Managing multiple milling constraints

Milling is a complex process bound by multiple constraints such as bending moments, chatter, tool/workpiece wear mechanisms, available power, tool geometry, and workpiece geometry. The bending moment equals the cutting force times the distance from the cutting zone to the toolholder/spindle interface. If the bending moment is too great, the shank of a slender tool may break or separation can occur where the toolholder face contacts the spindle, allowing the toolholder to pull out of the spindle. The bending moment can be reduced by shortening the tool or by reducing the cutting force, which requires reducing the axial DOC, radial WOC or the chip load. Chatter arises due to insufficient dynamic stiffness, which, in turn, is caused by long slender tools, small-diameter spindles, thin workpieces, and the low-damping characteristics common in mechanical systems. Strategies that change the machine and tooling configuration include adjusting the tool length and applying tools with nonproportionally spaced teeth. Knowledge of the constraints is the first step in managing them.