i spent much of the past few days modeling a conical burr grinder. the project requires a number of complex sweep features, which are difficult both to measure and to model, and with which i have limited experience. the process was interesting.
the burr is ceramic (more about this in the future) and has two sets of tapered helical features. the large helices seem to funnel coffee beans down into the assembly and begin to break them down, and the smaller features do most of the work of producing the intermediate and fine grind steps.
the large features seemed - at first - relatively straightforward to design. the profile is easily measurable from the top of the part, and establishing a path (albeit one i would later realize was inaccurate) wasn't too bad. here, i'm applying fillets to all the sharp edges left behind after the sweeps were cut into the base body.
in parts like this, one tends to model a single feature and then apply a pattern on the part using the initial feature as an input. here i'm patterning the small corrugations on the perimeter of the part. i'll do this process a number of times; once you apply the pattern, you'll notice things about the feature that weren't apparent when there was only one occurrence visible. i'll roll back the pattern and modify the underlying feature, and then reapply the pattern again and check out the result.
the real result is that i shouldn't be doing this whole process on a 2008 iMac >> Boot Camp >> Windows 7 >> Inventor: a dedicated windows box would be *way* more efficient. here's to hoping that AutoDesk gets real about some WebGL modeling software?
the only way i know to model these features is by using Sweeps, which require a profile and a path as input. i would prefer to be creating a 3d helical sketch and using that as the path, but i can't for the life of me figure out how to use Inventor's helix creation toolbox on complex shapes like this. instead i've been creating planes that approximate a portion of a helical shape, and then drawing arcs on those planes. it's a pretty hokey setup, but for my purposes it's more or less adequate.
the red lines here are the remnants of one of these sketches, with the part's cut edges projected onto it. on the left, you can see the arc that i'm using to define the small corrugations' path.
honestly, most of this here is overkill. i'll probably end up getting one of these burrs 3D printed, but it's mostly academic at that point: the hard part of my project isn't the burr design, but the software that supports its function.
either way, it was a fun part to model - and a bit above my head, i'll admit. it's still far from perfect - the modeled version isn't nearly as bell-shaped as the original - but i'll let it go for now. after all, i've got the other half of the burr to model now, and it's possible i'll learn something there that'll be applicable to remodeling this half.