Sweep spiral self intersecting, trim away inside


#1

Hi all,

i’m trying to sweep a circle around a flat spiral like curve. My aim is to create a self intersecting solid and somehow trim away the inside. Is that possible at all?


#2

From my experience you can’t trim an object against itself. Split it along by isocurve. As to “why?”…


#3

i don’t really get what you’re saying. The second object is there to show what i mean by “insides”. I would like to put a fillet on the concave corners and export the object for machining.


#4

If I get what you’re saying, you can do this - you first need to split the pipe section along isocurves lengthwise and then you can get the intersections between the halves, and split/delete/join. See attached…

SpiralPipeOverlap.3dm (2.7 MB)

–Mitch


#5

Perfect!

thank you! :smile:
Cheers^^


#6

Hi
Returning to this old post with a similar question, but perhaps a bit more messy.

In this case it seems like a long and complicated thing to split and trim at intersections,
probably due to the sweep1 resulting Poli-Srf not being that great to begin with.

Perhaps my first question should be: how to make this a cleaner Srf/Poli-Srf,

The goal is similar as in the original post, to Trim the self-intersecting portions in order to make filets or blends

with thanks
akash

self Intersecting sweep1.3dm (4.4 MB)


(Pascal Golay) #7

Hi Akash - the best would be not to have a polysurface at all - you can do this if you place all the section curves (circles and ellipses) with the orientation the same so that the points line up, like so:

And make sure to align the arrows in Sweep1 snapping to Knot,to hit the corresponding part of each curve.

self Intersecting sweep1_PG.3dm (668.5 KB)

And work from there.


#8

Yes thank you Pascal.
you made a perfect sweep here.

important lesson for me here with sweep1

all the best

akash


#9

Dear Pascal
i did the sweep 1 according to your instructions, and it came out good as well.
split with shrink the sweep at both directions. and run intersect.
this gave a few trim-able intersections but didn’t work for most places?
It also seems to be a very long process, looking for additional valid splitting ways…

it would seems that a simpler shorter way is very much needed in this case?

here is split model each split piece is on it’s own layer for clarity.
self-intersecting sweep intersected.3dm (1.7 MB)

thanks a lot
akash


#10

Hi Akash,

Split the surface by Isocurve and then intersect to get the curves you need for trimming and self intersections.

Work with two models - have one that you split up to create trimming curves with and have the original single surface to copy over the curves and trim. That way you’ll end up with a really nice surface without all the splits you’ve created to achieve the result you want.

self-intersecting sweep intersected_01.3dm (922.9 KB)

Andy


#11

Thank you Andy
I’ll do as you say,

good learning for me here
nice


#12

Hi Andy
Following your method, it has worked beautifully to a point…
i was able to trim a couple of intersections, and then, attempting to trim the others result in good parts being removed…
and i have no idea why.

  • a couple of intersections were not closed, [i joined them] but the trim is failing also with the originally closed ones…?

self-intersecting sweep 2 halfs.3dm (5.8 MB)

with thanks
akash


#13

Take another look at the detail… What needs cutting and how will it be cut?

You either need to extract another isocurve or join the elliptical curves and create a face:

Having said that though, due to the way the surface has been constructed (and as someone stated earlier) there are problems with self intersecting surfaces - even by pulling the curves to the surface, extruding curves into surfaces that bisect the area you want to trim, it still creates issues:

I’m afraid I don’t know any way around it - you’re going to have to split the model up a little but maybe not to the full extent of your first example.

Sorry I couldn’t find the solution.

Andy

One split: