MRRmilling

MRRmilling is the practice of maximizing the material removal rate during milling operations. It is used as a productivity metric to evaluate and optimize milling strategies by estimating how quickly a milling operation can remove material from a workpiece, subject to tool life, workpiece quality, and machine constraints. The material removal rate (MRR) for milling is commonly expressed as MRR = v_f × a_p × w, where v_f is the feed rate in millimeters per minute, a_p is the axial depth of cut, and w is the width of cut. For milling with multiple flutes, the feed rate can be written as v_f = f_z × N × z, where f_z is the feed per tooth (mm/tooth), N is spindle speed (rpm), and z is the number of teeth. Therefore, MRR = f_z × N × z × a_p × w.

MRRmilling is influenced by tool geometry (diameter, number of flutes, helix angle), cutting speed, feed per tooth, depth of cut, and width of cut, as well as workpiece material properties and cooling/lubrication. Higher spindle speeds and larger depth/width of cut generally increase MRR but also raise cutting forces, heat generation, and risk of tool wear, chatter, and surface defects. In practice, operators balance MRR against tool life and required tolerances, selecting strategies such as aggressive roughing passes, slotting, or pocketing while maintaining acceptable surface finish.

Limitations: MRR is an idealized metric that does not alone guarantee productivity; real optimization also considers tool wear, energy consumption, rigidity, machine power, and part quality. Methodologies include process simulations, empirical testing, and adaptive control to approach optimal MRR for a given setup.