I’ve been playing around with this design for a while. It’s been modelled in Fusion 360 and loosely based on a Triskele but uses a golden mean spiral generated from Fibonacci’s sequence. Then machined on the Taig and then a slice taken off with the metal lathe.
I came across this youtube video on Golden spiral - Fusion360 Importing equations. I learned how to generate a series of 3D points using Excel and then save these as a CSV file. You can then import these points into Fusion360 with a neat Addin script called importSplineCSV.
Once the spline curve is in a sketch you can do all sorts of neat stuff. I did a simple loft and circular pattern to get the base Triskele-like pattern that I was after. I added a circle to allow this part to be held in a lathe chuck. The outer square was for work holding in the CNC machine.
Here is a screen capture of my Fusion 360 Model.
After the dealing with the usual CAM paths (Face, Adaptive Clear, Contour) it was off to the Taig for machining. I discovered that my outside corners were just a wee bit to tight as I managed to jam my bit and it snapped. Whoops. The original stock was 4"x5"x.5" aluminum flat bar.
My original idea was to make a spinning Top but I decided just to make this ornamental and see if I could just cut off a thin slice. This part is only 0.5" thick so I wasn’t sure if I would be able to chuck it on the lathe. I used the dial indicator to get the face as perpendicular as I could.
So after checking the cutting tool will clear all the head stock it was time to make some chips! The cool thing about this is that you can actually see the parting tool at work through the front.
This is one slice removed from the base. You lose about 1/8" of material from the parting tool. The finish from the parting tool is really rough compared to the top finish from the CNC facing operation. It could use some sanding with high grit wet sandpaper.
So this slice is approx. 1/16" thick. It is the thinnest and largest diameter piece that I’ve made to date at VHS.
Shadows look pretty neat.