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Simple and better solution for transition two shape

Phenom
Phenom

Hi,

my colleague had sent me a problem. He wants to transition from two different shapes.

Attached the file original and Parasolid for users without NX1847 series.

2019-06-10_12-31-43.png

Thank you...

Using NX1867
RuleDesigner PDM

10 REPLIES 10

Re: Simple and better solution for transition two shape

Gears Phenom Gears Phenom
Gears Phenom

Hi @cubalibre00,

 

Here's one way to accomplish this - we do this all the time for tubing with flattened areas between round sections.  I prefer one surface at a time to show the tangent blend transitions but the TCM could be done all at once such that a solid body is created instead of one surface at a time.

 

Hope this helps.

Tim
NX 11.0.2.7 MP11 Rev. A
GM TcE v11.2.3.1
GM GPDL v11-A.3.6

Re: Simple and better solution for transition two shape

Phenom
Phenom

@TimF ,

thank you for the solution. Sure the result is good, but strange that NX needs to much work to accomplish this transition. I have an ex-Catia colleague and has told me that Catia does it better...as italian Smiley Very Happy

Thank you...

Using NX1867
RuleDesigner PDM

Re: Simple and better solution for transition two shape

Gears Phenom Gears Phenom
Gears Phenom
@cubalibre00,

Can't say I disagree about it needing to be a bit simpler but it is what it is for now. It could be simpler with a Swept feature but then one doesn't have continuity control. Sounds like more ERs for your list.

Personally, once I figured out how to do this type of transition, I usually just make all the curve portions non-associative (except for maybe the Bridge Curves) - doesn't take me long to create them or fix them.

It would be nice if the Transition Feature would support closed curves for these scenarios. It's been around for awhile and I've yet to see much done with it - but I don't use it for anything either, so I could have easily missed some tweaks here and there.
Tim
NX 11.0.2.7 MP11 Rev. A
GM TcE v11.2.3.1
GM GPDL v11-A.3.6

Re: Simple and better solution for transition two shape

Phenom
Phenom

Folks that do more surfacing than I have more experience, but when the transition edges are a mix of splines, arcs, and straight lines, I find that I get pretty good results using Fill Surface. John Baker demonstrated this five years ago in NX 9. https://www.youtube.com/watch?v=0Jx81mrmm_c

 

transition_shape.png 

 

  1. I divided the problem into quarters based on the symmetry of the given shape using Divide Face.
  2. I added two bridge curves. (Blue lines above.)
  3. In order to create tangency at the bridge curves, I extruded them to create ribbons.
  4. I used Fill Surface, setting G1 tangency on all the boundary surfaces.
  5. I hid the ribbon surfaces and mirrored the new Fill Surface.

 

Yes, it still is a lot of steps, but 

(1) The bridge curves give control over the transition between the sections,

(2) Not as many bridge curves are required. (Really just two, and then mirror the resulting geometry.)

(3) The shape where the rectangular section transitions between the lines and arc comes in pretty nice without any manual tweaking.

 

 

 

Re: Simple and better solution for transition two shape

Gears Phenom Gears Phenom
Gears Phenom

Ciao @cubalibre00 ,

 

I fully agree with @TimF because it is possible to better control the transition surfaces.
In the video I divided the circle into angular sectors. The construction is perhaps(!?) a little longer but I prefer to have everything under control.

 

Ciao

(view in My Videos)

Re: Simple and better solution for transition two shape

Gears Phenom Gears Phenom
Gears Phenom

@cubalibre00,

 

Here are 2 more methods that would work.  If you don't care about seeing the blend surfaces fully defined, look at the alternative 1 model and replace the Studio Surface with the TCM surface where applicable (mainly the Mirror Features).

 

I think you get the idea of how to tackle this in NX.  I still agree with you in that there should be simpler ways to accomplish fairly simple transitions where we don't have to jump through extra hoops to define alignment and/or add Bridge Curves to get rid of wrinkling in faces/surfaces.  However, I don't know what all is necessary as far as the background math is concerned.

 

@MarkLawry,

 

I've gone that route in the past but I typically don't use Mirror or Pattern because there have been times where the tangency between edges gets hosed amongst the copies, more often than not when trying to work in a Unite for the freeform solid versus other methods.  In order to speed things up and cut out very basic tangent analysis, I go to my Visualization Preferences and set my Smooth Edges to a Phantom font.  Non-tangent edges will now be solid.

 

Plus, I don't enjoy using View Dependent editing on the Drafting side, and I don't care to see tangent edges at planes of symmetry (yeah, I know - OCD) so I avoid using Mirror with B-Surfaces most of the time.

 

@Cesare,

 

Thank you for the comments.

 

EDIT:  I tried to work a Transition feature in but it's not maintaining tangency between the 3 surfaces (radially around the tube - refer to image below - solid lines are not tangent, phantom are tangent).  It does maintain tangency between the sections though - very odd duck and this needs to be improved IMO.

NX11.Transition.Feature.png

 

Tim
NX 11.0.2.7 MP11 Rev. A
GM TcE v11.2.3.1
GM GPDL v11-A.3.6

Re: Simple and better solution for transition two shape

Siemens Phenom Siemens Phenom
Siemens Phenom

All,

 

If this was me I would have a look into the defining process. I would break it down to simpler entities with a bit of "directional sence".

 

Best Regards

Fred

 

(view in My Videos)

 

 

Re: Simple and better solution for transition two shape

Phenom
Phenom

Hi @Sandman ,

I've tried your solution but I'm not able to have the radius big like the square.

Thank you...

Using NX1867
RuleDesigner PDM

Highlighted

Re: Simple and better solution for transition two shape

Siemens Phenom Siemens Phenom
Siemens Phenom

Hi Cubalibre00,

 

When creating transitions, it is a good practice to create a good distance between the two entities (the destination would be based on the downstream blend requirements) to be bridged allowing for an optimal lead in at both ends – especially valid when you have an S-shaped transition. If too short the resulting transition will be rather “sharp” with a small radius and that often causes downstream issues. In this specific case I would consider providing a longer transition distance allowing for the intended solution to work. There are several options for the blends here however to target the situation in the specific part “as is” you would have to consider a different approach. The attached shows how to use regular blends where applicable and Blend Corner will create the smooth transition for you.

 

Best Regards

Fred

 

(view in My Videos)