Page 83 - Cam Design Handbook

THB3 8/15/03 12:58 PM Page 71

MODIFIED CAM CURVES 71

Skewed displacement
Symmetrical displacement

Displacement acceleration Transition h 2 h

point
h/2
h 1
b Cam angle q
b 1 b 2
b /2 b /2
b
1 Symmetrical acceleration
Skewed acceleration
A 1 Asym

A 2
Cam angle q Asym
2
FIGURE 3.7. Skewed modified trapezoidal curve.

and
p
b = b
2
1+ p
(3.11)
p
h 2 = h.
1+ P
The relationship between the skewed and corresponding symmetrical acceleration, since
the maximum velocity is the same in both skewed and symmetric cases, is:
2b a = a sym b = V max
11
b
\ a = a
1 sym
2b
1
Thus using Eq. (3.10)
Ê 1+ p ˆ
a = a . (3.12)
Ë 2 p ¯
1 sym
Similarly
Ê 1+ p ˆ
a = a . (3.13)
2 Ë 2 ¯ sym