This model prints in two halves to allow cables that have been spliced to be inserted and protected by the shell. Then the two halves can be screwed together with 4 M3x8 metric screws and hex nuts.

The photo is of my prototype that is not exactly the same as the enclosed STLs and SCAD file. I don't have my 8mm screws yet, so the photos shows much longer screws than desired.

Note I have not printed the enclosed STLs, but they should be a corrected version of the prototype. One cable diameter is 6mm and the other is 8mm.

The OpenSCAD file is also enclosed and has parametric values to allow adjustment of the size of the cable splice shell thickness, internal void for the splice, the two cable end diameters, and length of the cable channels. I haven't played with changing the parameters much, so be sure to check the rendered models carefully before printing. The screw hole locations could interfere with the cable entrances if they are large or be too close to the edge if the overall ellipsoid is too small.

CAUTION: This model is intended for low-voltage cables only. Use with power cables should never be with this kind of model.