Multiple Constraints along Array path

[Anonymous]

Afternoon All,

     I am attempting to model a piece that will move along a conveyor path. It will be constrained by two hanging points. I cannot get the array path command to constraint both hanging points along the path. It will only seem to constrain the single point I click around the array. A screenshot of what I'm attempting to achieve is here, as well as a shot of the piece. Please let me know if anyone needs anything else. Sorry, I know it seems elementary, but I cannot solve this problem! Thanks in advance all!

[Anonymous]

Afternoon All,

     I am attempting to model a piece that will move along a conveyor path. It will be constrained by two hanging points. I cannot get the array path command to constraint both hanging points along the path. It will only seem to constrain the single point I click around the array. A screenshot of what I'm attempting to achieve is here, as well as a shot of the piece. Please let me know if anyone needs anything else. Sorry, I know it seems elementary, but I cannot solve this problem! Thanks in advance all!

[john.vellek]

Hi @Anonymous,

Is it possible to share your drawing file too? It is a little hard for me to understand the two constraining points. it would help if I could see what you have tried already.

[Anonymous]

@john.vellek, Please find a dwg attached with three sections, one where I've arrayed and constrained each one manually, one where I've attempted an array, and the original pieces.

[Ranjit_Singh]

I think array allows only 1 constraint point. You will need some custom routine to add another constraint. Search the LISP forums; someone may have a routine already. Or maybe move your thread to the LISP forums and someone can write a routine.

[Anonymous]

@Admin could you please move this thread to the LISP customization forum? Hopefully I can find some luck over there! Thank you in advance. (maybe @john.vellek could do this??) Have a great afternoon all!

[parkr4st]

this looks like an AD Inventor problem?  Jvellek opinion?

if the piece is pulled by a chain to the right around a sprocket for example, only the right most pin will be hooked to the chain, the left most will be on a track to trail along around the curve?  Leftmost pin can't be pinned to the chain as the center distance will no remain the same as the chain link pin center distance's around the corner?

constraint the lead pin and calculate the angle of turn for an increment of travel, i.e. link length of the chain, around the corner.  the straight sections will be straight path arrays?

[Ranjit_Singh]

I don't think multi-point constraint is available in AutoCAD. But since @john.vellek has not commented yet I maybe wrong. Meanwhile you could try the below routine. Routine generates copies of the object. Minimal testing done. see screencast on how it works. Give it a shot.

;:Ranjit Singh
;;5/22/2017
(defun c:somefunc  (/ adoc a d d1 f obj obj1 p1 p2 v)
(vla-startundomark (setq adoc (vla-get-activedocument (vlax-get-acad-object))))
 (setq obj  (vlax-ename->vla-object (car (entsel "\nSelect Path: ")))
       obj1 (car (entsel "\nSelect Object to follow along path: "))
       v    (mapcar 'getvar '(osmode cmdecho nomutt))
       p1   (getpoint "\nSelect constraint point 1: ")
       p2   (getpoint "\nSelect constraint point 2: ")
       d1   (getreal "\nEnter distance along path: ")
       d    (distance p1 p2)
       a    (angle p1 p2)
       f    (- (vlax-curve-getdistatparam obj (vlax-curve-getendparam obj)) d1))
 (mapcar 'setvar '(osmode cmdecho nomutt) '(0 0 1))
 (while (<= (vlax-curve-getdistatpoint obj p2) f)
  (command-s "._copy" obj1 "" p1 (setq p1 (vlax-curve-getclosestpointto obj
                                                  (vlax-curve-getpointatdist obj
                                                                             (+ d1 (vlax-curve-getdistatpoint obj (vlax-curve-getclosestpointto obj p1)))))))
  (command-s "._rotate" (setq obj1 (entlast)) "" p1 "_r" p1 (polar p1 a d) (setq p2 (somefunc2 obj p1 d))) (setq a (angle p1 p2)))
 (mapcar 'setvar '(osmode cmdecho nomutt) v)
 (vla-endundomark adoc))


(defun somefunc2  (a b c / ent rpt)
 (setq rpt (caar
            (vl-sort (vl-remove-if '(lambda (x) (minusp (cdr x)))
                                   (mapcar '(lambda (x) (cons x (- (vlax-curve-getparamatpoint a x) (vlax-curve-getparamatpoint a b))))
                                           (somefunc3
                                            (vlax-invoke a 'intersectwith (vlax-ename->vla-object (setq ent (entmakex (list '(0 . "circle") (cons 10 b) (cons 40 c))))) 0))))
                     '(lambda (x y) (< (cdr x) (cdr y))))))
 (entdel ent)
 rpt)


(defun somefunc3  (x)
 (cond ((null x) ())
       (t (cons (list (car x) (cadr x) (caddr x)) (somefunc3 (cdddr x))))))

[mcardonne]

Thanks, I was looking for something like that for quite some time. 😀

[Sea-Haven]

The forklift wide load. Just uses a simple get angle at point along a pline.

Nice code doing the twist in the array.