Practical problems and... an improvement suggestion

[florin.adamescu]

Hi guys!
As a newcomer to the Fusion 360 space I want, first of all, to congratulate the development team for making such a complex software to be so friendly for someone to learn and to have encouraging results even from the
beginning!
(I would like the Revit team to learn something from your approach and solutions in order to simplify the workflow in their software, which now - after seeing the available possibilities in Fusion 360 - appears to be obsolete, uninspiring and unjustifiedly difficult even for doing simple things).

However, after having a lot of fun with experimenting techniques and reproducing tutorials, I've proposed myself to try a concrete design task and... I entered very quickly into troubles :), so I need some help!

Basically, what I'm trying to do is a cylinder - dome object with a decorative cut, something like here:

The object must have a hollow interior, a wall thickness of 5 mm and is intended to be realized from grey iron by sand casting process.

(For those who don't know, I mention that the sand casting process has several specific requirements, of which
the most important are:
a) the geometry of the pattern object must permit to slide it out from the sand in one direction without damaging
the mold (so that the internal and external elements must be designed in such a manner to avoid any obstacles);
b) the wall thickness has to be as uniform as possible throughout the object, because any thicker section may
cause uneven cooling and can result in shrinkage, porosity, or cracking.)

So, my workflow was this:
1. I modeled (very easy) the basic form of the object in the Sculpt environment, starting from a T-spline cylinder: 
2. In the Patch module, I split the body by a spline, then, using the Press Pull command, offset the resulted face
4 mm inside: 

And here, looking at the result in the section below, I realized the first issue, namely that the face in the red circle would not permit the sliding of the interior mold to the left and of the exterior mold to the right (conflict with the condition a) of sand casting):
But, with an idea in my head, I continued:

3. I thickened the two surfaces 5 mm to the inside:

then offset (Press Pull) the lateral faces of the inner object to the outside, in order to combine the two objects:

Here, of course, the second issue appeared, though expected: the thickening of the wall to 9 mm in the overlapping area of the two objects (conflict with the condition b)

But, as I said above, I already had an idea of how to solve both problems at the same time. Or, at least, so I
thought ...
My idea was that using the Sweep, to cut the inner and the outer edges as in the following image, obtaining an (almost) perfect profile:

But... as you all of you on this forum already know (as I've read a lot of related topics) the Sweep command is very pretentious and unpredictable.
I've tried for two hours to make different adjustments to the shape, to the distance (hoping to see even a
partial result, in order to understand what happens), to the twist angle, but nothing worked! Only different error messages, as exemplified here:

So, I surrender! I declare myself unprepared for this task and I ask the more skilled colleagues to help me with ideas
for better methods/workflow! Please, I really need some good advice!

But, as I mentioned in the title, I also think I can suggest a simple way of improvement for this kind of situations.
Specifically, this would be an added option in the Press Pull command that would permit to chose a different angle
(other than the default one that is perpendicular to the translated surface) for the lateral faces - thus resulting in a more accentuated conic form - as I sketched here:

After that, I think that the thickening operation would happen exactly just as I would have wanted for my task:

So, dear Fusion Team, do you consider my suggestion feasible and useful?

[davebYYPCU]

Whilst not an expert, my fix would be back here, at this pic, 

Would cut the new body again with the same or modified splitting tool, (don't want the bottom to be effected,) 

Another horizontal cut, Delete or Remove the top sections of the new body and the perpendicular top face of the original body.  Then use the Loft tool (join) to close the gap.  All this is before the thicken command... 

Might help....

[florin.adamescu]

Thanks, @davebYYPCU, sounds interesting, I'll try tomorrow (now it's 1 am for me) and I'll tell if worked!

[florin.adamescu]

Well, starting from the idea of @davebYYPCU(thanks again!) - in which I found "Loft" to be the keyword - I realized I could try another approach.
So, after I split the body, I just "played" with scaling and moving the inner surface until a satisfactory result:
Then I made a loft between the two surfaces, reversed its normals and stitched all the faces into a single body:
And, after all, the thickening worked exactly as needed:

Hurray! 

However... I feel that scaling and moving that surface isn't the best way to get things right, as it is impossible to control precisely, but only visually adjusted by "trial and error".
So, I still maintain the suggestion of improvement that I made in the first post.
I just hope that someone in the development team will read it, so far it seems like no... 

[laughingcreek · Accepted solution]

I think instead of moving and scaleing the face, you should make a second cut.  Then press/pull the smaller face.  Then you can use the draft analysis tool to make sure the shape meets your needs for the mold.

As an aside, I made my cone shape with regular modeling tools.  Sometimes this work flow works with tspline, sometimes it doesn't.  When it doesn't it's impossible to tell why.

Here's a screen cast, most of the work flow is the same as what you did.  sorry for the length, I didn't start with a plan,  so there are some missteps in there.

[florin.adamescu]

Wow, this is the most elegant solution, indeed! Thanks a lot, @laughingcreek!

The reason I modeled in the t-spline was that I needed a transition from a circular section (at the larger and open end) to an elliptical section (at the domed end), maybe this can be better seen in these pictures:
But I hope I'll manage to apply your solution on a t-spline body, too!

[laughingcreek]

just in case your interested-

[chrisplyler]

...and using Laughingcreek's method, you can certainly start with a circle at the bottom if that's what you want.

[florin.adamescu]

Of course I'm interested, thank you! 

[florin.adamescu]

Thank you, @chrisplyler