Connect spline and offset?

[cjmason]

Hi, 

I'm new to Fusion 360 and trying to record my struggles in the hope it would be useful.  I know that some of this is probably obvious to others more experienced users of the software, but I think one of the biggest challenges I have as a software developer myself is getting myself to think like a naive user.

I'm trying to do what I thought would be simple: create a vase shape from a spline.  There's probably some more straightforward way to do this, but my thought process was:

• Draw the outline of the vase as a open spline on a construction plane.
• Offset this spline by the thickness of the vase wall.
• Join the ends together to create a profile.
• Revolve that profile to create a solid.

I can draw a closed loop spline (with "thickness") but then how do ensure symmetry (parallelism) between the inner and outer wall?

Here's a screenshot.  I was able to do the inner one by manually drawing a close spline, but the walls aren't parallel.  I had to trim the edges of the spline so that they did not overlap the axis I revolved around.

Some things I've tried using the upper spline and offset:

• Revolving directly: won't let me select an open spline.  Makes sense, I guess.
• Joining the ends: There's no control points on the offset curve.  Is this because it's parametric somehow?  If so, why doesn't it change when I modify the original spline?  Is there a way to convert the offset curve to an editable spline that I could join the ends of?  Also: why isn't there a right menu option to join two points (cf Illustrator)?
• Extending the spline.  I get "Extend spline error."
• Trimming the offset curve.  It seems to trim the wrong side:

   ->    ->  Wat?

One of the biggest problems I had with Rhino was not being able to do a thing I wanted because the object wasn't the right type.  Ok, why won't you let me select that?  Or: ok, given an X, how do I get the Y that you want to let me do Z?  Some visual feedback about this would be great.  For instance, if I linger over an open spline when trying to select the profile for a revolve, show a tooltip: "You can't select that because it's an open spline. Revolve requires a profile."

Thanks,

-c

[kingson138]

Hello, I think it is a matter of how you construct you sketches (the work flow). I would say there are a few ways to form your model. One of the ways, which I think is better is to use "Create Form" to create a cylinder. Shape the cylinder and then thicken the cylinder (using Sharp or Smooth option). Try to use the new creasing capabilities as well, you will like it a lot!

But you can of course use revolve to form your model. Maybe I can give you a few screen shots to demonstrate this. I am just a user of this program. Not an expert but I am just exchanging some thoughts here.

I would say you should start with a line as an axis, change that to a construction line by "left clicking" on the line to change color to blue. Then "right clicking" to toggle between Normal/Construction and change the line to a dotted construction line. The right click menu has different options  between "Right Click" or "Left Click then Right Click" or "Holding the Click for a few seconds". You can experiment with that. You should also experiment with the use of "Constraints" when sketching. These are very useful tools for precision works.

Then on the same plane you can sketch your curve. That is the first screen shot. Then you can add the bottom and top lines (or you can use the same sketch and form a right angle turn to form the the whole shape). You might want to use "Constraints" to make sure that the two straight lines are perpendicular to the axis. You can then offset the curve. You can join them into a closed sketch. Bear in mind that you should do all these within the same "Sketch" environment. You can then select the profile and axis and revolve.  To form a smooth edge use Fillet. 

Again this is just an exchange of ideas and others might have more ideas on this.

Sorry for so many editing. English is not my first language.

[cjmason]

Hi Kingson,

Thanks so much for your detailed post with lots of ideas and things to explore!

I tried this again with a slightly different spline and it works!

I think maybe I was expecting there to be control points on the offset spline that I would need to join to, but apparently I can choose the spline tool again and just click at the ends of the offset spline (where there are no control points):

I think there's something special about offset splines that makes them not behave like splines?

Thanks!

-c

[kingson138]

HI -C,

Thanks for the wonderful news. Yes I know you are an experienced 3D program user as I had seen your other posts. Fusion360 behaves a little differently. One of the most interesting things is the ability to shape TSpline bodies. I would say that you should use "Create Form" and explore the infinite possibilities of shaping bodies. There is one point that I would like to say. I am not sure if the team had fixed that or not. To move an offset plane in all direction by right clicking the plane and select move, you can move the plane in any direction and angles. But that only works in "Create Basic Feature" and "Create Form" workspace. The planes cannot be moved at the parametric workspace. Just to give you a little hint. Well have fun with your shaping!