How to maintain 1 mm rounding when I need 3 mm in a single axis?

Question

I have planned a simple object in TinkerCAD from a box with radius set to 1 mm.

However I would need to get a 3 mm rounding on the vertical axis, therefore I have added a quarter circular eraser.

Please see both of these in this shot:

Now it's time to round the red one:

Looks good from top-angle:

But it's not rounded properly from other angles:

I wish to maintain the 1 mm rounding on the whole edge, how can I do that?

I tried many things:

1.) Inverse ring eraser: almost good, but I would need 2 mm width, and 3 mm outer radius which is impossible (for a ring).

2.) Inverse half sphere: not good, as it's not the shape I need

Finally

I succeeded with a "hack": ring with 4 mm width and 6 mm radius, then scaled back to 50 %, making it 3 radius and 2 mm width. Then create variuos inverse-quarters from it (eraser) and tune them even further removing unnecessary halves:

Using these erasers I could finally reach my goal:

However this is super-tedious, is there a better software out (I'm sure it is), which can do this "rounding" effect on any object? Now I'm satisfied, but if I need to

• increase the height
• change the size

I'm screwed up: will have to "slice" this object to 3 pieces, increase the size of the middle, and then put them back together. Do this for every single axis. (= scale operation I'll need to slice this object to 9 pieces).

Answer 1

TinkerCAD is a fine tool for simple designs, but when you need to fillet or chamfer corners, this involves too many actions where you cut out the parts to get the requested fillet/chamfer. It might be interesting to save time to move to a different design tool.

This geometry is recreated in a few minutes in e.g. Fusion360, considering this is a simple design, you need to change the order of the actions to fillet the object properly. Fillet the corners of the box prior to filetting the box itself:

In case the design is way more complex an alternative solution would be to join a cube in the corner and round that: