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Defect and Scratch Inspection for Surface Quality

Detects scratches, dents, stains and colour deviation on machined, moulded and coated surfaces, with the illumination chosen for the material.

This Category positioning

Surface defect inspection of flat and near-flat formed parts: first make the defect form a clear image, then separate it from the normal texture, and only then make the judgement

Solution Category · 03
Quick answers

This solution is designed for Flat stamped parts, sheet metal parts, powder metallurgy parts, die castings, ceramic parts and automotive components flat-surface appearance quality inspection, combined with 2D area-scan vision, 2D line-scan vision, 2.5D surface topography inspection, 3D measurement, and AI vision algorithms, covering surface defects such as scratches, scuffing, indentations, pits, pockmarks, blowholes, sand holes, burrs, chipped corners, short shots, cracks, discoloration, oil stains and dirt. From image acquisition, defect recognition and dimensional inspection to OK/NG judgement and data recording, it provides complete automated visual inspection capability for flat and near-flat formed parts.

Stamped parts, sheet metal parts, powder metallurgy parts and automotive parts usually show different types of surface quality problems during production. These defects share one characteristic: The product itself may show no obvious color change, yet its surface topography has already changed. For example, shallow scratches show little color change, slight indentations have a gray level close to that of the normal surface, and tiny pits cover only a very small area; powder metallurgy parts have complex surface texture of their own; die castings have pitting, porosity and rough texture on the surface; stamping can also produce tearing, indentations and local deformation, while reflections on metal surfaces affect the stability of conventional 2D images.

Therefore, visual inspection of flat metal parts is not simply "taking a photo". What really needs to be solved is: How to image defect characteristics consistently and then judge them accurately with algorithms. This is also why this type of solution puts "imaging method selection" before "algorithm selection" — the same scratch may be invisible under diffuse light, but becomes very obvious under low-angle or directional illumination.

In actual projects, solutions of this kind are usually configured according to Product dimensions, production method, surface material, defect types, and inspection cycle time Combining vision technologies: for flat products that are stationary or fed intermittently, prefer 2D area-scan; for long, large or continuously moving products, consider 2D line-scan; when 2D struggles to resolve topography-type defects such as shallow scratches, tiny pits and indentations, add 2.5D surface topography inspection; when measurement items such as flatness, warpage and height difference are required, introduce 3D; when defect shapes vary widely and are hard to enumerate with rules, use AI defect inspection to supplement the judgement capability.

inspection Pain Points

Why surface defects on flat parts are hard to inspect

The problems with manual visual inspection are low efficiency and inconsistent inspection standards, with the judgement scale drifting after long working hours. Ordinary vision solutions, meanwhile, are easily disturbed by material, texture and reflection in the inspection of fine surface defects. The table below lists the most common difficulties in projects of this type.

Defects Have No Clear Color Difference

Shallow scratches show little color change and light indentations have a gray level close to that of the normal surface, so a single gray threshold can hardly separate them reliably.

Small Defect Scale

Tiny dents, pitting and pinholes have very small areas; under a field of view and resolution that do not match, only a few pixels remain after imaging.

The Normal Texture Is Complex in Itself

The porosity and sintering texture of powder metallurgy parts and the rough surface of die castings both produce signals similar to defects, so "normal texture" must be distinguished from "real defects".

Metal Surface Reflections

Highly reflective areas on polished surfaces, platings and aluminum parts make the gray-level distribution of 2D images unstable, so the imaging method must be specifically designed.

Topography defects cannot be seen

The core characteristic of defects such as indentations, bulges and local deformation is not color but a change in surface height, which appears very weakly in ordinary 2D images.

Combined Inspection of Multiple Items

A single workpiece often has multiple requirements at once — appearance defects, dimensions, hole positions, characters, and so on — so several classes of judgement must be completed on one machine.

There is no single way to deal with the difficulties above: some are solved by changing the imaging method, some by combining several technologies, and some require the acceptance criteria to be quantified with the quality department first. The specific route must be evaluated together with the workpiece and the site conditions.

Core Technologies Solution

2D area scan + 2D line scan + 2.5D surface topography + 3D measurement + AI defect inspection

Depending on product dimensions, production method, surface material, defect types and inspection cycle time, a project can choose different vision technologies, or combine several of them on the same workpiece.

01 | 2D Area-Scan Visual Inspection

Suitable for static and intermittent flat product inspection, using an industrial camera to acquire high-resolution images of the product surface.

  • Inspection: off-color, oil stain, dirt, short shot, chipped corner, visible scratch
  • Inspection: characters, printing, hole position, contour, dimensions
  • Applicable: stamped parts, sheet metal parts, flat metal parts, automotive parts, powder metallurgy parts, ceramic parts

02 | 2D Line-Scan Visual Inspection

For long, large and continuously moving products, it performs continuous acquisition of long products that an ordinary area-scan camera cannot easily cover in one shot.

  • Process: continuous motion → line-scan acquisition → image stitching
  • Process: defect recognition → OK/NG judgement → automatic rejection
  • Applicable: long stamped parts, metal sheet, continuously produced products, large sheet metal parts, web materials and long-format products

03 | 2.5D Surface Topography Visual Inspection

When 2D cannot resolve a defect clearly, vision looks further into the surface topography. Surface topography features are acquired through specific optical imaging methods.

  • Available data: height information, normal information, curvature information
  • Obtainable: shadow features, texture features
  • Applicable: shallow scratches, slight indentations, tiny pits, slight raised areas, pitting and localized surface anomalies

04 | 3D Dimension and Geometric Inspection

For measurement items such as flatness, warpage, local deformation and height difference, quantitative judgement is completed using point cloud data.

  • Algorithm: point cloud preprocessing, outlier filtering, ROI extraction
  • Algorithm: datum plane fitting, multi-point height sampling, Z-direction deviation calculation
  • Output: 3D data, measurement points, height values, flatness results, and out-of-tolerance positions

05 | AI Defect Inspection

When defect forms are highly variable and difficult to describe exhaustively with rules, deep learning models perform the recognition and classification.

  • AI defect classification, AI object detection
  • AI semantic / instance segmentation
  • Anomaly detection, 2D and 3D data fusion

06 | Multi-Station Fusion

2D, 2.5D, 3D and dimensional measurement are assigned to different stations, completing multiple judgement types within one machine.

  • Independent triggering of multiple cameras and light sources
  • Results merged and output uniformly as OK / NG
  • Can interlock with loading/unloading and sorting mechanisms

inspection Scope

Common Inspection Items and Preferred Imaging Methods for Flat Formed Parts

Key Inspection Points

Scratch | scuff | indentation | dent | pitting | blowhole | sand hole | burr | chipped corner | short shot | crack | discoloration | oil stain | dirt | surface anomaly

Defect CategoryTypical DefectsPreferred Visualization / Inspection Method
Linear DamageScratches, scores, drag marks, scuffs, gougesLow-angle or stripe light reveals them; diagonal scratches need multi-directional illumination, combined with 2.5D topography when necessary
DeformationIndentations, crush marks, pits, bulges, local deformation, warping2.5D topography / fringe light; height and flatness measurement items switch to 3D point cloud
Surface ContaminationOil stains, dirt, foreign matter, rust spotsDiffuse light / coaxial light; must be distinguished from the material's own normal texture
ChromaticityOff-color, color difference, oxidation discoloration, local darkeningStable light source + white balance datum; the acceptable color difference range must be defined first
CastingBlowholes, sand holes, cold shuts, shrinkage depressions, flow linesCombination of diffuse and low-angle light; shallow pits are evaluated with 2.5D
Powder Metallurgy CategoryShort shot, powder loss, chipped corners, delamination, abnormal porosity, pitting2D + 2.5D + AI combination, with the focus on separating normal porosity from abnormal defects
EdgeBurrs, edge burrs, flash, chipped edges, missing corners, gate residueBacklight or coaxial light for contour measurement; burr-height items combined with 2.5D/3D
CrackCracks, micro-cracks, delamination crackingHigh resolution + side light; must be distinguished from scratches and machining marks
ProcessMissing material, missed punch holes, stamping anomalies and abnormal machining marks2D contour and area analysis; hole position items switch to measurement algorithms
DimensionalHole diameter, hole spacing, outer diameter, inner diameter, length, width, contour dimensionMeasure after calibration, and note how fixturing, positioning and material travel affect the measurement
The table lists the inspection item commonly covered by this type of solution. For a specific project, the inspection item, acceptance criteria and thresholds must be confirmed individually according to the workpiece and quality requirements; you can send us the workpiece, defect samples and inspection requirements for an assessment first.

inspection Object

Common product, material and part types inspected

The following groups are based on material and part type. Workpieces in the same group can often reuse the same optics and algorithm route; products across groups usually need the imaging method evaluated separately.

Flat Stamped Parts / Sheet Metal Parts

Stamped panels, chassis brackets, automotive structural parts, sheet metal parts, metal housings, stamped gaskets and metal brackets.

Powder Metallurgy Parts

Powder metallurgy structural parts, sintered parts, automotive parts, oil-impregnated bearings, gears and precision metal parts.

Die Castings

Aluminum alloy die castings such as automotive housings, brackets, valve bodies, motor housings and metal structural parts.

Ceramic and Flat Structural Parts

Ceramic substrates, ceramic structural parts, insulating parts, ceramic valve plates, and precision ceramic parts.

automotive parts

Stamped parts, sheet metal parts, die castings, powder metallurgy parts, metal brackets, structural parts and decorative parts.

Other Precision Metal Parts

Precision machined parts, hardware and fasteners — parts whose appearance is mainly flat or nearly flat.

View Inspection Highlights by Defect Type

View Application Solutions by Workpiece

The above are common inspection objects. If your workpiece is not in the list above, you can also submit samples for a separate evaluation.

Typical defect

Which defects this type of solution mainly targets, and what to watch for in each case

defect Typical ManifestationsInspection Focus Points
Scratch / ScuffSurface linear damage with clear directionalityLow-angle light reveals the feature; diagonal scratches may be masked by directional illumination, and shallow scratches on dark glossy materials require dedicated validation
Indentation / Compression DamageShallow dents formed by local pressure, with little color changeThe gray-level difference in 2D is small, so 2.5D topography is often used for confirmation; it must be distinguished from normal process embossing
Pits / BulgesLocal height anomaly, the area may be very smallTopography features rather than color features; for very small areas, the field of view and resolution must be confirmed first
Pitting / Sand HolesDense small dot-like surface anomaliesDistinguishing these from normal material grain and residual molding sand is the main source of false calls
Porosity / Cold ShutHoles and flow marks formed by the casting processCombination of diffuse and low-angle light; shallow porosity needs 2.5D evaluation
Burr / Edge ChippingExcess material at the edge or local damageBacklight or coaxial light for contour measurement; burr height requires 2.5D/3D
Short Shot / Missing Punched HoleMissing material or skipped process stepCompare with the normal contour; note false calls caused by workpiece placement deviation
Crack / Micro-CrackThin, discontinuous linear defectsRequires high resolution + side lighting, with attention to distinguishing them from scratches and machining marks
Discoloration / oxidation color differenceChromaticity deviation within a part or between batchesRequires a stable light source and a white balance reference; the quality department should first define the acceptable color difference
Oil stains / dirt / foreign matterSurface deposits or embedded particlesDistinguishing them from the material's natural texture is essential; same-color foreign matter has low contrast and requires dedicated illumination
Defect names and judgement definitions are not standardized across the industry. Before implementation, we recommend that the quality department quantify the defect categories, limit samples, and acceptance criteria, and retain boundary samples to avoid disputes at the acceptance stage.

inspection Capabilities

From single-defect inspection to comprehensive multi-item judgement

Products such as automotive parts have high requirements for appearance and manufacturing quality, and visual inspection can cover the following five categories of judgement on a single machine.

appearance inspection

Recognition and classification of surface defects such as scratches, impact marks, compression marks, pits, dirt, off-color, foreign matter and burrs.

dimensional inspection

Measurement items such as length, width, outer diameter, inner diameter, hole diameter and hole spacing, judged against the upper and lower tolerance limits after calibration.

Contour Inspection

Contour comparison and deviation calculation for the outer contour, edge position, and hole position relationships.

defect inspection

Judgement rules are established by defect type, area, length, width and position, and a defect grade is output.

character recognition

Presence of characters, missing characters, abnormal characters and content recognition, used to confirm model and batch.

Form and Position Inspection

Flatness, warpage, height difference and local deformation are handled through 3D point clouds and datum plane fitting.

The capabilities above are the range the solution can cover; which defects a specific project can detect and to what level must be confirmed through sample trial validation with real samples.

AI vision algorithm

Rule-based algorithms and deep learning used in combination according to defect characteristics

Traditional vision algorithm

Suited to inspection items with regular shapes and quantifiable criteria, where results are explainable and parameters traceable.

  • Edge extraction and contour analysis
  • Sub-pixel dimensional measurement, circle fitting, line fitting
  • Blob region analysis, gray level/color difference inspection
  • Scratch inspection, foreign matter and dirt inspection, burr inspection
  • Defect region segmentation with area, length and width calculation

Deep Learning Algorithms

Suited to defects with highly variable shapes that are hard to cover with exhaustive rules, and requiring sample training and maintenance.

  • AI Defect Classification
  • AI Object Detection
  • AI semantic / instance segmentation
  • Anomaly detection (modeling the normal state when defects are hard to enumerate)
  • OCR character recognition, 2D and 3D data fusion

In the same project, the two types of algorithms are usually used in parallel: Rule-based measurement items go to traditional algorithms, ensuring stable values and traceability; Defects of varying shape are handled by deep learning, with the model performing recognition and classification; the two results are merged and output as a single OK/NG.

The practical performance of deep learning depends on sample quality and quantity. For the thresholds and common pitfalls of sample preparation, refer to How Many Defect Samples Are Enough and How to Determine Visual Inspection Accuracy .

vision software Platform

The inspection software completes acquisition, judgement, recording and external communication

Recipe and Parameter Management

Product recipe management and inspection parameter management, supporting fast switching between multiple products.

Permission Management

Tiered permissions for operation, debugging and maintenance keep specifications from being changed at will.

Statistics and Reports

OK/NG statistics, defect classification statistics, report output.

Image and Result Retention

Defect images are saved and inspection results can be queried, making re-judgement and review easier.

data traceability

Images, results and product information are linked together to support historical queries.

External Interfaces

PLC communication and MES / production system data interfaces can output OK signals, NG signals, defect types, inspection results and measurement data.

Software function modules are configured according to project needs rather than piling on features. If integration with an existing production line system is required, see How the Vision System Integrates with the PLC / Production Line .

Technology Architecture

Optical imaging layer · algorithm layer · vision software layer · automation control layer

The product is not a single "camera inspection" but a four-layer coordinated system: the optics layer determines whether a defect can be imaged, the algorithm layer determines whether it can be resolved, the software layer handles judgement and recording, and the automation layer handles integration with the production line.

First Layer: Optical Imaging Layer

Configure 2D area scan, 2D line scan, 2.5D vision, and 3D line laser according to the product characteristics, and select low-angle, coaxial, diffused, backlight, or pattern light sources according to the defect type.

Layer 2: Algorithm layer

A combination of multiple algorithms is established: sub-pixel measurement, contour analysis, region analysis, grayscale and color difference, defect segmentation, and AI classification / inspection / segmentation and anomaly detection.

Third Layer: Vision Software Layer

Unified management of product recipes, camera acquisition, algorithm calls, parameter management, inspection results, defect classification, data storage, image traceability and report statistics.

The Fourth Layer: Automation Control Layer

Integrates with the PLC, loading and unloading mechanism, conveyor mechanism, locating mechanism, sorting mechanism and MES / data system to complete triggering, sorting and data return.

The four-layer configuration varies by project: for projects with few inspection items and modest cycle time requirements, the first three layers are enough; only projects that need automatic loading and unloading and automatic sorting bring in the fourth layer.

inspection Method

What exactly is the difference between 2D and 2.5D

In One Sentence

2D mainly looks at what changes on the surface; 2.5D goes further and looks at whether the surface has height changes.

defect 2D Image Representation2.5D PerformanceResult
oil stainGray level changesSurface height remains essentially unchangedVisible in 2D
PitsThere may be only a very weak grayscale changeClear surface topography changes can be observed2D + 2.5D Is More Reliable
scratch May appear as a line of abnormal gray levelCan further analyze the surface topography changes caused by scratchesSelect the combination according to darkness and material

Therefore, for products such as flat stamped parts and formed metal parts, the appropriate option can be selected according to the actual defect characteristics 2D, or 2D + 2.5D Combined Inspection. The basis for judgement is not "which technology is more advanced" but whether this type of defect appears in the image mainly as a grayscale difference or mainly as a topography difference.

When to Use 2D

The defect shows a clear difference in grayscale, color or contour from the product background, for example oil stains, rust spots, obvious short shot, obvious chipping, off-color and abnormal hole position.

When to Add 2.5D

The defect features are mainly height variations, such as shallow scratches, tiny dents, indentations, slight bulges and surface topography anomalies.

When to Use 3D

Quantitative geometric values must be output, such as flatness, warpage, height difference and local deformation.

inspection workflow

  • 01 Collect real OK / NG samples (including borderline samples)
  • 02 Lighting and imaging trials to confirm that defects can be imaged
  • 03 Define the inspection zone and the smallest defect size that must be detected
  • 04 Label samples and train / tune parameters
  • 05 Trial run at batch scale and count escapes and over-rejections
  • 06 Adjust the threshold according to the cost asymmetry
  • 07 Go live while keeping a channel for review and retraining
For the choice of reveal method, refer to Light Source and Illumination Selection and Industrial Camera Selection .

Equipment and complete machine

Flat-Part Visual Inspection Equipment Configuration and Station Structure

The table below lists the equipment configurations commonly used for this type of solution. The cabinet structure, number of stations, and infeed/outfeed method are determined by the workpiece loading method, the number of inspection items, and the line cycle time: small products with a single inspection item usually use a single-station machine; products with multiple inspection items have the stations split by item; and products that require linked production are equipped with belt conveying or a rotary-table infeed/outfeed mechanism.

The above is an illustration of the equipment form. The optical configuration, number of stations, material in/out method, external dimensions and interfaces of a specific model must be determined according to the actual workpiece and production line conditions. [To be added]: outline dimension drawings, interface definitions and optional configuration lists for each machine model.

Applicable Industry

Typical Industries These Solutions Are Installed In

The above are the common applicable industries for this type of solution. Actual feasibility depends on the workpiece, material, and site conditions, and is subject to the results of a measured sample trial.

Typical Applications combination

Solution combinations by inspection purpose and their technical routes

Solution Core ApplicationsCore Vision TechnologiesCore Algorithms
Solution 1Combined inspection of flat stamped parts2D / 2.5D / 3DDefect + Measurement
Solution 2Scratch Defect Inspection2D / 2.5DDefect Segmentation + AI
Solution 3Hole Diameter Measurement2D area scanSub-Pixel Measurement
Solution 4Flatness Inspection3DPoint cloud + plane fitting
Solution 5Burr Edge Inspection2D / 3DContour Analysis
Solution 6Presence/absence / missing part inspection2DTemplate Matching + AI
Solution 7Powder Metallurgy Inspection2D / 2.5D / 3DDefect + Measurement
Solution 8Inspection of flat areas on die castings2D / 2.5D / 3DROI + Defect Algorithm
Solution 9Ceramic flat part inspection2D / 2.5DDefect Segmentation + AI
Solution 10Combined inspection of automotive parts2D / 2.5D / 3D + AIMulti-Algorithm Fusion
The table above classifies the technology combinations of this type of solution and illustrates the approximate route for different inspection purposes, does not represent the number of delivered cases. Actual projects usually start with one item or a combination of several, then expand based on the sample trial results. [To be added]: industry application cases that can be made public (published only with customer authorization).

Implementation Workflow

Ten steps from project overview to delivery

  • 01 Project overview: define the workpiece, material and inspection purpose
  • 02 Inspection requirements: confirm the inspection category and acceptance criteria item by item
  • 03 Overall Technical Architecture: Determining the Number of Stations and the Inspection Division of Work
  • 04 Optical imaging solution: light source, lens and camera selection with illumination validation
  • 05 Algorithm plan: division of labor between rules and AI, plus parameters
  • 06 Software plan: recipes, UI, statistics, and interfaces
  • 07 Automation solution: loading and unloading, conveying, sorting and PLC integration
  • 08 Performance validation: confirm item by item against the validation list
  • 09 Risks and countermeasures: boundary samples, special materials and cycle time risks
  • 10 Project delivery: acceptance, training, and operation and maintenance

Project Performance Validation Items

When the project is formally implemented, the following validation items are established according to the customer's specification, and the validation conclusions are subject to the samples and test conditions jointly confirmed by both parties.

Validation ItemValidation Content
Imaging AccuracyPixel accuracy, field of view, defect visibility
inspection capabilityOK / NG Sample Validation
Measurement AccuracyStandard parts and repeated measurement
RepeatabilityMultiple consecutive acquisitions
escape rateNG Sample Validation
Over-rejection RateOK Sample Validation
CTComplete inspection cycle per part
stabilityContinuous operation test
data traceabilityLinking images, results, and product information
The specific target values of the validation items must be determined during the sample trial stage according to the actual parts; this page does not presuppose figures. For how to draft acceptance criteria, refer to Machine Vision Inspection Acceptance: How to Write a Standard Nobody Will Argue About.

Why Choose EEK

Optics, algorithms, software and automation: all four layers delivered by the same team

Validate Illumination First, Then Discuss Algorithms

In projects of this kind the reason for failure is usually not the algorithm but the fact that the defect never shows up in the image at all. We make the imaging experiments solid at the solution stage and only define the algorithm route after confirming that the defect can be imaged.

Combine Technologies by Defect Characteristics Instead of Forcing a Single Solution

Do not add 2.5D where 2D is sufficient; introduce 2.5D or 3D only when topography judgement is needed, and bring in AI when defects are hard to enumerate. Technology selection is subordinate to inspection purpose and cost.

No Fabricated Metrics, Sample Trial Results Prevail

Specifications such as accuracy, cycle time and escape rate are strongly tied to the workpiece and site conditions; we do not make numerical commitments that have not been measured, but run a sample trial first and then jointly confirm the achievable level.

Equipment and Automation Delivered as One Package

Optics, algorithms, software, loading and unloading and PLC integration are handled by the same team, avoiding the interface finger-pointing common when vision and production line belong to different suppliers.

For more technical notes on this type of solution, see Illumination Selection, Accuracy Definition, Sample Thresholds, Acceptance Standards and PLC integration Five technical guides.

This Category Solution

Other solution pages for the same type of problem

Solutions in this category are subdivided by inspection purpose and workpiece type. The table below lists the related solution pages already built; slots for further workpiece-specific solutions are reserved and will be published as the information is completed.

Solution to Be AddedPowder metallurgy parts dedicated solution · Inspection Objects · Typical Defects · Applicable Equipment
Solution to Be AddedDie casting dedicated solution · Inspection Objects · Typical defects · Applicable equipment
Solution to Be AddedCeramic part dedicated solution · Inspection Objects · Typical defects · Applicable equipment
The remaining sub-solution slots in this category are reserved and will be published as the solution information is completed. If your workpiece is not covered above, you can submit samples directly for a separate assessment.

This Category Document Checklist

Confirmed items and outstanding items

Information ItemDescriptionStatus
Inspection Objects and Covered MaterialsStamped parts, sheet metal parts, powder metallurgy parts, die castings, ceramic parts, automotive partsExisting
Technical approach and algorithm capabilities2D area-scan / 2D line-scan / 2.5D / 3D / AI and software function modulesExisting
Implementation process and validation itemsTen-step implementation process and nine performance validation itemsExisting
Equipment Model SpecificationsOutline dimensions, interface definitions, optional configuration listTo be added
Defect list and acceptance criteriaMust be quantitatively defined by the customer's quality department, including borderline sample criteriaTo be added
Real defect samplesOK / NG and borderline samples, in sufficient quantity for training and validationTo be added
Minimum defect size to be detectedDetermines field of view and resolution; must be validated by measurementTo be added
Inspection cycle time and production line conditionsLoading and unloading method, available space and site lighting conditionsTo be added
Publicly shareable application casesPublication requires customer authorizationTo be added
Sample and defect photographsFor replacing the equipment diagram on this page and adding workpiece and defect sample imagesTo be added
Items marked "To be added" are content that requires real business data before it can be published; no speculative figures are filled in before it is completed — parameters, specifications and cases are all based on measurement and real data.

Common Question

Common Questions About Flaw Inspection of Flat Parts

Why can't surface defects on flat stamped parts be judged from a single photo?

This is because many defects have no obvious color change themselves; only the surface morphology has changed: shallow scratches show little color change, slight indentations have a gray level very close to that of a normal surface, and tiny pits are very small in area. Combined with the surface texture of powder metallurgy parts, the pitting and rough texture of die castings, and the reflections from metal surfaces, the gray level differences in an ordinary 2D image are often insufficient to reliably distinguish defects from normal surfaces.

So what such projects really have to solve comes down to two things: Image the defect characteristics consistently first, then judge them accurately with algorithms.

What exactly is the difference between 2D and 2.5D?

In one sentence: 2D mainly looks at what changes on the surface; 2.5D goes further and looks at whether the surface has height changes. Take oil stains as an example: the gray level changes in a 2D image, but the surface height barely changes. Take a dent as an example: 2D may show only a very weak gray-level change, while 2.5D can reveal an obvious change in surface topography. Take a scratch as an example: 2D may show it as a line of abnormal gray level, while 2.5D can further analyze the surface topography change caused by the scratch.

So 2D, or a 2D + 2.5D combination inspection, can be selected according to the actual defect characteristics.

When is line-scan vision mandatory?

For long products that a conventional area scan camera cannot easily cover in one shot, such as Long stamped parts, metal sheet, large sheet metal parts, and coil and long-format products, line-scan vision can be used for continuous acquisition: continuous product motion → line-scan image acquisition → image stitching → defect recognition → OK/NG judgement → automatic rejection. It is particularly suited to inspection scenarios where the production line runs continuously.

Why are powder metallurgy parts difficult to inspect?

Powder metallurgy parts themselves may have Lots of normal surface texture and pores, so the difficulty of visual inspection is not simply finding "black spots," but distinguishing normal surface texture from the abnormal defects that genuinely affect product quality. Common defects include short shot, powder loss, chipped corner, indentation, crack, delamination, pitting and abnormal porosity. Projects of this kind usually require 2D vision + 2.5D topography + AI algorithms for combined inspection.

Which die casting defects suit 2D, and which require 2.5D?

Common die casting defects include porosity, sand holes, cold shuts, shrinkage depressions, flow lines, flash, burrs, gate residue and scuffs. Among them Obvious surface defects can be inspected with 2D vision; for Shallow pits, local height anomalies, burr height and surface topography changes, so a 2.5D vision approach can be evaluated further.

What is the inspection accuracy?

[To be added] Accuracy depends on the field of view and camera resolution, as well as the contrast between defect and background—at low contrast, even sufficient resolution may not give reliable detection. The correct approach is to first determine the smallest defect size to be inspected, then work back to the field of view and resolution, and finally verify with a measured sample trial.

Can it replace manual visual inspection?

can replace Repeatable appearance judgement, and it is more consistent than manual labor—operators tire and standards drift. But it also has clear boundaries: internal defects cannot be seen by vision, and items that require tactile or destructive testing cannot be handled either. It also needs someone responsible for sample maintenance, threshold adjustment and NG review, so it is not completely labor-free.

What if the over-rejection rate is high after launch?

First clarify whether it is an imaging problem or a judgement problem: Pull up the images of the over-rejected parts and look at them. If a defective part and a normal part look clearly different on the image, it is a matter of thresholds or algorithm parameters; if the two images are almost identical, it means the illumination failed to reveal the difference and the imaging method must be changed. At this step we recommend keeping the original images on file, otherwise the case cannot be reviewed later.

Submit sample testing

Send us the workpiece, the defect samples, the inspection requirements and the line cycle time, and a solution engineer will determine which category of inspection problem it is and provide recommendations on the imaging method, the algorithm route and the equipment configuration.

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        A solution engineer will contact you within 1 business day after submission

        Need to assess imaging conditions, defect criteria and cycle time item by item? Go to the Full Requirement Assessment →

        Not Sure Which Category?

        Send us the workpiece, defect samples and inspection requirements, and a solution engineer will determine which category of inspection problem it is and give recommendations on the imaging method, algorithm route and equipment configuration.

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