Footwear Material
Visual inspection for shoe uppers, flyknit mesh and sole foam, identifying yarn breakage, dropped stitches, weaving defects, holes and foaming defects, suited to curved surfaces and regular-texture backgrounds.
Industry Production characteristics
How This Industry Produces Determines How Inspection Should Be Done
Visual inspection for footwear materials centers on two things: first, imaging the industry's most common defects clearly and consistently, and second, connecting the judgement results reliably into the production line. Common implementation constraints in this industry are "the flyknit / mesh fabric background is a strongly periodic texture, and defects share the same frequency as the texture, requiring frequency-domain or structural analysis" and "the EVA foam surface of soles has natural foaming bumps and hollows whose grayscale is close to that of real holes". Whether defects can be detected consistently depends on the material's optical properties, the minimum defect size and the cycle time, and is subject to the results of a measured sample trial.
The quality inspection challenges for footwear materials center on Uppers are mostly flyknit, mesh fabric and similar materials with regular texture: normal weave and mesh openings have a periodic structure of their own, while yarn breakage, dropped stitches and holes are also periodic anomalies. The two are similar in form, and telling them apart is the core difficulty.
In addition, footwear material is often Curved or semi-3D form (toe, upper, sole), where different regions receive light at different angles during imaging, so it must be assessed whether a single view or multiple views / unfolding tooling is needed to ensure coverage.
Industry Inspection issues
Where problems actually occur on site
- On flyknit uppers, yarn breakage, dropped stitches and weave texture are hard to distinguish
- Mesh fabric and jacquard backgrounds are regular, so real defects are easily masked
- EVA foam cell texture on shoe soles is confused with real holes
- Curved footwear material surfaces cause inconsistent light reception between edges and center
- Color difference and glue overflow at multi-color / multi-material joints
Typical Inspection Objects
The Most Common Inspection Objects in This Industry
Typical Inspection Task
The judgments to be made on these objects
- Flyknit / mesh fabric: yarn breakage, dropped stitch and hole recognition
- Distinguishing foam defects from real holes in shoe sole foam
- Identification of Stains, Discoloration and Dirt on Shoe Uppers
- Check of color difference and glue overflow at multi-material joints
- Dimension verification of cut-piece contour and alignment marks
Vision Inspection Challenges
Implementation constraints specific to this industry
- Flyknit / mesh fabric backgrounds are strongly periodic textures, and defects share the same frequency as the texture, requiring frequency-domain or structural analysis
- EVA foam soles have natural foaming bumps on the surface with gray levels close to those of real holes
- Footwear material is curved, so edge and center imaging conditions differ under a single view
- Color difference criteria at multi-color joints are affected by the contrast of adjacent colors
- The same style is scaled across shoe sizes, so inspection zones must scale and align with the size
Choosing the right algorithm
Choose by Acceptance Criteria Form, Not by How Advanced It Is
Periodic Texture Analysis
Periodic modeling of flyknit / mesh fabric marks positions that deviate from the normal weave period as yarn breakage or dropped stitches
Combined Shape + Gray-Level Criterion
Foam holes are judged by combining shape regularity with grayscale difference, distinguishing foaming marks from real holes
Multi-Scale Defect Segmentation
Multi-scale segmentation of stains and discoloration suppresses woven-texture background interference
acquisition and light source
Optical conditions set the upper limit of feasibility
- For mesh fabric / flyknit, use low-angle light or backlighting to highlight the abrupt contour change at a yarn breakage
- For curved footwear material, evaluate multi-angle or polarization to reduce uneven reflection on the curve
- For EVA foam, use diffuse light with polarization to lower highlights on the foamed surface
OK / NG Judgement
How results are judged and used
| Inspection Status | judgement | Interlocking Action |
|---|---|---|
| No yarn breakage or dropped stitches on the upper, no true holes in the sole | OK | Release to Molding |
| Presence of yarn breakage / holes / true holes | NG | Mark and Reject |
| Color difference or adhesive overflow beyond the datum | NG | Route to Re-Inspection or Sample Retention |
PLC and Automation Interlocking
How results connect to the production line
For footwear materials, we recommend completing inspection at the cut piece or before upper forming, rejecting defective pieces before they reach stitching / forming to avoid semi-finished product rework.
When one style comes in multiple sizes, it is recommended to scale-map the inspection areas by shoe size, so the size information automatically recalls the corresponding recipe.
Applicable equipment
Common configuration forms for this type of inspection
Related Solutions
View the corresponding solution by inspection task
Common Question
The Questions Most Often Asked in This Industry
How do you distinguish yarn breakage in flyknit from normal knit texture?
Flyknit / mesh fabric has a periodic structure, and the normal knit can be modeled as a regular pattern in the frequency or spatial domain. Any location that deviates from that period triggers an alarm. Modeling quality depends on a standard sample, so good knit samples must be provided.
How are foam texture and true holes distinguished on EVA soles?
The foam texture is a natural surface relief, whereas a real hole is usually accompanied by shape regularity and a gray-level difference (light transmission or a dark area). A combined morphological and gray-level acceptance criterion is needed, calibrated with samples of known holes.
The Shoe Upper Is Curved: Can It Be Imaged Clearly?
Surface unfolding must be assessed, or multi-view / polarization imaging adopted. Extremely curved surfaces may require flattening with tooling or shooting in separate regions. What is actually possible depends on the shoe upper curvature and the inspection scale.
What Is the Smallest Defect That Can Be Detected?
The minimum detectable size is determined by the camera resolution and the inspection field of view; the smaller the physical size each pixel represents, the smaller the detectable size. The configuration must be derived from the minimum defect size and confirmed by measurement. To be added.
Can the same recipe be used for the same style in different shoe sizes?
Not recommended. Different sizes of the same model are scaled proportionally, and inspection areas should be aligned by size scaling. The size information can be used to call the corresponding recipe, avoiding misalignment and escapes.
How is color difference at multi-color splices judged?
Contrast between adjacent colors interferes with color difference judgement; we recommend comparing each against the same-batch reference sample of that material separately, rather than using an overall mean.
Can Vision Inspection Check Sole Bonding Strength?
No. Vision only judges appearance (holes, short shot, stains, adhesive overflow, etc.); bond strength and wear resistance must be handled by mechanical and material testing, and the two have different roles.
For visual inspection in this industry, what needs to be solved first?
The implementation constraints commonly seen in this industry center on: "flyknit / mesh fabric backgrounds are strongly periodic textures, and defects share the same frequency as the texture, requiring frequency-domain or structural analysis"; "the EVA foam surface of shoe soles has natural foaming undulations with a gray level close to that of real holes"; "footwear materials are curved surfaces, so the imaging conditions at the edges and in the middle differ under a single viewpoint". These constraints affect both the imaging solution and the cycle-time design. Normally a sample trial is needed to validate before the configuration is finalized.
How does the inspection result interlock with the production line?
Footwear material inspection is best carried out on cut pieces or before the upper is formed, so that defect parts are rejected before they reach stitching / forming and semi-finished products do not need rework. For the same style in several sizes, we recommend scaling the inspection regions by shoe size so that the size information automatically calls up the corresponding recipe.
What Equipment Configuration Does This Type of Inspection Generally Require?
Common forms include "footwear material inspection equipment" and "AI vision cut-piece inspection equipment". The specific machine model and quantity depend on the inspection area, minimum defect size and line cycle time, and must be confirmed against site conditions.
Which process steps in this industry benefit most from a visual inspection station?
The most common is: "identification of yarn breakage, dropped stitches and holes in flyknit / mesh fabric"; "distinguishing foaming defects from true holes in sole foam"; "identification of stains, discoloration and dirt on the upper". Which process steps to actually instrument depends on the cost of defects escaping downstream and the cost of rework—the later a defect is found, the higher the cost.
How do we judge whether our product is suitable for visual inspection?
Please provide upper / sole samples (including samples of yarn breakage, dropped stitches, foaming defects and true holes) and a size list, and state whether the surface is curved and what the line cycle time is. In general, as long as the acceptance criteria can be stated clearly, the defects can image clearly and consistently, and the cycle time matches the field of view, the project's feasibility is confirmed.
What inspection accuracy can be achieved?
Accuracy is not a fixed value that holds regardless of conditions. To be added — the minimum detectable size depends on the combination of field of view and camera resolution, and is also affected by illumination, lens and algorithm; the configuration must be derived from your minimum defect size and validated by measurement.
Submit sample testing
Please provide upper / sole samples (including samples of yarn breakage, dropped stitches, foaming defects, and actual holes) and a size list, and state whether the surface is curved and what the line cycle time is.
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Inspection Configuration Based on Your Industry's Products and Cycle Time
Send us photos of the workpiece, the inspection requirement (what to inspect, and the tolerance for escapes and false calls), and the line cycle time, and our solution engineers will recommend the inspection method, optical solution, and interlocking configuration for that industry.