WO2002014002A1

WO2002014002A1 - Vibration damped turning tool

Info

Publication number: WO2002014002A1
Application number: PCT/NL2001/000598
Authority: WO
Inventors: Gerrit-Jan Kelder
Original assignee: Id-Nl Groep
Priority date: 2000-08-14
Filing date: 2001-08-14
Publication date: 2002-02-21
Also published as: AU2001294351A1; NL1015931C2

Abstract

Tool (1, 11) consisting of a clamping section (2, 12) a shaft section (4, 14) and an adjoining machining section (5, 15). The tool (1, 11), more particularly the shaft section (4, 14), has an appreciable length of, for example, twice the diameter of the shaft. In order to prevent vibrations in the tool on turning it is proposed to allow the cross-sectional surface area of the shaft section (4, 14) to decrease from the clamping end (3, 13) to towards the end close to the machining section (5, 15). This decrease can be continuous and/or in steps and is such that vibration generated in a certain (imaginary) section is damped by the adjacent sections tool.

Description

VIBRATION DAMPED TURNING TOOL

The present invention relates to a tool comprising a clamping section, a machining section and a shaft section joining the clamping section to the machining section, said tool having a longitudinal axis (x) and at least one surface of said shaft section extending at an angle to said longitudinal axis such that the cross-section of the shaft section decreases in the direction from the clamping section to the machining section.

A tool of this type is disclosed in "A vibration resisting turning tool" XP002166252. If, for example, deep holes have to be bored out by turning, it is necessary that the shaft section has an appreciable length. An appreciable depth is understood to be depths in excess of 80 mm or three times the diameter of the shaft. It has been found that with such relatively long shaft sections vibrations occur in the tool and possibly in the workpiece. As a result, it is particularly difficult to obtain an accurately finished surface. Moreover, the machiriing time increases because less material is machined away at one time in order to reduce the vibrations. The occurrence of vibrations is dependent on the material that is subjected to machining. It has been found that vibrations are detected in particular when turning cast iron and high-grade steel and types of stainless steel. Troublesome resonances in the tool have also been demonstrated with other materials. Furthermore, swarf removal is impaired by vibrations and the swarf breaks up, as a result of which the effect of vibrations is even further increased. In the prior art it is proposed to solve this problem using hard metal tools. These are particularly expensive. Another proposal is the use of tools filled with oil or lead. Damping takes place by the medium introduced. It has been found that these are particularly expensive and not very stable in the long term.

In the above XP 002166252 publication a tool is described that tapers towards the machining section. Tapering is exclusively in the plane that is perpendicular to a plane delimited by the longitudinal axis and the cutting edge of the tool. The width dimension of the tool in the plane delimited by the cutting edge and the longitudinal axis is essentially constant. This is except for the end section that is positioned at an angle. The dimension decreases somewhat close to the cutting tool. It has been found that optimum vibration damping is also not provided with such a tool.

Increasing the diameter of said shaft section does not lead to the desired result because this is technically not possible in connection with the diameter of the bore to be made or other operation to be carried out. Reducing the diameter results in bending of the tool.

The aim of the present invention is to provide a tool of appreciable shaft length with which the vibrations described above do not occur. This aim is achieved with a tool as described above in that the cutting edge of the machining section and said longitudinal axis (x) define a plane, the first intersecting line of said plane and the shaft section on the side of said cutting edge being essentially parallel to said longitudinal axis and the second intersecting line of said plane and the shaft section on the side opposite said cutting edge extending at said angle (90° - α₂) over the entire length of said shaft section. The sloping surface according to the invention extends at least in the plane formed by cutting edge and longitudinal axis opposite the side where the cutting edge is located. This cutting edge can be constructed to engage the plane perpendicular to the longitudinal axis or the plane in the extension of the longitudinal axis or a combination of the two.

In the case of a conically tapering shaft section the tool can be divided into a number of imaginary sections .

The division into sections described above always takes place in such a way that the length of each section always decreases in the direction from the clamping end towards the machining end. Moreover, the length of each section is not a whole number fraction of the other sections. That is to say, if the resonance frequency of one section is "a" the resonance frequency of an adjacent section is not n x a or a:n, where n is an integer. In this way any resonance vibration occurring in one section can never be amplified in the adjacent section and will, on the contrary, be damped by the latter. Moreover, according to the invention preference is given to the length of each (imaginary) section being at least twice the average diameter of that section. Further stabilisation of the tool and thus reduction in the vibrations can be obtained if there is a shoulder of an appreciable radius between the shaft section and the clamping section, as a result of which no clear end point (length) is produced, which shoulder is provided with a contact surface for bearing on the clamping device on the lathe. Clamping in the lathe is appreciably improved as a result. A completely different approach is to fit the clamping section such that it can move somewhat with respect to the lathe. Damping means can be present between the clamping section and the lathe (support). In this context consideration can be given to a rubber fill, oil damped means and the like. The material from which the tool is made can be any material known in the state of the art. That is to say no special materials such as hard metal are needed to produce the tool. The costs can be appreciably restricted as a result. The machining section can likewise be constructed in any manner customary in the state of the art, preferably with a tool made of hard metal. i some cases it has been found that a conicity of approximately 4-7° is particularly effective. The angle chosen is dependent on the material to be machined and the choice of the tool plate or tool. The cone angle can be reduced if material is less susceptible to vibration. Reduction in stability is generally not a problem. According to a further advantageous embodiment of the invention the shaft section is a cone. This can be of circular or elliptical cross-section.

The invention will be explained in more detail below with reference to the illustrative embodiments shown in the drawing. In the drawing:

Fig. 1 shows, diagrammatically, a side view of a first embodiment of the tool according to the invention;

Fig. 2 shows a second embodiment of the tool according to the invention.

The tool according to the invention is indicated in its entirety by 1 in Fig. 1. This tool consists of a clamping section 2, which is bordered by a shoulder 3 that provides an enlarged contact surface with the clamping device on the lathe. This shoulder 3 is followed by the shaft section 4 according to the invention which, in turn, is connected to the machining section 5 that comprises a hard metal tool 6.

Shaft section 4 is made up of a number of sections 7-10. The length of section 7 is indicated by a, that of section 8 by b, that of section 9 by c and that of section 10 by d. The length of the shaft section 4 is indicated by 1. This length is preferably at least three times the diameter, such as 80 mm and, for example, 180 mm. The length of the sections 7-10 is so chosen that a > b > c > d. Furthermore, the length of each of the sections is not divisible by the length of the other sections. It will be understood that the number of sections is chosen depending on the length of the tool and the desired stability. There is also a relationship between the diameter of the various sections and the length thereof. This is so chosen that adequate rigidity is obtained. The various aspects are also dependent on the material characteristics. If the material of the tool is harder, the resonance frequency will rise. The length of each section is preferably approximately twice the diameter thereof. Of course, variations are possible. Because the various sections have different lengths, resonance vibrations generated in the one section are damped by the following section. As a result of a suitable choice of the length, resonance in one section can never lead to the production of a (part) resonance in the adjacent section.

It can also be seen from Fig. 1 that side 17 is parallel to an axis x of the clamping section. This side can be constructed as a flattened part. That is to say angle α, is 90°. However, it is also possible that c^ differs from 90° and in particular is somewhat smaller. What is essential for the invention, however, is that α, is always greater than α₂.

A modified embodiment of the tool shown in Fig. 1 is indicated in Fig. 2. This tool is indicated in its entirety by 11 and comprises a clamping section 12 that adjoins a shoulder 13. The axis of the clamping section is indicated by x. The shaft section is indicated by 14 and the machining section by 15. It can clearly be seen from the drawing that the shaft section is of tapered construction. The flat side is indicated by 18 here. A conically tapering tool of this type is simple to produce. As in the case of the above embodiment, according to the invention the conical section is divided into a number of (imaginary) sections and the requirements specified above for restricting vibration as much as possible apply in respect of these.

Although the invention has been described above with reference to a rotary tool, it must be understood that the tool according to the invention is not restricted to this. This tool can be used for milling, drilling and other machining operations. It has been found that it is possible using the tool according to the invention to carry out various machining operations for which different tools were required in the state of the art. This means that the clamping and change-over time can be appreciably restricted, better swarf removal is achieved as a result of the small diameter on the machining side thereof, while, moreover, it has been found that the result of the machining operation is improved, so that the number of machining steps can be reduced, as result of which the costs are further lowered.

On reading the above description a person skilled in the art will conceive obvious variants of the invention. These are considered to fall within the scope of the disclosed invention as described in the claims.

Claims

1. Tool (1, 11) comprising a clamping section (2, 12), a machining section (5, 15) and a shaft section (4, 14) joining the clamping section to the machining section, said tool having a longitudinal axis (x) and at least one surface of said shaft section extending at an angle to said longitudinal axis such that the cross-section of the shaft section decreases in the direction from the clamping section to the machining section, characterised in that the cutting edge of the machining section and said longitudinal axis (x) define a plane, the first intersecting line of said plane and the shaft section on the side of said cutting edge being essentially parallel to said longitudinal axis and the second intersecting line of said plane and the shaft section on the side opposite said cutting edge extending at said angle (90° - α₂) over the entire length of said shaft section.

2. Tool according to Claim 1, wherein said second intersecting line is essentially straight.

3. Tool according to Claim 1, wherein said second intersecting line is stepped, in order to divide the shaft section into sections, the length of said sections decreasing towards the machining section.

4. Tool according to Claim 3, wherein the length of each section is not equal to a whole number fraction of any other section.

5. Tool according to one of Claims 3 or 4, wherein the length of each section is at least twice the average diameter of that section.

6. Tool according to one of the preceding claims, wherein the transition between shaft section and clamping section has an appreciable radius.

7. Tool according to one of the preceding claims, wherein the shaft section has a length (1) of more than twice the diameter of the shaft.

8. Tool according to one of the preceding claims, wherein the clamping section contains damping means.

9. Tool according to one of the preceding claims comprising a rotary tool.

10. Tool according to one of the preceding claims, comprising an asymmetric cone, one descriptive of said cone being parallel to said axis (x).

11. Tool according to Claim 10, comprising an asymmetric cone.