Short answer: a fill level inspection system is an inline camera station placed after the filler. It finds the fill line on every bottle, compares it with the tolerance band for that SKU, and ejects underfilled, overfilled and empty containers without stopping the line. Optomech builds these stations in Hyderabad, either standalone (₹6–9 lakh, ex-works, GST extra) or combined with bottle and cap inspection on the same liquid line.
Short fills are a compliance and customer-trust problem. Overfills quietly give product away and can cause sealing or shipping trouble. Both tend to be intermittent: a nozzle drifts, a valve sticks, foam builds up for a few minutes. Manual sampling catches the bottles it happens to pick up. This guide covers what to check before buying a fill level inspection system for a pharma, beverage, FMCG or agrochemical line.
What a Fill Level Inspection System Should Catch
Start with the defect list. These are the classes Optomech's fill-level station is built to handle:
| Defect | What it means | Why it matters |
|---|---|---|
| Underfill (short fill) | Fill line below the SKU minimum | Short quantity, compliance risk, customer complaints |
| Overfill | Fill line above the SKU maximum | Product giveaway, spill risk, sealing problems |
| Out-of-band fill height | Visible, but outside the programmed ± tolerance | Early sign that the filler is drifting |
| Empty or near-empty | No product, or a failed fill cycle | Critical reject before labelling or dispatch |
| Cap presence or tilt (optional) | Checked when fill level is combined with cap inspection (CIS) | One station view for fill and closure |
If your RFQ only says “fill level check”, vendors will quote different things. Write the classes down and say which ones are critical rejects. Our URS template for a vision inspection system shows how to make each requirement testable.
Camera Vision vs Checkweigher vs Manual Sampling
These methods answer different questions, so be clear about which one you need answered for every unit.
| Method | What it measures | Coverage | Watch out for |
|---|---|---|---|
| Inline fill-height vision | Position of the visible fill line against a height band | 100% of containers at line speed | The fill line must be visible; foam and container colour need the right lighting |
| Inline checkweigher | Gross weight of the whole pack | 100% of packs | Container and closure weight variation is mixed into the reading |
| Manual or offline sampling | Volume or weight of the samples taken | Sampling only | Intermittent filler faults between samples go through |
Many plants keep offline checks for process control and add 100% vision to stop the bottles that sampling misses. If you are weighing the trade-off, read AQL sampling vs 100% inline inspection.
Will It Work on Your Container and Liquid?
This is the first technical question, and the honest answer is that it depends on your bottle. A camera measures what it can see, so the fill line has to be imaged with good contrast at line speed. Things that decide feasibility:
- Container colour and material. Clear, amber, frosted and translucent packs need different lighting. Optomech chooses backlight, diffuse or side illumination so the meniscus stays measurable under factory light.
- Liquid behaviour. Foam, a curved meniscus or a liquid that clings to the wall all change how the fill line looks. Tell the vendor about them up front.
- Label and neck position. If a label or sleeve covers the fill zone, the check has to happen before labelling.
- Bottle handling. Bottles should be upright and spaced at the inspection point, with a stable trigger from the line encoder or a photocell.
Ask for a sample trial. Optomech validates lighting, optics and tolerance windows on your own bottles and liquid during the application survey and commissioning. Don't accept a fixed promise for a container nobody has imaged yet.
Where the Station Goes on the Line
A typical Optomech liquid line runs in this order:
- Empty bottle inspection (BIS), optional, before the filler
- Filler
- Fill level vision, right after the filler
- Capper and cap inspection (CIS)
- Label inspection (LIS) and induction seal verification (ISIVS) as the line needs
The station can sit before or after capping. Straight after the filler gives the quickest feedback when the filler starts to drift. After capping, one combined station can also check the cap. Foam settling time, bottle opacity and conveyor space usually decide it, and Optomech confirms the position during the site survey.
Do the Line-Speed Maths
At the inspection point the system has to capture the image, decide and fire the reject before the next bottle arrives:
| Line speed | Time per bottle | Bottles per 8-hour shift |
|---|---|---|
| 60 BPM | 1.0 s | 28,800 |
| 120 BPM | 0.5 s | 57,600 |
| 200 BPM | 0.3 s | 96,000 |
The shift column is why sampling struggles. A filler fault that lasts ten minutes at 120 BPM affects 1,200 bottles. Ask every vendor to confirm the speed for your container, pitch and reject mechanism, not a brochure maximum.
Send photos of the filled bottle and your line speed. Our vision team will tell you what lighting and placement it needs.
Setting Tolerance Bands and SKU Recipes
The system rejects against a band, so the band has to come from your QA team: the declared quantity, your process limits and the rules that apply to your product. For pre-packaged goods in India that includes the Legal Metrology (Packaged Commodities) Rules, 2011. A vision station doesn't decide what is legal; it applies the band you approve on every container.
- Per-SKU recipes. Optomech stores fill bands, camera settings and reject logic as named recipes, so a changeover recalls the right window without re-teaching.
- Access control. Role-based access stops fill tolerances being changed casually, with reporting that supports QA and customer audits.
- False rejects. A band that is too tight rejects good bottles. Agree a challenge set and a false-reject target at FAT. Our guide on false rejection rate explains why it matters.
On pharma lines, plan qualification from the start. See IQ, OQ and PQ for machine vision systems.
Rejection and Data
Rejected containers should leave the line without stopping it. Optomech's fill-level station uses pneumatic ejection, and confirm-eject can be added where the line needs proof that the reject actually left. The operator touchscreen shows live images, fill statistics and recent rejects, so operators see filler drift early instead of after a whole shift of short fills. Reject images and counts also help maintenance tune the filler. Integration is through PLC I/O for trigger and eject on your existing conveyor.
Standalone or Combined? Price and Scope
| Scope | When it fits | Price guidance |
|---|---|---|
| Standalone fill level station | Existing line where short fill or overfill is the main problem | ₹6–9 lakh, ex-works, GST extra |
| Fill level + cap inspection | Liquid lines that also need cap presence, tilt or closure checks | Combined quote |
| Bottle + fill + cap + label/seal programme | New or upgraded lines planning one quality programme | Multi-station quote; see the vision price guide |
Price bands are starting-from figures for a base configuration. Camera count, lighting, line speed, rejection hardware and validation scope move the final number. To estimate payback with your own figures, use the manual inspection cost and payback calculator. If you are adding the station to an existing line, read retrofitting machine vision on an existing line.
Your RFQ Checklist
- Container drawings or photos, filled with your actual liquid
- Liquid type, colour and whether it foams
- Target fill band per SKU, approved by QA
- Line speed, conveyor pitch and available space after the filler
- Before or after capping, and whether cap or bottle inspection is wanted too
- Reject mechanism, confirm-eject and lockable reject bin needs
- Data, access control and qualification requirements
- Service, spares and training arrangements
For a wider vendor comparison, use our 15 RFQ questions for a machine vision supplier, or go straight to the fill level inspection system page.