漸開線的公式是 . Z0 }6 R; a) t9 D
x=r(cos(theta)+theta*sin(theta)) % [# F" h/ C: s u
y=r(sin(theta)-theta*sin(theta)) % J- g# ~( S6 U
r - 基圓半徑
% A) {; A7 x7 {/ B! u* `theta - 成形角,弧度值 / ?$ x/ z, [3 m5 B Z. Q2 N
在不同theta時算出x和y即可,。
" z1 F5 A' F5 x7 s/ Z/ z- e我用Autolisp做了個程序,,希望對大家有用,。歡迎大家討論,。這里用的極坐標。
! C) M+ @- B6 c;************************************************************************************* ;This program is to draw a involute in AutoCAD, anyone can use it freely without permission. ;Take the risk youself, suggest you to open a new drawing and run this program first, then ;copy it to your drawing. ;Chen Xiangsong ; ;Distance Offset: means when you draw a curve rather than a standard involute. ; it starts to draw the curve not from the base circle. ; it is curtate or prolate involute. it is useful as you draw gear root. ; standard involute, enter 0 ; ;Radius of Base Circle: You have to know the meaning, or the program is useless to you ; ;Angle to go: means the length of involute you want. in degrees. it is not pressure ; angle, it is the pressure angle add involute Phi. ; ;Accurancy: the density of points you want on the curve, the smaller the more accurate. ; but will slow down your pc's speed. I normally enter 0.01 ; ;Center of Curve:  LEASE PICK A POINT ON THE SCREEN RANDOMLY, IT IS VERY IMPORTANT. ; DON'T PICK A SPECIAL POINT. That's the disadvantage of my program.
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0 ]% g; I X Z(defun c:involute () (command "_undo" "be") (setq os (getvar "osmode")) (setvar "osmode" 0) (setq q 0) (setq f 0) (setq h (getreal "\nDistance Offset:")) (setq r (getreal "\nRadius of Base Circle:")) (setq t (getreal "\nAngle to go:")) (setq n (getreal "\nAccurancy:")) (setq cent (getpoint "\nCenter of Curve:")) , m6 [& C% C" i U. a+ [3 Q
(if (= h 0) (command "pline" (list (+ 0 (car cent)) (cadr cent)) (list (+ (/ r 2) (car cent)) (cadr cent)) "" ) (command "pline" (setq trimpoint (list (+ h r (car cent)) ((if (> h 0) - +) (cadr cent) (/ r 1)))) (list (+ h r (car cent)) ((if (> h 0) - +) (cadr cent) (/ r 2))) "" ) )
' i5 R$ L1 P: M7 X" ?! W9 ~/ N(while (< f (* t (/ pi 180))) (setq a (atan (* r f) (+ r h))) (setq ri (/ (+ r h) (cos a))) (setq q (- f a)) (setq pt0 (polar cent q ri)) (command "pline" "" pt0 "") (setq f (+ f n)) ) (command "pedit" (entlast) "j" "all" "" "f" "") (command "circle" cent r) (setq bs (entlast)) (command "line" cent (list (+ 1 r h (car cent)) (cadr cent)) "") (setq lt (entlast)) (if (= h 0) (command "trim" bs "" cent "") (command "trim" lt "" trimpoint "") ) (command "erase" lt "")
4 N, A5 P, {0 J(setvar "osmode" os) (command "_undo" "e") (princ) ) |