machining Engineering

Milling chatter is a regenerative self-excited vibration: each tooth cuts into the wavy surface left by its predecessor, so the instantaneous chip thickness depends on the phase shift between successive tooth paths. When spindle speed places that phase shift in an unstable range, the cutting process pumps more energy into the machine structure than damping dissipates, and vibration grows spontaneously. A stability lobe diagram gives the critical depth of cut at each speed; choosing a speed inside a higher-order lobe or reducing axial depth restores stable cutting.

At low cutting speeds the pressure and friction between chip and rake face are extreme; the chip's underlayer work-hardens severely under this heat and pressure and bonds to the rake face, growing layer by layer into a built-up edge. It tears off intermittently and scratches the machined surface, worsening roughness and dimensional accuracy, although it partly protects the cutting edge and enlarges the effective rake angle. Raising the cutting speed beyond the bonding regime, applying lubricating cutting fluid, or using coated tools effectively suppresses it.

CNC machines are mainly driven by G-code, which sets toolpath, spindle speed and feed, usually generated by CAM software from a part model.