Reduced Peak Height
Is 'Reduced Peak Height' a standardized surface parameter?
Not as a standalone ISO surface-roughness symbol. In practice it is used descriptively to mean reduced peak height or reduced scallop height on a machined surface, often quantified by Rp, Rz, or scallop geometry.
What process variable most directly controls reduced peak height in 3D finishing?
Stepover is the primary variable, with tool radius as the other major driver. Smaller stepover and larger radius lower the residual peak left between passes, following h = s² / 8r for ball-nose tools.
Why does reduced peak height matter on functional CNC parts?
Peak reduction improves contact conditions on sealing, bearing, sliding, and cosmetic surfaces, where tall asperities can cause leakage, friction, premature wear, or visible finish defects.
Reduced peak height in CNC machining refers to lowering the maximum surface peak on a machined profile, typically by decreasing Rp or Rz roughness. In three-dimensional finishing, it specifically means minimizing scallop height between adjacent toolpaths through smaller stepover or larger tool radius. This yields tighter, more uniform surfaces with fewer pronounced ridges, improving finish quality and functional performance.
On the shop floor, reduced peak height becomes a practical goal during finishing passes on mills and routers. When a ball-nose end mill cuts a contoured part, it leaves a scalloped ridge between each toolpath; that ridge is the peak being controlled. Reducing stepover or switching to a larger tool radius lowers these peaks dramatically, since scallop height follows roughly h = s² / 8r. Machinists use this when surface requirements tighten from general Ra 3.2 µm to finer callouts like Ra 1.6 or 0.8 µm. A lower peak profile means fewer visible cutter marks, better sealing and sliding contact, and less secondary sanding or polishing. In millwork and edgebanding, the same principle applies to eliminating glue-line witness marks and cutter ridges before finishing. However, smaller stepover increases toolpath count and cycle time. Smart programming balances finish against throughput, and verification often requires Rz or profilometer traces.
Stepover reduced too aggressively without cycle-time control: The surface gets smoother, but toolpath count increases sharply, extending finishing time and reducing throughput.
Wrong tool radius or worn cutter: A smaller effective radius or worn ball nose leaves higher residual scallops and more pronounced peaks, so the programmed finish may not match the actual surface.
Lower peaks but persistent chatter: A part can show improved peak height yet still fail if chatter, runout, poor rigidity, or feed marks create isolated high spots that drive up Rz or cause sealing and wear issues.