Maybe I should change the whole program. I need to cut out a circular area of two nested cones:
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Maybe I should get a regular square end mill and mill out two circular pockets (wider on top and narrower on the bottom). Then change tool to ball endmill and finish the sides and bottom.
That's how it's generally done. If you can find some info on CNC moldmaking, you'll learn a lot about this kind of job. I haven't checked recently but some of the CAD and CAM companies have, in the past, had illustrated online descriptions of their pocketing, profiling, and contouring routines.
If my old articles on the subject were still online, I could point you to a couple of them. I covered the subject for _Machining_ and _Machine Shop Guide_.
That's why I don't want to do CNC at home. It's too close to what I did for work.
That follows the same concept of using a roughing mill and then a finish mill.
If you ramp your regular end mill down in small Z steps, say 0.100" and are at your top 3,000 RPM, you can move at a much higher feed rate, say
30 IPM as a starting point.
Your spindle RPM and the number of flutes on the end mill determines the feed rate that will give you a reasonable chip load. Your available HP determines how deep a cut you can take at that chip load.
With your 2-3 HP available, I expect you can take deeper than 0.100" cuts with ease, but you probably want to limit it to 0.100" cuts to leave a smaller stairstep for your finish pass. This doesn't mean you can't optimize things with a roughing and finish pass with the regular end mill, using a much deeper cut for the initial bulk removal passes, and a 0.100" step for the final pass with the regular end mill.
My interest in machining as a hobby is mostly about the historical methods for achieving amazing things. If I wanted to sink a lot more money into a hobby, I might get into CNC. But I have a lot of fun making things to
0.0002" accuracy on antiques, using antique methods.
I'm less interested in having finished products than I am in the processes of making things. I get off on clever faceplate work. d8-)
Yes, that is an excellent plan. There are also bull-nose end mills that have a radius at the tip, but a flat center. But, you never want to do roughing with a ball-end mill, due to the center not having any rotation. It is forced to "churn" the metal instead of cutting it. This is likely your problem, that churning causes both the work and tool to run extremely hot. The curved side of the ball-end mill can cut, but any contact with the center should be avoided.
Yes. The machine is currently functional. Maybe not functioning at the top of its possible capacity and convenience (still have to do all those buttons, rigid tapping, look at the servo driven table for 4th axis, tune it better, etc etc). Despite that, I can already use it. As you can easily tell, I barely know anything about CNC, so there is much to learn.
See if you can find a copy of "Machining Fundamentals" ISBN
1-56637-662-9, it will give you a good foundation of the various machining processes. It covers some CNC, but the key thing to remember is that the CNC is doing basically the same thing as the manual, so the same machining principles apply.
I've never used ball end end mills so I'm speculating here.
Can you rough out the cavity with a conventional square end end mill?
Since you piqued my interest about ball nose, I'm looking around a bit. Go read page
28-30+
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Also read:
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Do you know the difference between climb milling vs conventional? I prefer climb whenever the machine can handle it. I usually climb mill on bridgeports with leadscrews and on a cnc it is the normal way since you don't have backlash to any degree compared to lead screws.
You shouldn't have any trouble with it at all in aluminum. But pay close attention to how your machine behaves when climb-cutting in steel. In a small, conventional machine like yours, everything has to be tight or it will chatter or generate some other vibration.
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