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Machine Theory
Mechanism and Machine Theory 43 (2008) 1198–1209
ate/mechmt
munication
Influence of reinforcement posite gear metrology
S. Senthilvelan a,*, R. Gnanamoorthy b
a Department of Mechanical Engineering, Indian Institute of Technology Guwahati, Guwahati 781 039, India
b Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036, India
Received 4 May 2007; received in revised form 7 August 2007; accepted 13 September 2007
Available online 29 October 2007
Abstract
Injection molded posite gears are being used in many power and motion transmission applications. In
order to widen the utilization of reinforced polymers for precision motion transmission and noise less applications, the
quality or accuracy of molded gears should be increased. Since the injection molded gear quality is significantly influenced
by the material shrinkage behaviour, there is a need to understand the influence of fiber orientation on part shrinkage
behaviour and hence the gear quality. Unreinforced and 20% short glass fiber reinforced Nylon 6/6 spur gears were injec-
tion molded in the laboratory puter aided simulations of gear manufacturing was also carried out. Results of the
mold flow simulation of gear manufacturing were correlated with the actual fiber orientation and measured metrological
parameters of the molded gears. Actual orientation of the fibers near the tooth profile, weld line region and injection points
of molded gears were observed using optical microscope. Fiber alignment along the tooth profile restricts shrinkage and
induces anisotropic shrinkage, which significantly decreases the deviation of involute profile parameter from the design
value. Fibers embedded in the molded skin surface increases the gear tooth profile form and lead form deviations.
Non-alignment of fibers across the gear tooth section increases the tooth thickness, tooth-to-tooth spacing and radial run-
out deviati