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How to choose a reasonable cutting parameters?

The cutting parameters is not only important parameter which must be determined before the adjustment of the machine tool, but also has a very important influence on the processing quality, processing efficiency, production cost and so on.

1, Factors need to be taken into account when determine the cutting parameter:

(1) Cutting productivity

In the cutting process, the metal removal rate and the three elements of cutting parameter:ap, f, v maintain a linear relationship. If any parameter changed to be twice, the productivity will also be twice. However, due to the constraints of tool life, when any parameter increases, the other two parameters must be reduced.

(2) Tool life

For the three elements, the order of significance of influencing tool life is v, f, ap. To ensure a reasonable tool life, when determine the cutting parameter, the back engagement of the cutting edge should be as much as possible; and then use a large feed; finally calculate the cutting speed.

(3) Machining parts surface roughness

In finish machining process, the surface roughness will be increased when increase the feed. It is a main factor that suppresses the improvement of the productivity in finish machining process.

2, principles of choosing cutting tool life

Cutting tool life and the cutting parameter are closely related. In the development of cutting parameter, a reasonable tool life should be selected at first. The following points can be considered when select the tool life:

(1) Tool life of complex and high precision tools should be selected as higher than the single-blade tool.

(2) For the indexable tool, because the tool change time is short, in order to give full play to its cutting performance, improve production efficiency, tool life can be selected lower, generally take 15-30min.

(3) For the multi-blade machine tools, combined machine tools and automated processing tools with complex way of tooling, tool change and knife adjustment, tool life should be selected higher, especially should ensure that the tool reliability.

(4) When the productivity of a process limits the productivity of the whole workshop, the tool life of this process should be chosen to be lower; when the whole plant cost M is larger in a certain unit time, the tool life Should also be selected lower.

(5) For finish machining of large workpieces, in order to ensure complete machining in one pass, to avoid change cutting tools during machining process, the tool life should be defined in accord with the surface roughness.

3, Three steps to define the cutting parameter

(1) choose the back engagement of the cutting edge

(2) choose the feeds

(3) determine the cutting speed

(4) check the machine power

4, four ways to increase the cutting parameter

(1) use tool with new materials and better cutting performance ;

(2) improving the workpiece material processing ability;

(3) improve the cooling and lubrication conditions;

(4) improve the tool structure, improve tool manufacturing quality. Continue reading “How to choose a reasonable cutting parameters?”

Surface roughness of machining parts and its influence factors

The surface Geometry characteristics of machining parts includes surface roughness, surface wave, surface processing texture etc. Surface roughness is the basic unit of surface geometric characteristics of the machining parts. When processing with metal cutting tools, the surface roughness is mainly affected by geometric factors, physical factors and mechanical processing factors.geometric elements

1, From the geometric point of view, the shape and the geometric angle of the cutting tool have a greater impact on the surface roughness.

2,  physical factors

(1) from the physical considerations of cutting process, the cutting edge of the blade and the  extrusion and friction  at the back of the tool make metal materials plastic deformation, it deteriorates the surface roughness seriously. In the processing of metal machining, high hardness BUE(built-up edge) can be generated easily. It can replace the cutting edge to cut, change the geometry of the tool angle and the back engagement of the cutting edge. The contour of the BUE is very irregular, so the knife marks can be found on the workpiece with depth and width changed constantly. Some BUE embedded into the workpiece, also increased the surface roughness.

(2) the vibration of cutting will also increase the surface roughness.

3, process factors

From the process point, there are factors related to cutting tools, and the workpiece material-related factors and processing conditions etc.