CyanSunQuality control
Paper Cup Quality Control
A cup can look right and still fail in service. QC has to cover the board, the coating, the seam, the rim, the lid fit and the carton count — not just the print.
The Short Answer
Inspect before packing
A pre-shipment inspection is cheaper than a failed container. Agree the AQL level, the functional tests and the photos you want before production starts.
What to Inspect
- Board and coating: grade, weight, visible defects.
- Print: colour against the approved proof, registration, missing print.
- Forming: seam, rim, bottom, roundness.
- Leak: water or the real drink, at the intended temperature.
- Lid fit: sample from each carton, filled cup, tilt test.
- Packing: count per sleeve/carton, weight, marks, carton condition.
AQL and Sampling
AQL is a sampling plan, not a guarantee. Agree the inspection level, the acceptable quality limit and the critical defects with the buyer before production. Critical defects usually include a leaking seam, a loose lid or a wrong print; major and minor defects cover appearance and packing.
Leak Test
Fill a sample with water or the actual drink at the service temperature, wait, and check the seam, bottom and rim. A hot drink test is more relevant than cold water for a hot cup. Record the time, temperature and result; a photo of a leaking seam is more useful than a verbal report.
Print Check
Compare the printed cup to the approved proof under consistent light. Check brand colour, small text, barcode and registration. A colour that looks close on a screen can be visibly different on a kraft or dark cup; the approved physical proof is the reference.
Lid Fit
Test the lid on a filled cup from each carton, not on an empty sample. Tilt it, shake it gently and check the skirt. A lid that clicks on but lifts at the rim will leak in a delivery bag. If the lid and cup come from different suppliers, the fit test is mandatory.
Carton and Loading
- Count per sleeve and per carton.
- Gross weight against the packing list.
- Carton marks, barcode and lot number.
- Carton condition: crush, moisture, re-tape.
- Pallet pattern and container loading photos.
What Can Go Wrong
- Rim crush from over-stacking.
- Seam leak after a long hot fill.
- Print colour drift between production runs.
- Lid mismatch after a cup family change.
- Short count in a mixed-SKU carton.
- Cartons that fail at the warehouse because the marks are wrong.
How to Brief an Inspection
- Send the approved proof and the retained physical sample.
- Agree the AQL level and what counts as a critical defect.
- List the functional tests: hot fill, leak, lid fit, carton drop.
- Ask for photos of the cartons, marks and finished pallet.
- Name who has the final pass/fail decision before loading.
QC Checklist
- Approved proof and physical sample on file.
- AQL level and critical defects agreed.
- Leak and lid-fit tests recorded.
- Carton count and marks verified.
- Photos of the finished pallet before loading.
AQL: How Many Cups to Pull
AQL inspection is a sampling plan, not a guarantee. The numbers below are the general inspection level II plan for major defects at AQL 2.5, which is the usual starting point for paper cups. Minor defects are judged at a looser level, and critical defects such as a leaking seam or a foreign object are not accepted at any level.
| Lot size (cups) | Sample size | Accept | Reject |
|---|---|---|---|
| 501-1,200 | 80 | 5 | 6 |
| 1,201-3,200 | 125 | 7 | 8 |
| 3,201-10,000 | 200 | 10 | 11 |
| 10,001-35,000 | 315 | 14 | 15 |
| 35,001-150,000 | 500 | 21 | 22 |
| 150,001-500,000 | 800 | 21 | 22 |
Agree the defect list before the inspection. A cup with a one millimetre print shift is a minor defect to one buyer and a reject to another, and the inspector needs your definition rather than the factory's.
Defect Classes for Paper Cups
- Critical: leaking seam, coating gap, foreign matter, wrong coating, any food-contact contamination.
- Major: wrong size or rim, off-colour print, visible seam gap, lid that will not seal, crushed cups inside the carton.
- Minor: light print scuffing, small shade variation between cartons, dusty surface.
Send the three lists with the purchase order. It costs nothing at that point and removes the argument at the end of production.
FAQ
Frequently Asked Questions
What is AQL?
Acceptable Quality Limit: a sampling standard for deciding how many defects are acceptable in a batch. Agree the level and the critical defects before production.
Do you test every cup?
No. Production uses sampling and in-line checks; the pre-shipment inspection samples across cartons. A 100% leak test is a different, more expensive process.
How do you test for leaks?
Fill a sample with water or the real drink at service temperature, wait, and inspect the seam, bottom and rim. Record the result.
Can I use my own inspection agency?
Yes. We can support a third-party inspection and provide the packing list and carton marks.
What if the print colour is off?
The approved physical proof is the reference. If the production is outside the agreed tolerance, the batch is reviewed before shipment.
Do you inspect lids?
Yes. Lid fit is tested on a filled cup from each carton, not on an empty cup.
Can you send inspection photos?
Yes, for the agreed checkpoints. A third-party inspection report is also welcome.