You're changing the geometry of the part facing outwards (away from the center), and so it's no longer consistent and shading issues appear. One way to produce a nice topology in such case is to just have a cylinder and after subdiv modifier shrinkwrap its top/bottom onto a profile:
- Add a cylinder without caps, add a Solidify modifier and apply it. Duplicate the cylinder, name it
profile and move up:
- On the bottom cylinder add creases with ShiftE like on the picture, add a Subdivision Surface modifier with Ctrl2, enable Auto Smooth:
- Assign the top to a
shrinkwrap vertex group:
- Add a Shrinkwrap modifier projecting vertices from the
shrinkwrap vertex group on the Z axis on the duplicated profile object:
The offset is there just to make it easier to see the effects of modifying the profile.
- Modify the profile and bevel it like so:
(consider making the profile slightly thicker to be on the safe side)
Beginner Friendly Version
- ⬆ ShiftA, Mesh, Cylinder, F9 to open operator settings, decrease depth, disable filling. ⬆ ShiftDZ to duplicate and limit movement to Z axis, to make sure it's exactly above. ⭾ Tab enter Edit Mode and S scale the cylinder down slightly (actually I scale it down quite a lot to make it more clear on the GIF). Then ⭾ Tab go back to Object Mode, add a Solidify modifier to the bottom cylinder, with negative thickness to grow outside. Select the top cylinder, Numpad 7 go to Top Orthographic View and add the Solidify modifier, make sure to set the thickness so that the outer side is definitely further away from the center than the outer side of the bottom cylinder (in this view it's easy):
- With the top cylinder selected and your mouse over the modifier, ✲ CtrlA to apply it, then with the mouse back in the 3D Viewport, ⭾ Tab to go to Edit Mode, select two neighboring faces (you may need to press 3 to go to Face Selection Mode), G, then Z to move those faces on Z axis (and move them down). Now, 2 for Edge Selection Mode, ⎇ Alt$\color{green}{█}\color{#888}{0█}$ left mouse button on an edge to select an entire loop, and then ⎇ Alt⬆ Shift$\color{green}{█}\color{#888}{0█}$ left mouse button on another edge to add another loop to the selection. Repeat the last step to select remaining loops you want to bevel, then press ✲ CtrlB to bevel those edges. Drag your mouse to control the amount of bevel - you may want to press C to limit the bevel, as well as you may want to scroll your $\color{#888}{█}\color{green}⬆\color{#888}{█}$ mouse wheel up, to increase the number of added segments for a smoother transition.
- Once you're done with the profile (you can still edit it later), ⭾ Tab to return to Object Mode, select the bottom cylinder, apply the Solidify modifier like in p. 2., ⭾ Tab Edit Mode, 3 Face Selection Mode, click somewhere outside the mesh to deselect, ⎇ Alt$\color{green}{█}\color{#888}{0█}$ left mouse button on an edge going from inside faces to outside faces of the top of the cylinder, then go to
Object Data Properties, and add a vertex group, name it shrinkwrap, and be sure to press Assign button to assign selected vertices to that group.
- In Object Data Properties scroll down and look for Normals > Auto-smooth - enable it. Deselect everything, 2 for Edge Selection Mode, select one of the edges being a part of a circle, ⬆ ShiftG to Select Similar, and choose F Face angles. Now ⬆ ShiftE to Crease, and 1↩ Enter to set full crease on those edges. ⭾ Tab to go to Object Mode, and ✲ Ctrl3 to add a Subdivision Surface modifier lvl 3.
- Add a Shrinkwrap modifier. As a target choose the top cylinder, as a method Project, as axis Z, and remember to use the
shrinkwrap vertex group.
