CAM for CNC code for cutting trispokedovetiles (3-spoke dovetailing tiles)

[Neale]

Hmm. Not quite what I hoped for.

Nope - not quite what I would have hoped for either!

I've just had a look at what might have happened here, starting with a freshly-downloaded copy of my design. I suspect that what you have shown is not the very first operation that you carried out, and that at some point you changed one of the parameters to something that F360 did not like. If you open a fresh copy of the file and just change Outer_circle_dia to 70, you should see the correct result. I tried changing Hex_spacing to something less than Outer_circle_dia (which the comment in the parameter table tells you not to do, but the comments field is typically off-screen and need the table to scroll sideways to read). This gave a silly shape, but because it modifies some aspects of the drawing, when you change it back the drawing does not go back to where it was. What you end up with is something similar to your picture. It seems to be to do with the way that the corner fillets are calculated. They are tied to the corresponding sides and arcs by tangent constraints which manage to flip through 180deg under some circumstances. It's a F360 feature, I think. The kind of artefact that comes from using a general-purpose tool for a very specific purpose when a special-purpose tool like yours can trap and defend against this kind of thing. There's an awful lot of power in F360; sometimes this is a good thing and sometimes it turns round and bites you in the bum. You get the same result if you try, for example, to set the Corner_rad to zero; this fouls up the related geometry in the drawing as an arc with zero radius upsets things. Make the value very small (I have tested it with Corner_rad = 0.001mm, for example) and all is fine. I guess that it's all to do with getting used to the way the package works.

I had been going to post directions to find the parameters table but I see that you found it first. Well done - it took me ages! You will see from your view of the basic sketch (in your previous post) that creates one spoke that every dimension is parameterised (is preceded by "Fx:", which indicates that the dimension was not typed in as a value but is calculated from something else) except angles which are invariant as they are part of the basic geometry. However, you could play with some of these angles (another parameter?) to create an underlying "skewed" hexagon, which might give interesting results...

I did read your post 5, which is where I found the diagram that was my starting point. However, as I said before, there was this optical illusion effect that meant that I just could not see the shapes that your dimensions referred to. Going back to the diagram having spent time studying the basic geometry meant that it made sense, as did your description. The problem was my eye/brain view of the diagram and starting from a different view of that, the words made no sense to me. Mea culpa.

Nice design, and I shall probably have a go at making it once my new router (designed in F360, of course!) is fully commissioned.