Working on the skateboard parts again, and decided to switch up the toolpaths a bit to get a better surface finish.
The primary issue I was dealing with yesterday was tool vibrations (see the previous post), which left small marks all over the part. The cause of this consisted of two factors that played nicely together.
The first was the tool stick out; due to the height of the piece, I had to have the ball endmill stick out over an inch from the edge of the collet; this makes the endmill not as stable, and change in axis (x&y) could cause the tool to deflect (jumping side to side).
The second is how much material I was cutting with the ball endmill; I had the part roughed out with a 1/2" square endmill and ten thou (0.01") stepdowns leaving eight thou on all sides to be removed at the final finishing passes; because of the amount of material that needed removing coupled with the long stick out caused a lot of vibrating and small marks on the part.
I decided to come in first with a 1/4" ball to clean up the steps from the 1/2" endmill and leave two thou (0.002") to clean up with the smaller ball cutter. For the tool stick out @tuesdayandthursday suggested I try a tapered ball endmill; this would give it much more rigidity when reaching down the tall walls on the sides of the part. Thankfully I found a ball endmill roughly the same size as the one I was using previously (so I could make a fair comparison) and tried it out. I got a significantly better finish, and I didn't hear any tool vibrations throughout the whole operation.
The only thing I am not super pleased with is where the tool changed directions on the machine, and the endmill dwelt for a fraction of a second, just enough to leave a slight mark. I haven't looked into it too much, but I'm pretty sure there is a feature to allow the tool to glide around corners instead of doing a hard turn. I tried playing around with the tolerance and smoothing tolerance settings in the passes tab but couldn't see any significant changes (used 0.00021" tolerance for both).