Need help designing an interlock between two 3D printed components

[fred_dot_u]

If you require that there be no bracing on the back of the angled support, it's critical that you have sufficient mass at the bottom where you plan the interlock. Additionally, consider the direction of the layer lines to ensure maximum strength in the design. As an example, consider the lowly cylinder, or in this case, an upright cylinder. Layer lines means the cylinder get printed as if it was a stack of coins. It's going to be just about as weak as a stack of coins, too, since it's easy to snap it into two pieces. If your display support is printed in the same orientation as the photograph/image, it will snap easily if not printed thick enough to handle the stress.

It's the kind of structure that would print better on edge, that is, rotate it 90° on the Y-axis. This would put the left edge on the print bed and the right edge at the very top, but the layer lines would be in the best position for handling the load.

And now to the joint.

I would create a slide-in type of joint for maximum strength and ease of printing and assembly. If you picture the base in the orientation I suggested, the layer lines would be set down in a straight line at the front of the part, left to right, with the back side of the part containing the joint.

From the top view, here's a coarse, simplistic drawing of how the bracket/base support could look. Obviously rounded corners, faired in edges, plenty of room for improvement.