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Factors affecting the processing of knife

Update:08 Dec 2018
Summary:

The surface of the machined part cannot be absolutely f […]

The surface of the machined part cannot be absolutely flat and smooth. In fact, there is a certain degree of macroscopic and microscopic geometric shape error, which is generally expressed by the roughness value, so the surface roughness is a reflection of the micro geometry error. The index, the surface roughness value is the degree of the small peaks and valleys and the spacing. Previously, the machined surface roughness was referred to as surface finish, and its representation and numerical conversion were as follows.

First, the non-standard blade geometry parameters

Among the geometric parameters of the non-standard blade, the influence on the surface roughness is the lead angle Kr, the minor declination Kr and the radius of the tool nose arc re. When the primary and secondary declination are small, the height of the residual area of the machined surface is also small, so the surface roughness can be reduced; the smaller the secondary declination, the lower the surface roughness, but the reduction of the secondary declination is likely to cause vibration, so it is reduced. The secondary declination depends on the rigidity of the machine tool. The effect of the radius of the tool nose radius re on the surface roughness: When re increases, the surface roughness will decrease, and increasing re is a good method to reduce the surface roughness. Therefore, reducing the main declination Kr, the minor declination Kr, and increasing the radius r of the cutting edge can reduce the height of the residual area, thereby reducing the surface roughness.

Second, non-standard blade materials

When the non-standard blade material has a large affinity with the metal molecules of the material to be processed, the material to be processed is easy to bond with the cutter to form built-up edge and scale. Therefore, if the bonding is serious and the friction is severe, the surface roughness is large, and vice versa. It is small. Processing the same workpiece, different tool materials get different surface roughness.

Third, non-standard blade wear

Non-standard blade wear is divided into three phases: initial wear, normal wear and severe wear. Because there are some burrs and irregular micro-protrusions, micro-cracks, etc. on the surface of non-standard blades, the wear is more severe in the initial stage of cutting, resulting in a large change in surface roughness. After entering normal wear, the cutting process is relatively stable. Therefore, the surface roughness variation is reduced; as the wear amount increases, the blade enters the intense wear phase, the tool flank wear rate increases sharply, the system tends to be unstable, the vibration increases, and the surface roughness The magnitude of the change has also risen sharply.

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