Unwanted Egde will not Combine or Stitch in body

[James8X5JR]

Hello,

Very new to fusion. Apologies if this is covered somewhere else. I've exhausted my googling abilities to search the forum/web and have not found any workable fix.

I work for a bicycle manufacturer and we're looking to get some tubing laser cut to the miter/specifications in this file. I'm hoping it's somewhat apparent in the file design history, but we're creating our tubing/miter profiles from a .step file of a solid object that is created from another program. Obviously Fusion isn't creating the shape or edge, just reading it. My question is why can't I just combine/stitch the faces together. The edge prevents this somehow? 

Thanks in advance for any insight/help. 

Best,

-James

[jhackney1972]

It is not clear what you want done to this Body.  Do you want to remove the end profiles?  Give some more clarity to your question.  Maybe a hand sketch.  There is one body shown in the Browser and there is one body on the screen.

[johnsonshiue]

Hi! This is a modeler behavior. When two spline surfaces are stitched together, though the boundary edges are knitted together, they are not merged. It is because the two surfaces originate from two different base surfaces. You can see the base surface by untrimming both surfaces.

In order to merge the edges, the entire base surface will need to be redefined. I tried using Convert to TSpline workflow and Merge Edges on the Freeform. However, on converting it back to Brep, there is still a seam edge in the middle, which is also a modeler behavior to keep topology consistent.

Unfortunately, I am not aware of an easy way to remove those edges.

Many thanks!

[jhackney1972]

If it is the line along the length, you can get rid of one side but not both.  One has to remain.  It is only graphical so do not worry about it.  Model is attached with one side removed.

[TrippyLighting]

Looking at the tube you posted, you have several surface bodies in it and one solid body that looks like the tube you want to manufacture. The solid body obviously does not need stitching.

Also I would say that the workflow you are using does not crate a tube that will fit into the frame.

If the original orange tube fits, then the pinkish part fill not fit. At least not in the CAD model.

[James8X5JR]

Thanks to everyone for the prompt and helpful replies. I truly appreciate the insight, but i'm still a little unclear on why these edges on the tube can't be combined/resolved is there in the first place compared to my other tubing i'm working with. 

Attached is an example of what i'm trying to achieve with the Seatstay file. The geometry did not start with a seam, but this is what i'm trying to achieve. Also attached a screenshot for clarity of the edges running along the tube that i'm trying to get rid of on the Seatstay file.

Some have noted that the edge seem running along the tubes should not matter, i'm checking on this with the Lasercutter but it's my current understanding the files need to be very accurate and have no extra geometry.

Sincere thanks again for the help. I know i'm showing my colors here as a novice, i'm the only one in our shop with any minute 3d ability.

[James8X5JR]

Thank you for the insight. 

I'm checking with the cutter, but it's my current understanding on there end it will still read those inside edges as a 'cut'. Waiting to hear back.

I understand these miters are not chamfered perfectly as if they were cut by hole saw, we expect a small amount of fit up. 

[James8X5JR]

John,

Thanks for your help!

I'm double checking but it's my understanding on the lasercutters end the edge would be read as a 'cut'. Waiting to hear back.

Is there a reason for this line? I'm confused why it's neccesarry on my 'seatstay' file but the 'downtube' geometry doesn't show it? Of all the tubes on the frameset this is the only tubing that has it.

[James8X5JR]

Thanks for the help and effort!

I've attached another tube that is what i'm trying to achieve with this on. I'm confused on why this is the only one showing this edge/seam that can't be removed or turned into one smooth object like the 'downtube'

[TrippyLighting]

Can you provide the original STEP files you imported in to Fusion 360 ?

I can then check in a range of other CAD software (Inventor, SolidWorks, ZW3D) how the imported geometry looks there.

My guess is that the seam is exported from your CAD software. 

Can you elaborate why you conclude the the surface transition across the seam is not smooth?

The seam simply indicates the transition from one NURBS surface to the adjacent NURBS surface.

That does not mean it isn't smooth e.g tangent or curvature continuous.  

[James8X5JR]

Hi @TrippyLighting ,

Thanks again for the continued help. I've heard back from the lasercutter and they confirmed their software reads the edge as a 'cut'. I've attached the original step files. These were created through a 2d cad program (bikecad) that exports a python script of the bicycle geometry that Freecad interprets and can export .step, from there I have to take the mitered solid tube file to fusion and convert it to a proper tube with the right wall thickness. Unfortunately- the 2d Bikecad software does not export the tubing profiles, so it creates solids that then must be hollowed out, hence this workflow. 

Attached are the two .step files of the Downtube and Seatstay from Freecad. 

Hoping this helps provide more insight! Thanks again. 

[TrippyLighting · Accepted solution]

Both of the tubes have 2 seams!

One can be eliminated, one has to remain. That is how NURBS surfaces work in any of the multiple CAD software packages I know. The shape of a NURBS surface is governed by a rectilinear arrangement of control points with a U and  V coordinates. Imagine it like a rolled blanket.

Both of the tubes are created from two identical circular tubes. The top half was trimmed of one of them, the bottom half of the other. I don't know why the seam is not visible in Fusion 360 for the downtube. I assume that is because the seam goes right through the holes in the wall of the tube.  

For the seat stay tube you can simply select one of them and hit the delete key. Then you're left with one seam.

[James8X5JR]

@TrippyLighting 

Alright, understood. However i'm still stuck with an unusable tube for our project. I'm going to call this resolved as it seems best to start fresh and model the whole frame in fusion to have a better control of the results. 

Truly appreciate the help, i'm going to explore a different approach to this workflow to try and get the deliverable we need.

Thanks again and hopefully I won't be back causing trouble too soon!