[mfg-smartcam] OT -- need help with machining strategies

[Chris . Kocourek]

Hi all, I have little experience in 3D machining, so I would like to tap into the knowledge base here. Though I am using Mastercam (gasp!) for this 3D work, I still use Smartcam for most of our 2-1/2 axis work.   I am machining soft A2 tool steel for a draw die which will produce a shape similar to the flip-up part of a cell phone, so it has relatively shallow surfaces across most of its shape blending into steep surfaces at the edges. The piece will be hardened after milling.   I roughed it out with an inserted end mill using planar cuts, semi-finished it with a coated 1/2 ball end mill using a parallel zig-zag tool path, and I am finishing it with an SGS Zcarb Tialn coated 5mm ball em, also running a parallel zig-zag tool path, at a 45 deg toolpath angle.   The roughing and semi-finishing ops left about .020" stock. I am running the SGS ball end mill at 6000 rpm and 20.0" feed for the finishing passes, with the maximum step over set at .005" (slightly less than .0002" maximum scallop height).   The finish is not bad, but I'm always on the look out for possible improvements, both in cycle time and in finish.   -- Am I on the right track, or can any of you make some suggestions which may provide superior results? -- How about using an inserted bull mill to make the finish passes (can run much higher feed rate; about 75 to 100 IPM because of the shallow finishing cuts -- only .020")? -- Do you have any suggestions as to which strategies are best for "fine-finish" finishing? How much stock should be left in the roughing passes? Which size and type end mills work best?   Thanks for your time with this. As always, any help is greatly appreciated.   Regards,   Chris Kocourek Tool Designer FLEXTRONICS CTC