topic Re: Loft along a curve - broken curve? in Fusion Design, Validate & Document Forum

Loft along a curve - broken curve?

NYC_CNC — Tue, 04 Apr 2017 20:46:59 GMT

I'm stuck! I am trying to loft from the large rectangle to the small rectangle along the curve (Golden Ratio!). For reasons I don't understand, Fusion does not see the curve as continous; this means even when using a centerline guide rail, I cannot get it to work!

Thanks!

F3D Attached.

Re: Loft along a curve - broken curve?

HughesTooling — Tue, 04 Apr 2017 21:28:36 GMT

I think the problem is you have several coincident points at the end of the arcs, for some you have the end point of 2 arcs and 2 construction lines. I deleted the shorter construction lines and replaced some with horizontal\vertical constraints and some with coincident constraint to the longer construction lines. Also deleted the tangent constraints between the arcs and lines and replaced them with tangent constraints just between the arcs. I think everything is still correct but you probably better double check. File's attached.

Mark

Re: Loft along a curve - broken curve?

davebYYPCU — Tue, 04 Apr 2017 21:51:18 GMT

Gooday John,

Quick look and running out of time to say much more for today,

There are coincident problems with small end of the rail, from the large end, the first 360 degrees are ok, the last 180 is the problem

So, starting at the small end of the rail line, the first curve falls on the origin,

the second curve - small end point is not coincident to the origin, but overlaps the first curve,

the second curve and third curve ends are not coincident,

The white dots give it away,

I copied all the lines to another sketch without the construction stuff, to find it.

Might help

Re: Loft along a curve - broken curve?

NYC_CNC — Tue, 04 Apr 2017 23:04:21 GMT

Thanks! I see how that fixes it. Any tips on how to model this correctly from the start? E.g. my method seems flawed given the results, but unclear how I should be doing this going forward. Thanks.

Re: Loft along a curve - broken curve?

TrippyLighting — Tue, 04 Apr 2017 23:37:48 GMT

The center rail sketch can be designed fully constrained without using any construction lines and then lofts without problems.

The construction lines have basically been replaced by horizontal/vertical constraints.

This way only arc end points are connected and don't coincide with construction line end points which is possibly what confuses Fusion 360 here.

Re: Loft along a curve - broken curve?

HughesTooling — Wed, 05 Apr 2017 09:28:38 GMT

@NYC_CNC wrote:

Thanks! I see how that fixes it. Any tips on how to model this correctly from the start? E.g. my method seems flawed given the results, but unclear how I should be doing this going forward. Thanks.

Only advise is keep it simple. I've tried to help a few people struggling with sketches on the forum and having several collinear connected lines causes problems because it's hard to tell which constraints apply to which line, one edit and the sketch explodes. If you have a construction line you need longer use extend don't draw another line on the end. With arc endpoints it can be a good idea to snap the endpoints together before snapping to the construction lines\points so you know they're joined together not joined to the line end point.

Mark

Re: Loft along a curve - broken curve?

mufadal89 — Wed, 05 Apr 2017 09:43:24 GMT

There should be an option to join sketches or curves into one entity for such things.

Like a combine option but for sketches.

Going back to redesigning the sketch is very tedious.

Re: Loft along a curve - broken curve?

TrippyLighting — Wed, 05 Apr 2017 10:23:12 GMT

@mufadal89 wrote:

Going back to redesigning the sketch is very tedious.

True, but you only have to re-design it when you start on the wrong foot 😉

Re: Loft along a curve - broken curve?

mufadal89 — Wed, 05 Apr 2017 10:42:38 GMT

Acknowledged.

But i am wondering as to why Fusion doesn't detect the curve as a whole even though it is continuous with correct curvature when we double click it.

Re: Loft along a curve - broken curve?

TrippyLighting — Wed, 05 Apr 2017 10:49:43 GMT

Likely because there are more than line/arc endpoint joined in one location, which makes it impossible for Fusion 360 to decide which element belongs to the path and which does not.

Re: Loft along a curve - broken curve?

HughesTooling — Wed, 05 Apr 2017 10:54:14 GMT

If you zoom in on the highlighted arc you'll see it's end is not coincident with the end of the other arc, inside red box. Actually this is a good example of the colour status for constrainment not working. At the other end of the highlighted arc there are 4 end points so god knows what's joined to what/

Mark

Re: Loft along a curve - broken curve?

HughesTooling — Wed, 05 Apr 2017 11:07:14 GMT

@mufadal89 Here's why it fails at the other end, buried under the pile of construction lines there are 2 more lines the need to be change to construction line for it to work.

Mark

Re: Loft along a curve - broken curve?

mufadal89 — Wed, 05 Apr 2017 14:17:09 GMT

Thank you @HughesTooling & @TrippyLighting for the in depth explanation .

Re: Loft along a curve - broken curve?

cekuhnen — Wed, 05 Apr 2017 15:23:34 GMT

@HughesTooling

" Actually this is a good example of the colour status for constrainment not working."

Good to know !