Thank you for returning to my Kinetic art project series. Today’s blog is focused on modeling the fins. If you missed my previous post, you can read that here: Kinetic Art Project: Worm Gear.
I wanted to push the print volume boundaries of our Stratasys Fortus 250mc, which is 10”x10”x12.”
Figure 1 – The Loft
The general shape is pretty simple. It is a cylindrical extrusion and a loft. The cylinder will be how we attach to the hub. The loft was a 90° angle and 12” in the X and Y directions (see Figure 1). I needed to trim the wide end such that it will be inscribed within a 36” circle. The trick here is to create some construction geometry to locate where the center of the hub would be (see Figure 2).
Figure 2 – The Cut
Lastly, I mirrored the fin to create an opposite hand version. To make it easier to switch between the different versions, I created a different configuration for each hand to make it easier to use in the assembly.
When initially planning this portion of the project, I identified an opportunity to make a mold and cast the fins. Casting will be beneficial because of the large number of identical parts. With this in mind, I did a Draft Analysis of the part and realized I need to modify the profiles of the loft to remove the undercut (see Figure 3).
Figure 3 – Draft Analysis before and after
Later, I added the fins to the assembly which you can see in Figure 4, and this became a problem: I realized the two layers would be crashing into each other. I went in and again modified the profile for the loft to keep the overall thickness of the part uniform, thereby reducing materials, and keeping them from colliding.
Figure 4 – Side view of the assembly showing before and after
The last hurdle with modeling the fins is getting this to correctly 3D print. I was using a Stratasys Fortus 250mc with a build envelope of 10”x10”x12”, yet the bounding box for the fin is 15.2”x5.5”x1” so, in order to print, I had to orient the fin to go from corner to corner. I was able to print both orientations of the fin in one print.
Stay tuned; the next article will go over the fiasco of making the mold of the fin.
Figure 5 – Preparing for print
About Brandon Harris
Brandon is a BYU-Idaho graduate with a Bachelor’s Degree in Mechanical Engineering. He is an avid tinkerer, and consummate rapid prototype hobbyist with prior experience designing for the Architectural/Construction industry. Brandon is part of the technical support team for GoEngineer serving as a PDM specialist since August 2018.
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