How to tidy messy corners generated by solidify modifier? I use a mesh with cross section like 1 as input to solidify modifier, and I expect to have a result like 2. However, it gave me messy results in corner parts like 3. How can I tidy the messy corner in some simple way? Currently I made a self-crossover cut and manually remove the messy faces, which is pretty much work.

And this is the snapshot of actual result. I hide the outer shell and most flat parts of the inner shell, only showing the corner part to ease the editing procedure.
There is not any magic way to avoid the overlapping, even with a new complex Solidify Modifier (if I'm not mistaken).

When Solidify modifier was set to Complex mode with Thickness mode Fixed, you can try ...
Weld Modifier
It worked with small distances, but already here it started to change outer topology.

With higher value of Thickness ...

... you would have to apply Solidify modifier, select inner vertex and press L to select Linked and assign those to Vertex Group under Data Properties.

Than use this vertex group as a limit for modifier.

Remesh Modifier
But ... this Weld works only because of the big flat faces inside. Probably useless in your situation. You will probably more lucky with Remesh modifier &gt; Voxel type.