It depends on what cam software you have. I have meshcam for doing 3D work and this has a basic 4th axis setting so all you would do is make a 3D model in say Alibre Express and then export an STL file. You would then cut down to say half the depth of the blank and do it in four 90 degree sections, meshcam doesn't keep the 4th axis revolving it just steps it round the treats the job as a new surface profile to do stepover milling with a ball cutter, most likely long and tedious.
You may be able to get a program that can use a flat ended cutter and just revolve the 4th axis round while the Z goes up and down but I suspect this will be quite complicated to work out as the ramps on the cam lobe will not be cut by the centre of the cutter, it'll move to the side of the axis of rotation as the cam profile rotates, just the same as using a flat follower. You cutter would also need to be quite a bit bigger diameter than the cam profile, also the full cutter diameter will only be effective on the centre of the cut so you would end up with a scalloped cut on the ramps.
A better method is to hold the blank vertical in a chuck bolted to the table and use a special cutter that like a T slot cutter (effectively using a horizontal mill), you use a 21\2D CAM program then like lazycam to create the code from a normal cad drawing. Advantage with this method is you don't need the 4th axis
The real problem is creating the cam profile in the first place, you can use a spread sheet to drive the cad programs generation of the profile but I've never done this so I have to basicly draw points and use a spline to join them and create a smooth profile.
I'm in the process of making an Edwards radial 5 and the latter method is what I'm doing, I've got the profile and the blank done, I used sheetcam to create the gcode but I've not yet cut the cam, I may get it done this weekend, I'll take some pics if I do then you can see how I did it.
Steve
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