basic inspection and procedures
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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
8
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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14
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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