This paper shows an experimental study on the fatigue lifetime of high-heat polyamide (Stanyl) gears running in oil at 140°C. Based on previous works (Refs. 1–2), an analysis is made correcting for tooth bending and calculating actual root stresses. A comparison with tensile bar fatigue data for the same materials at 140°C shows that a good correlation exists between gear fatigue data and tensile bar fatigue data. This insight provides a solid basis for gear
designers to design plastic gears using actual material data.
The quality of molded plastic gears is typically judged by dimensional feature measurements only. This practice overlooks potential deficiencies in the molding process.
Creating standards for plastic gears calls for a deft touch. The challenge is to set uniform guidelines, yet avoid limiting the creative solutions plastic offers gear designers.
Plastic gears and transmissions require a different design approach than metal transmissions. Different tools are available to the plastic transmission designer for optimizing his geared product, and different requirements exist for inspection and testing.
This paper will present some of the new technology available to the plastic gear user, including design, mold construction, inspection, and testing of plastic gears and transmissions.
"We're taking over," says Art Milano. It's a bold statement from the engineering manager of Seitz Corporation, one of the largest manufacturers of injection molded plastic gears, but Milano has reason for his optimism. Plastic gears are big business-probably bigger than most gear industry "insiders" realize.