Effect of cutting speed: As cutting speed increases in metal cutting (with other parameters held similar), how do the steady cutting forces typically change?

Introduction / Context:
Cutting forces arise from shear deformation in the primary zone and friction on the rake face. Changing cutting speed affects temperature, strain rate, and chip formation dynamics, which in turn influence measured forces and power consumption for a given feed and depth of cut.

Given Data / Assumptions:

• Feed and depth of cut remain fixed while speed increases.
• Tool and work material are within their recommended speed ranges (no catastrophic wear).
• Steady cutting (not severe built-up edge conditions).

Concept / Approach:
As speed increases, cutting temperature rises, which often softens the work material locally and reduces flow stress in the shear zone. Built-up edge, common at low speeds, tends to diminish at higher speeds, reducing friction on the rake face. These effects generally lower measured cutting forces, although power may rise because power = force * velocity.

Step-by-Step Reasoning:

Verification / Alternative check:
Dynamometer data typically show declining tangential and feed force components as speed rises, up to a point. Extremely high speeds may introduce other effects (tool softening or chatter), but within normal ranges forces decrease.

Why Other Options Are Wrong:

• Constant or increasing forces ignore thermal softening and reduced BUE at higher speeds.
• Non-monotonic trend is not typical within normal speed windows for conventional machining.

Common Pitfalls:
Confusing force reduction with power reduction; power often increases because velocity increases faster than force decreases.

Final Answer:
Decrease