1. The effects of cutting force and friction. During precision part machining, the tool's cutting edge radius and the compression and friction against the workpiece surface can cause plastic deformation in the metal material. This leads to distortion or deepening of existing residual areas, increased surface roughness, and can cause brittleness in the machined material. At this point, the cutting chips become broken particles, and the machined surface often shows signs of particle collapse, leaving many pits and resulting in a rough surface.

2. The Impact of Swarf. When cutting tools cut plastic at a certain speed, some small particles of the chips adhere to the tip of the leading edge, forming a high-hardness built-up edge that can substitute for the leading edge and cutting edge to perform cutting.

When the friction between the chip and the堆积 edge exceeds the cold welding strength between the堆积 edge and the front cutting face, or when it is subjected to impact or vibration, the堆积 edge will fall off, leading to the gradual formation of a new-up edge in the future. The formation, growth, and shedding of the堆积 edge significantly affect the surface roughness of the part.

3. The Impact of Scaling. During the cutting process, due to the friction and cold welding of chips on the cutting surface during precision part machining, the chips will periodically remain on the leading edge, thereby compressing the newly machined surface. In severe cases, the surface may tear. Scaling spikes form on the surface, making it rough and uneven.

Due to the aforementioned physical factors' impact on roughness, to minimize surface roughness, it is essential to avoid the formation of tumors and scales from accumulated debris during precision part machining, in addition to reducing plastic deformation caused by cutting forces.

Key process measures include: increasing material cutting performance by choosing a cutting speed that minimizes edge堆积 and burrs, and correctly selecting cutting fluids.