Gasket Presence/Absence Inspection
Judges whether flat washers, spring washers and insulation washers are installed, missing or wrongly fitted, for post-assembly inspection and pre-packaging verification stations.
inspection Overview
Gasket presence/absence inspection: determine whether flat washers, spring washers, insulating washers and similar parts are installed, and whether any are missing or wrong; applicable to post-assembly inspection and pre-packaging verification stations. The judgement usually does not check details such as threads or dimensions, but rather determines Whether the visual feature at that position exists and matches expectations, output OK / NG and interlock with the production line.
Verifies whether flat washers, spring washers, insulating washers, and similar parts are installed, missing, or wrongly fitted; applicable to post-assembly inspection and pre-packaging verification stations.
The feasibility of "gasket presence/absence inspection" depends on Whether the visual features of the object are stable and distinguishable, as well as the on-site optical and tooling conditions. Each item is expanded below in the order commonly used in inspection engineering.
Object Characteristics
How the object appears in the image
- Thin profile and little color difference, so it appears indistinct in the image
- Often covered by the screw head, with only a very small ring of edge exposed
- Flat washers and spring washers look clearly different (spring washers have a gap), so they can be distinguished on that basis
- Materials include metal, nylon, rubber, insulating materials and more
inspection Challenges
Where Problems Really Occur on Site
- When hidden by a screw head, the only visible feature is the ring of exposed edge
- Metal gaskets are reflective, so edge details are easily blown out by highlights
- Thin parts show almost no thickness features from an oblique viewing angle
- Contrast is extremely low when the gasket and workpiece are the same color
Vision Judgement method
How acceptance criteria are set and why
A common approach is to judge Whether a ring-shaped contour larger than the screw head exists around the screw head — with a gasket, the outer edge of the head shows an extra ring of larger diameter.
If the gasket is completely hidden, change the angle or the acceptance criterion: observe the gap height between the screw head and the workpiece from the side - the gap is usually larger when a gasket is present.
Applicable algorithm
Choose by the Form of the Acceptance Criteria, Not by Complexity
Ring Region Inspection
Set an annular ROI around the screw head to determine whether a gasket rim is present
Diameter Comparison
Measure the equivalent diameter of the head; with a gasket the diameter is larger
Optical Precautions
Imaging conditions set the upper limit of feasibility
- Ring illumination helps highlight the edge boundary between the screw head and the gasket
- If the gasket is the same color as the workpiece, try Low-angle grazing light Create a shadow at the edge of thin parts
- Insulating washers and nylon washers are usually non-metallic, and their texture is more stable under diffuse light
OK / NG Output
How results are judged and passed to the production line
| Inspection Status | judgement | Interlocking Action |
|---|---|---|
| Gasket presence detected | OK | release |
| Gasket not detected | NG | Block as missing part |
| Gasket model mismatch (e.g. flat washer / spring washer mixed up) | NG | Treat as wrong part |
Applicable Industry
This type of inspection is common in the following industries
Common Question
The most common questions about this object
If the gasket is completely hidden by the screw head, can it still be inspected?
From a top-down view it is very difficult. Feasible approaches are to change the viewing angle or change the acceptance criteria: check the assembly gap height from the side, or use an angle that exposes the edge of the gasket. If the structure makes observation impossible, changing the tooling or using another inspection method must be considered.
Can flat washers and spring washers be distinguished?
Yes. Spring washers have an opening, giving a discontinuous feature on the contour, while flat washers have a fully closed contour. The distinguishing features are clear and form a reliably achievable acceptance criterion.
What are the acceptance criteria for this object?
A common approach is to check whether a ring-shaped contour larger than the screw head exists around the head — with a gasket in place, an extra edge of larger diameter appears outside the head.
What are the illumination requirements for this type of object?
Ring light helps highlight the edge boundary between the screw head and the gasket. If the gasket is the same color as the workpiece, try low-angle grazing light to cast a shadow at the edge of the thin part.
What Are the Inspection Accuracy and Minimum Detectable Size?
It depends on the combination of field of view and camera resolution, and is affected by the lens, illumination and algorithm. To be added — the configuration must be derived from your minimum defect size, subject to the results of a measured sample trial.
How Do We Verify That Our Product Can Be Detected?
Please provide samples with the gasket installed and with the gasket missing, along with a list of gasket models; our engineers will confirm whether the distinguishing features are stable.
Submit sample testing
Please provide samples with the gasket installed and with the gasket missing, along with a list of gasket models; our engineers will confirm whether the distinguishing features are stable.
Submitted successfully
We have received your sample testing request. A solution engineer will contact you within 1 business day via contact you.
Need to assess imaging conditions, defect criteria and cycle time item by item? Go to the Full Requirement Assessment →
Send Us Your Workpiece and We Will Show You the Measured Results
Provide several OK and NG samples, and the solution engineer will run actual imaging and judgement tests on the equipment, then give inspection configuration recommendations that can be implemented, rather than just reading a specification table.