Selecting tool geometry parameters to improve tool life

The slower the wear rate is, the higher the tool durability is. Therefore, all the factors affecting tool wear will affect tool durability, and tool durability is an important indicator of tool cutting performance. Therefore, it is necessary to analyze the factors affecting tool durability, so as to effectively control the relationship between these factors, so as to obtain a reasonable tool durability, so that the tool has better cutting performance.

Selection method

The first method is to make durability according to the principle of minimum per workpiece, called maximum productivity durability Tp; the second method is to make durability according to the principle of minimum cost per workpiece, called minimum cost durability Tc; the third method is to make durability according to the maximum profit per unit time, called durability. Maximum profit durability Tpr.

The analysis shows that there is a relationship between the three kinds of durability, that is, Tp selection elements.

For simple and inexpensive tools, such as turning tools, drills, etc., the durability can be set at a lower level; otherwise, such as milling cutters, broaching cutters and gear cutters, the durability should be selected at a higher level.

For multi-tool machine tools, modular machine tools and automatic machining tools, which are more complicated to install, change and adjust cutters, the durability should be higher. The tool changable cutter and ceramic tool have shorter tool changing time and lower durability.

In order to balance the production of the workshop, the durability of the key process which does not meet the production rhythm should be selected to be lower, and the tool durability should be selected to be lower when the expenditure per unit time of a process is larger.

In order to avoid changing the tool in the process of machining the same surface, the durability of large parts should be higher, and the tool should be run at least once.

The tool life of the production line should be specified as one or two classes, so that the tool can be changed during the shift.

Consideration of factors

The factors affecting tool durability can be divided into five aspects: cutting parameters, tool geometry parameters, workpiece materials, tool materials, tool grinding quality and lubrication cooling conditions.

Influence of cutting parameters on tool durability

The influence of cutting parameters, i.e. cutting speed v, feed F and cutting depth ap, on tool durability is as follows: with the increase of cutting parameters, cutting temperature increases, tool wear is faster, tool durability decreases. But the influence of cutting speed, feed rate and cutting depth on cutting temperature is different, so the influence on tool durability is different.

Influence of tool geometry parameters on tool durability

The influence of rake angle gamma on tool durability is obvious. The rake angle is too big, the strength of the blade is reduced, the heat dissipation is poor, and the tool is easy to be damaged; the rake angle is too small, and the cutting force and cutting temperature are increased too much. In both cases, the tool durability will decline, and the rake angle has a "hump shape" effect on tool durability, and the rake angle durability is the highest. Reduce the main angle of kappa gamma 1, increase tool strength, improve heat dissipation conditions and increase durability. In addition, the tool strength, heat dissipation and tool durability can be improved by reducing the offset angle and increasing the arc radius of the tool tip. Geometric parameters of cutting tools have a significant impact on tool durability, which is one of the important symbols of reasonable and advanced geometric parameters of cutting tools.

Effect of workpiece material on tool durability

The higher the strength and hardness of the workpiece material, the higher the cutting temperature, so the faster the tool wear, the lower the tool durability. When carbon structural steel is cut, the carbon content of the steel has a great influence on the tool durability. The higher the carbon content, the greater the proportion of cementite and pearlite, the higher the hardness, and the faster the tool wear. Therefore, the tool wear is faster and the durability is lower when cutting high carbon steel, and the tool wear is slower and the durability is higher when cutting medium carbon steel. In addition, the main factors affecting the ductility and durability of cutting materials, such as improving the tool elongation or low thermal conductivity, can make the cutting performance of cutting materials. The cutting temperature with high hardness increases, and the tool durability decreases. It also has higher wear resistance. Tool cutting parts of the material is also a major factor affecting tool durability, improve the cutting performance of tool materials, the use of high hardness materials, its wear resistance is also high.