Dome Feature: Bottle bottom identation

Lewis_Maina

Hi, am modeling a bottle that has a bottom indentation (dome-shaped) feature, see two attached images.

I have tried the Loft feature which has several errors, I have tried fill surface, am out of options, please assist

NeilCooke

Fill does a good job with 2 vertices

S1mon

Fill with a couple of arcs or splines as guide curves should get you what you need. See “guides that intersect at tangent plane” in the help. https://cad.onshape.com/help/Content/fill.htm

dirk_van_der_vaart

something like this?
https://cad.onshape.com/documents/6a28c67cf47e4531c67ee71c/w/62b6e4f244d9267a67350cc6/e/dbd5f51499620fa484b2487b

NeilCooke

Fill does a good job with 2 vertices

adam_richardson

The way that Neil suggests works well if you are OK with the surface going to tangent at the edges, which isn't what your PB jar example does (so far as I know there isn't a way to control the tangency with a fill as there is with a loft). However, it would work well if you knew ahead of time that you were going to dome this surface, and you could create an over-size surface with the desired shape and then extrude the body up to it, and then add the fillets afterward. This can be a bit trial and error though as you don't necessarily have a lot of control over how straight the edges will end up looking in orthographic, which can be important (the red curves in picture below). The simple method works fine for doming a cylinder but not for a more complex shape like yours.

The way I solved this is the same as what @S1mon suggested, which is to construct your body, then create a fill surface with 2 guide curves (rather than just vertices) so that I could more exactly define the shape of the domed surface.  (As always with these guide curves you have to make sure they intersect the profile edges as well as each other in the middle). Here's the step by step:



Then thicken the surface to turn it into a solid so it can be used as a tool in a boolean


And the resulting shape after using the thickened surface to remove the domed area


I did this with the fillets already in place but actually it would be better to do this boolean operation before filleting to ensure true tangency.

Hope that helps!
There could be a better/quicker way to do it, this is how I typically do this sort of thing. The advantage of this approach over the over-building surface approach is that if you change the main body shape or size, the domed surface moves along with it but keeps the edges nice and straight.

S1mon

@adam_richardson

One suggestion - create the surface with a fill, and then use replace face. No reason to thicken and boolean. If you moved the dome surface before the fillet, it would be challenging to keep the bottom flat. With a revolved bottle, it would be no problem, but the variable dihedral angle between the outside and the bottom would cause the fillet to do all kinds of unwanted waviness where it wants to be tangent to the ground/table.

adam_richardson

Ah, that's a more streamlined approach, I knew there had to be a way to do it in fewer steps, thanks @S1mon!