Metal-cutting machine tool

Abstract

This disclosure relates to a metal-cutting machine tool with a base body, which is rotatable about an axis of rotation relative to a workpiece to be machined, at least one plate seat disposed outside the axis of rotation on the base body and a cutting insert, which is inserted into the plate seat and held therein by at least one fastening means and which is provided with a coating, at least in the area of its cutting edge. In order to compensate for positional tolerances, according to this disclosure the plate seat comprises a positioning surface oriented toward the axis of rotation, and the cutting insert has a reference surface lying against the positioning surface and facing away from the axis of rotation, for radially determining the position of its cutting edge, wherein the coating is also applied to the reference surface.

Claims

1. A metal cutting machine tool, comprising: a base body rotatable around a rotational axis relative to a workpiece to be processed, the base body having a peripheral surface intersecting a front end surface, which is orthogonal to the rotational axis; a plate seat arranged on the front end surface outside the rotational axis and having a positioning surface facing the rotational axis; a tangentially mounted cutting plate held in the plate seat by a fastener, the cutting plate having a cutting edge and a reference surface configured for radial positioning of the cutting edge, wherein (i) the reference surface abuts the positioning surface and faces away from the rotational axis, (ii) the reference surface is transverse to a shortest imaginary connecting line running through a radially outer point of the cutting edge and the rotational axis, and (iii) the connecting line encloses a smallest angle in a range of 80° to 90° with the reference surface; the fastener having a longitudinal axis parallel to the rotational axis; a coating provided on the cutting edge and on the reference surface; wherein the plate seat has an axial support surface for abutting a bottom surface of the cutting plate, the axial support surface being arranged orthogonal to the rotational axis, the axial support surface is entirely disposed radially outward of the positioning surface; and wherein the positioning surface is orthogonal to the axial support surface; wherein the plate seat defines a free space radially inward of the positioning surface and wherein a radially inward facing surface of the cutting plate is spaced apart from an opposing surface of the plate seat whereby the free space defined by the plate seat allows radial inward compensating displacement of the cutting plate as a function of the thickness of the coating.

2. The machine tool according to claim 1, wherein the reference surface is orthogonal to the connecting line.

3. The machine tool according to claim 1, wherein the plate seat has a tangential support surface that lies parallel to a plane spanned through the rotational axis and the radially outer point of the cutting edge or encloses a smallest angle between 0° and 20° with the plane.

4. The machine tool according to claim 1, wherein the cutting plate has a substrate formed from metal or cermet.

5. The machine tool according to claim 1, wherein the cutting edge is soldered to a substrate.

6. The machine tool according to claim 1, wherein the coating comprises a ceramic or diamond material coating.

7. The machine tool according to claim 1, wherein the coating comprises ceramic or diamond and has a hardness with a Vickers Number of more than 800 HV.

8. The machine tool according to claim 1, wherein a thickness of the coating at the cutting edge and on the reference surface is substantially the same.

9. The machine tool of claim 8, wherein the thickness of the coating is in a range of 0.5 to 50 μm.

10. The machine tool according to claim 1, wherein the positioning surface is arranged in a recess adjacent the axial support surface.

11. The machine tool according to claim 1, wherein the fastener is detachable, the fastener being engageable with the plate seat and extending through an opening in the cutting plate, and in an installed state, the fastener is eccentrically disposed in the opening in the cutting plate whereby a force component directed against the positioning surface is applied to the cutting plate.

12. The machine tool according to claim 1, wherein the fastener is a clamping screw or a clamping spring.

13. The machine tool according to claim 1, wherein the cutting edge has been ground to a desired diameter of the machine tool in an uncoated state of the cutting plate.

14. The machine tool according to claim 1, wherein the cutting plate comprises at least two alternately engageable cutting edges and associated reference surfaces.

15. The machine tool according to claim 1, wherein the plate seat is formed by a replaceably fixable cutting plate holder on the base body.

16. The machine tool according to claim 1, wherein the position of the positioning surface is adjustable.

17. The machine tool according to claim 1, wherein the fastener is a threaded fastener.

18. The machine tool according to claim 1, wherein the radially inward facing surface is spaced apart in its entirety from the opposing surface of the plate seat.

19. The machine tool according to claim 10, wherein the axial support surface is entirely disposed radially outward of the recess.

20. The machine tool according to claim 1, further comprising a clamping wedge on the front end surface for providing additional radial clamping of the cutting plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

(2) FIG. 1 is a perspective view of a machine reaming tool with coated cutting plates inserted in the plate seats of a base body;

(3) FIG. 2 is a partial sectional view through a cutting plate along the line 2-2 of FIG. 1, provided with a radial reference surface;

(4) FIG. 3 is a front side view of an embodiment of a reaming tool with cutting plates in cassettes;

(5) FIG. 4 is a partial sectional view along the line 4-4 of FIG. 3;

(6) FIGS. 5 and 6 show another embodiment of a reaming tool with a screw-clamping cutting plate against a positioning surface, in an axial section and in a sectioned enlargement;

(7) FIGS. 7 and 8 show an embodiment of a reaming tool with spring-clamping cutting plates against each positioning surface, in an end view and in an axial section along the line 8-8 of FIG. 7;

(8) FIG. 9 shows a coated turning-cutting plate with a reference surface in a section view;

(9) FIG. 10 is an end view of the turning-cutting plate of FIG. 9 shown in a sketched installation position; and

(10) FIGS. 11, 12, 13, 14, 15 and 16 show further embodiments of coated turning-cutting plates with the corresponding representations of the reference surface in FIGS. 9 and 10.

DESCRIPTION

(11) The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure.

(12) For purposes of this disclosure, terms such as “horizontal” and “vertical” are generally used herein to establish positions of individual components relative to one another rather than an absolute angular position in space. Further, regardless of the reference frame, in this disclosure terms such as “vertical,” “parallel,” “horizontal,” “right angle,” “rectangular,” “orthogonal” and the like are not used to connote exact mathematical orientations or geometries, unless explicitly stated, but are instead used as terms of approximation. With this understanding, the term “vertical,” for example, certainly includes a structure that is positioned exactly 90 degrees from horizontal, but should generally be understood as meaning positioned up and down rather than side to side. Other terms used herein to connote orientation, position or shape should be similarly interpreted. Further, it should be understood that various structural terms used throughout this disclosure and claims should not receive a singular interpretation unless it is made explicit herein. By way of non-limiting example, the terms “plate seat,” “cutting plate,” “fastener,” to name just a few, should be interpreted when appearing in this disclosure and claims to mean “one or more” or “at least one.” All other terms used herein should be similarly interpreted unless it is made explicit that a singular interpretation is intended.

(13) Reaming tools 10 shown in the drawing can be rotationally driven around a rotation- or tool axis 12 for the fine processing of a prefabricated bore in a workpiece by means of a machine tool, and thereby axially advance to cuttingly remove a reaming allowance, and thus to create a precisely fitting bore with a high surface quality. However, tool axis 12 can also be a rotational axis for a workpiece, which rotatingly moves around a tool axis for processing with a stationary machine tool.

(14) As shown in FIGS. 1 and 2, reaming tool 10 has base body 14, which is connectable to a recess, connectable to a machine spindle at its rear end via interface 16. At the front end of base body 14, a plurality of cutting plates 18 is fixed on each plate seat 20, distributed in the circumferential direction by means of clamping screws 22. The radially outer active cutting edge 24 of these cutting plates 18 revolves on a common cutting circle coaxial to the tool axis 12.

(15) Plate seat 20 provides one or more thrust bearings, to which the associated cutting plate 18 is directly applied. The contact between the thrust bearing and cutting plate 18 can be generally surface-, line- or point contact. In this case, the thrust bearing is positioned so that cutting plate 18 is pressed by the force impact during the application (cutting forces) against one or more thrust bearing, thus the thrust bearing surfaces, in addition to the positioning of cutting plate 18, absorb the cutting forces and pass it to base body 14.

(16) For additional radial clamping of cutting plates 18, respective clamping wedges 26 are provided, which are also retractable axially into base body 14 by means of screws 28, as will be described in more detail below.

(17) As shown in FIG. 2, cutting plates 18 consist of a support body or substrate 30, for example, of a hard metal or cermet, and a full-surface hard material coating 32 applied to its outside surface. This may have a layer thickness, for example, in a range of 1 to 30 μm, of which the tolerance would affect the radial position of cutting edge 24 without compensating measures. To avoid this, cutting plate 18 has a reference surface 34, which, like cutting edge 24, is provided with coating 32 and abuts positioning surface 36 in the region of plate seat 20.

(18) The location determination or compensation is carried out in that positioning surface 36 is oriented radially inwards to tool axis 12, whereas the coated reference surface 34 points radially outward, away from the tool axis 12, so that depending on the thickness of coating 32, a corresponding compensation of the radial position of cutting edge 24 is achieved. For this purpose, it is advantageous that reference surface 34 is orthogonal to a connecting line virtually running on the shortest distance through the radially outer point of cutting edge 24 and through rotational axis 12.

(19) Suitably, such a compensatory surface pairing can be realized by a gradation or angle piece 38 of cutting plate 18, in which the angle piece 38 protrudes into plate seat 20 in the installed state of the cutting plate 18. It is favorable that plate seat 20 has axial support surface 40 pointing in the direction of rotational axis 12 for the bottom surface of cutting plate 18, so that positioning surface 36 can be arranged in recess 42 adjacent to support surface 40.

(20) As seen in FIG. 2, clamping screw 22 is guided into the threaded bore of base body 14 under axial support surface 40 eccentrical to the opening of cutting plate 18, by which a force component against positioning surface 36 is directedly applied. In order to support the surface pressure and in order to ensure a reliable radial support of the cutting plate, clamping wedge 26 can be fixedly clamped to wedge slope 46 by means of screw 28. The wedge clamping results in an additional support of cutting plate 18 against radial forces from the machining process.

(21) In the following embodiments, the same or similar parts are provided with the same reference numerals, as described above.

(22) FIGS. 3 and 4 show an embodiment with cassettes 48 for indirectly holding cutting plates 18 on base body 14. Here, positioning surface 36 is formed as part of the plate seat in the respective cassettes 48.

(23) Cassettes 48 can be fixed to base body 14 by means of screws 52 and supported radially adjustably by clamping wedges 26 as an adjustment means. Cutting plates 18 can be easily replaced, if necessary, by loosening their clamping screw 22. It is also conceivable that cassettes 48 can be optionally built on base body 14 in different sizes for different cutting plates 18.

(24) As can also be seen from FIG. 3, the plate seat comprises support surface 54 with tangential surface normal for receiving tangential forces introduced to cutting edge 24. This tangential support surface 54 should be as parallel as possible to a plane 56 spanned through the rotational axis and the radially outer point of cutting edge, so that by the coating tolerances of cutting plate 18, only a tangential adjustment, but no appreciable radial adjustment of cutting edge 24, is carried out. When viewed from the perspective shown in FIG. 3, plane 56 defines a shortest imaginary connecting line running through a radially outer point of the cutting edge and the rotational axis and enclosing a smallest angle in a range of 80° to 90° with the reference surface.

(25) FIGS. 5 and 6 show a particularly simple embodiment, in which each of the cutting plates are held in base body 14 only by clamping screw 22 without additional elements. Again here, by an eccentric screw-through, the radial clamping of reference surface 34 is achieved against positioning surface 36.

(26) The embodiment of FIGS. 7 and 8 is optimized so that cutting plates 18 are not weakened by transverse openings for clamping screws, but are clamped by the segments of an annular leaf spring 58 in their respective plate seats in base body 14. This solution can also reduce the manufacturing- and assembly costs. Leaf spring 58 is axially clamped by central screw 60, in which the spring segments are held in plate seats 20 by lugs 62. The redundancy in more than three cutting plates 18 as well as geometric deviations are compensated by “spring deflection.”

(27) FIGS. 9 to 16 show various embodiments with cutting plates 18 formed as turning cutting plates. These each have two cutting edges 24, which are alternately engageable by loosening the clamping screw and suitably turning the cutting plate. An exact radial positioning is guaranteed despite coating 32 in that each cutting edge 24 is assigned to a reference surface 34, which can be brought into contact with positioning surface 36 on base body 14.

(28) To maintain tight tolerances, cutting plates 18 can be wholly or partially ground. In another procedure, the diameter accuracy is increased in that the cutting plates are mounted on base body 14 and machine tool 10 is ground to the desired diameter, rotating around rotational axis 12. Cutting plates 18 are then removed again in a next step for coating. In this procedure, during the grinding process, the expected oversize needs to be maintained in the grinding size by the subsequent coating.

(29) While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.