Quote Originally Posted by Kitwn View Post
I was pondering along these lines as well, a good excuse to swot up on exactly how G2 and G3 instructions work and whether Excel will export files delimited with cariage returns. The arc centres are all the same and the end points progress outward in symetrical straight lines so it should not be too dificult. If the angles match then using a V-bit will help smooth the edges but that would only be possible for very short cones with most V-bits.

Kit
Did a bit more thinking about this and to get a smooth toolpath the arc centres aren't the same, you need to offset them ever so slightly to get the arc ends to join up and get the best approximation - as Neale pointed out, on a true spiral the radius is continually increasing, hence if you divide the circumference into a small-ish number of sections with the same centre there would be a slight bump in-between sections. In the end for prototyping I took the crude but simple approach, slicing the model to create a number of 2D toolpaths which I outputted together. Wasn't as much work as I thought thanks to the speediness of Generic CADD (actually took less time than I'd spent playing around with the maths of an elegant solution!), and has ended up greatly reducing the machining time as I've been able to include the flutes which I was going to cut into the cone as a separate operation. The 303 stainless cuts nicely on my little machine using blue-nano coated cutters, only running at 800mm/min at the mo but from the noise it feels like it could go a fair bit faster - but I'll leave pushing the limits until the development work is done!