Machine An Interrupted Semi-Circular Groove Using 4th Axis

[redmond.limited]

I am trying to set up the toolpath to machine this semi-circular, helical groove using the 4th axis capability in Fusion360 (I haven't got any machine extensions).

I have tried 2D pocket but cannot get that to work.  I have tried 2D contour on the "complete" bit of the groove, with "Wrap Toolpath".  The 2D contour will machine that bit of groove but in the wrong place.  I can't get it to work, at all, on the bits of the groove that has the hole in the middle.  I also tried drawing a 3D sketch of a spiral that sat in the middle of the groove at the bottom and tried selecting that in 2D contour, thinking that, maybe, the ball nose cutter could just machine all the way around the full 360 degrees, machining air where there wasn't any metal to machine, if you see what I mean.  It just went a bit mad and generated some kind of toolpath that didn't go anywhere near the grooves.  I have attached the Fusion file.  It's just a test piece, so that I can start learning a bit of 4 axis stuff.

I would be very grateful for any advice anyone can offer.

Thanks,

Clem.

[seth.madore · Accepted solution]

So, this is going to require two separate 2D Contour toolpaths, as some of the geometry presents limitations as far as some of the settings. I'm sure there was a mathematical formula to use to figure out how to get the ball endmill positioned correctly, but I just did some trial and error guessing and got it pretty spot on in a few tries. Take a look at this file, especially the Stock to Leave

 

[redmond.limited]

Thank you very much for your reply and all your help.  That has really helped.  The stock-to-leave values seem to get the toolpath very, very close.  If anybody knows what the maths behind those stock-to-leave values is, I would be very, very interested.  I like maths a lot but I am stumped by how those values could be worked out mathematically.

Thank you, again, for your help,

Clem.