Burr and Flash Defect Visual Inspection
Burr and flash visual inspection: for excess material, overflow and burrs on the edges of injection-molded, die-cast, stamped and die-cut parts, low-angle light or 3D height information forms a clear image of edge anomalies, distinguishing material fuzz from true flash.
defect Overview
Making excess material at the edge form a clear image; the difficulty is distinguishing material fuzz from true flash or burrs
Burr and flash are excess material left at the edge or parting line after forming or cutting: overflow (flash) from injection molding and die casting, burrs from machining and stamping, and rough edges from die cutting. Under low-angle light these protrusions become visible through their shadows, or they can be quantified using 3D height information. Machine vision judges on this basis; the main risk is misjudging the material's own fiber fuzz or parting line as flash, so the threshold must be defined by the quality department.
Burrs and flash appear in the image as local protrusions or excess material at edges or the parting line. With low-angle light from the side, a raised flash casts a clear shadow and images more readily than with flat lighting; for parts with tight requirements, quantifying the protrusion directly with 3D height information is the most reliable method.
These defects are very easily confused with the "normal edge condition". Fiber fuzz on die-cut parts, loose strands after cutting woven / composite materials, and the parting line of an injection-molded part are not necessarily defects. Judgement must know the "normal edge morphology" of the process, and only protruding material beyond the allowed range should be judged as flash / burr.
The other difficulty is position: flash tends to appear on the parting surface, around ejector pins and at gate remnants, and these positions must be registered first so that designed features (such as ribs and clips) are not misjudged. For tiny burrs, the detection limit depends on the field of view and the resolution of the 3D/camera, and must be confirmed by measurement.
Occurrence Causes
Only when the cause is known can you decide which station should check for it
- Mold clamping and clearance: insufficient clamping force in injection molding or die casting and mold clearance cause flash
- Tool dulling: dull stamping / die-cutting blades produce burrs and rough edges
- Machining parameters: improper cutting parameters leave burrs on the edge
- Normal edges: fiber fray and parting lines are normal and must be excluded by template
- Ejector Pins/Gates: Excess Material Around Ejector Pins and Residual Material at Gates
imaging Key Points
Whether it can be detected depends first on whether it can be captured
Low-Angle Light
Side grazing light amplifies the shadows of raised edges, making flash and burrs visible
3D Height Information
Directly quantifies the amount of edge protrusion; the most objective, suitable for strict parts
Template Registration
Register normal structures such as parting lines / ribs to avoid false calls
Backlit Contour
Use backlight on die-cut parts to get a clear edge and check for burr overflow
judgement Method
The judgement centers on "edge protrusions or excess material beyond the allowed range". The template first excludes normal structures such as parting lines and ribs, then measures protrusion height (or shadow length) and position on the edge saliency map. 3D height measurement is better than 2D shadows but costs more.
Threshold bias: burrs on functional surfaces may affect assembly, so rejection should be on the strict side; but misjudging fiber fuzz creates over-rejection, so the baseline for normal edge morphology must be accurate. The specific protrusion tolerance is defined quantitatively by the quality department and saved with the recipe.
| Judgement Dimension | Description |
|---|---|
| Protrusion Height | Excess material height at the edge measured in 3D, or shadow length in 2D |
| Position | Whether it lies in flash-prone areas such as the parting surface / gate; exclude normal structures by template |
| Continuous / Discrete | Distinguishing continuous flash from discrete burrs |
| Material Fray | Graded handling of loose fiber strands and true burrs |
| Functional Impact | Burrs on assembly surfaces are rejected first |
Applicable algorithm
Edge Saliency Map
Low-angle light / 3D brings out edge protrusions and extracts suspect regions
- Multi-directional coverage to avoid blind spots
- 3D height quantification
Template Exclusion
Register parting lines/ribs to exclude normal structures
- Avoid false rejection of structural features
- Recipe recall on mold change
Contour Comparison
Backlight contour inspection for burr overflow on die-cut parts
- Suitable for cut parts
- Filter by overflow amount
Common Materials
Common Industry
Common Question
How do you distinguish burrs from material fray?
Can Parting Lines Be Misjudged as Flash?
Why is 3D recommended for flash measurement?
Can tiny burrs be detected?
Who Sets the Rejection Threshold for Flash?
What Is the Smallest Burr That Can Be Detected?
Does Switching the Mold Model Require Reconfiguration?
Submit sample testing
Burr and flash inspection relies on low-angle light and 3D data to form a clear image of the raised edge, and distinguishes material fuzz from genuine flash.
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Send Us Your Defect Samples and We Will Measure Them and Show You the Results
Whether a defect can be detected depends on whether imaging captures the defect features. Provide OK and NG samples and we will run actual imaging and judgement tests on the equipment.