BNL’s unique technology and design expertise result in plastic ball bearings that deliver exceptional wear rates.

GAF Materials Corp, North America’s largest roofing and ventilation manufacturer, has significantly improved the performance of its Master Flow® rotary roof turbines with a suite of custom-designed plastic ball bearing assemblies from BNL.

Moulded from a specialist grade of acetal available only in Europe, the bearings are quiet, low-friction and lubrication-free. BNL’s unique fully moulded bearing raceways, manufactured using a technique perfected during the company’s 35-year history, result in exceptional wear rates. This gives the GAF turbine a far greater life expectancy than competing products that use bearings with machined raceways.

Tests conducted by BNL show that its new fully moulded bearings for GAF will outlast similar fully machined bearings by up to 700%.

The superior wear rates achieved by fully moulding a bearing raceway are due to the existence of a fine crystalline layer, which forms as the hot plastic rapidly cools upon contact with the tool. This fine crystalline boundary layer is very hard. However, as the tool fills, it insulates the core and the plastic subsequently cools more slowly, allowing more time for the crystal structure to grow with larger, less-resistant crystals.

Therefore, the thicker the fine crystalline region, the greater the wear resistance of the part’s surface, including the raceway. Competitors typically machine a raceway into this surface as a secondary operation, removing the hard crystalline layer and significantly reducing its wear resistance.

BNL’s specialist in-house design expertise has added further value to the bearings through the integration of additional features. Clips on the caps make them easy to snap into place, while an upper bearing incorporating a bayonet fastening feature means that a simple ‘push in and twist’ movement is all that is needed to install and secure it to the roof turbine.

Another integral snap feature on the bearing inner secures the bearing to the central turbine shaft. These cost-reducing design features remove the need for additional heavy and expensive metal screws and bolts that are time-consuming to assemble.

“BNL’s technical ability and execution of this project enabled us to market a greatly improved product that is taking away market share from the competition. The company delivered an integrated bearing solution that was superior to designs from several other manufacturers and stayed within our budgeted cost targets.”

Steven Boehling – Engineering Manager – LL Building Products, Inc (a wholly-owned subsidiary of GAF Materials Corp.)