How to set endpoints of a sweep?

lars_andersson

Beginners question, I tried to sweep a circular cutout on the outside of a solid. Sketch 4 is the circle.

The endpoints of Sweep1 did not turn out as I expected, I had expected the sweep to run a full 360 .

How can I set the endpoints?

3dcad

You might wan't to use revolve for this particular case.

andrew_troup

You'll find it worthwhile, I think, investigating why things don't work the way you expected in a solid modeller, so I think it's good that you're curious.

(I agree that revolve is definitely the best option, but I reckon as a separate issue, the key to using a modeller well is being able to predict how it will behave, so it's worth eliminating mismatches between how you think commands work, and how they really work)

By outer surface, I'm guessing you picked an edge at the top or bottom of that surface. (A surface cannot act as a path)
Those edges happen to be incomplete arcs of a circle. And your "profile" does not line up with either of them.
The result you got is exactly what could be expected from the choices made.

If you wanted to understand the implications of those choices, you could check out this recent post
https://forum.onshape.com/discussion/comment/12030/#Comment_12030

Scroll down to where it says "... tentative mental model of what's happening"

Narayan_K

@ lars_andersson ,Here sweep length is same as your sweep path but sweep section is away from the sweep path.If you make section at the start point of sweep path,you can get the correct result.


You can also make that with revolve as below

3dcad

You might wan't to use revolve for this particular case.

andrew_troup

What did you use for your path?

lars_andersson

I used the outer surface of the large extrusion 1 for path. Just curious what defines start and end of the sweep.
Tried revolve instead, as suggested, and that gave me a full 360 cutout.

andrew_troup

You'll find it worthwhile, I think, investigating why things don't work the way you expected in a solid modeller, so I think it's good that you're curious.

(I agree that revolve is definitely the best option, but I reckon as a separate issue, the key to using a modeller well is being able to predict how it will behave, so it's worth eliminating mismatches between how you think commands work, and how they really work)

By outer surface, I'm guessing you picked an edge at the top or bottom of that surface. (A surface cannot act as a path)
Those edges happen to be incomplete arcs of a circle. And your "profile" does not line up with either of them.
The result you got is exactly what could be expected from the choices made.

If you wanted to understand the implications of those choices, you could check out this recent post
https://forum.onshape.com/discussion/comment/12030/#Comment_12030

Scroll down to where it says "... tentative mental model of what's happening"

Narayan_K

@ lars_andersson , For sweep,start and end point of sweep curve defines the start and end point.

You can select one direction option in revolve,



 

andrew_troup

A brief explanation of why, despite what @Narayan_K says, your sweep stops short of the end of the path, on the side nearest the viewer in your screengrab:

This is because the swept cut starts before the beginning of the path.

It starts at the profile sketch, in midair, and travels some distance before it starts cutting into your part.

lars_andersson

I made a public document "Prov 2" there i made  "Revolve 1" and  "Sweep 1" from "Sketch 4"
"Sweep 1" is made along the intersection edge of "Revolve 1" and "Extrude 1".

I do not understand why "Sweep 1" ends squarely slightly after the Top plane

Narayan_K

@ lars_andersson , Can you please paste the URL here so that we can look in to that.

lars_andersson

Hope it is this one:
 https://cad.onshape.com/documents/83409d532f4b46bd83ba32cd/w/2e1ea2949d804e7d8f616d0f/e/bd7b845248e64299889a2437

I think I see something now, the length of the sweep is taken from the sweep target, but the sweep is moved forward by the distance between the sweep source and the sweep target.

Narayan_K

@ lars_andersson ,Here sweep length is same as your sweep path but sweep section is away from the sweep path.If you make section at the start point of sweep path,you can get the correct result.


You can also make that with revolve as below