Technical press news

Boring machining on CNC machining centers

The so-called boring / (Boring /) refers to the expansion or refinement of the original hole in the workpiece. It is characterized by correcting the eccentricity of the lower hole, obtaining the precise position of the hole, and achieving high precision roundness, cylindricity and surface finish. Therefore, boring processing is often used as a high-precision machining method in the final process. For example, the bearing holes of various machines and the processing of the casings and cover covers of various engines.

Boring is a difficult process compared to other machining. It only needs to adjust one blade / (or blade seat /) to process micron holes like H7, H6. With the popularity of Machining Center, the current boring process requires only programming, buttoning, and the like. Because of this, there is a need for simpler, more convenient, and more sophisticated tools to ensure product quality. Here, the boring processing of the machining center is mainly analyzed from the perspective of tool technology.

Characteristics of the boring processing of the machining center

1.tool rotation

Different from the lathe processing, it is impossible to adjust the cutting edge amount in the machining process due to the rotation of the tool during machining. It is also impossible to change the machining diameter by adjusting the CNC button just like a CNC lathe. This has become a big obstacle to fully automated processing. It is also because the machining center does not have the automatic machining diameter adjustment function / (except for the U-axis function), it is required that the file must have a fine adjustment mechanism or automatic compensation function, especially in the case of fine boring, depending on the tolerance, sometimes it must be in the micrometer. Level adjustment.

In addition, since the direction in which the chips flow out is constantly changing during the boring of the machining center, the cutting edge, the cooling of the workpiece, and the discharge of the chips are much more difficult than in the lathe processing. Especially when the blind hole roughing of steel is processed by a vertical machining center, this problem has not been completely solved so far.

2.Flutter / (Chatter /)

The most common and most troublesome problem with boring is the chatter. The main reasons for the chattering at the machining center are as follows:

a.Rigidity of the tool system: including the rigidity of the shank, the mast, the hoe and the intermediate joint. Because of the Stub Boring, the rigidity of the tool system is especially important when machining small holes, deep holes and hard workpieces.

b.Tool system dynamic balance : Relative to the rotating axis of the tool system, the tool itself has an unbalanced mass, which causes the chattering due to the unbalanced centrifugal force during the rotation. Especially in the high-speed machining, the dynamic balance of the tool has a great influence.

c.The workpiece itself or the workpiece's fixed rigidity: Like some small, thin parts due to their own lack of rigidity, or due to the shape of the workpiece and other reasons can not be adequately fixed with a reasonable fixture.

d.Geometry of Edge: The cutting resistance of the blade differs from the rake angle, escape angle, tool nose radius, and chip breaker shape.