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Cutting machine tool knowledge

- Mar 29, 2018 -

First, cutting machine tool wear patterns and causes

When cutting metal, the tool cuts chips on the one hand, and the tool itself also has to be damaged. There are two main types of tool damage: wear and damage. The former is a continuous gradual wear; the latter includes brittle damage (such as chipping, broken broken, peeling, crack damage, etc.) and plastic damage two. After the tool is worn out, 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 vibration occurs, and normal cutting cannot be continued.

Therefore, tool wear directly affects processing efficiency, quality, and cost. There are the following types of tool wear:

Front rake wear

Back face wear

Boundary wear

From the perspective of temperature dependence, the main cause of normal tool wear is mechanical wear and thermal and chemical wear. Mechanical wear is caused by the sculpting of hard spots in the workpiece material, and thermal and chemical wear are caused by bonding (combination of the distance between the tool and the workpiece material when it comes into contact with the atoms) and diffusion (friction between the tool and the workpiece). The chemical elements on the surface cause each other, corrosion, etc.).

Second, the tool wear process, wear standard and tool life

As the cutting time increases, tool wear increases. According to the cutting experiment, the typical wear curve of the illustrated tool during the normal wear process can be obtained. This figure uses the cutting time and flank wear amount VB (or crater crater wear depth KT) as abscissa and ordinate, respectively. From the figure, the tool wear process can be divided into three stages:

Initial wear stage

Normal wear stage

Rapid wear stage

Cutting tool wear to a certain limit can not continue to use. This wear limit is called the dullness standard. The actual cutting time experienced by a new knife (or reground tool) from its initial use until it reaches the dullness standard is called tool life.