topic Re: A little directional help please in Fusion Design, Validate & Document Forum

A little directional help please

Anonymous — Sat, 25 Apr 2020 21:18:48 GMT

I had a part scanned locally and they supplied me with .stl, .igs and .stp files. This is the forward edge of the engine cowl for an RV8 (small plane). The intent is to create two sleeves that will slide into the two outer openings giving me the ability to neck down that opening size. Seems simple enough and the perfect project while under lockdown. Start with a scan of exactly what I have to work with, create an overlay of that part, trim it, thicken it where needbe and edge it. I've done some STL to solid, modify, back to STL work for my 3d printer in F360 and that has all worked out pretty well. This project I can't get past step one. Every path I've attempted from thickening the part and pulling faces to shelling, offset edges....I can't get the overlay made so I can modify it into what I'm attempting. I've been watching videos and reading forums for two days, attempted dozens of different paths...and I'm out of ideas. This doesn't seem like it should be as difficult as I'm making it. What am I missing?

I could really use a nudge in the right direction. Here is a photo to help visualize the hole I'm attempting to sleeve. The sleeve will wrap around the front of the opening and reshape the leading edge to accommodate the thicker top and bottom, metal trim in the foreground will be removed and remade to anchor that side. Screws visible anchor the other. Am I right in assuming of the three files I have, the .stp file to use? I attached it.

Re: A little directional help please

davebYYPCU — Sat, 25 Apr 2020 22:31:45 GMT

That STP has nice clean geometry.

I Split body with an offset plane, just deep enough to cut the part into three along the filleted edge,

I was able to thicken this part 0.04 in, takes a while, but I didn't know what clearance you wanted to build in.

Section through the bolt hols has shown the depression they made, so looks too real.

See how you go...

Might help....

Re: A little directional help please

davebYYPCU — Sat, 25 Apr 2020 23:09:31 GMT

Arhh, some more digging and Fusion started to not recognise the body to split, (might be of my doing though)

I noticed the starboard side is typical fibreglass, and not totally square / parallel. Was able to thicken a parallel cut on that side too with an Extrude cut off a 3 point plane.

Re: A little directional help please

Anonymous — Sun, 26 Apr 2020 04:19:12 GMT

Believe me I understand what you mean. I get a lot of body doesn't intersect, operation failed to create a valid result etc. So I extrude cut instead of split body....but why? 3 seconds later I cut off something else with split body and it works fine. I'm just not sure what is causing it or which direction to go. You were able to thicken to .04in which as it turns out is 1mm which is as far as I got. Let me run this by you, tell me if I'm crazy.

Since this is a scan it starts off with no thickness. It's just a surface. When I thicken it, I thicken it out..towards the front which means the starting point is still the surface of the scanned part. Meaning, I now have a 1mm thick skin, that should in theory lay right on that cowl. Right? In reality, I assume, that side of the part that lays on the cowl will need a relief of say .5mm (WAG) but I can't seem to make that happen....software doesn't like what I'm trying to do. The part is also going to need to be 12mm ish thick on the top and bottom inside the hole (long sides) and the sides of the part inside the opening thick enough to be structural...so 3 or 4mm? Surely there is a pulled face or thicken part or some software trickery to change the thickness, but damned if I can find it.

This is essentially the part I'm trying to produce without the extra thickness anywhere:

I get that far and I am stuck. I did cut off a 1 inch piece off the backside of that opening. Basically it's a rectangle about an inch high..., saved as an STL, sliced and printed it and I'll go down to the hangar tomorrow and see if it slides in the hole...something to do while I see if those with a lot more understanding of F360 and point me in the right direction. I do appreciate the help Dave.

Re: A little directional help please

laughingcreek — Sun, 26 Apr 2020 04:53:06 GMT

the surface quality of the stp is pretty noisy. It's not surprising your having trouble with tool like thicken. I think you might be able to improve on the quality some with a better conversion. it looks like the original stl was converted to a quad mesh, from which the stp was obtained. but the quad mesh conversion wasn't very good.

if the stl where run through something like insta meshes, and topology flow was paid attention to, the resulting quad mesh would probably convert a little better using the quad mesh->tspline->brep conversion process.

Being a fairly simple surface it could be manually re-topo'ed also.

@TrippyLighting is a bit more knowledgeable about this type of workflow, maybe he'll stop by.

Re: A little directional help please

davebYYPCU — Sun, 26 Apr 2020 05:54:24 GMT

On top of Alex's info, I was not getting much joy from the stp.

There are a few attempts running around in my head, I arrived at this one

is original surface, 2 offset planes and boundary fill,

followed by surface loft to cut the hole. So only fudge left is shrinking the external surface to fit the original hole.

But Fusion does a good job of the inside of the insert.

Might help....

Re: A little directional help please

TrippyLighting — Sun, 26 Apr 2020 11:18:01 GMT

Hopefully, no one paid any money for the conversion from the .stl to the NURBS surface!

This was most likely done using a re-meshing software such as InstantMeshes or one of the Autodesks solutions e.g Recap Photo. Numerous software possesses re-meshing abilities. ZBrush, 3D coat etc. This can be seen in the structure and asymmetric and irregular layout of the NURBS patches.

to do this right takes some skill even if the end result is a quad mesh that is then converted into PolyNURBS or T-Splines.

That workflow is good for organic meshes, but I would not recommend it to re-create technical surfaces.

If a quad mesh approach is taken, then this is best done by manually re-topologizing, for example using TopoGun or Blender with the RetopoFlow plugin (or others).

However, the success of such efforts greatly depends on a good scan.

Is there any way you can share the scanned .stl ?

Re: A little directional help please

Anonymous — Sun, 26 Apr 2020 15:08:16 GMT

Sure, I can share the scanned STL. Am I reading you right in that the stp is likely inaccurate, or I'm making my life harder trying to work with it?

Re: A little directional help please

davebYYPCU — Sun, 26 Apr 2020 19:29:05 GMT

That’s a yes and no. Alex’s colour map shows that the scan is too accurate, contains all the lumps and bumps (and probably insignificant to us) of the original. Fusion is seeing those and finds it hard to work with.

I don’t know the detail / techniques, but Peter knows how to modify to a usable outcome, with external software.

If you have looked through my loft example, I extracted the profile curves, and for each spline

the original curve was variously jagged / lumpy, and I have introduced a smooth curve for the inlet’s new face with the measured offset for the necking.

Knowing that the hidden side of the necking, can be fixed for fit in the workshop, I pushed on with the example with that intent.

So the scan is better than not having it to start with, how would you detect the almost symmetry errors without it.

Re: A little directional help please

TrippyLighting — Sun, 26 Apr 2020 23:05:41 GMT

The scan is actually pretty clean.

I would use mesh section sketches and build splines (manually) then I'd loft and try to re-build geometry that way.

Definitely more work, but much easier to work with down the line.

Re: A little directional help please

Anonymous — Mon, 27 Apr 2020 19:28:54 GMT

I knew in the beginning there was a concept or tool I was missing...and that tool is LOFT. I have never had use of loft before and had no idea what it could do. I'm on a steep learning curve with loft but there are a lot of videos out there to teach me and I am pretty sure you guys have put me on the path. Thank you so much, you guys are the best!

Re: A little directional help please

Anonymous — Tue, 28 Apr 2020 21:20:00 GMT

Well, I have been busy and believe I believe I have the concept of the loft command. This morning I managed to create a nice loft of this part. It was a bit thin on the top, so I created another profile higher, recreated all of the rails to include that profile and now it's broken and I can't figure out where I went wrong. I can't get the loft command to recognize my new profile (named Top profile) and somehow I managed to break Cowl profile as well...thought it worked this morning. I suspect it has to do with the sketches, the centers don't turn blue, so I can't select them as a whole. I selected Cowl Profile line by line this morning and that worked...now it will not. Again, I feel like there is something basic I'm missing here. Can I trouble you for a bit more guidance? The profile I added is the highlighted one named Top Profile:

I'm not sure where the entrance to this rabbit hole disappeared to. I'm hoping you can put me back on the path. The loft this morning was gorgeous...and I've spent the entire day attempting to get back to that place without much luck. It sure feels like I'm close.....

Re: A little directional help please

Anonymous — Tue, 28 Apr 2020 21:22:01 GMT

Re: A little directional help please

Anonymous — Tue, 28 Apr 2020 21:27:17 GMT