Newbie here. I am messing around with OpenSCAD and a Flashforge Creater Pro and have run into an interesting problem:

I am printing a tube with reinforcing fins inside to increase stiffness. When the fins are at o and 90 degrees, all is well, but when a fin is oriented at 45 degrees, the resulting structure is hollow(!). I have confirmed that the 45 degree orientation is the problem by successively commenting out the fins. The 0 and 90 degree ones print well and are solid. The 45 degree one results in both the fins and the surrounding tube being hollow.

In all cases, the slicing was performed in the same fashion.

Any thoughts?


module tube (od, thickness, length){
// od = outer diameter
// thickness = wall thickness
// length = length
difference(){
cylinder(h=length, d=od);
translate([0,0,length-.5]);
cylinder(h=length+1, d=od-2*thickness);
}
}
//--------------------------------------------------------------------------------------------------------------
module tube_with_reinforcement (od, thickness, length, web_thickness){
// od = outer diameter
// thickness = wall thickness
// length = length
// web_thickness= reinforcement web thickness
union(){
tube(od, thickness,length);
translate ([-od/2,-web_thickness/2,0]) cube([od, web_thickness, length]);
rotate([0,0,90]) translate ([-od/2,-web_thickness/2,0]) cube([od, web_thickness, length]);
rotate([0,0,45]) translate ([-od/2,-web_thickness/2,0]) cube([od, web_thickness, length]); <== THIS ONE CAUSES A PROBLEM!
}
}