INSPECTION

Inspection Methods

  • Essential Role in Manufacturing
    • Inspection has become an essential part of any manufacturing system.
    • It serves as the means of rejecting nonconformities and ensuring the production of high-quality products.

    Importance of Inspection

  • Traditional Methods
    • Historically, inspection involved labor-intensive methods, leading to increased manufacturing lead times and elevated production costs.

Automated Inspection

  • Definition
    • Automated inspection can be defined as the automation of one or more steps involved in the inspection procedure.

  • Implementation Methods
    • There are several alternative ways to implement automated or semi-automated inspection:

    1. Automated presentation of parts by an automatic handling system while a human operator still conducts the examination and makes decisions.

    2. Automated examination and decision-making performed by an automatic inspection machine, with manual loading of parts into the machine.

    3. A completely automated inspection system where parts presentation, examination, and decision-making are all done automatically.

Inspection Timing and Location

  • When and Where to Inspect • Inspection can occur at multiple points throughout the production process:

    1. Receiving Inspection

      • Performed when raw materials and parts are received from suppliers.

    2. In-process Inspection

      • Conducted at various stages of manufacture.

    3. Pre-shipment Inspection

      • Conducted before shipping the product to the customer.
        • The main focus is on in-process inspection—when and where to inspect during production.

Testing vs. Inspection

  • Definitions
    • Testing refers to the assessment of functional aspects of a product.
    • Inspection is utilized to assess the quality of a product according to its design specifications.

Off-Line and On-Line Inspection

  • Importance of Timing in Inspection
    • The timing of the inspection procedure in relation to the manufacturing process is a vital consideration in quality control.

  • Types of Inspection Timing

    1. Off-line Inspection

    2. On-line Inspection

Off-Line Inspection

  • Characteristics
    • Off-line inspection is conducted away from the manufacturing process, generally leading to a time delay between processing and inspection.
    • Manual inspection is common in this method.

On-Line Inspection

  • Definition
    • On-line inspection occurs concurrently with the manufacturing process.

  • Types of On-Line Inspection
    • Two distinct on-line inspection procedures exist:

    1. On-line/In-process

    2. On-line/Post-process

On-Line/In-process Inspection

  • Details
    • This inspection method is performed simultaneously as parts are being manufactured.
    • The inspection procedure measures or gauges the parts during the production process.
    • Technologically, automated on-line/in-process inspection is often complicated and costly; therefore, on-line/post-process procedures are frequently adopted as an alternative.

On-Line/Post-process Inspection

  • Explanation
    • The measurement or gauging procedure takes place immediately after the production process.
    • Although this is post-process, it remains considered an on-line method because it is integrated with the manufacturing workstation, allowing immediate influence on subsequent production operations.

Inspection Techniques

  • Categories of Inspection Techniques • Inspection methods can be broadly divided into two categories:

    1. Contact Inspection

    2. Non-contact Inspection

Contact Inspection Techniques

  • General Characteristics
    • Contact inspection involves making physical contact with the object using a measuring or gauging instrument.
    • Typically concerned with the physical dimensions of the part, it is heavily utilized in manufacturing processes, especially for metal parts.

  • Principal Contact Technologies
    • Various contact technologies include:

    1. Conventional measuring and gauging instruments (manual and automated).

    2. Coordinate Measuring Machines (CMMs).

    3. Stylus-type surface texture measuring machines.

Examples of Contact Inspection Techniques

  • Profile Data Acquisition
    • Stylus-type profilometer usage for measuring profiles:

    • Stylus tip is positioned to measure the profile against an original machined surface.

  • Types of CMM
    • Different CMMs include:

    1. Moving Ram Horizontal Arm Coordinate Measuring Machine.

    2. Moving Table Horizontal Arm Coordinate Measuring Machine.

Importance of Contact Inspection

  • Reasons for Technological and Commercial Relevance

    1. Most widely used inspection technologies today.

    2. Renowned for accuracy and reliability.

    3. Frequently the only available methods for specific inspection tasks.

Non-Contact Inspection Techniques

  • General Characteristics
    • Non-contact inspection methods utilize sensors located at a distance to measure or gauge features of the object without physical contact.

  • Categories of Non-Contact Inspection Technologies

    1. Optical Inspection

    • Utilizes light for measuring or gauging.

    1. Non-optical Inspection

    • Employs forms of energy other than light, such as electrical fields, radiation, and ultrasonics.

Tolerances and Measuring Tools

Symbols of Form and Position Tolerances


  • Types of Tolerance Symbols

    TYPE OF TOLERANCE

    CHARACTERISTIC SYMBOL

    DATUM REFERENCE


    Straightness

    H

    Individual/Related


    Flatness

    H

    Individual/Related


    Circularity

    H

    Individual/Related


    Cylindricity

    H

    Individual/Related


    Profile of a Line

    H

    Individual/Related


    Profile of a Surface

    H

    Individual/Related


    Angularity

    H

    Individual/Related


    Perpendicularity

    H

    Individual/Related


    Location

    H

    Individual/Related


    Parallelism

    H

    Individual/Related


    Concentricity

    H

    Individual/Related


    Symmetry

    H

    Individual/Related

    Tools for Precision Measuring

    • Measuring Instruments
      • Steel Rule
      • Micrometer
      • Digital Caliper
      • Dial Caliper

    Dial Caliper Description

    • Functionality
      • The dial caliper is a precision measuring instrument whose blade graduations are in inches and tenths of an inch (0.1 in).

    Reading a Dial Caliper

    1. Reading Increments
      • Each inch is divided into ten tenths for precise measurement.

    2. Dial Graduations
      • The dial shows graduations in thousandths of an inch (0.001 in).

    3. How to Read
      • Step 1: Read inches from the blade.
      • Step 2: Read tenths of an inch from the blade.
      • Step 3: Read thousandths of an inch from the dial.

    Measurements Possible with Dial Calipers

    • Types of Measurements
      • Thickness or outside diameter.
      • Inside diameter or space width.
      • Depth.

    Summary of Steps to Measure

    • Step Distance: Using the dial caliper for accurate dimension assessments while considering configuration for varying measurement attributes.