Abstract
Formed beverage can ends present a small‑radius countersink where coating lubricity and integrity strongly influence panel fracture risk, yet there is no widely used, geometry‑specific post‑form friction test. Here we provide a practical test method that addresses this gap by using a precision tribometer (e.g., an Rtec MFT5000) fitted with custom fixturing that mounts a can end concentrically on a rotating stage and positions a 1/8 inch (3.175 mm) spherical ball on a pin set at 45 degrees to contact a defined locus on the countersink. The setup supports both rotational motion at controlled revolutions per minute (RPM) and linear reciprocation with specified stroke and frequency, at chosen locations and rolling‑direction orientations. Normal load, speed or stroke, environment, and/or dwell are controlled while friction force is recorded to compute coefficient of friction and stability, and post‑test metrology documents wear scars and any transfer films on the ball or surface. Careful alignment and fixturing overcome access and repeatability challenges in the small‑radius countersink, enabling direct testing on coated, as‑formed ends rather than relying on flat coupons that may not reflect formed geometry. Comparative runs show that reciprocating motion can be especially sensitive to coating differences, revealing wear contrasts between sample sets that are less apparent under purely rotational sliding. Variations in ball material and size, contact angle, load, motion profile, and environmental conditions can be used to customize sensitivity and simulate line conditions, and the fixtures can be adapted to other tribometers with equivalent motion and load control. The result is a geometry‑specific, reproducible way to differentiate coating‑related friction and wear behavior from metallurgical factors implicated in panel fractures, supporting faster root‑cause analysis, improved process control, and reduced scrap.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Norton, Eric and Liska, Juraj, "Countersink Tribometry on Formed Can Ends: A Geometry-Aware Friction and Wear Test Method", Technical Disclosure Commons, (December 10, 2025)
https://www.tdcommons.org/dpubs_series/9004