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Introduction to visual inspection

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  • This presentation was developed to provide students in industrial technology programs, such as welding, an introduction to visual inspection. This presentation is one of eight developed By Chris Kay Introduction to Nondestructive Testing Penetrant Testing Ultrasonic Testing Magnetic Particle Testing Radiographic Testing Eddy Current Testing Welder Certification PMI Inspection All rights are reserved by the author and the presentation cannot be copied or distributed except by Qualified trained NDT/NDE Instructors. A free copy of the presentations can be requested by contacting the Chris Kay on c.kay1966@btinternet.com
  • Fillet Gauge set, Palmgren gage, VWAC Gauge
  • Transcript

    • 1. CChinahina OOutsourcingutsourcing Visual Inspection IntroductionVisual Inspection Introduction
    • 2. OutlineOutline • IntroductionIntroduction • Basic principlesBasic principles • Manual Vision InspectionManual Vision Inspection – Human VisionHuman Vision – Common Inspection applicationsCommon Inspection applications – EquipmentEquipment • Automated or Machine VisionAutomated or Machine Vision InspectionInspection – Machine VisionMachine Vision – Common Inspection ApplicationsCommon Inspection Applications – EquipmentEquipment • Advantages and LimitationsAdvantages and Limitations
    • 3. IntroductionIntroduction • Visual inspection is commonly defined as “theVisual inspection is commonly defined as “the examination of a material, component, or product forexamination of a material, component, or product for conditions of nonconformance using light and the eyes,conditions of nonconformance using light and the eyes, alone or in conjunction with various aids.alone or in conjunction with various aids. • Visual inspection often also involves, shaking, listening,Visual inspection often also involves, shaking, listening, feeling, and sometimes even smelling the componentfeeling, and sometimes even smelling the component being inspected.being inspected. • Visual inspection consists of at least two majorVisual inspection consists of at least two major processes.processes. – The first is a search process.The first is a search process. – The second is a process of combining relevant knowledge,The second is a process of combining relevant knowledge, sensory input, and pertinent logical processes to provide ansensory input, and pertinent logical processes to provide an identification that some anomaly or pattern represents a flawidentification that some anomaly or pattern represents a flaw that poses a risk to the performance of the part.that poses a risk to the performance of the part. • Visual inspection is commonly employed to support otherVisual inspection is commonly employed to support other NDT methods.NDT methods. • Digital detectors and computer technology have made itDigital detectors and computer technology have made it possible to automate some visual inspections. This ispossible to automate some visual inspections. This is known as “machine vision inspection.”known as “machine vision inspection.”
    • 4. IntroductionIntroduction • Visual inspection is the most basic and mostVisual inspection is the most basic and most commonly employed NDT method.commonly employed NDT method. • It is applicable to a wide variety of material typesIt is applicable to a wide variety of material types and product forms.and product forms. • Several characteristics about the part beingSeveral characteristics about the part being examined may be determined, which includeexamined may be determined, which include dimensional conformance, the presence ofdimensional conformance, the presence of discontinuities, general fit and wear, and simplediscontinuities, general fit and wear, and simple cosmetic compliance.cosmetic compliance. • It can be performed by direct or indirect methodsIt can be performed by direct or indirect methods during various stages of manufacturing or afterduring various stages of manufacturing or after the component has been placed in-service.the component has been placed in-service.
    • 5. • The quality of an inspection are affectedThe quality of an inspection are affected primarily by four factors.primarily by four factors. – The quality of the detector (eye or camera).The quality of the detector (eye or camera). – The lighting conditions.The lighting conditions. – The capability to process the visual data.The capability to process the visual data. – The level of training and attention to detail.The level of training and attention to detail. IntroductionIntroduction
    • 6. IntroductionIntroduction –– Manual Versus AutomatedManual Versus Automated InspectionInspection • The majority of visualThe majority of visual inspections are completedinspections are completed by an inspector, butby an inspector, but machine vision is becomingmachine vision is becoming more common.more common. • The primary advantage of anThe primary advantage of an inspector is their ability to quickly adapt to ainspector is their ability to quickly adapt to a variety of lighting and other non-typical conditions,variety of lighting and other non-typical conditions, and their ability to use other senses.and their ability to use other senses. • The primary advantage of a machine visionThe primary advantage of a machine vision inspection system is their ability to make veryinspection system is their ability to make very consistent and rapid inspections of specific detailsconsistent and rapid inspections of specific details of a component.of a component. • Machine vision is primarily used in productionMachine vision is primarily used in production applications where a large number of componentsapplications where a large number of components require inspection and the inspection conditionsrequire inspection and the inspection conditions
    • 7. BasicBasic Principles –Principles – The Human EyeThe Human Eye • Light enters the eyeLight enters the eye through the pupil and anthrough the pupil and an image is projected on theimage is projected on the retina.retina. • Muscles move the eyeballMuscles move the eyeball in the orbits and allow youin the orbits and allow you to focus the image on theto focus the image on the central retina or fovea.central retina or fovea.
    • 8. • Rods are sensitive to blue-green light and are used for visionRods are sensitive to blue-green light and are used for vision under dark or dim conditions.under dark or dim conditions. • Cones operate only in relatively bright light, but they provide usCones operate only in relatively bright light, but they provide us with our sharpest images and enable us to see colors. There arewith our sharpest images and enable us to see colors. There are three types of conesthree types of cones – L-cones are red absorbing cones or those that absorb best at theL-cones are red absorbing cones or those that absorb best at the relatively long wavelengths peaking at 565 nmrelatively long wavelengths peaking at 565 nm – M-cones are green absorbing cones with a peak absorption at 535M-cones are green absorbing cones with a peak absorption at 535 nmnm • S-cones are blue absorbing cones with a peak absorption at 440S-cones are blue absorbing cones with a peak absorption at 440 nm.nm. Basic Principles –Basic Principles – The Human EyeThe Human Eye The retina is a mosaic of two basic types of photoreceptors, rods and cones.
    • 9. • Cones provide us with our sharpestCones provide us with our sharpest images because most of the 3 millionimages because most of the 3 million cones in each retina are confined tocones in each retina are confined to a small region just opposite the lensa small region just opposite the lens called the fovea. The maximumcalled the fovea. The maximum concentration is about 180,000concentration is about 180,000 cones per square mm.cones per square mm. • Our sharpest and most colorfulOur sharpest and most colorful images are produced in the fovea.images are produced in the fovea. • Outside of this region our vision isOutside of this region our vision is relatively poor but, since we canrelatively poor but, since we can quickly redirect our eyes we tend notquickly redirect our eyes we tend not to be aware of our poor peripheralto be aware of our poor peripheral vision.vision. Basic Principles – Visual AcuityBasic Principles – Visual Acuity
    • 10. •Normal visual acuity or 20/20 vision is defined as the ability toNormal visual acuity or 20/20 vision is defined as the ability to resolve a spatial pattern separated by a visual angle of one minuteresolve a spatial pattern separated by a visual angle of one minute or 1/60 of a degree of arc.or 1/60 of a degree of arc. •One degree of a scene is projected on about 290 micrometers of theOne degree of a scene is projected on about 290 micrometers of the retina.retina. •In 290 micrometers there are 123 cones and in 1/60 of a degreeIn 290 micrometers there are 123 cones and in 1/60 of a degree there 2 cones which is the number required to resolve an object.there 2 cones which is the number required to resolve an object. •The size of an object that can be seen at a given distance can beThe size of an object that can be seen at a given distance can be calculated using the following formula: X = (d tancalculated using the following formula: X = (d tan /2)2/2)2 b 2  ’ d d’ n b’ c ’ ~425 by 425 cones 180,000 Cones 1 mm 1 mm X X/2 Basic Principles – Visual AcuityBasic Principles – Visual Acuity When visually inspecting an object for a defect, a comfortable viewing distance “d” might be around 12 inches. At 12 inches, the normal visual acuity of the human eye is 0.0035 inch. (It must be noted that this value is for the situation where there is good lighting and high contrast between the objects being viewed.) There is a limit to what the unaided eye can see.
    • 11. Basic Principles –Basic Principles – Contrast SensitivityContrast Sensitivity • Contrast sensitivity is a measure of how faded or washed out an object can be before it becomes indistinguishable from a uniform field • It has been experimentally determined that the minimum discernible difference in gray scale level that the eye can detect is about 2% of full brightness • Contrast sensitivity varies with – the size or spatial frequency of a feature – The lighting conditions – Whether the object is lighter or darker than the background The graph to the right plots the visibility of a spot as a function of the above variables
    • 12. In this image:In this image: – The luminance of pixels is variedThe luminance of pixels is varied sinusoidally in the horizontalsinusoidally in the horizontal direction. The spatial frequencydirection. The spatial frequency increases exponentially fromincreases exponentially from left to right.left to right. – The contrast also variesThe contrast also varies logarithmically from 100% at thelogarithmically from 100% at the bottom to about 0.5% at the top.bottom to about 0.5% at the top. – The luminance of peaks andThe luminance of peaks and troughs remains constant alongtroughs remains constant along a given horizontal path through the image.a given horizontal path through the image. It should be noted, however, that larger objects are not always easier to see than smaller objects as contrast is reduced. Campbell, F. W. and Robson, J. G. (1968) Application of Fourier analysis to the visibility of gratings. Journal of Physiology (London) Image Courtesy of Izumi Ohzawa, Ph.D. University of California School of Optometry Basic Principles –Basic Principles – Contrast SensitivityContrast Sensitivity If object visibility was dictated solely by image contrast, the alternating bright and dark bars should appear to have equal height everywhere in the image. However, the bars seem to be taller in the middle of the image.
    • 13. • Under normal lighting conditions the cones are operating and the eye has good visual acuity and is most sensitive to greenish yellow color, which has a wavelength around 555 nanometers (photopic curve). • When the light levels drop to near total darkness, the response of the eye changes significantly as shown by the scotopic response curve on the left. • At this level of light, the rods are most active and the human eye is more sensitive to any amount of light that is present, but is less sensitive to the range of color. • At this very low light level, sensitivity to blue, violet, and ultraviolet is increased, but sensitivity to yellow and red is reduced. Basic Principles – Light LevelsBasic Principles – Light Levels
    • 14. • Effective visual inspection requiresEffective visual inspection requires adequate lighting.adequate lighting. • The type of inspection will dictate theThe type of inspection will dictate the lighting requirements. Inspection oflighting requirements. Inspection of components with fine detail and low contrastcomponents with fine detail and low contrast will require greater illumination thanwill require greater illumination than components with large details and highcomponents with large details and high contrast.contrast. • Light intensity may be measured with aLight intensity may be measured with a suitable light meter. The unit of measuresuitable light meter. The unit of measure for white light is foot-candles (fc) =(for white light is foot-candles (fc) =( 10.76410.764 luxlux )) – A foot-candle is equal to the amount of directA foot-candle is equal to the amount of direct light thrown by one standard candle at alight thrown by one standard candle at a distance of 1 foot. Min Inspection Lighting 46distance of 1 foot. Min Inspection Lighting 46 fc= 500 lux.fc= 500 lux. • Inspection of components with fine detailInspection of components with fine detail and low contrast may require 100 foot-and low contrast may require 100 foot- candles or more. (1076 Lux min)candles or more. (1076 Lux min) • Specification requirements for lightingSpecification requirements for lighting should be reviewed prior to performing anshould be reviewed prior to performing an Basic Principles –Basic Principles – Light Intensity MeasurementLight Intensity Measurement
    • 15. Basic Principles –Basic Principles – Light DirectionalityLight Directionality • The directionality of the light is a very important consideration. • For some applications, flat, even lighting works well. • For other applications, directional lighting is better because it produces shadows that are larger than the actual flaw and easier to detect.
    • 16. Is the book facing towards or away from you? Basic Principles – Perspective The eye/brain need visual clues to determine perspective.
    • 17. Are the horizontal lines parallel or do they slope? How many black dots do you see? Sometime the eye/mind has trouble correctly processing visual information. Basic Principles –Basic Principles – Optical IllusionsOptical Illusions
    • 18. • When evaluations are made byWhen evaluations are made by an inspector, eye examinationsan inspector, eye examinations must be done at regularmust be done at regular intervals to assure accuracyintervals to assure accuracy and sensitivity. Theseand sensitivity. These examinations may consistexaminations may consist of the following:of the following: • Near Vision (Jaeger)Near Vision (Jaeger) • Far Vision (Snellen)Far Vision (Snellen) • Color DifferentiationColor Differentiation • When using machine vision,When using machine vision, different but similardifferent but similar Basic Principles – VisionBasic Principles – Vision
    • 19. • For best results the inspector orFor best results the inspector or machine vision operator must have:machine vision operator must have: – A basic knowledge of materialA basic knowledge of material processing, forming, machining andprocessing, forming, machining and joining processes.joining processes. – A general understanding of designA general understanding of design features, application and servicefeatures, application and service requirements.requirements. – Specific instructions on what to look forSpecific instructions on what to look for and specific accept/reject criteria.and specific accept/reject criteria. Basic PrinciplesBasic Principles
    • 20. InspectionInspection ApplicationsApplications • Detection of surface anomalies such asDetection of surface anomalies such as scratches, excess surface roughness, andscratches, excess surface roughness, and areas void of paint or plating.areas void of paint or plating. • Crack, porosity, corrosion or other flawCrack, porosity, corrosion or other flaw detection.detection. • Dimensional conformance.Dimensional conformance. • Precision measurements.Precision measurements. • Foreign object detection.Foreign object detection. • Component location.Component location. Applications for visual inspection and many and range from looking a product over for obvious defect to performing detailed inspections. Some of the common applications include:
    • 21. • Visual inspection ofVisual inspection of manufacturedmanufactured materials andmaterials and components is a costcomponents is a cost effective means ofeffective means of identifying flaws.identifying flaws. • Visual inspection of aVisual inspection of a casting reveals acasting reveals a crack between acrack between a threaded opening andthreaded opening and a pressed fit.a pressed fit. • The aluminum sandThe aluminum sand casting has hot tearscasting has hot tears and shrinkage at theand shrinkage at the transition zones.transition zones. Inspection Applications –Inspection Applications – Flaw DetectionFlaw Detection
    • 22. • In this example, visualIn this example, visual inspection of a fireinspection of a fire escape reveals a failureescape reveals a failure in a handrail tube.in a handrail tube. • The failure is in theThe failure is in the tube seam and is likelytube seam and is likely the result of icethe result of ice expansion.expansion. Inspection Applications –Inspection Applications – Flaw DetectionFlaw Detection In-service inspections of existing components and structures is commonly accomplished visually.
    • 23. Normal inspectionNormal inspection practices for highwaypractices for highway bridges rely almostbridges rely almost entirely on visualentirely on visual inspection to evaluate theinspection to evaluate the condition of the bridges.condition of the bridges. Inspection Applications –Inspection Applications – Flaw DetectionFlaw Detection
    • 24. Over 80 percent of all aircraft inspections are performed visually. Inspection Applications –Inspection Applications – Flaw DetectionFlaw Detection
    • 25. • Weld quality requirementsWeld quality requirements are commonly determinedare commonly determined through visual inspection.through visual inspection. • Many standards haveMany standards have established acceptanceestablished acceptance criteria for welds.criteria for welds. Slag rolled into toe of weld Transverse weld crack Inspection Applications –Inspection Applications – Flaw DetectionFlaw Detection
    • 26. DimensionalDimensional ConformanceConformance • Visual inspection is commonly employedVisual inspection is commonly employed for general dimensional conformance,for general dimensional conformance, assembly fit, and alignment betweenassembly fit, and alignment between components.components. • Common applications include determining:Common applications include determining: – Weld size and tolerance.Weld size and tolerance. – Component dimensions.Component dimensions. – Material alignment and allowable distortion.Material alignment and allowable distortion.
    • 27. DimensionalDimensional ConformanceConformance Welds are commonly inspected for dimensional tolerance.Welds are commonly inspected for dimensional tolerance. • There are several types of gages used to inspect weldingThere are several types of gages used to inspect welding fit up and finished weldments.fit up and finished weldments. • These gages are intended for general inspection whereThese gages are intended for general inspection where close tolerances are not required.close tolerances are not required. • The gage used is determined by the application.The gage used is determined by the application. Fillet gauge set Palmgren gauge VWAC gauge Cambridge gauge
    • 28. Dimensional ConformanceDimensional Conformance Visual inspection is commonly used to determine weld sizeVisual inspection is commonly used to determine weld size and tolerances according to standards and engineeringand tolerances according to standards and engineering specifications.specifications. Throat measurement using a Palmgren gauge. Leg size determination with fillet gauge. Convexity measurement with VWAC gauge.
    • 29. Undercut in a weld is readily seen visually. In manyUndercut in a weld is readily seen visually. In many cases its depth must be measured to determine if itcases its depth must be measured to determine if it exceeds code requirements.exceeds code requirements. Measurement of undercut depth with VWAC gage. Dimensional ConformanceDimensional Conformance
    • 30. Dimensional ConformanceDimensional Conformance Component finish dimensions are checked withComponent finish dimensions are checked with the use of measurement devices, such asthe use of measurement devices, such as transferring gages and precision measurementtransferring gages and precision measurement gages.gages. The finished depth of a machined mold is determined with a depth micrometer. Small hole gage used in determining hole diameter.
    • 31. Dimensional ConformanceDimensional Conformance Alignment/DistortionAlignment/Distortion • Visual inspection frequently involvesVisual inspection frequently involves checking materials and components forchecking materials and components for fit and alignment.fit and alignment. • Many standards establish allowableMany standards establish allowable tolerances for fit and distortion.tolerances for fit and distortion. • Structural fabrication requiresStructural fabrication requires dimensional inspection of finisheddimensional inspection of finished components prior to shipment to thecomponents prior to shipment to the field site.field site. • Basic tools are used for the inspection.Basic tools are used for the inspection. An inspector will set up string lines atAn inspector will set up string lines at known distances and plum them usingknown distances and plum them using a tape measure. Measurements area tape measure. Measurements are then taken at various locations andthen taken at various locations and compared to code requirements.compared to code requirements. In this image a fabricated girder is being inspected for distortion, sweep and web flatness.
    • 32. EquipmentEquipment • Visual inspection equipment includes a varietyVisual inspection equipment includes a variety of different tools. These may range from basicof different tools. These may range from basic rulers, tape measures and spring type calipersrulers, tape measures and spring type calipers to rigid or flexible borescopes and remoteto rigid or flexible borescopes and remote crawlers with cameras.crawlers with cameras. • Many tools have been designed for specificMany tools have been designed for specific applications such as the various weld gauges.applications such as the various weld gauges. • Some of the specialized tools such as crawlersSome of the specialized tools such as crawlers have been designed to satisfy the inspectionhave been designed to satisfy the inspection needs in applications where conventionalneeds in applications where conventional techniques are not feasible.techniques are not feasible.
    • 33. Equipment – BasicEquipment – Basic MeasurementsMeasurements • One of the most commonOne of the most common tools used in visualtools used in visual inspection is the rule orinspection is the rule or scale.scale. • Used to measure linearUsed to measure linear dimensions, when properlydimensions, when properly used will measure withinused will measure within 0.015” or 1/64” and smaller.0.015” or 1/64” and smaller. • Rules are made in a varietyRules are made in a variety lengths, widths, andlengths, widths, and thicknesses.thicknesses. • They are graduated inThey are graduated in common fractions, decimalcommon fractions, decimal units, and metric units, orunits, and metric units, or combinations of both.combinations of both. • The specific type of rule isThe specific type of rule is typically chosen relative totypically chosen relative to the application.the application.
    • 34. • Sliding calipers are aSliding calipers are a precision refinement ofprecision refinement of the common rule, whichthe common rule, which results in greaterresults in greater accuracy ofaccuracy of measurements.measurements. • They may incorporateThey may incorporate either a dial indicator oreither a dial indicator or digital readout.digital readout. • Sliding-type calipers areSliding-type calipers are commonly used to checkcommonly used to check dimensional tolerances ofdimensional tolerances of machined components,machined components, wear on components, andwear on components, and fit between components.fit between components. Equipment –Equipment – Precision MeasurementsPrecision Measurements
    • 35. Equipment –Equipment – Precision MeasurementsPrecision Measurements • Micrometers are preciseMicrometers are precise measurement instrumentsmeasurement instruments used to make accurateused to make accurate direct readings in contactdirect readings in contact measurements.measurements. • Micrometers are designedMicrometers are designed for inside, outside, andfor inside, outside, and depth measurements, anddepth measurements, and are available in a wideare available in a wide variety of shapes andvariety of shapes and sizes.sizes. • Micrometers may be eitherMicrometers may be either thousandth inch (.001”) orthousandth inch (.001”) or ten thousandth inchten thousandth inch (.0001”) measurement(.0001”) measurement capable.capable.
    • 36. • Micrometers operate onMicrometers operate on the principle that athe principle that a precision made screwprecision made screw with a pitch of fortywith a pitch of forty threads per inch willthreads per inch will advance one fortieth of anadvance one fortieth of an inch (.025”) with eachinch (.025”) with each complete turn.complete turn. • On a one inchOn a one inch micrometer, the sleeve ismicrometer, the sleeve is marked longitudinally withmarked longitudinally with forty lines to the inchforty lines to the inch which corresponds to thewhich corresponds to the number of threads on thenumber of threads on the spindle.spindle. EquipmentEquipment –– PrecisionPrecision MeasurementsMeasurements
    • 37. • The reading line on theThe reading line on the sleeve is divided into fortysleeve is divided into forty equal parts by verticalequal parts by vertical lines, each designateslines, each designates 1/401/40thth ” or .025” and every” or .025” and every fourth line denotesfourth line denotes hundreds of thousandthshundreds of thousandths and is numbered 1 – 0.and is numbered 1 – 0. • The beveled edge of theThe beveled edge of the thimble is divided intothimble is divided into twenty five equal partstwenty five equal parts with each representing .with each representing . 001”, with every line001”, with every line numbered from 0 -24.numbered from 0 -24. Equipment –Equipment – Precision MeasurementsPrecision Measurements
    • 38. Example:Example: – One major division on theOne major division on the sleeve is visible, representingsleeve is visible, representing one tenth of an inch.one tenth of an inch. – Two minor divisions areTwo minor divisions are visible, which each representvisible, which each represent an additional 25 thousandths.an additional 25 thousandths. – Line 15 on the thimbleLine 15 on the thimble coincides with the readingcoincides with the reading line on the sleeve indicatingline on the sleeve indicating that fifteen one thousandthsthat fifteen one thousandths of an inch should be added toof an inch should be added to the measurement.the measurement. – By adding all three values,By adding all three values, the micrometer reading isthe micrometer reading is obtained.obtained. Equipment –Equipment – Precision MeasurementsPrecision Measurements 0.100” (2 X 0.025) 0.050” (15 X .001) 0.015” 0.165”
    • 39. Reading the ten thousandths micrometer.Reading the ten thousandths micrometer. • The ten thousandths micrometer incorporates a vernier scale.The ten thousandths micrometer incorporates a vernier scale. • The vernier consists of ten divisions the sleeve, whichThe vernier consists of ten divisions the sleeve, which occupies the same space as nine divisions on the beveledoccupies the same space as nine divisions on the beveled edge of the thimble.edge of the thimble. • The difference between one of the ten spaces on the sleeveThe difference between one of the ten spaces on the sleeve and one of the nine spaces on the thimble is 1/10and one of the nine spaces on the thimble is 1/10 thth of aof a division or 0.0001”.division or 0.0001”. Equipment –Equipment – Precision MeasurementsPrecision Measurements Example: − The second major divisions (line 2) on the sleeve is visible (2 x 0.100” = 0.200”) − Three minor divisions after line 2 are visible (3 X 0.025” = 0.075”) − The beveled edge of the thimble is between 0 and 1 (0 x 0.001 = 0) − The vernier scale has the sixth line on the sleeve perfectly lined up with one of the marks on the thimble ( 6 x 0.0001 = 0.0006”) − The micrometer reading is: 0.2756” 0.200” 0.075” 0.000” 0.0006” 0.2756”
    • 40. Equipment – TransferringEquipment – Transferring GaugesGauges • Transfer instruments areTransfer instruments are used to takeused to take measurements which aremeasurements which are transferred to directtransferred to direct measurement devices.measurement devices. • They consist of calipers,They consist of calipers, dividers, telescopingdividers, telescoping gages and small holegages and small hole gages.gages.
    • 41. Equipment – TransferringEquipment – Transferring GaugesGauges • Spring type calipers areSpring type calipers are available for contactavailable for contact measurements of inside andmeasurements of inside and outside dimensions.outside dimensions. • They are useful for measuringThey are useful for measuring distances between and overdistances between and over surfaces.surfaces. • They are commonly used toThey are commonly used to transfer dimensions or sizestransfer dimensions or sizes between the work piece andbetween the work piece and standard measuring devices,standard measuring devices, such as graduated rules.such as graduated rules. • The size of a linear or roundedThe size of a linear or rounded indication of a discontinuity mayindication of a discontinuity may be measured with dividers.be measured with dividers.
    • 42. Equipment – TransferringEquipment – Transferring GaugesGauges • Small hole gages are a type of transfer instrument used toSmall hole gages are a type of transfer instrument used to measure small holes or slots.measure small holes or slots. • They are generally supplied in sets with a range of 1/8” -They are generally supplied in sets with a range of 1/8” - 1/2”.1/2”. • The actual measurement is determined by transferring aThe actual measurement is determined by transferring a properly adjusted gage to a micrometer.properly adjusted gage to a micrometer.
    • 43. Equipment – TransferringEquipment – Transferring GaugesGauges • Telescoping gages makeTelescoping gages make inside measurements suchinside measurements such as hole diameter and slotas hole diameter and slot width.width. • They are designed to beThey are designed to be measured by a micrometermeasured by a micrometer after being set to the holeafter being set to the hole or slot size.or slot size. • To make accurateTo make accurate measurements it ismeasurements it is important to make sure theimportant to make sure the telescoping gage istelescoping gage is aligned properly in thealigned properly in the measuring faces of themeasuring faces of the micrometer.micrometer.
    • 44. Equipment – Screw Pitch GageEquipment – Screw Pitch Gage • The screw pitch gage is aThe screw pitch gage is a basic visual aid forbasic visual aid for checking the number ofchecking the number of threads per inch and roughthreads per inch and rough inaccuracies of threads.inaccuracies of threads. • The gage consists of aThe gage consists of a steel case with a numbersteel case with a number of folding leaves at eachof folding leaves at each end.end. • Each leaf is number andEach leaf is number and contains teethcontains teeth corresponding to a specificcorresponding to a specific thread pitchthread pitch ..
    • 45. Direct and RemoteDirect and Remote Visual InspectionVisual Inspection • Many codes refer to direct visual examination asMany codes refer to direct visual examination as a visual inspection which requires that access toa visual inspection which requires that access to the area is sufficient to place the eye within 24the area is sufficient to place the eye within 24 inches of the surface to be examined and at aninches of the surface to be examined and at an angle of not less than 30angle of not less than 30 º to that surface.º to that surface. • If these requirements cannot be met, thenIf these requirements cannot be met, then remote visual inspection may be used.remote visual inspection may be used. • Remote visual inspection may be accomplishedRemote visual inspection may be accomplished with the use of a number of optical aids such as,with the use of a number of optical aids such as, mirrors, magnifiers, and rigid or flexiblemirrors, magnifiers, and rigid or flexible borescopes.borescopes.
    • 46. Optical AidsOptical Aids • Mirrors are valuable aids inMirrors are valuable aids in visual inspection, they allowvisual inspection, they allow the inspection of threaded andthe inspection of threaded and bored holes, inside surfaces ofbored holes, inside surfaces of pipes and fittings, as well aspipes and fittings, as well as many others.many others. • Magnifiers assist the visualMagnifiers assist the visual inspector by enlarging the sizeinspector by enlarging the size of the object being examined.of the object being examined. • Comparators are a magnifierComparators are a magnifier with a measuring capability.with a measuring capability. The comparator hasThe comparator has interchangeable reticles whichinterchangeable reticles which provide measurements forprovide measurements for threads, angles, linearthreads, angles, linear measurement, diameters andmeasurement, diameters and
    • 47. Optical AidsOptical Aids • Borescopes are visual aids used for the inspection ofBorescopes are visual aids used for the inspection of internal surface areas.internal surface areas. • They are designed for remote viewing in difficult toThey are designed for remote viewing in difficult to reach areas such as jet engines, cylinders, tanks, andreach areas such as jet engines, cylinders, tanks, and various enclosed chambers.various enclosed chambers. • Borescopes are available in many different diametersBorescopes are available in many different diameters and lengths, and are classified as rigid or flexible.and lengths, and are classified as rigid or flexible.
    • 48. Visual Inspection With A Borescope Clean Surface Corrosion Damage
    • 49. Optical AidsOptical Aids • Advances in technology has allowed videoAdvances in technology has allowed video equipment to be adapted to portable and roboticequipment to be adapted to portable and robotic devices.devices. • Portable video probes allow inspectors toPortable video probes allow inspectors to remotely perform examinations in closedremotely perform examinations in closed chambers which are inaccessible by conventionchambers which are inaccessible by convention inspection means.inspection means. • Robotics have been developed whereby camerasRobotics have been developed whereby cameras can be affixed to crawlers and submersibles.can be affixed to crawlers and submersibles. – Retrieval tools can be affixed to robotics to removeRetrieval tools can be affixed to robotics to remove foreign objects.foreign objects. • Conventional recording techniques mayConventional recording techniques may be employed for image capture andbe employed for image capture and storage with many of the remote videostorage with many of the remote video inspection methods.inspection methods.
    • 50. Machine Vision InspectionMachine Vision Inspection
    • 51. • Machine vision technology uses an imagingMachine vision technology uses an imaging system and a computer to analyze an image andsystem and a computer to analyze an image and to make decisions based on that analysis.to make decisions based on that analysis. • In inspection applications, the machine visionIn inspection applications, the machine vision optics and imaging system enable the processoroptics and imaging system enable the processor to "see" objects precisely and thus maketo "see" objects precisely and thus make decisions about which component meet a specificdecisions about which component meet a specific inspection criteria.inspection criteria. • Machine vision can eliminate human factor errorMachine vision can eliminate human factor error that might result from doing difficult, tedious, orthat might result from doing difficult, tedious, or boring tasks. It also allows process equipment toboring tasks. It also allows process equipment to be utilized 24 hours a day.be utilized 24 hours a day. Machine Vision – BasicMachine Vision – Basic PrinciplesPrinciples
    • 52. The following process steps are common to allThe following process steps are common to all machine vision applications:machine vision applications: • Image acquisitionImage acquisition : An optical system gathers an image, which is: An optical system gathers an image, which is then converted to a digital format and stored into computer memory.then converted to a digital format and stored into computer memory. • Image processingImage processing : A computer processor uses various: A computer processor uses various algorithms to enhance elements of the image that are of specificalgorithms to enhance elements of the image that are of specific importance to the process.importance to the process. • Feature extractionFeature extraction : The processor identifies and quantifies: The processor identifies and quantifies critical features in the image (e.g., the position of holes on a printedcritical features in the image (e.g., the position of holes on a printed circuit board, the number of pins in a connector, the orientation of acircuit board, the number of pins in a connector, the orientation of a component on a conveyor) and sends the data to a control program.component on a conveyor) and sends the data to a control program. • Decision and controlDecision and control : The processor's control program makes: The processor's control program makes decisions based upon the data. Are the holes within specification?decisions based upon the data. Are the holes within specification? Is a pin missing?Is a pin missing? Machine Vision – Basic Principles
    • 53. Machine Vision - Applications As mentioned previously, machine vision is primarily used in production applications where a large number of components require inspection and the inspection conditions can be closely controlled. Uses include: • Assembly verification (caps, fasteners, electronic board components, etc.) • Surface inspection (dents, scratches, porosity. and other undesirable features) • Verification of colors, gradients, patterns in fabrics and labels. • Confirmation of proper labeling for medications, foods and other products. • Inspection of coating coverage. • Feature measurements. Assembly Verification Spark Gap Measurement
    • 54. Key System ElementsKey System Elements • A variety of components areA variety of components are included in a machine visionincluded in a machine vision system, which depend on thesystem, which depend on the environment, the application,environment, the application, and the budget. However, theand the budget. However, the following components arefollowing components are common to all vision systems :common to all vision systems : – Front-end opticsFront-end optics : this includes the lighting, the lens, and the: this includes the lighting, the lens, and the camera.camera. – Frame grabberFrame grabber : this is a computer processor board that: this is a computer processor board that accepts the video input from the camera, digitizes it, and storesaccepts the video input from the camera, digitizes it, and stores it for analysis.it for analysis. – ProcessorProcessor : A computer processor is required to control the: A computer processor is required to control the vision application.vision application. – Control SoftwareControl Software : Computer software is used for controlling: Computer software is used for controlling and executing vision tasks.and executing vision tasks. Machine Vision - Equipment
    • 55. Advantages of Visual InspectionAdvantages of Visual Inspection • Readily used on almost all materials.Readily used on almost all materials. • Simple to perform.Simple to perform. • Low in cost, (application dependent).Low in cost, (application dependent). • Relatively quick.Relatively quick. • Results may be permanently recorded.Results may be permanently recorded. • Can be automated.Can be automated.
    • 56. Limitations of Visual InspectionLimitations of Visual Inspection • Direct inspections are limited to surfaces only.Direct inspections are limited to surfaces only. • Indirect inspections require greater inspectorIndirect inspections require greater inspector knowledge and training.knowledge and training. • Inspector dependent, knowledge of materialsInspector dependent, knowledge of materials and processing, eye sight.and processing, eye sight. • Standards (workmanship) may be difficult toStandards (workmanship) may be difficult to obtain.obtain.
    • 57. Glossary of TermsGlossary of Terms • Borescope: A visual inspection aid used for the inspection ofBorescope: A visual inspection aid used for the inspection of internal surfaces. Borescopes are rigid and flexible.internal surfaces. Borescopes are rigid and flexible. • Corrosion: The deterioration of a metal by chemical or electro-Corrosion: The deterioration of a metal by chemical or electro- chemical reaction with its environment.chemical reaction with its environment. • Defect: A discontinuity which interferes with the usefulness of aDefect: A discontinuity which interferes with the usefulness of a part. A fault in any material or part which is detrimental to itspart. A fault in any material or part which is detrimental to its serviceability.serviceability.
    • 58. Glossary of Terms, Cont.Glossary of Terms, Cont. • Direct Visual Inspection: Visual inspection conducted where the eyeDirect Visual Inspection: Visual inspection conducted where the eye can be place within 24” of the area to be inspected at an angle ofcan be place within 24” of the area to be inspected at an angle of not less than 30not less than 30˚.˚. • Discontinuity: An interruption in the normal physical structure orDiscontinuity: An interruption in the normal physical structure or configuration of a part.configuration of a part. • Foot Candle: The amount of direct light thrown by one standardFoot Candle: The amount of direct light thrown by one standard candle on a surface one foot away. 1 Foot-candle = 10.764 Lux.candle on a surface one foot away. 1 Foot-candle = 10.764 Lux.
    • 59. Glossary of Terms, Cont.Glossary of Terms, Cont. • Inherent Discontinuity: Discontinuities which are ordinarily normal toInherent Discontinuity: Discontinuities which are ordinarily normal to the material at the time it originally solidifies from the molten state.the material at the time it originally solidifies from the molten state. They consist of porosity, inclusions, and pipe.They consist of porosity, inclusions, and pipe. • Magnifier: An optical glass which enlarges the real size of an objectMagnifier: An optical glass which enlarges the real size of an object being inspectedbeing inspected • Micrometer: A precise measuring instrument used to take accurateMicrometer: A precise measuring instrument used to take accurate readings in contact measurement.readings in contact measurement.
    • 60. Glossary of Terms, Cont.Glossary of Terms, Cont. • Pocket Comparator: A magnifier with measuring capability throughPocket Comparator: A magnifier with measuring capability through a system of interchangeable reticles.a system of interchangeable reticles. • Power of Magnification: The amount that the real size of an objectPower of Magnification: The amount that the real size of an object is enlarged. The power if designated by “X”.is enlarged. The power if designated by “X”. • Remote Visual Inspection: Inspection conducted where the eyeRemote Visual Inspection: Inspection conducted where the eye cannot be placed within 24” of the area to be inspected, or at ancannot be placed within 24” of the area to be inspected, or at an angle less than 30angle less than 30˚.˚.
    • 61. Glossary of Terms, Cont.Glossary of Terms, Cont. • Reticle: A series of lines, dots, cross hairs, or wires in the focus ofReticle: A series of lines, dots, cross hairs, or wires in the focus of the eyepiece of and optical instrument.the eyepiece of and optical instrument. • Rule or Scale: A measuring device used to make linearRule or Scale: A measuring device used to make linear measurements.measurements. • Screw Pitch Gages: A visual aid used to check the number ofScrew Pitch Gages: A visual aid used to check the number of threads per inch and rough inaccuracies in threads.threads per inch and rough inaccuracies in threads.
    • 62. Glossary of Terms, Cont.Glossary of Terms, Cont. • Secondary Processing: Metal removal processes, heat treatmentSecondary Processing: Metal removal processes, heat treatment and plating processes used to produce and article of the desiredand plating processes used to produce and article of the desired shape and finish from the formed material.shape and finish from the formed material. • Service Discontinuity: Discontinuities induced in components afterService Discontinuity: Discontinuities induced in components after they have been placed in service.they have been placed in service. • Transfer Instruments: A group of instruments used to takeTransfer Instruments: A group of instruments used to take measurements which are transferred to precise direct measuringmeasurements which are transferred to precise direct measuring devices. They consist of calipers, dividers, telescoping gages, anddevices. They consist of calipers, dividers, telescoping gages, and small hole gages.small hole gages.
    • 63. Glossary of Terms, Cont.Glossary of Terms, Cont. • Vernier Scale: A device for indicating a fraction of a whole divisionVernier Scale: A device for indicating a fraction of a whole division of a scale readingof a scale reading • Visual Scale: The ability to see. The keenness of perception.Visual Scale: The ability to see. The keenness of perception. • Wear: Wear is deterioration due to use. Wear will cause aWear: Wear is deterioration due to use. Wear will cause a reduction in cross section and strength.reduction in cross section and strength. • Weld Inspection Gages: A group of measuring devices used toWeld Inspection Gages: A group of measuring devices used to inspect welding fit up and finished weldments.inspect welding fit up and finished weldments.
    • 64. Questions?Questions? • Thank you for your time.Thank you for your time.