Failure of Polyurethane Urethane Industrial Wheels Rollers in Heavy Caster and Wheel Applications
Failures of poly treads on industrial caster wheels, drive wheels, and industrial rollers cost companies not only in money to replace the wheels but also in the down time of equipment. Many of these failures can be prevented, including:
Delaminating of Polyurethane Tread – In a wheel or roller application, the polyurethane is generally chemically bonded to a metal or plastic substrate. Delaminating occurs when the tread becomes separated from the wheel or roller hub. In some cases this can be caused by a poor application of adhesive before the polyurethane was applied to the hub. It can also be caused by overheating the wheel or exposure to water and/or solvents at the bond line. Additionally there are some hub materials which are difficult to achieve a bond. If the adhesive has been applied properly, there are no environmental factors to interfere with the bonding, and the tread is still delaminating; a mechanical bond might prove to be a better option.
Flat-Spotting – A flat spot can form on the polyurethane tread when the wheel is loaded in a stationary position. This spot may or may not ”roll-out” when the wheel resumes rolling. Either way it will make moving the wheel from a stop more difficult. A polyurethane material’s tendency to flat-spot is determined by its compression set value. Choosing polyurethane with lower compression set values could solve the problem. Another approach is to use a wheel with a larger diameter or width, which reduces the stress on the urethane.
Blow Out – When polyurethane treads undergo cyclic loading and unloading, frictional heat is generated within the material due to the mechanical hysteresis of the polyurethane. If the heat buildup is excessive (more heat generated than can be dissipated), the polyurethane tire will melt internally and cause build up pressure as the material expands causing a blow out. Most commonly this is caused by overloading the part or operating the wheel or roller at too great a speed. It can also be caused by an uneven loading of the wheel or roller. The solution to this would be to change urethanes to one with lower heat generating characteristics, increase the diameter, increase the width of the wheel or change other operating parameters of the wheel or roller
Cracking – The polyurethane tread can crack if the wheel or roller is carrying too great a load in a dynamic position. This can be alleviated by replacing the tire material with a material that is better suited for this particular application., Another alternative is to distribute the weight different by either by increasing the diameter of the wheel or increasing the width of the wheel or roller.
When a polyurethane wheel or roller fails it is critical that a full evaluation of the failure mode be undertaken to understand all the potential issues. These issues can be production issues or the miss application of a particular wheel or roller. The engineering staff at Reaction Industries can help you understand the failure and to properly design your industrial caster wheel or roller to minimize/prevent polyurethane tire failure.