New deep hole boring tool Dimple mast (Figure)

The main failure of the inner hole machining is the deterioration of the surface quality caused by chattering and chip removal, and the chipping and breaking of the tool. Among them, flutter is one of the important reasons. The occurrence of chattering is due to the fact that the ratio of the tool extension length to the shank diameter (L/d) is too large and the tool rigidity is insufficient. In addition, the boring tool is different from the drill bit. The drill has two cutting edges for cutting, which is a relatively balanced tool, and the boring tool is cut by a cutting edge, so-called single-point cutting tool, so it is flexed and The effect of torsional performance is very obvious, and it is easy to induce chatter vibration.

In order to suppress the generation of chatter vibration, the following measures are usually taken in actual production:

1 shorten the length of the tool as much as possible

2 reduce the cutting speed; 2 increase the feed amount, let the cutting force transfer to the axial side

3 Use large rake angled blades or positive rake angle blades to reduce cutting force

4 reduce the cutting edge arc R to reduce the resistance of the knife

5 When cutting small depth of cut, reduce the chamfering width of the cutting edge to maintain good cutting performance.

However, the above measures are subject to cutting conditions, and sometimes even counterproductive, making the elimination of chatter becomes a very difficult problem. If the workpiece needs deep hole machining, the length of the file can not be shortened; reducing the cutting speed will reduce the machining efficiency; increasing the front angle will easily cause chipping; reducing the tool edge arc R will make the surface roughness Deterioration, etc. Especially in the processing of deep holes and blind holes, it is difficult for the chips to be discharged from the machined holes, and the cutting is continued, and the tool is extremely easy to chip or scratch the machined surface. When the chip is clogged, the tool may break. Especially when machining small diameter deep holes, because the clearance between the tool and the material to be processed is very small, chip removal is more difficult and the failure is more.

The thorny problems of deep hole boring are endless, so users are eager for tool manufacturers to develop high efficiency and high reliability boring tools. In order to meet the user's requirements, Japan's Mitsubishi Materials Co., Ltd. has recently developed a dimple mast with excellent anti-vibration performance. There are two types of steel monolithic and hard alloy shank. The characteristics and cutting effects are described below. .

First, steel dimple mast

1. Characteristics

In the design of the tool shape, the steel monolithic dimple mast is designed to reduce the weight of the boring head as much as possible while maintaining good rigidity, thereby greatly improving the damping performance of the vibration reduction. The characteristics of the steel dimple mast are as follows:

(1) Deep pockets are machined on the back of the boring head to reduce the weight of the head.

(2) The cross-sectional shape can suppress the deformation of the tool, and the lightweight boring head can reduce the chattering, and the extension length is 5 times that of the similar products in the past.

(3) There are chip pockets in both directions, and the chip removal performance is good.

(4) There is a laser-printed scale on the side of the knife bar, which is convenient for the operator to refer to the application.

(5) The knife body is coated with Ni-based material and is silver-white. Compared with the past blackening treatment, the rust-proof performance and service life are greatly improved.

(6) The blade has various shapes such as 80°, 55° and 35° diamond, 80° convex triangle, square, triangle, etc., which can meet the needs of different processing.

(7) The diameter of the cutter bar is φ8-25mm six specifications for 80° diamond, triangle and convex triangle blades; φ10-20mm four specifications for 55° diamond blades.

(8) The blade adopts 11° positive rake angle, which has excellent cutting sharpness; the chipbreaker adopts MV type, and the chip discharging performance is good; in addition, there is a milled chip breaker to further improve the surface precision.

(9) The blade material is made of hard alloy, ultra-high pressure sintered body and various coated blades, which have been standardized.

2. Cutting effect

(1) Reduce vibration and prevent deformation

When the dimple mast of the φ16mm arbor is used to machine the L/d=5 deep hole under the same conditions as the original mast, the dimple mast reduces the vibration effect by 21%. In addition, since the dimple boring head adopts the optimal shape configuration, the axial force and the radial force are distributed along the section, and the tool deformation is reduced by 17% compared with the original mast.

(2) chip breaking effect

The MV-type chipbreaker used in the dimple mast is a new chipbreaker structure composed of a spherical groove and two other chute walls. It has a wide range of chip handling functions. The chips are broken into regular, finely curled shapes with smooth chip removal and do not scratch the surface of the machined holes.

(3) Processing examples

When the SCM440 material is processed under conditions of a depth of cut of 0.5 mm, a feed rate of 0.1 mm/r, a cutting speed of 80 m/min, and a tool extension length of L/d=5, the masts of other companies are prone to chattering, and many processes are performed. The surface is scratched, while the dimple mast is smooth and the surface quality is good. If the cutting speed is increased to 160m/min and L/d=4, after the mast processing of other companies, there will be obvious corrugated flutter marks on the machined surface, while the processing surface of the dimple mast is very smooth and flat. Accuracy can still be maintained at an extremely excellent level.

Second, the hard alloy dimple mast

1. Features

The elastic modulus of cemented carbide is more than three times that of steel, so the material itself has good anti-vibration performance. The cemented carbide used by Mitsubishi Materials Corporation has higher rigidity than ordinary cemented carbide and is a tool material with good anti-vibration performance. The head of such a mast is still made of steel, the shank is made of cemented carbide, and the combined shape is tapered. This way can increase the bonding strength of the two. Due to the good rigidity of the cemented carbide mast, its extension length is about 1.6-2 times that of the steel mast.

The positional structure of the carbide dimple mast oil supply hole ensures that the coolant flows directly to the cutting edge. This feature is extremely important for deep hole machining. The internal liquid supply effect makes the chip discharge very smooth, and the blade used can be an 80° diamond blade or an economical triangular blade. The diameter of the arbor has five specifications of φ8-20mm, two of which are short handles (equivalent to 1/2, 2/3 of the full length) and three standard lengths, which can be selected according to the workpiece.

2. Processing effect

The SCM440 (185HB) is machined under the conditions of cutting speed 80m/min, depth of cut 0.5mm, feed rate 0.1mm/r, and extension length L/d=8. Significant chatter marks, while the surface of the carbide dimple mast is very smooth, similar to the turning trace. The boring of L/d=8 is a very difficult process. Due to its good damping effect, the dimple mast of the carbide can still perform high-precision and stable cutting under such severe conditions.

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