Autodesk Inventor: Fillet Frenzy

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I have often heard (and said) that "filleting* is an art-form"...because it is.

(* I will use 'fillet' to refer to both fillets and rounds as it is a single command).

There are many nuances to filleting a 3D model, depending on what you end goal is and what types of parts you design. Regardless of those things, a few things hold true for adding fillets to your model: fillet order is important, and add fillets as late as you can in the design process. Simple rules...so, we're done here, right?

Nope.

I think we can agree, it isn't that easy. Filleting can be completely different depending if you are modeling plastic parts, castings, forgings, simple extrusions, etc. One thing you really have to understand is how using different techniques affects your final topology.

Way back when I started in this crazy 3D CAD industry (which, as of tomorrow, will have officially spent 1/3 of my life in) a customer asked me to model what he called his 'fillet killer'. I think he was testing me more than the software...but, I have used this example ever since. It is a pretty simple model that can really help you improve your filleting techniques. Simply model two 1" cube extrusions (placing the corner of the second extrusion at the center of a face on the initial extrusion...or just look at the image).

Then fillet all the edges with 1/4" fillets.

Oh yeah, there are a lot of ways this can turn out. Some better than others...again, depending on what you are looking for. Let's dive into a few of these a bit deeper.

This first example I did as quick as possible. Just grabbed the Fillet command and went at it...just wanted to see how it turned out. I picked some logical edges based on wanting to have the cubes rounded to help with fillet propagation. You will notice, it took me an extra feature at the end (four total Fillet features on this one) to get all the hard edges off the model.

...and that is just my first go at this. I tried out the Rule Fillet tool.

Some G2 and Variable Radius fillets (this one is a hot looking dual cube for sure)

I also played with some Full Round and Face Fillets too. But, after trying out all these options, I wanted to get serious. I wanted to take a look at making a super smooth blend where the two cubes intersect. It needed to be as smooth as possible...kind of like Shaft (the original...not the remake).

For this to come out right, it was all about fillet order. I tried a variety of options...and used more individual Fillet features than in my prior examples. But, in the end I ended up with a really nice transition (I am biased...but, I'm right)...which was my goal on this.

So, there you have it. If you want to test your filleting skills, whip up this model and take a crack at it. Worst case, you will be a better designer at the end of the day...and maybe learn a few new Fillet options along the way.

You know what, I think this model needs a better name. It isn't the 'Fillet Killer' anymore...it is the 'Fillet Treadmill'. You get a good fillet workout whether you are walking or running.

-lw