Yaskawa MotionWorks IEC Toolboxes - Manual (Page 26)

Cam Toolbox: Cam Tables and Curves
MotionWorks IEC61131-3 Toolboxes: 2013-09-13 13
Creating Cam Tables
Cam Curve Characteristics
Cam Curve does not mean a shape curve which expresses a cam profile, but rather a ”motion curve” of the
follower moved by the cam. A motion curve is generally shown with time on the horizontal axis and
displacement on the vertical axis. The purpose of a cam is to move an object smoothly in a minimum time,
without vibration and with minimum power. For this purpose, various motion curves have been developed.
These curves are not only used for cam mechanisms but can also be applied to various other motions. The
maximum non dimensional values such as Vm, Am, and Jm are called the characteristic values of the cam
curve. From these characteristic values and from the shapes of the acceleration curves, the general properties
of the cam curves can be known.
Curve Selection
The procedure for selecting a curve is as follows:
1. Velocity V and Acceleration A are to be continuous
2. Low values of Vm and Qm are needed in low speed and heavy load applications.
3. Low values of Am and Jm are needed in high speed and light load applications.
4. Asymmetrical curve having the longer period of deceleration than acceleration should be used for
situations when positioning accuracy is critical and residual vibration must be avoided.
5. A one-dwell curve should be used when the motion has no stop at the endpoint and must return
immediately.
6. Select a curve from the modified constant velocity group when constant velocity is required in the middle
part of the stroke.
7. Select a curve from the modified trapezoid group when acceleration is to be minimized.
8. The modified sine curve is recommended if there are no limitations.