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ptc-49820881-Visitor
1-Visitor
February 24, 2013
Question

Trimmed edge offset

  • February 24, 2013
  • 1 reply
  • 3025 views

Hi,

I am trying to offset a trimmed edge with the OFFSET command.

As you can see in picture attached, although the edge is being offset, i am not able to control the direction in which it is being offset.

As it seems, the offset is kind of sliding along the surface behaving like a COS. I want it to be offset inwards, kinda like a radial flange direction, actually that is the purpose of my offset, to build a "lofted surface from that trimmed edge to the offset curve. I would like to ask you some questions, and i will enumerate them to make things more organised:

1. How to specify a direction, or vector, for the offset? I want the curve to be "flush" with that trimmed edge (when looked form side view), and offset inwards... not to the front of the edge as shown in picture.

2. How could i move this offset curve, back and forth, so i could position it where i want? In STYLE, i m not able to move it, because i cannot even pick it. I can pick the curve to show a curvature plot, for example, but i cannot pick it for moving. Why?

3. The offset doesnt really look like a offset, but rather like a scaled curve... The distance from edge to offset curve is not constant, which is what an offset is. Why is this so? How to fix?

4. How could i simply make a radial flange (inwards) of this trimmed edge? Would just be a quicker way of achieving what i am trying to do.

Could you please answer these 4 questions? It would help me a lot to understand how Creo works.

Thank you all, in advance.

Regards.

1 reply

T
TomD.inPDX17-Peridot
17-Peridot
February 25, 2013

I suspect you already have a surface that created the cut region. If not, create one. You can then offset that surface and intersect this with the face you want to build the flange from.

I cannot envision exactly what you are trying to achieve, but obviously the offset curve isn't it. Surfaces, trims, and intersects will get you the features you need. from there, you can blend, solidify, thicken... whatever.

P
ptc-49820881-VisitorAuthor
1-Visitor
February 25, 2013

Thank you very much for replying. I thought i was pretty explicit, but it doensnt seem to be the case...No problem, i ll try to be more concise.

Regarding your 1st paragraph, is not what I want at all, in fact that is what is already in the picture of previous attachment.

What i want is a radial offset. To help you better picture it, imagine u give thickness to this shape inwards.

I want that curve on the edge of the inner wall.

How do i achieve such curve, which is a offset of the edge u see highlighted on the pic attached?

How to do it in CREO?, I know fully well how to do it in Catia or NX, or alias.

Not in Creo, as i am learning it.

Thank you!example2.jpg

T
TomD.inPDX17-Peridot
17-Peridot
February 25, 2013

I see. I have done this in several ways but not with an offset of the existing edge in the way you are trying to do it. For some reason, Creo doesn't know how to make that edge smaller... only larger.

However, it is easy to achieve what you want with a projection rather than an offset. In this case, you would offset the edge in the sketch. You can then project it on that inner surface.

I was able to achieve the same as you describe by offsetting the outer surface toward the inside. Not quite as straight forward as the surface must intersect the inner surface. Never the less, it too created the offset you want, and probably more accurately.

In the following image, you can see various offset edges. You can offset the edge from the inner surface or the outer and they will behave differently. But they must both grow "outward" for some reason.

The stepped flange was done with an offset; the top surface was the original cutting plane. The inner surface was an offset from the outside but it can be any intersecting plane.

bowl.JPG

I find it very difficult to work with curve geometry when creating surface features. The only place that the curves are useful is in 2D (sketch). However, the offset command does have some very powerful features to properly map 2D onto surfaces. But whenever you, you want to manipulate surfaces with surface rather than curves.

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