topic Re: How does one accept the self-intersection in a sweep operation? in Inventor Forum

How does one accept the self-intersection in a sweep operation?

joh13399 — Thu, 04 Feb 2021 06:48:15 GMT

I'm trying to sweep this circle along the spline you can see in the image, but when sweeping along the line, inventor gives the error that the result would self-intersect.

There is no option to accept this, so I'm here on the forums asking how I tell inventor that a self-intersection is fine.

To specify further, I'm expecting this to work like a normal sweep, where the circle is translated with the normal plane being parallel to the tangent of the line. I want to tell inventor to handle the result as a boolean OR operation, meaning that if there is an intersection from two points along the line, the intersection should be solid if it's solid at point X OR point Y.

How do I do this operation?

Re: How does one accept the self-intersection in a sweep operation?

JDMather — Thu, 04 Feb 2021 12:07:47 GMT

Did you Attach the correct file?

The file that you Attached here does not look like your image?

If you attempt to Offset the path - what do you observe?

Re: How does one accept the self-intersection in a sweep operation?

joh13399 — Thu, 04 Feb 2021 15:47:39 GMT

I thought I attached the correct one, but I've re-attached it to be sure.

I can't select the path with the thicken/offset tool.

Re: How does one accept the self-intersection in a sweep operation?

JDMather — Thu, 04 Feb 2021 17:22:08 GMT

@joh13399 wrote:

~~I can't select the path with the thicken/offset tool.~~

Edit sketch.

Attempt to Offset the sketch path.

What do you observe?

Re: How does one accept the self-intersection in a sweep operation?

joh13399 — Thu, 04 Feb 2021 17:48:17 GMT

This is what I see:

Re: How does one accept the self-intersection in a sweep operation?

j.palmeL29YX — Thu, 04 Feb 2021 18:37:31 GMT

Re: How does one accept the self-intersection in a sweep operation?

joh13399 — Thu, 04 Feb 2021 18:43:13 GMT

I don't see the issue. The solid should still be able to be created...

The result should be the same as splitting the sweep into two, three, etc. sweeps excluding only the intersecting portions.

Re: How does one accept the self-intersection in a sweep operation?

j.palmeL29YX — Thu, 04 Feb 2021 18:53:33 GMT

I don't understand what you want to say, but:

The radius of the circle must not be greater than the radius of the path curve.

To check this try a sweep with a diameter 19 or 18.5 (I dont know the path radius at the marked points).

If this works you should consider another path or a smaller circle (I don't know your intention).

Re: How does one accept the self-intersection in a sweep operation?

joh13399 — Thu, 04 Feb 2021 18:57:39 GMT

I'm saying that the sweep should create a crease where the intersection is, and that the intersection itself is acceptable to me in the geometry.

I'm also saying that there is no apparent problem with the path, even if there is an intersection, the resulting geometry should still be able to be solved and created.

Re: How does one accept the self-intersection in a sweep operation?

j.palmeL29YX — Thu, 04 Feb 2021 19:04:35 GMT

@joh13399 wrote:

... the sweep should create a crease ...

... the resulting geometry should still be able to be solved

That's YOUR opinion. Inventor has an other one, sorry.

Re: How does one accept the self-intersection in a sweep operation?

joh13399 — Thu, 04 Feb 2021 19:07:39 GMT

@j.palmeL29YX wrote:
@joh13399 wrote:
... the sweep should create a crease ...

... the resulting geometry should still be able to be solved
That's YOUR opinion. Inventor has a other, sorry.

No, no. That is no opinion. It is a fact that the geometry is solvable, and it is another fact that the geometry will have a crease. How do I do this?

Re: How does one accept the self-intersection in a sweep operation?

JDMather — Thu, 04 Feb 2021 19:12:55 GMT

@joh13399 wrote:
No, no. That is no opinion. It is a fact

@joh13399

What are you modeling?

How will it be manufactured?

What is the material that will crease?

Do you have a photograph of similar real world part with the crease?

Re: How does one accept the self-intersection in a sweep operation?

joh13399 — Thu, 04 Feb 2021 19:14:14 GMT

This is a support peg that will be 3D printed with PLA plastic. The crease will not be bent via press, roller or brake, but be baked into the print itself.

Re: How does one accept the self-intersection in a sweep operation?

swalton — Thu, 04 Feb 2021 19:15:34 GMT

As I understand it, Autodesk programed Inventor's sweep function to error on self-intersections. While it is possible to define results from self-intersections, Autodesk didn't.

You won't be able to get a creased shape with a single Inventor sweep function. You might be able to get the shape you want by combining several features, or with some sort of multi-body workflow.

Why do you need the crease? How do you intend to get that shape on a real-world part? Maybe there is another workflow that can get you the shape you want.

I've never had to to model such a shape, so I'd have to make several attempts before I could give you a recommended workflow.

Re: How does one accept the self-intersection in a sweep operation?

johnsonshiue — Fri, 05 Feb 2021 00:58:29 GMT

Hi! Indeed, Sweep in general does not like self-intersection, particularly at the same path segment or the profile itself. There are workarounds. Here is one solution. Basically, you make the circle smaller like 10mm diameter. The sweep will work without a problem. Then use Thicken feature (9.5mm) to enlarge the tube. Please take a look at attached part.

Many thanks!