| USER GUIDE
D47CAM AND D57CAM CAM DESIGN PROGRAMS
Download D47CAM
Self-Extracting Program (198k)
The purpose of both of these programs is to design roller follower cams efficiently and
quickly without any negative radii of curvature. With these programs, much shorter event
lengths can be designed without negative flanks than when using plain polynomial type
curve fits. The programs are similar in operation and structure but D57CAM uses 5 exponent
curve fits for the nose and ramp segments. D47CAM uses 4 exponents for these portions.
Exponents for D57CAM include 2, P, Q R, S, and T where P, Q, R, S, and T can be any
decimal numbers from 4. to 99. with the restriction that no two exponents can be equal.
With 5 exponents (D57CAM), there is a slightly smoother transition from the base circle
into both the opening side ramp and the closing side ramp.
Operating either program consists of choosing a base circle diameter, follower
diameter, maximum lift and two event lengths (usually cam durations measured at .050 and
.020 follower lifts) and then selecting angular transition points and appropriate flank
radii for open and close sides (with a computer graphic screen) which yield the desired
final cam design.
To understand why these programs were developed, a brief look at cam design over the
last 50 years will be helpful. During this time period, automotive cam design techniques
evolved from circular arcs through polynomial curve fits. Suffice to say that before small
computers were available, the cam calculation work was tedious and any kind of speed or
efficiency was not possible. Cam design arithmetic (even with calculators) became
overwhelming.
Circular arc designs can be effective but calculating the angular transition points
(especially for a 4 arc system with ramp arcs) will be very challenging. And there is
still the problem of discontinuities at arc transition points. Also even with graphic
plots of acceleration and jerk curves, the use of circular arcs will require true expert
knowledge and a lot of time.
As more powerful personal computers became available, cam design techniques using
polynomial curve fitting produced very smooth lift and acceleration curves. However with
higher lifts and/or shorter event lengths, small negative radii of curvature appeared on
the cam flanks, creating a serious manufacturing problem. The flanks of these short
duration, high lift cams had negative radii of curvature which were smaller than most
grinding wheels and therefore could not be made easily or if ground with small dia.
wheels, were very inefficient to grind. Cam grinding machines had to run too slowly to be
cost effective.
To over come these drawbacks, new design techniques are now available from Andrews
Products, Inc. By using a flank segment that is actually part of a circle, inverse radius
cams can be eliminated while still yielding cam designs which can have very high lifts and
short duration events while still maintaining good control over acceleration and jerk
curves. The results are cam designs producing more power with the added benefit that they
can be manufactured with standard size wheels.
To accomplish this purpose, both programs start with user specified lifts and durations
(usually at .050" and .020") but other numbers can be used including metric
input. Then with interactive graphics (VGA), various angular transition points and flank
radii can be rapidly tried until stable, continuous acceleration and jerk curves are
generated. With only one or two hours practice, excellent designs are rapidly attainable.
For a knowledgeable user, a complete design should not require more than 20 minutes.
All design input data can be saved to a disc file for future reference and use.
Manufacturing files, inspection data and single page lift data outputs can be made with
simple keyboard commands.
Various program input data parameter definitions are listed below:
1. YMAX Maximum cam follower displacement.
2. ACC(0)Acceleration at tip of cam (0 degrees).
3. RF & RBASFollower Radius & Base Circle Radius.
4. EVENTOverall event length (open or close) from nose of cam to base circle.
5. ANGLE1Beginning angle of circular arc segment (tip = 0 degrees).
6. ANGLE2Ending angle of circular arc segment (tip = 0 degrees).
7. DESPT1 Angular distance from tip to first check height (usually
.050).
8. DESPT2 Angular distance from tip to second check height (usually
.020).
9. SPANAngular distance between DESPT1 & DESPT2 (6, 7, 8, 9, or 10 deg.).
10. FLANK R.Radius of circular arc segment at flank.
11. TIP EXPON:Polynomial exponents of tip segment (0 deg. to ANGLE1).
12. L,V,A,J,SLift, Velocity, Acceleration, Jerk, Snap @ ANGLE2 (Data listing only).
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