Fusion 360 Tutorial - Jet Engine Bracket (remodelling a bad part)

Hi, and welcome to this Fusion 360 design tutorial. My name is David and today, I’m going to be designing and optimising a jet engine bracket for CNC machining in Fusion 360. I got the idea from a design challenge, held by grabcad and general electric in which they challenged engineers to optimise a bracket. Unfortunately, the competition is over but go and check it out to see some of the great designs the winners made.

For this video, I closely recreated the bracket that was provided for the challenge and added some design aspects that could make CNC machining more complex, that are very common and that we see quite often here at Protolabs Network. Specifically: the use of sharp corners and thin walls. First, I’ll show the bracket with the thin walls and sharp corners and explain why these are problematic for manufacturing of this and any other design. Next, I’ll remodel the whole bracket, paying extra attention to avoiding thin walls and sharp corners. Let’s get started.

Preventing sharp corners

So, here we have the bracket and you can see what we mean by sharp corners looking at this ….. The problem with sharp corners is that they are difficult to machine. This is due to the fact that the two most common CNC cutting tools — end mills and drills—are cylindrically shaped and have a limited cutting length. That means that the geometry of the tool determines the radii on the part. And so, the inside corners of the part will always have a radius.

Note that there are ways to make 90 degree corners in CNC machining by using undercuts and special tools as well as EDM. However, this requires more time and money in comparison to the standard end mills and drills.

Avoiding thin walls

Next on the bracket you can see here that these walls on the edges of the bracket are very thin. Decreasing the wall thickness reduces the stiffness of the material, which increases vibrations during machining and lowers the achievable accuracy. This might not be so problematic with metals but especially plastics are prone to warping and thermal softening, so a larger minimum wall thickness is necessary.

Now that we’ve discussed why sharp corners and thin walls should be avoided, let’s remodel the bracket.

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That’s it for this video. I hope you enjoyed it and were able to take something away from it. If you have any questions, drop them in the comments below and we’ll get back to you.

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