Empty container and preform inspection
Base, sidewall, finish and gate checks on empty glass and plastic bottles, jars and PET preforms, before filling or blowing.
Technical review: Frank GuoReviewed
A camera station can inspect empty bottles, jars and preforms before filling or blow moulding: the base, the sidewall, the finish and, on preforms, the gate and body. It finds chips, cracks that catch the light, deformation and opaque foreign objects. Each position needs its own view and lighting. It is weakest on clear liquid residue and on cracks that do not reflect light, and it cannot see into opaque containers. We confirm what is visible on your containers first.
Inspection positions on containers and preforms
Four positions, each with its own camera and lighting. Most lines need two or three, chosen from the faults that matter to you.
Base
Foreign objects, dirt, glass and base damage, lit from below.
Sidewall
Stones, bubbles, dirt, scuffs and misshapen containers, seen against a backlight.
Finish and neck
Chips, cracks and uneven sealing surfaces that would stop a cap sealing.
Preform gate and body
Gate holes, long gates, black specks, bubbles, haze and short shots on PET preforms.
Why one camera is not enough
A camera sees one side of a round container. The far side, the shoulder and the base each need another view, so stations add cameras or mirrors, or turn the container or preform in front of the camera.
What a camera can and cannot see inside an empty container
Contamination is why most plants ask, and where the limits matter most.
| Contamination or fault | Can a camera see it? | Where it stops |
|---|---|---|
| Opaque objects and dirt | Usually: they block the light. | Very small or pale objects are confirmed on samples. |
| Clear liquid residue | Often not: a thin clear film looks like an empty base. | Dedicated empty-bottle inspectors add non-camera sensors for this. |
| Cracks in glass | When the crack reflects or bends light to the camera. | A hairline crack at the wrong angle can pass. |
| Specks and bubbles in the wall | Yes, in clear glass or PET against a backlight. | Not in opaque, dark or fully sleeved containers. |
Not detectable with a camera
- Inside opaque containers. Dark, opaque or sleeved containers block the light.
- Strength and leak-tightness. A camera does not test burst pressure, wall thickness or sealing.
Works reliably when
- Light passes through. Clear or lightly tinted glass and PET, shielded from daylight.
- Handling is stable. Containers are spaced, gripped or turned the same way each time.
How an empty container station is laid out
Plan view of a typical station, with a preform station inset. The real layout follows your handling.
Swipe sideways to see the whole drawing →
What a pass and a reject look like
Illustrations, not images from a real line. Which faults count, and how small, is agreed with you on real containers during the sample test.
Finish complete
The sealing surface shows as an even, unbroken ring under the ring light.
Chip on the finish
A break in the bright ring shows a chip that could stop the cap sealing.
Foreign object on base
The opaque object blocks the base light and is found. The clear liquid beside it barely shows.
Removing the right container at line speed
An encoder on the conveyor lets the PLC or vision controller track each container by position, not time, so the reject fires on the right one when the line changes speed. The air jet, pusher or diverter is chosen for the container, and a confirmation sensor raises an alarm if a failed container did not leave.
| Condition | What we need to know | Why it matters | Confirmed during |
|---|---|---|---|
| Container range | Glass, PET or HDPE; colours; new or returnable; every format. | Decides which positions are feasible. | Sample test |
| Handling | Conveyor, star wheel, side-grip belts, rollers or hopper. | Base, gate and all-round views need gripping, lifting or turning. | Site survey |
| Speed and spacing | Containers per minute and how evenly they arrive. | Sets exposure and whether each container can be rejected on its own. | Site survey |
| PLC and reject | PLC make and model, spare I/O, existing reject. | Glass must leave without breaking or toppling its neighbours. | Design review |
How the station is accepted
Agreed before FAT and SAT.
False reject rate
Good containers rejected, measured on agreed samples that cover normal variation.
Missed defect rate
Defective containers that pass, measured with known defects at each position.
Test containers
Marked containers with known faults, run at shift start or changeover to show each position still detects.
What to prepare for the sample test
We image your containers at each position before proposing a station.
Sample preparation guideGood containers
Containers or preforms that pass today, across colours and moulds.
Defective containers
Each fault to catch, including borderline ones, marked.
Container drawings
Drawings or photos of every format that runs.
Line information
Speed, handling, PLC make and model, existing reject.
Empty container and preform questions
Where on an empty bottle or jar can a camera inspect?
Can a camera detect residual liquid in an empty bottle?
Can machine vision find cracks in glass bottles?
What can a preform inspection find?
How are rejects handled when containers run close together?
Should preforms be checked at the moulding machine or before blowing?
Request an assessment for this application
Tell us which containers you run and which faults matter. We will tell you which positions can be inspected and where the limits are.