CHAMFERING TOOL WITH GUIDE FOR ELIMINATING VIBRATIONS

Abstract

The invention relates to a cutting machine with a receiving area for a tube section and with a tool head (1) which can be rotated relative to the receiving area about a longitudinal axis (L), has at least one cutting tool (6) for machining a tube section end (40) of the tube section located in the receiving area, and has a support component (2), wherein the support component faces the receiving area and has an annular component (3) which rotates relative to the support component (2) about the longitudinal axis (L) and is designed to be randomly supported on a tube wall (42, 42) of the tube section end (40). The invention further relates to a corresponding method for reducing vibrations.

Claims

1. A cutting machine comprising: a receiving area for a tube section and a tool head (1) which can be rotated relative to the receiving area about a longitudinal axis (L), has at least one cutting tool (6) for machining a tube section end (40) of the tube section located in the receiving area, and has a support component (2) which faces in the direction of the receiving area and has an annular component (3) which is rotatable about the longitudinal axis (L) relative to the support component (2) and is configured to be randomly supported on a tube wall (42) of the tube section end (40).

2. A cutting machine according to claim 1, characterized in that the support component is configured as a mandrel (2) and the annular component (3) is arranged so as to be rotatable externally on the mandrel (2), and an external diameter of the annular component (3) is smaller in cross-section perpendicular to the longitudinal axis (L) than an internal diameter of the tube section end (40).

3. A cutting machine according to claim 1, characterized in that the support component is configured as a bushing and the annular component (3) is arranged so as to be rotatable internally in the bushing, and an internal diameter of the annular component (3) is greater than an external diameter of the tube section end (40).

4. A cutting machine according to claim 1, characterized in that a support surface (20) of the annular component (3) has a profile.

5. A cutting machine according to claim 1, characterized in that the profile has, in cross-section, recesses (21) in the direction away from the tube wall (41, 42).

6. A cutting machine according to claim 1, characterized in that the profile has a meandering shape in cross-section.

7. A cutting machine according to claim 1, characterized in that the annular component (3) is mounted in a ball bearing (43) on the support component (2).

8. A cutting machine according to claim 1, characterized in that the annular component (3) is replaceable by another annular component with another radius.

9. A method for reducing vibrations, in particular the regenerative chatter of a cutting machine, wherein a tube section rotates relative to a tool head (1) with at least one cutting tool (6), the tool head (1) cuts walls (41, 42) of the tube section end (40) by means of the at least one cutting tool (6), the tool head (1) is vibrationally excited during the cutting, the tool head (1) is supported on one of the walls (41, 42) of the tube section end (40) by means of a support component (2) which has an annular component (3) rotating about a longitudinal axis (L), and as a result vibrational excitement is interrupted.

10. A method according to claim 9, characterized in that the annular component (3) has an angular velocity which decreases during contact with the wall (41, 42), whilst a rotational speed of the tool head (1) is not changed by the contact.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0031] The invention is described with reference to an embodiment with six drawings. In the drawings:

[0032] FIG. 1 shows a side view of a tool head according to the invention;

[0033] FIG. 2 shows a perspective view of the tool head in FIG. 1;

[0034] FIG. 3 shows a front view of the tool head in FIG. 2;

[0035] FIG. 4 shows a sectional view of the tool head along the line IV-IV in FIG. 3, wherein a mandrel of the tool head according to the invention is additionally inserted into a tube section end;

[0036] FIG. 5 shows a sectional view according to FIG. 4 without the tube section end; and

[0037] FIG. 6 shows a perspective view of the tool head according to FIG. 4 inserted into a tube section end.

DETAILED DESCRIPTION OF THE INVENTION

[0038] A tool head 1 illustrated in FIG. 1 additionally has a mandrel 2 projecting with respect to tool heads, which are known for example from EP 2 106 313 B1, along a longitudinal axis L of the tool head, an annular component 3 being rotatably mounted on the outer end of the mandrel. The annular component 3 and the mandrel 2 are substantially circular in cross-section perpendicular to the longitudinal axis L and are arranged concentrically around the longitudinal axis L of the tool head 1. On one end of the tool head 1 opposite the mandrel 2 a spindle receiving area 4 is provided, by which the tool head 1 is interchangeably fastened on a spindle (not shown) in a controlled manner.

[0039] The tool head 1 in FIG. 1 has four cutting plates 6, of which three can be seen in FIG. 1. The cutting plates 6 are intended for machining of a tube section end 40 which in cross-section has a circular internal diameter and a circular external diameter. Two of the cutting plates 6 are intended for application of an outer chamfer on the tube section end 40 and two other cutting plates 6 for application of an internal chamfer on the tube section end 40. The tube section end 40 is preferably made of metal, particularly preferably steel, but other materials can also be envisaged. By comparison with the embodiment in FIG. 1 the tool head 1 can also have a different number of cutting plates 6, in particular one, two, three or a higher number of cutting plates 6.

[0040] According to FIG. 4, the tool head 1 and the tube section end 40 rotate about the longitudinal axis L relative to one another, and in this case the tube section end 40 can be held fixedly in space relative to the tool head 1, whilst the tool head 1 rotates about the longitudinal axis L, but conversely the tool head 1 can also be held fixedly in space and the tube section end 40 can be rotated about the same longitudinal axis L. During the rotation operation the cutting plates 6 remove chips from an outer wall 41 or an inner wall 42 of the tube section end 40.

[0041] During the cutting operation load changes of the cutting forces can occur, for example due to the outer wall 41 or the inner wall 42 being not exactly circular, which in reality is actually always the case, so that in the real cutting operation the removed chips have slightly differing thicknesses, and even in the case of an ideally circular tube section 40 load changes will occur which lead to the tool head 1 first of all being set in slight vibrational movements out of the longitudinal axis L which, however, can be periodically strengthened by continuous relative rotation of the tool head 1 and the tube section 40 and thus lead to the so-called regenerative chatter.

[0042] The corrugation of the outer surface 42 of the tube section 40 or of the inner wall 42 of the inner wall 42 of the tube section end 40 periodically repeatedly excites the tool head 2 to the same vibrations. Usually tool heads rotate at approximately 5,000 r.p.m., but other rotational speeds are also conceivable. The tool head 1 is mounted on a rotating spindle (not shown) oriented in the longitudinal direction L and can vibrate out of the longitudinal axis L. The vibrational behavior of the tool head 1 is determined substantially by a rigidity c of the tool head 1 mounted on the spindle, a damping d and a mass m of the tool head 1 with the spindle. In particular a natural frequency f.sub.eigen of the tool head 1 is a function of these three parameters, and in this case natural frequency f.sub.eigen means the natural frequency with which the tool head 1 mounted on the spindle vibrates out of the longitudinal axis L. The invention makes use of the idea of introducing a disruption into the natural vibration of the tool head 1 by the mandrel 2 with the annular component 3 mounted rotatably about the longitudinal axis L on the mandrel 2.

[0043] FIG. 2 shows the tool head 1 in FIG. 1 in a perspective view, which illustrates somewhat more clearly the design of the mandrel 2 of circular cross-section with the annular component 3 mounted rotatably on the mandrel. Furthermore, two of the four cutting plates 6 can be seen. The cutting plates 6 are interchangeably mounted on the tool head 1. According to the invention a support surface 20 externally surrounding the annular component 3 is not exactly circular in cross-section, but the support surface 20 has a meandering configuration in cross-section. In other words, the cross-sectionally exact circular shape is periodically interrupted by depressions in the radial direction inwards towards the longitudinal axis L, so that recesses 21 running along the longitudinal axis L are provided in the outer wall of the annular component 3 and extend over an entire longitudinal extent along the longitudinal axis L of the annular component 3.

[0044] FIG. 3 shows the tool head 1 in FIGS. 1 and 2 in a front view, and in this case the cross-sectionally circular mandrel 2 can be seen, as well as the annular component 3 projecting radially over a mandrel diameter, wherein the outer support surface 20 of the annular component 3 has the meandering shape described above which deviates from the exact circular shape. In cross-section according to FIG. 3 radially outer raised areas 22 of the annular component 3 form regions of an exactly circular shape with a first greater radius, and the recesses 21 of the annular component 3 form areas having an exact circular shape with a second smaller radius. Both the smaller radius and also the greater radius of the annular component 3 are in each case greater than the radius of the mandrel 2.

[0045] FIG. 4 shows the tool head 1 according to the invention in its intended application, and in this case the mandrel 2 is introduced into the open tube section end 40, an internal diameter of the tube section end 40 is greater than each diameter of the annular component 3, so that in the event of exact introduction along the longitudinal axis L of a tube section the mandrel 2 with the annular component 3 does not touch the inner wall 42 of the tube section end 40. The annular component 3 is rotatably mounted on the mandrel 2 by means of a ball bearing 43, but it is not radially movable to and fro relative to the longitudinal axis L of the tool head 1, the annular component 3 being exclusively rotatably mounted on the tool head 1. The mandrel 2 has a removable cap 44. After removal of the cap 44 the annular component 3 can be replaced by another annular component, and in this case the other annular component can in particular have another large radius and thus can be suitable for machining of tube section ends 40 with other internal diameters.

[0046] During the cutting operation the cutting plates 6 remove chips from the inner wall 42 or outer wall 41 of the tube section end 40, and thus apply an inner or outer chamfer 46, 45 to the edge of the tube section end 40. During the cutting operation slight vibrations of the tool head 1 occur, which lead to the annular component 3 of the mandrel 2 coming into contact with the inner wall 42 of the tube section end 40. In this way the vibration process of the tool head 1 is disrupted, and the tool head 1 is not excited to natural vibration. However, due to the rotatable mounting of the annular component 3 on the mandrel 2, on the one hand the actual cutting operation is not interrupted, because the annular component 3 only generates a very slight friction on the inner wall 42, and on the other hand the inner wall 42 is also not damaged, since the annular component 3 does not rub along the inner wall 42 but, in the event of contact due to its low mass relative to the tool head 1, is immediately transferred from rotational movement to a standstill.

[0047] In FIG. 5 the schematic structure of the tool head 1 according to the invention in FIG. 4 is shown without the tube section end 40, and in particular the rotatable annular component 3 with the circulating ball bearings 43 is illustrated as well as the cap 44 of the mandrel 2, which can be removably screwed in place on a mandrel connection piece 50 and which makes it possible to replace the annular component 3 when the cap 44 is removed. The spindle receiving area 4 opposite the mandrel 2 can be seen on the left in FIG. 4.

[0048] FIG. 6 shows the tool head 1 with the tube section end 40 in operation, the spindle is not shown, but it can be seen that the mandrel 2 is introduced invisibly into the tube section end 40 and the cutting plates 6 have already applied the outer chamfer 45 discernibly and the internal chamfer 46 indiscernibly to the tube section end 40. The tube section is even longer along the longitudinal axis L than the tube section end 40 illustrated in FIG. 6.

LIST OF REFERENCE NUMERALS

[0049] 1 tool head [0050] 2 mandrel [0051] 3 annular component [0052] 4 spindle receiving area [0053] 6 cutting plates [0054] 20 support surface [0055] 21 recesses [0056] 22 radially outer raised areas [0057] 40 tube section end [0058] 41 outer wall [0059] 42 inner wall [0060] 43 ball bearing [0061] 44 cap [0062] 45 outer chamfer [0063] 46 internal chamfer [0064] 50 mandrel connection piece [0065] c rigidity [0066] d damping [0067] m mass [0068] f.sub.eigen natural frequency of the tool head [0069] L longitudinal axis