to detect any discrepancies in accuracy and

adjust it to bring it within its tolerance for accuracy

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BASIC INSPECTION AND PROCEDURESCalibration

Inventory and Classification Systematic approach of calibration control

1. Calibration Masterlist2. Record card3. Equipment Marking with Control number4. Calibration sticker

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Calibration (cont)

BASIC INSPECTION AND PROCEDURES

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BASIC INSPECTION AND PROCEDURESCalibration

Function of Calibration room1. To detect deteriorations of instruments and provide

services for rectification or adjustments2. To ensure that newly purchased instruments are

within the specified limits3. To keep instruments in proper condition to maintain

accuracy4. Centralized location for gauge issuing5. Place for development and verification of test

methods6. Acceptance inspection prior to production7. Room temperature 20+ 1°C and humidity at 55%+3.

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BASIC INSPECTION AND PROCEDURESCare of Measuring Instrument

1. Calibrate the instrument periodically before use

2. Do not use instruments as tools3. Protect the instruments from dust, rust, shock

and wear4. Store the instruments in a proper place5. Do not store the instruments with other tools6. Avoid rough handling and dropping the

instruments

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