Cutting force
(1) Total cutting force Total cutting force refers to the force generated in the cutting process that acts on the workpiece and the tool in equal magnitude and in opposite directions. In layman's terms, it refers to the resistance of the workpiece material to the cutting of the tool during cutting. As shown in Figure 2-6-12a, the total cutting force is always composed of the elastic deformation force and plastic deformation force generated by the cutting layer, chip layer and machined surface, as well as the friction force generated by the chip and machined surface with the rake and flank faces, respectively. For ease of analysis, the total cutting force is broken down into three components that are perpendicular to each other.
1) Cutting force F: the component force in the direction of the main motion. It is an important basis for checking and selecting the power of the machine tool, checking and designing the strength and rigidity of the main motion mechanism of the machine tool, the tool and the fixture.
2) Back force F: the component force perpendicular to the working plane. It is the main reason that affects the machining accuracy and surface roughness.
3) Feed force F: the component force in the direction of feed movement, which makes the workpiece elastic bend and cause vibration. It is the main basis for checking the strength of the feed mechanism.
(2) The main factors affecting the cutting force
1) The higher the strength and hardness of the workpiece material, the higher the shear yield strength, and the greater the cutting force. For materials with similar strength and hardness, the greater the plasticity and toughness, the greater the cutting force.
2) The effect of cutting amount.
(1) Double the amount of back eating knife and feed (/), and double the cutting force.
(2) The feed rate ('v') is doubled, and the cutting force is increased by 68%~86%.
3) The influence of the geometric angle of the tool. The rake angle (y.) increases, the deformation decreases, and the cutting force decreases; The entering angle (κ,) increases, the back force (F) decreases, and the feed force (F) increases. The inclination angle (A) decreases, F increases, F decreases, and the cutting force F. The impact was not significant.
4) The effect of tool wear. The flank face wears to form a zero relief angle, and the cutting edge becomes dull, and the extrusion and friction between the flank face and the machined surface intensify, resulting in an increase in cutting force.
5) Cutting fluid can play a lubricating role, which can reduce the friction between the tool and the workpiece, and reduce the cutting force. 6) The influence of the tool material. The affinity and friction factors between the tool material and the machined material are the main factors affecting the cutting force, so the tool material has high mushroom resistance, small surface roughness value after grinding, and small cutting force.
