topic Re: Smoothly transition between lines on different planes in AutoCAD Forum

Smoothly transition between lines on different planes

Anonymous — Wed, 22 Aug 2018 12:29:38 GMT

I have a simple case of having two lines, L1 and L2, drawn perpendicular to each other with one line on a high plane and one on a lower plane. The two work planes are parallel, they just differ in elevation.

I need to transition between these lines using a curve of a set radius which does not 'kink' at any of the tangents in all directions.

3D image below:

When I adjust the UCS so I can draw the arc between them, it is fine in plan but kinks in one of the elevations. How do I achieve a smooth transition?

For a wider context, this is for cable pulling, so the path of the cable cannot kink.

Re: Smoothly transition between lines on different planes

Kent1Cooper — Wed, 22 Aug 2018 13:13:15 GMT

I don't think that's geometrically possible with one Arc. It can be done with two, meeting mid-way:

I did it this way: FILLET in plan with the Lines in the same plane; place a POINT at the midpoint of the ARC; MOVE the higher LINE up to its different elevation, and the POINT up half that distance; UCS picking the two ends of a LINE and for the 3rd prompt, the POINT; draw an ARC starting at the near end of the LINE, Ending at the POINT, and with the Direction option and Ortho on to make it come tangentially off the LINE; same UCS and ARC with the other LINE.

Re: Smoothly transition between lines on different planes

Patchy — Wed, 22 Aug 2018 14:09:02 GMT

Can it be 3darc?

Re: Smoothly transition between lines on different planes

Kent1Cooper — Wed, 22 Aug 2018 14:30:35 GMT

@Patchy wrote:

Can it be 3darc?

I think the images in Message 1 are from the same kind of arrangement. Yours has the same non-tangential connections between the Arc and the two Lines that they don't want:

I'm attaching the drawing I made my images from. While the two Arcs are tangential to the Lines, they are not quite exactly tangential to each other, but a lot closer to it than that.

Re: Smoothly transition between lines on different planes

Anonymous — Wed, 22 Aug 2018 14:26:50 GMT

Would you be able to post a screen shot looking in the X-Z plane?

How do I access a 3D arc? When I type that, it's not recognising the command.

Re: Smoothly transition between lines on different planes

Kent1Cooper — Wed, 22 Aug 2018 14:37:36 GMT

@Anonymous wrote:

.... How do I access a 3D arc? When I type that, it's not recognising the command.

It's just an Arc in a UCS set up [or the result of some 3DRotating and maybe Scaling] to get the ends to meet the Line ends. I suspect it's the same as [or very similar to] yours in Message 1.

Re: Smoothly transition between lines on different planes

Patchy — Wed, 22 Aug 2018 14:35:11 GMT

Open the attached drawing and do a 3dorbit in model space to see what it looks like in 3d.

Here is the link for that command:

http://www.cadforum.cz/cadforum_en/qaID.asp?tip=5757

Re: Smoothly transition between lines on different planes

Anonymous — Wed, 22 Aug 2018 15:04:30 GMT

That arc is kinking in the Z-X plane.

I used the rotate UCS to make the arc in my original post, but I don't think it's possible to create what I'm after by just rotating the UCS.

Re: Smoothly transition between lines on different planes

Kent1Cooper — Wed, 22 Aug 2018 21:36:26 GMT

@Anonymous wrote:

.... I don't think it's possible to create what I'm after by just rotating the UCS.

No, and I've decided I don't just think any more [as in my first Reply], but am certain, that it's not possible with a single Arc under any circumstances. Does a double-Arc solution, similar to my 2ArcTransition drawing [attached to Message 4] work for you?

Re: Smoothly transition between lines on different planes

Anonymous — Thu, 23 Aug 2018 07:43:36 GMT

[removed]

Re: Smoothly transition between lines on different planes

GrantsPirate — Thu, 23 Aug 2018 14:03:51 GMT

I would use the BLEND command. You can use the control vertices, grips, etc. to adjust it afterwards.