Experimental study on circular eccentric cam–follower pairs

Abstract

Experimental verifications of cam–follower contacts are very important owing to the difficulties faced during a reliable simulation due to the continuous variation of load, speed and geometry of the lubricated contact. Some experiments have been carried out with a new apparatus, specifically designed and realised for investigation on cam–follower and gear teeth contacts, in order to test its capability to measure film thickness and contact forces. Circular eccentric cams have been used because they feature lower transient effects and comparison of the results with the theoretical/numerical ones is easier. The tests have been performed using cams with two different eccentricities and surface roughness, and two different followers, one made of steel and one made of glass. The behaviour of the cam–follower contacts at several different rotational speeds, ranging from 50 to 500 r/min, and different pre-loads have been investigated. Lubrication regimes ranged from boundary to complete, with most of the tests being performed under mixed lubrication conditions. Localised wear has occurred during some tests. Data of all contact force and moment components as well as of the cam shaft driving torque have been acquired at high acquisition frequency. Some methodologies for numerical data elaboration have been identified. Optical interference images have been correctly recorded at the desired frequency. The trends of the normal and friction forces measured in the different tests as well as the evaluated trends of the friction coefficient are presented in the paper. Some sample optical interference images are also shown. The results furnish encouraging indications about the capabilities of the experimental apparatus.