[Konstantin]

Hello everyone.
I have been playing with the Rhino3D and made this octagonal part and I would like to generate the tool paths for it. Which are my options as for going from the model to the tool path free/mid range/high cost?

From reading this sub forum I have the idea that VisualMill does 4th axis but with 2 position only and I think my part would need to be rotated quite a lot.

Thanks for your help.
Konstantin.

[chmillman]

VisualMill 5 and RhinoCAM both handle continuous 4 axis, so you can do your part, but probably not optimally, as the 4th axis options are somewhat limited. You can also 3 axis continuous machine and 4th axis index as much as you want (3+1) - you are not just limited to turning the part over. --ch

[HuFlungDung]

Depending on the job, it is sometimes more efficient to just write the program by hand.
Compare a helix written by a CAM program, compared to helix written as a cycle that the cnc controller understands. Both methods will work, but one is shorthand, one is longhand

That part appears to have a typical helical twist to it, and is uniform along its length, with simple rotational moves at each end.

Each groove could be programmed as a 'helical rectangle' with as few as four lines, and use 8 repeats. But, you have to understand what the geometry of the part really is.

The longhand method would be using a 4th axis wrap, I don't know if VM offers that. 4th axis wrap is kind of a different animal though, as it starts from a flattened map of the surface. The rotational aspects of the program are then accomplished through a simple conversion of Y to A with a scaling factor applied. 4th axis wrap would likely be the best solution if there is any amount of complexity to the toolpath, such as lots of roughing passes with a small tool, extra work squaring out the 'unfriendly square corners', etc

[chmillman]

I would agree with much of what you say. Visual Mill does not have a "wrap" function (yet). That might indeed be the best way to program this part.

If there was any significant surface area involved, the pocket might need to be surface milled (ball mill and stepover), and programming that by hand would be laborious, if you are good at macro programming, it shouldn't be too hard, though.

The outer surface coud possibly be programmed with swarf milling, fairly easy, a linear move with simultaneous A rotation.

However it will be very easy to design something in Rhino that is very hard to program manually, it's all in the details.

Compare a helix written by a CAM program, compared to helix written as a cycle that the cnc controller understands. Both methods will work, but one is shorthand, one is longhand

I don't necessarily agree here, a good CAM program will output a helix the same way as you would program it at the machine - a G2/G3 move with a Z depth. --ch

[Konstantin]

Thanks you guys for the explanations.
I have cut a helix octagon already with the gcode I wrote, and it was indeed very basic linear interpolation. I haven yet learned how to program tool compensation or multiple passes with different tools.
About the unfriendly square corners, well I just modeled it in Rhino for simplicity, I would settle with the tool radii and do the corners manually later.

I don't necessarily agree here, a good CAM program will output a helix the same way as you would program it at the machine - a G2/G3 move with a Z depth.

Which would that be?


Thank you.
Konstantin.

[chmillman]

Which would that be?

Well, I have worked with Surfcam, that will do it. Mastercam probably as well. I have not been able to determine whether Visual Mill will, the post processor has settings for it, but I haven't been able to get it to output so far... --ch