Cura imports FreeCAD stl wrong I am trying to import an STL file, I created in FreeCAD. It has a hole in the hull of the object and behind that hole there are two pins inside the object (see attached FreeCAD screenshot).

When I import the STL in Cura, there are no walls around the whole object where there is the hole in the hull (see attached Cura screenshots). However the wall and the hole are visible in light grey, Cura just doesn't print it.

Update:

 I understand the problem. It's not a watertight solid. I found a way to import it somewhat fine using meshmixer to create a hollow with an offset which makes the outer Hull actually have a thickness to it. Now the problem is, that's not really what I want. The result in cura now can't be printed with infill since the actual inside of the model is only within the walls. Also cura sees both sides of the wall as outer Perimeter. I understand the problem but actually am looking for a way to just prevent printing part of the regular model's wall.. In other words: I would basically like to set the whall line count to zero in that particular area. I just tried to use the support blocker and "Modify settings for overlap" but that doesn't do anything.

CURA:


 

FreeCAD:
I suspect that your method to create the hole for the pins may not be consistent with the modeling practice that FreeCad and other programs of this nature require.

Consider the following:

Import your base shape.
Create a second shape that matches the hole you wish to create. It must be a solid object, not a plane or other single surface item.

Consult one of the many FreeCad tutorials that present the method to use next, that is to place the shape to be subtracted in the desired location, then perform a Boolean operation involving both objects. In the linked tutorial, it's referred to as a cut, which is an accurate description.

Performing this action will create a surface where the two objects intersect, removing the smaller one, leaving a solid, rather than a zero thickness surface. 

You would then create and place the cylinders in a manner consistent with the original model.