# How to create recesses in a curved surface?

I want to make a simple cylinder box that has a very simple twist lock. I have seen a lot of maze puzzle boxes on the net but I just want something simple.

Ideally The lid will have 3 'L' shaped recesses in it that a lip with 3 pins in the base will key into. The lid presses down with the pins in the recess and then a twist to close.

The base would look something like this:

 I found the torus mesh. It seems like I need to play with some maths but this is kind of what I'm after, but without the continuous loop really (oh, and imagine a closed top).

Can anyone provide any good examples or links on how to do this easily.

• Would be good if you could add some images of the object you are trying to make. – Ray Mairlot Nov 29 '14 at 16:59
• @Ray, I haven't made it yet :) The image above is what I have for the base at the moment. I'm looking at a lid, or a better way to do the whole lot. – Nigel Johnson Nov 29 '14 at 17:34
• I have found the torus mesh which can give a nice channel. You could cut some some bits out and then add half spheres on to make it rounder. I struggled to get sizes and tolerances in as well. Hopefully there is an easier way? – Nigel Johnson Nov 29 '14 at 17:35
• @ray, added another screenshot of the lid bit I'm trying to make a little better, hopefully it makes more sense now. – Nigel Johnson Nov 29 '14 at 17:48
• look into using boolean modifiers, in other words: use other objects to cut or add the shapes you need into your mesh. – user1853 Nov 29 '14 at 18:13

Anything that has to be cut into a curved surface, I tend to build flat and curve into shape later. Using this method I have a model of one 'L' section and a bezier circle (origins of both objects matching each other):

Using an Array modifier with a count of '3', followed by a Subsurf set to '2' subdivisions and finally a Curve modifier:

I get this result:

Using modifiers allows you to easily manipulate the original non-curved section, while also seeing how it will look when curved into a circle.

Once you are happy, modifiers can be applied and the two ends of the circle can be merged (either by W> Remove Doubles, if the vertices are close enough, or more manual merging if they are not).

Also note that increasing the resolution of the curve on the curve's 'Data' tab will improve results. This example had a curve resolution of 30.

• Nice one. Easy and flexible. If the vertices are not close enough, retopology is also an option. – p2or Nov 29 '14 at 18:47
• @ray, is there some way I can message you some screenshots or a link to my blend file directly as I can't get the subsurf to work properly, as it destroys the ridge inside. To be fair I did use a mesh instead of a plane as I think you have (I'm relatively new to blender so I don't get how make this into a solid object) – Nigel Johnson Nov 30 '14 at 0:54
• Actually, I made it in the end. I went with the plane, then had to fiddle a lot to get the normals in the right direction and then add a topp and bottom, then used the booleans. I did that for both parts of the lock and it's finally busy printing :) – Nigel Johnson Nov 30 '14 at 12:23