First, the shape and reason of tool wear
When the four-post cutting machine is cutting metal, the cutting tool on the one hand will cut the chip, on the other hand, the tool itself will be damaged. There are two main forms of tool damage: wear and tear. The former is continuous gradual wear; The latter includes brittle damage (such as chipping edge, broken, peeling, crack damage, etc.) and plastic damage. After tool wear, the machining accuracy of the workpiece is reduced, the surface roughness is increased, and the cutting force is increased, the cutting temperature is increased, and even the vibration can not continue to normal cutting. Therefore, tool wear directly affects machining efficiency, quality and cost. There are several forms of tool wear:
Front cutter face worn
The rear knife face is worn
From the point of view of the degree of dependence on temperature, the main reasons for normal tool wear are mechanical wear, thermal wear and chemical wear. The mechanical wear of four-column cutting is caused by the scratching of hard points in the workpiece material, and the thermal and chemical wear is caused by the bonding (the combination phenomenon between the tool and the workpiece material and the distance between atoms) and the diffusion (the chemical elements of the two friction surfaces of the tool and the workpiece are mutual to each other, corrosion, etc.).
Two, tool wear process, blunt grinding standard and tool life
With the prolongation of cutting time, tool wear increases. The tool wear process can be divided into three stages:
Initial wear stage
Normal wear phase
Sharp wear phase
The tool is worn out to a certain extent and can no longer be used. This degree of wear is called blunt standard. The actual cutting time experienced by a new (or resharpened) tool from the beginning of service until it reaches the dulling standard is called tool life.