ESDU 94011:2010

Follower type

The method presented in this Item is applicable to the design of
disc cams with any one of the four types of crowned follower
illustrated in Sketch 2.1. The algorithm used to calculate the
compressive contact stress at the surface (taken from ESDU 78035,
Derivation 1) is strictly applicable only to static contacts where
no traction forces act. In the contact zone between a cam and a
domed or a flat-faced follower traction forces (due to friction)
are present. However, if the cam and follower are separated by a
film of lubricant, the coefficient of friction is likely to be very
low (less than 0.1) and the values of compressive contact stress
predicted by the algorithm will be sufficiently accurate. Therefore
this Item is applicable to the analysis of sliding contact (domed
or flat-faced) followers only if the lubrication regime can be
described as "mixed" or "elastohydrodynamic" as described in ESDU
94008 and ESDU 94017 (References 22 and 23). If "boundary"
lubrication is predicted (ESDU 94008 and ESDU 94017) it is more
difficult to be certain that the coefficient of friction is less
than 0.1 and so results obtained using the computer program (see
Section 7) should be treated with caution.

Follower motion

The method presented in this Item can be used to analyse cams
with a wide range of profiles. In cam design the relationship
between the motion of the cam and the motion of the follower,
during a dwell-rise-dwell (DRD) or a dwell-return-dwell (DRD)
motion, is usually governed by a mathematical equation known as a
cam law (see ESDU 82006, Reference 6). Although the theory
(presented in Section 3 of this Item) is general, in that any
mathematical cam law can be specified, the computer program (see
Section 7) contains only six commonly-used cam laws (identified in
Section 7.3.1). If the required cam law for a particular motion
segment is not included in the current version of ESDUpac A9411,
then the data can be entered as a motion data file.

This motion data file must contain values of follower
displacement, follower velocity, follower acceleration and follower
jerk at intervals of one degree of cam rotation. The required
format of the file is described in Section 7.3.2 and the reasons
for specifying motion in this way are explained in Section
4.1.1.

This document does not provide a preview.