Thanks curious aardvark using your openscad script I printed pretty much a perfect funnel. Being very new to this, I had assumed that either I was screwing up the settings while slicing, or that my printer was too low quality to print a funnel. I guess not everything you find on thingiverse can be trusted.

My funnel is just very slightly too big in the spout though. In openscad, it clearly shows that the inside of the spout should be 16mm across. But the resulting funnel has a spout that's 17mm across. Is this level of precision not possible with a low quality printer, or am I doing something wrong? I notice in cura there is a setting called "wall thickness" which is set to 0.8mm, is that affecting it some how?funnel.jpg