I do not know much about CNC operation but need to ask a question about
the operation similar to this gear cutting.
Machinery's handbook (20th) describes how to construct an involute on
page 288. I read this as the involute is the length of a line tangent
to the circle, equal to the cord of the circle part.
Why do we not just calculate this in a spread sheet and plug it into G code?
R = radius of gear
angle goes from 0 to 90 degrees
Angle /rad is angle in radians
Xc and Yc are points on the radius of the circle where the cord is
tangent to the circle
length of cord is the length of the cord around the circle
X Y Are points on the involute This is what you want the cutter to be.
x mil y mil are used to add to a G0 line to make the G code
R = 0.75
ANGLE angle/RAD Xc YC LENGTH OF CORD X Y x mil
y mil
0 0 0.75 0 0
0.75 0 750 0
1 0.02 0.75 0.01 0.01
0.75 0 750.11 0
2 0.03 0.75 0.03 0.03
0.75 0 750.46 0.01
3 0.05 0.75 0.04 0.04
0.75 0 751.03 0.04
4 0.07 0.75 0.05 0.05
0.75 0 751.83 0.09
5 0.09 0.75 0.07 0.07
0.75 0 752.85 0.17
6 0.1 0.75 0.08 0.08
0.75 0 754.1 0.29
7 0.12 0.74 0.09 0.09
0.76 0 755.58 0.46
8 0.14 0.74 0.1 0.1
0.76 0 757.28 0.68
37 0.65 0.6 0.45 0.48
0.89 0.06 890.45 64.56
38 0.66 0.59 0.46 0.5
0.9 0.07 897.25 69.78
39 0.68 0.58 0.47 0.51
0.9 0.08 904.13 75.25
88 1.54 0.03 0.75 1.15
1.18 0.71 1177.39 709.34
89 1.55 0.01 0.75 1.17
1.18 0.73 1177.92 729.55
90 1.57 0 0.75 1.18
1.18 0.75 1178.1 750
This seems so simple to me. I know that I need to adjust for cutter
size and also for root, pitch and outside diameter of the gear. And, I
have not run a formal analyze of my math. What am I missing?
I may have to turn the spread sheet into a text doc and then add the "x
mil" and "y mil" column's to a G0 column but that seems trivial to me.
As I say, What am I missing?
Thanks, My problem is I can't get the computer to wiggle the parallel
port. I'm working on it, and I will get it sometime.
bill Jacobs
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