Export your design to an .stl file.
Load it into MeshMixer.
Go to Edit and make it solid.
Go to Meshmix and select the cone shape
and drag it to the right.
Got to edit and select align. Align it center point , World Origin / Y-up.
Go to Edit and select Transform.
Make sure the Uniform Scaling box is checked and increase the scaling a little… 1.2x will do.
Uncheck the Uniform Scaling box and change the Size Y to get the angle that you need.
Move the cone down until you see the bottom edge of your design and accept the changes to the cone.
Select your design by clicking on it in the object browser window. It should be the one that has (solid) in it’s name.
Hold down the control key and click on the Mesh object in the object browser window.
Select Boolean Intersection on the popup menu.
If the result is blue with red on the sides, export it to a new .stl file, otherwise, adjust the position of the cone and try it again.