Cameras
Five views of the seam
Four side cameras spaced around the can see the full 360° of the seam. One top camera looks down on the end to check that the seam is circular.
Station
Can seam and seal inspection station.
Cameras image every can as it leaves the seamer and measure the visible seam against the can maker’s spec. A can outside the window is rejected, and a run of rejects tells maintenance to check the seamer itself.
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Full write-up: How vision inspection catches double seam defects on a canning line
How it checks
How does the station check every seam?
The measurement happens on the line, on every can, between the plant’s scheduled seam checks.
Lighting
Dark-field light
Light comes in at a low angle, so flat surfaces stay dark and the top and bottom edges of the seam light up. Sharp edges are what a repeatable measurement needs.
Measurement
Seam height against spec
Seam height is measured in thousandths of an inch around the whole seam and compared with the can maker’s limits. Too short fails. Too tall fails.
Reject
Encoder-tracked air reject
A failed can goes to an encoder-tracked pneumatic reject driven by a PLC output. Its image, measurement, reason and timestamp are saved.
Defects
What does vision seal inspection catch on a can?
The double seam is the can’s seal. The cameras check what shows on the outside of it, on every can.
Seam height
A short or tall seam
A seam outside the height window anywhere on its circumference is rejected. The four side cameras see the whole seam, so one low spot is not averaged away.
Shape
A seam that is not round
The top camera checks that the seam is round and centered on the end. An off-center or out-of-round seam is a sign to check the seamer setup.
Local faults
Droops, vees and a Rim dent
A droop, a vee or a Rim dent changes the seam outline at one spot. Measuring all the way around catches that local change.
Trend
A seamer that is drifting
Consecutive rejects point to the seamer, not the can. The station alerts maintenance to check the rollers and chuck.
Reject logic
What does a run of rejects tell maintenance?
One bad can and a string of bad cans mean different things, so the station treats them differently.
One reject
One bad can
A single can outside the window is a bad can. The reject takes it off the line and the run continues.
Consecutive rejects
The seamer itself is failing
Several rejects in a row point to the seamer, not the can: for example, a worn second-operation roller or chuck. When the station sees consecutive rejects, it alerts maintenance to check the rollers and chuck.
Why sooner matters
Stop making bad cans
A failing seamer keeps making bad cans until someone stops it. Catching the run sooner means the crew can fix the cause sooner, instead of finding it at the next scheduled teardown.
On the line
What changes at higher line speeds?
Cans leave the seamer fast and close together. The setup has to freeze each seam and keep track of each can.
Exposure
Strobed light, short exposure
The light is strobed and the exposure kept short, so the seam edge is sharp on a moving can.
Trigger
One trigger per can
A sensor after the seamer triggers all five cameras on the same can, and an encoder tracks that can to the reject.
Interface
GigE Vision cameras
The cameras connect over GigE Vision to the vision controller, which sends pass or fail to the PLC.
Handling
Spacing and stable cans
Cans need a gap between them and stable handling through the view. The study checks your conveyor and speed with sample cans.
Where it fits
What does seam vision not replace?
Teardowns
Internal dimensions still need a teardown
A camera cannot see inside the seam. Body hook, cover hook, overlap and tightness are measured by teardown, by a qualified person, on the schedule in the plant’s closure program. Seam vision supports, and does not replace, those teardowns.
Calibration
Calibrated against a teardown
The station is set up against a reference can whose seam was measured by teardown, and re-checked against the same can at changeover. If the camera and the teardown disagree, the teardown wins.
Risk
Why the seam matters
A seam that doesn’t seal can let contaminants in after processing, including the organisms that cause botulism. The inspection helps catch those cans. A joint GMA, FMI and GS1 US survey (2010) put the average direct cost of a food recall at about $10 million.
Limits
What can’t vision seal inspection catch?
A camera sees the outside of a seal. These checks stay with the plant’s own tests.
Inside the seam
Internal seam dimensions
Body hook, cover hook, overlap and tightness need a teardown. Seam vision supports the teardown program and does not replace it.
Leaks
Seal strength and leaks
Whether a seal holds is checked by the plant’s own tests, such as teardowns for cans and peel or burst tests for pouches.
Other packs
Pouch, flow-wrap and tray seals
Open seals, product in the seal or a channel show from one side. A single-camera station images the seal area.
Scope
The seam you can see
The station checks the visible double seam. Panel, body and coating defects need a different view, which the study can add.
FAQ
Questions about seal inspection
QWhat is vision seal inspection?
A camera station images the seal on every package and rejects the ones outside the limits. On a metal can, the seal is the double seam. This station measures the visible seam all the way around every can and compares it with the can maker’s spec.
QDoes seam vision replace teardowns?
No. Body hook, cover hook, overlap and tightness are inside the seam, so they need a teardown by a qualified person on the schedule in the plant’s closure program. The station is set up against a torn-down reference can, and if the camera and the teardown disagree, the teardown wins.
QCan it keep up with the seamer?
Line speed decides the exposure, the light and the can spacing the station needs. The feasibility study runs your sample cans at your speed and states in writing whether the setup holds.
QCan the same approach inspect pouch or tray seals?
The method is different. A pouch, flow-wrap or tray seal is imaged from one side for open seals, product in the seal and channels. The film and the seal pattern decide the camera and the light, which is what the sample test checks. See vision inspection.
Next step
Start with your line.
Tell us what you make and what is getting through. Start with a feasibility study.
Every station is tuned and reported on two numbers kept apart: false rejects, good packs thrown out, and escapes, bad packs let through.
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