I. Introduction

Boring is the process of expanding the original hole in the workpiece to meet the required requirements. Through high-efficiency rough (usually double-edged boring tool), the metal can be quickly cut to the required size; through the fine boring, the eccentricity of the lower hole is corrected, the precise position and shape accuracy and the surface finish are obtained, and the fineness is often used as a high Precision machining is used 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. Fine boring is generally done by adjusting the fine-tuning device to process micron-sized holes such as H7 and H6. With the popularity of machining centers, the current boring processing requires only programming, button operations, and the like. Therefore, there is a need for simpler, more convenient, and more sophisticated tools to ensure product quality.

Second, the machining center's boring processing

1, the tool rotates

Different from lathe machining, 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), so the boring tool must have a fine adjustment mechanism or automatic compensation function, especially in the fine boring, according to the tolerance requirements, sometimes it must be adjusted in the micrometer level. .

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 the lathe processing. In particular, it is particularly difficult to use a horizontal machining center for rough hole drilling of steel.

2, flutter

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

1 tool system rigidity

It includes the rigidity of the shank, the mast, the hoe and the intermediate connection. The rigidity of the tool system is particularly important because of cantilever machining, especially for the machining of small holes, deep holes and hard workpieces.

2 tool system dynamic balance

Relative to the axis of rotation of the tool system, the tool itself has an unbalanced mass that causes chattering due to unbalanced centrifugal forces during rotation. Especially in the high-speed machining, the dynamic balance of the tool has a great influence.

3 the workpiece itself or the fixed rigidity of the workpiece

Some small, thin parts cannot be adequately fixed with a reasonable jig due to their insufficient rigidity or due to the shape of the workpiece.

4 blade tip shape

The shape of the blade, the rake angle, the lead angle, the tip radius, the shape of the chip breaker, etc., all result in different cutting resistance.

5 cutting parameters selection

Including cutting speed, feed, feed amount and cooling method.

6 machine spindle system, etc.

The rigidity of the machine spindle itself, the performance of the bearings and gears, and the rigidity of the connection between the spindle and the shank.

The selection criteria of the file are different depending on the processing content. Generally speaking, attention should be paid to the rigidity, dynamic balance, flexibility, reliability, ease of operation, life and cost of the system itself.

3.Integral boring tool and modular boring tool

In the past, the integral boring tool was mainly used in the production line of a batch product or a special machine, but in fact, the specifications of the machine are various: BT, JT, ST, CT, MT, and the like. Even with the same specifications, the size is different. For example, BT has 15, 30, 40, 45, 50, 60, and so on. Even if the size and size are the same, it is possible to draw the nail shape, the thread is not the same, or the flange surface shape is different. All of these make the overall boring tool encounter great difficulties in application. In particular, in recent years, the market structure, the need to change with each passing day, and the shortened product cycle have required more flexibility for processing machinery and processing tools. So most of the integral boring tools have disappeared from the factory.

The modular boring tool divides the boring tool into: main handle, intermediate module (equal diameter, variable diameter), boring holder, boring head, blade and other parts, and then according to the specific processing content (rough, fine The diameter, depth, shape of the hole, workpiece material, etc. are freely combined. This not only greatly reduces the number of shanks, reduces the cost, can quickly cope with various processing requirements, and at the same time, due to the presence of high-precision joint faces, it plays a role in damping, thus greatly improving the rigidity of the boring tool. More than 80% of the world's machining industry uses modular boring tools, all of which use the national standard TMG21 interface (ABS interface), which makes the boring tool extremely versatile, high connection accuracy and high connection rigidity.

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