two months of x4 experiences - design flaws, safety issues, and performance problems

[neilw20]

It is ALL about stiffness.
If your direction of cut is such that the main cutting force is towards or away from the tower you can take a heavier cut (read that as steel instead of aluminum). With say a 3/8" cutter you want maybe 0.001" or 0.002" cut per tooth. If the cut is putting torsional force into the tower this will not be as stiff and hence performance will be worse moving in X.

With these light weight machines you must keep the side loads on the cutter low enough that the machine deflects a fair bit less than the chip load, otherwise the cutter gets pushed away or digs in depending on the various forces.

The best way to get performance (meaning amount of material removed in a given time) is to run as fast a spindle speed as possible, with the feed low enough that the deflection forces don't screw it all up.
Now when then surface speed is so high flood coolant is the only option so you don't cook the cutter.

In summary High speed, low feeds, lots of coolant, Short cutters. Keep the head low (the tower is stiffer near it's attachment).
You can always get better performance from a carbide cutter / insert over High Speed Steel. Due to the cost of cutter, now you need to make sure the G-Code is well behaved so they survive.

Now the problem is keeping the coolant from flooding the rest of the world.
Lose coolant for 1 second and something will fail.
Full enclosed and fully drowned will work best.

The reasons there is good results with plastics is that the machine deflections are low enough not to upset the cutting process.