Eng Metrology Topic 4 [Noncontact Inspection]

of 28

  • date post

  • Category


  • view

  • download


Embed Size (px)



Transcript of Eng Metrology Topic 4 [Noncontact Inspection]


  • Noncontact Inspection methodsUtilize a sensor located at a certain distance from the objectThis sensor measure or gauge the desired features2 categories


  • Optical Inspection TechnologiesUse light to measure or gaugeOptical Inspection is specialized to industries Examples : Toolmakers microscopeMachine VisionOptical comparatorAutocollimators

  • Nonoptical Inspection TechnologiesUtilize energy forms other than light to measure or gaugeEnergy includes electrical field, radiation and ultrasonicsSpecialized metrology methodUtilized in certain industry only

  • Noncontact Vs Contact Avoidance of damage to the surface Inherently faster Inspection cycle timeNo additional handling of the parts to be measuredNoncontact is suitable for 100% automated inspection

  • Faster Inspection Cycle TimeContact inspection procedure requires the contacting probe to be positioned against the part, which takes timeNoncontact methods use a stationary probe that does not need repositioning for each part100% inspection is thus more feasible in automated inspection

  • Noncontact less handlingOften noncontact can be accomplished on the production line without the need for any additional handling of the partsContact methods require special handling and positioning of the parts on the production line100% inspection is thus more feasible in automated inspection

  • Automated InspectionUses variety of sensor systems that monitor the relevant parameters during the manufacturing process (on-line inspection) / immediately after they are produced (in-process inspection)Automated inspection is integrated in manufacturing operationsFlexible and responsive to product design changes

  • Sensors in automated inspectionDetect dimensional accuracy, surface roughness, temperature, force, power, vibration, tool wear, the presence of external or internal defects2 types tactile or nontactileAble to be linked to microprocessor and computers for graphics data display

  • 1) MicroscopesOptical instruments used to view and measure very fine details, shapes and dimensions Suitable to small and medium-sized tools, dies and workpieces.Different microscopes available for specialized inspectionsTypically equipped with electronics

  • Toolmakers microscopeAble to read up to 2.5 mMost common and versatile in tool rooms.

  • Toolmakers microscope

  • FEATURESThe eyepiece section of the optical tube incorporates a vernier. Angle measurement is performed easily by turning the protractor to align the cross-hair reticle with the workpiece image. Both the transmitted and reflected illumination intensity can be adjusted to obtain the optimal illumination intensity for the workpiece.

  • 2) Machine VisionMachine vision systems typically used for visual inspections that require high-speed, high-magnification, 24-hour operation, and/or repeatability of measurements.Machine vision encompasses computer science, optics, mechanical engineering, and industrial automation.

  • Technologies in machine vision

  • Machine Vision - UsesRange of applications ie.gauging/measurement identification optical character recognition (OCR) presence verification print inspection surface inspection colour analysis code reading

  • A typical machine vision system components:One or more digital or analogue camerasInput/Output hardwareA synchronizing sensor for part detectionA program to process images and detect relevant features.

  • CamerasOne or more digital or analogue cameras (black-and-white or colour) with suitable optics for acquiring images, Example are lenses to focus the desired field of view onto the image sensor and suitable, often very specialized, light sources

  • Camera

  • Input/Output hardwareExample digital I/O) or communication links e.g. network connection or RS-232 to report results

  • Input/Output

  • Sensor and softwareA synchronizing sensor for part detection (often an optical or magnetic sensor) to trigger image acquisition and processing and some form of actuators to sort, route or reject defective parts A software program to process images and detect relevant features.

  • Data process and output

  • Gauging/measurement

    Can inspection in the food industryInspection must take place at high speed; in this one at 20 parts per second. The requirement is to inspect a can for ovality and the bottom of the can for defects, and check for absence of dents, edge rollovers and foreign objects.

  • Can inspection

  • IdentificationNeedle-stamped ID codes on metal Metal parts are often coded by needle stamping characters. This results in a very robust ID that will easily survive subsequent manufacturing process

  • Presence verification

    Locating screwsAble to do 100% inspection solution for checking the contents of flat packed furniture prior to dispatch.

  • Print InspectionCircular syringe barrel Verifying the quality and position of print on a tubular structure like a syringe barrel requires a different approachUse a linescan camera rather than a CCD camera and pre-processing to orient the image for checking - and all in 100 milliseconds.