漸開(kāi)線的公式是 6 _/ q3 {$ @" P3 {/ Q V. G, z: Q
x=r(cos(theta)+theta*sin(theta))
7 N) l9 |, y. D- y3 ]& B6 Yy=r(sin(theta)-theta*sin(theta)) ' ^9 d H$ F/ b5 Z& X8 w, J, l% Z- v
r - 基圓半徑
( a4 t! A: s; ntheta - 成形角,弧度值 - [* Z' I0 d3 n2 V
在不同theta時(shí)算出x和y即可。
$ J1 ~2 k6 j6 Y1 f* c2 S我用Autolisp做了個(gè)程序,希望對(duì)大家有用。歡迎大家討論。這里用的極坐標(biāo)。 % P$ D6 S" X9 j( R {$ [
;************************************************************************************* ;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. , q& k) _2 W% _5 O- h* u+ X
: m! c) ~3 H2 }) W5 q3 V" }(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:")) / x2 z- `- }, w9 z& n; i
(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))) "" ) ) / }& K! @2 \/ N' D- s- D
(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 "") ! o5 g' b0 J* f
(setvar "osmode" os) (command "_undo" "e") (princ) ) |