Effect of ae/ap Ratio on Cutting Forces, Tool Life,and Surface Quality in Hard Steel Machining

In hard milling of tool steels, productivity and quality are rarely limited by spindle power alone. The practical limit is typically the coupled effect of cutting forces, temperature-driven wear, and vibration sensitivity that can trigger edge chipping and surface damage. Radial width of cut (ae) and axial depth of cut (ap) are two engagement variables that strongly influence these mechanisms, but they are usually tuned independently, even though their combined effect defines the shape and distribution of the chip cross section along the cutting edge. This paper studies the dimensionless ratio R = ae/ap as a compact compound indicator of the engagement regime. A controlled dry end-milling campaign on hardened WCLV steel (۵۸ HRC) is reported using TiAlN-coated solid carbide end mills, with cutting forces measured by a piezoelectric dynamometer, surface roughness (Ra, Rz) measured by contact profilometry, and tool wear monitored by optical microscopy using a flank-wear criterion. In addition, finite element (FE) machining evidence reported in the open literature is synthesized to interpret stress and temperature concentration trends across R regimes. Results show a clear sweet spot in R: intermediate ratios around ۰.۵–۰.۷ produce the lowest resultant cutting forces, suppress force signatures associated with unstable cutting, delay reaching the wear limit by approximately ۶۴% relative to high-R conditions, and deliver the best surface finish (Ra about ۰.۲۸ µm). Very low ratios reduce average force but introduce intermittent engagement and micro-chipping risk, while very high ratios increase radial force and concentrate thermal loading near the tool corner, accelerating crater and notch wear and degrading surface integrity. The findings provide actionable guidelines for CAM parameterization in die/mold and precision manufacturing where hardened steel machining must balance throughput, tool longevity, and surface quality under dry cutting constraints.

کلیدواژه ها:

Hard milling ، hardened tool steel ، ae/ap ratio ، cutting forces ، tool wear ، surface roughness