Jan.vanderlinden wrote:Interesting thoughts and comments here, and I appreciate all of them.
I tried using this process in an effort to get cleaner detail and less wear on the tapered end mill.
I used to do the roughing pass and then go directly to the TBEM
In doing so, I was experiencing greater tool wear and the detail was not as clean due to cutter deflection of the TBEM and or fuzzies
But coming from a tool & die background, we always used and roughing pass, simi finish pass, and then a finial finish pass.
So I thought, why not try it.
When I go to the finial finish pass with the TBEM I may or may not drop the Z ~.005" ( depending on how the simi finish cut looks)
Yes, we are all looking for a faster way to do our machining, and this definitely takes more machine time.
The upside is a more detailed and cleaner (fuzzies) carving, and minimal hand sanding.
For me the extra machine time is worth it and It's now my new process.
In the above deer scene
My roughing pass is with a .25" EM, .06" depth of cut, .06" step over and 100 IPM, Z level
My simi finish pass is with a .25" BEM, .025" step over, 100 IPM, Raster at 45°
My finish pass is with a 4.8° .02" Dia. TBEM .005" step over 100 IPM Raster at 0°
You won't get less wear on your tapered bullnose by using this double finish tool path method. You are still getting wear on the very tip of the tapered ballnose, which is the area you want to remain the sharpest. The rest of the cutter, which you never use anyway, will remain sharp but that is useless anyway when you cut like this since you only ever use the very tip. Cutting wood is VERY different than cutting steel. Often we need to do the exact opposite of what makes sense in milling steel.
If you want to get the least wear on your cutters, you want to be removing enough of a chip size so that you actually cutting instead of simply 'burnishing' the edge. For maximum cutter longevity, you would go straight to a single finish tool path with a tapered ballnose cutter and skip the roughing pass and the first finish tool path.
Now, most people will tell you that skipping the roughing tool path is hard on your tools. But think about what you are actually doing. With a 1/16" tip on a tapered ballnose, at 8% stepover, you are only cutting 0.005" per pass. This does not put any stress on your ballnose, or your machine, even if you are cutting to a depth of 1". The first pass is the only pass that is putting stress on your cutter, so you may want to slow down the first pass, then speed back up for the rest.
What the roughing tool path does (and this is important for some projects) is remove the stresses from your wood before the finish toolpath. It also removes extra material that may get in the way of a short cutting edge on your finish tool path tool, which usually isn't a problem with the tapered ballnose bits because they usually have longer cutter lengths.