Robertspark wrote:which I must admit I've never come across.
Really?
It's very helpful for those of us with low-power, low-rigidity milling machines using smaller cutters.
BTW, there are many trade names for this type of toolpath. Fusion360 calls it adaptive or adaptive clearing. Watching some youtube videos indicates Esprit CAM calls it "Profit Milling" (snort).
There are subtle differences between CAM software - some do a simple circle, some make a "D" shape. Some have an option to lift the tool during the non-engaged moves. F360 recently introduced "both-ways-adaptive" which cuts climb and conventional. Sort of a back and forth saw-tooth pattern while still keeping the tool engagement angle appropriate. You can even reduce the chip load on the conventional moves while still keeping the feed up during climb cutting.
It's really useful for clearing out corners without plowing in and having the tool suddenly taking a 270 degree bite. In addition, the constant (mostly) load on the end mill means you can take full depth cuts pretty safely. Instead of multiple depths with a large WOC at slow speed, trochoidal permits high speed at full (or increased) depth. I generally use 7% WOC stepover (hard steels/alloys) up to 30% (aluminum, plastics) with full flute length.
There are some times when trochoidal is not really appropriate. Using a wide cutter to slot/pocket ratio means a million tiny moves - not efficient. I've switched to full width slotting in some of those cases (say, profiling a part) as I can use a bullnose endmill like a poor-man's high feed mill. I slot with a DOC a bit less than the nose radius and a very high chipload/IPT. I ramp down 2-3 degrees (steel) to about 10% of the tool diameter and walk around the profile. Repeat the stepdowns until I'm through and do a cleanup contour. Very fast, chips clear extremely well, no bogging or loading the cutter up.
Probably not all that useful for wood cutting routers or other really soft materials where tool load isn't very high.
-Ralph
