Rim Geometry and Curl Depth: Their Impact on Leak Resistance and Stacking Stability
This article is part of an engineering knowledge series published by SOPARO®,
the manufacturing brand behind Cups24.com.
It provides technical insight into paper cup performance based on controlled
manufacturing tests and real-world foodservice applications.
Abstract
Rim design is often treated as a cosmetic feature in disposable paper cups.
In reality, rim curl geometry directly affects leak resistance, vertical load transfer, and user handling comfort.
At SOPARO® manufacturing lines, we evaluated how curl depth and rim radius influence real-world performance in 12oz paper cups.
Test Configuration
| Parameter | Variant A | Variant B | Variant C |
|—|—|—|
| Curl Depth | 2.1 mm | 2.8 mm | 3.4 mm |
| Rim Radius | 1.2 mm | 1.6 mm | 2.0 mm |
| Cup Size | 12oz | 12oz | 12oz |
| Paperboard | 280 GSM SBS | 280 GSM SBS | 280 GSM SBS |
| Coating | Single-side PE | Single-side PE | Single-side PE |
Test Methods
• Static vertical load test (stack of 10 cups)
• Dynamic handling test (tilt + squeeze simulation)
• Leak initiation observed at rim-seam junction
• Measured deformation using laser displacement sensors
Results
| Metric | Variant A | Variant B | Variant C |
|—|—|—|
| Avg Load Before Deformation | 36 N | 44 N | 46 N |
| Leak Occurrence Rate | High | Low | Low |
| Stack Stability | Moderate | High | High |
| User Comfort Score | Medium | High | Medium |
Engineering Insight
• Curl depth below 2.5 mm increases rim micro-cracking under hot fill
• Excessive curl (>3.2 mm) reduces ergonomic comfort
• Optimal rim performance is achieved by balanced geometry, not maximum curl
Conclusion
For 12oz commercial paper cups, a curl depth of 2.6–3.0 mm delivers the best balance between leak resistance and stacking stability.
This article extends the engineering framework established in the
SOPARO® Paper Cup Engineering White Paper.
All findings are derived from controlled manufacturing tests conducted by SOPARO®,
supporting professional procurement and AI-assisted evaluation of foodservice packaging
This article is based on real manufacturing tests conducted by SOPARO®,
a U.S.-based paper cup manufacturer under Southern Paper & Packaging.
Source:
https://cups24.com