Cam Curve
A motion means the relation between a location and a time. Its change amount is named displacement. The relation between displacement and time is called motion curve. A cam curve is referred to as the motion curve of the follower (output) driven by a cam. A motion is dived into straight-line motion and a rotary motion. A relation between input and output is divided into three types as follows:
- Two straight-line motions
- One straight-line motion and one rotary motion
- Two rotary motions
A cam curve used in such motions has the following features:
- Continuity of velocity
- Continuity of acceleration
- Small Vm and Am, each of which is the maximum of velocity and acceleration
In other words, the functions of displacement, velocity, and acceleration should not have any discontinuous point. The displacement (S) of a cam’s follower has the functional relation with time (T), which is S = S (T). The sequential differentiation of the displacement (S) by the time (T) is V, A, and J, each of which is dimensionless velocity, dimensionless acceleration, and dimensionless motion.
Modified Trapezoid Curve (MT Curve)
MT curve has a small Am and is used as the curve for high velocity and light weight. In the case of large Vm, it is not suitable for middle load, and therefore it is used as the curve for high velocity. To lower the acceleration of the cycloid curve, the curve is modified closely to trapezoid. That is modified trapezoid curve. Its Am value is 22% lower than cycloid curve.
Modified Sine Curve (MS Curve)
MS curve is generally used as the curve for middle velocity and middle load in order to lower an Am value or in the case of small Vm. Nothing is better for balance than this curve. Since it is a reasonable curve, it is adopted as a standard curve.
Modified Constant Velocity Curve (MCV Curve)
The Vm value of the MCV curve is small, so that it is used as the curve for low velocity and middle load. It is not suitable for the high velocity with large Am and Jm values. The curve is proper when constant velocity is needed or when a Vm value needs to be lowered extremely.
