Customizable offset pipe reducer

thingiverse

I was going to design a quirky pipe reducer recently for a new cooker hood ductwork installation. Unfortunately, OpenSCAD's cylinder command doesn't allow the axis to be skewed so I couldn't model it. Luckily, we were able to fit the ducting without it. This model lets users specify two pipe inner diameters and wall thicknesses. The upper pipe can be offset by a percentage of its radius (0% is concentric, 100% is fully eccentric) and the center can be rotated if needed (though both axes run vertically). Finally, the gap between the two pipes can be specified and whether the inner wall or outer wall should take precedence for modeling. With 100% offset and a narrower upper wall, the pipe will pass through if the inner wall takes precedence. If the opposite is true, there would be a step in the outer wall. You'll see it's easier to understand than describe - have a play! Print Settings Notes: I haven't tried printing this model, just ran it as a modeling exercise. I checked sliced several STL outputs with Repetier to ensure the solids were manifold. How I Designed This I've revisited the project now as a modeling exercise. The transition piece has been modeled as a set of polyhedral blocks in order to guarantee that varying wall thicknesses (specified by upper and lower parameters and implied by the rotational geometry) all calculate correctly. Trying to reduce the number of faces to just inner and outer surfaces causes non-manifold problems so I've left the full polyhedron definition intact.