Method for producing a green body and method for further processing the green body to form a machining segment

Abstract

Method for producing a green body for a machining segment (51) from a powdered or granular first matrix material (56) and first hard material particles (57), the machining segment being connected by an underside (61) to a basic body of a machining tool. The machining segment (51) has a projection (Δ) of the first hard material particles (57) on an upper side (62) opposite from the underside (61).

Claims

1-7. (canceled)

8. A method for producing a green body for a machining segment from a powdered or granular first matrix material and first hard material particles, the machining segment being connected by an underside to a basic body of a machining tool, the method comprising the following steps: applying a powdered or granular supporting material, the supporting material being different from the first matrix material; arranging the first hard material particles in the supporting material according to a defined particle pattern, the first hard material particles being partially arranged in the supporting material; and applying the first matrix material to the first hard material particles and the supporting material.

9. The method as recited in claim 8 wherein the supporting material has a melting temperature higher than the sintering temperature of the first matrix material.

10. The method as recited in claim 8 wherein the supporting material has a melting temperature lower than the sintering temperature of the first matrix material.

11. A method for forming a machining segment comprising: further processing the green body produced by the method as recited in claim 8 to form the machining segment.

12. The method as recited in claim 11 wherein the further processing includes compacting the green body under the action of pressure to define a compact body and further processing the compact body to form the machining segment.

13. The method as recited in claim 12 wherein the compact body is further processed to form the machining segment by free-form sintering or hot pressing.

14. The method as recited in claim 11 wherein the green body is further processed to form the machining segment by free-form sintering or hot pressing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Exemplary embodiments of the invention are described hereinafter with reference to the drawing. It is not necessarily intended for this to illustrate the exemplary embodiments to scale; rather, the drawing is produced in a schematic and/or slightly distorted form where this is useful for purposes of explanation. It should be taken into account here that various modifications and alterations relating to the form and detail of an embodiment may be undertaken without departing from the general concept of the invention. The general concept of the invention is not limited to the exact form or the detail of the preferred embodiment shown and described hereinafter or limited to subject matter that would be restricted compared to the subject matter claimed in the claims. For given dimensioning ranges, values within the stated limits should also be disclosed as limit values and should be able to be used and claimed as desired. For the sake of simplicity, the same reference signs are used hereinafter for identical or similar parts or parts having an identical or similar function.

[0023] In the drawing:

[0024] FIGS. 1A, B show two variants of a machining tool designed as a core drill bit;

[0025] FIGS. 2A, B show two variants of a machining tool designed as a saw blade;

[0026] FIG. 3 shows a machining tool designed as an abrasive disk;

[0027] FIG. 4 shows a machining tool designed as a cut-off grinding chain;

[0028] FIGS. 5A-C show a green body (FIG. 5A), which is compacted into a compact body (FIG. 5B) and is further processed to form a machining segment (FIG. 5C);

[0029] FIGS. 6A-D show the production of the green body of FIG. 5A by means of the method according to the invention for producing a green body;

[0030] FIGS. 7A, B show a green body (FIG. 7A), which is further processed to form a machining segment (FIG. 7B).

DETAILED DESCRIPTION

[0031] FIGS. 1A, B—show two variants of a machining tool designed as a core drill bit 10A, 10B. The core drill bit 10A shown in FIG. 1A is referred to below as the first core drill bit, and the core drill bit 10B shown in FIG. 1B is referred to as the second core drill bit; in addition, the first and second core drill bits 10A, 10B are both included under the term “core drill bit”.

[0032] The first core drill bit 10A comprises a number of machining segments 11A, a tubular basic body 12A and a tool fitting 13A. The machining segments 11A, which are used for core drilling, are also referred to as drilling segments, and the tubular basic body 12A is also referred to as a drilling shaft. The drilling segments 11A are fixedly connected to the drilling shaft 12A, for example by screwing, adhesive bonding, brazing or welding.

[0033] The second core drill bit 10B comprises an annular machining segment 11B, a tubular basic body 12B and a tool fitting 13B. The annular machining segment 11B, which is used for core drilling, is also referred to as a drilling ring, and the tubular basic body 12B is also referred to as a drilling shaft. The drilling ring 11B is fixedly connected to the drilling shaft 12B, for example by screwing, adhesive bonding, brazing or welding.

[0034] The core drill bit 10A, 10B is connected via the tool fitting 13A, 13B to a core drill and, in drilling operation, is driven by the core drill in a direction of rotation 14 about an axis of rotation 15. During the rotation of the core drill bit 10A, 10B about the axis of rotation 15, the core drill bit 10A, 10B is moved along a feed direction 16 into a workpiece to be machined, with the feed direction 16 running parallel to the axis of rotation 15. The core drill bit 10A, 10B creates a drill core and a borehole in the workpiece to be machined.

[0035] The drilling shaft 12A, 12B in the exemplary embodiment of FIGS. 1A, B is of a one-piece form and the drilling segments 11A and the drilling ring 11B are fixedly connected to the drilling shaft 12A, 12B. Alternatively, the drilling shaft 12A, 12B may be of a two-piece form, composed of a first drilling shaft section and a second drilling shaft section, with the drilling segments 11A and the drilling ring 11B being fixedly connected to the first drilling shaft section, and the tool fitting 13A, 13B being fixedly connected to the second drilling shaft section. The first and second drilling shaft sections are connected to one another via a releasable connection device. The releasable connection device takes the form for example of a plug-and-twist connection as described in EP 2 745 965 A1 or EP 2 745 966 A1. The design of the drilling shaft as a one-piece or two-piece drilling shaft has no influence on the structure of the drilling segments 11A or of the drilling ring 11B.

[0036] FIGS. 2A, B show two variants of a machining tool designed as a saw blade 20A, 20B. The saw blade 20A shown in FIG. 2A is referred to below as the first saw blade and the saw blade 20B shown in FIG. 2B is referred to as the second saw blade; in addition, the first and second saw blades 20A, 20B are both included under the term “saw blade”.

[0037] The first saw blade 20A comprises a plurality of machining segments 21A, a disk-shaped basic body 22A and a tool fitting. The machining segments 21A, which are used for sawing, are also referred to as sawing segments, and the disk-shaped basic body 22A is also referred to as a blade body. The sawing segments 21A are fixedly connected to the blade body 22A, for example by screwing, adhesive bonding, brazing or welding.

[0038] The second saw blade 20B comprises a plurality of machining segments 21B, an annular basic body 22B and a tool fitting. The machining segments 21B, which are used for sawing, are also referred to as sawing segments and the annular basic body 22B is also referred to as a ring. The sawing segments 21B are fixedly connected to the ring 22B, for example by screwing, adhesive bonding, brazing or welding.

[0039] The saw blade 20A, 20B is connected to a saw via the tool fitting and, in sawing operation, is driven by the saw in a direction of rotation 24 about an axis of rotation 25. During the rotation of the saw blade 20A, 20B about the axis of rotation 25, the saw blade 20A, 20B is moved along a feed direction, the feed direction running parallel to the longitudinal plane of the saw blade 20A, 20B. The saw blade 20A, 20B creates a sawing slit in the workpiece to be machined.

[0040] FIG. 3 shows a machining tool designed as an abrasive disk 30. The abrasive disk 30 comprises a number of machining segments 31, a basic body 32 and a tool fitting. The machining segments 31, which are used for abrasive removal, are also referred to as abrading segments, and the disk-shaped basic body 32 is also referred to as a pot. The abrading segments 31 are fixedly connected to the pot 32, for example by screwing, adhesive bonding, brazing or welding.

[0041] The abrasive disk 30 is connected via the tool fitting to a tool device and, in abrading operation, is driven by the tool device in a direction of rotation 34 about an axis of rotation 35. During the rotation of the abrasive disk 30 about the axis of rotation 35, the abrasive disk 30 is moved over a workpiece to be machined, the movement running perpendicular to the axis of rotation 35. The abrasive disk 30 removes the surface of the workpiece to be machined.

[0042] FIG. 4 shows a machining tool taking the form of a cut-off grinding chain 40. The cut-off grinding chain 40 comprises a number of machining segments 41, a number of basic bodies 42 in the form of links, and a number of connecting links 43. The machining segments 41, which are used for cut-off grinding, are also referred to as cut-off grinding segments, and the basic bodies 42 in the form of links are also referred to as driving links.

[0043] The driving links 42 are connected via the connecting links 43. In the exemplary embodiment, the connecting links 43 are connected to the driving links 42 via rivet bolts. The rivet bolts allow a rotation of the driving links 42 relative to the connecting links 43 about an axis of rotation which runs through the center of the rivet bolts. The machining segments 41 are fixedly connected to the driving links 42, for example by screwing, adhesive bonding, brazing or welding.

[0044] The cut-off grinding chain 40 is connected via a tool fitting to a tool device and, in operation, is driven by the tool device in a direction of rotation. During the rotation of the cut-off grinding chain 40, the cut-off grinding chain 40 is moved into a workpiece to be machined.

[0045] The production of a machining segment 51, which has hard material particles with a projection with respect to the matrix material on its upper side, takes place with the aid of the method according to the invention for the production of a green body and the method for further processing the green body to form a machining segment. In a first stage, a green body 52 is produced; in a second stage, the green body 52 is compacted to form a compact body 53 and, in a third stage, the compact body 53 is further processed to form the machining segment 51. Alternatively, a green body can be produced in a first stage and further processed to form the machining segment in a second stage.

[0046] FIGS. 5A-C show the green body 52 (FIG. 5A), the compact body 53 (FIG. 5B) and the machining segment 51 (FIG. 5C). The machining segment 51 is built up from a machining zone 54 and a neutral zone 55. The neutral zone 55 is required if the machining segment 51 is to be welded to the basic body of a machining tool and the combination of matrix material and basic body cannot be welded; in the case of weldable combinations of matrix material and basic body, there is no need for the neutral zone 55.

[0047] The machining zone 54 is built up from a powdered or granular first matrix material 56 and first hard material particles 57 which are arranged according to a defined first particle pattern, and the neutral zone 55 is built up from a powdered or granular second matrix material 59. The term “matrix material” covers all materials for building up machining segments in which hard material particles can be embedded. Matrix materials may consist of one material or be composed as a mixture of different materials. The term “hard material particles” covers all cutting agents for machining segments; these especially include individual hard material particles, composite parts made up of multiple hard material particles and coated or encapsulated hard material particles.

[0048] The machining segment 51 corresponds in structure and composition to the machining segments 11A, 21A, 21B, 31, 41; the machining segment 11B designed as a drilling ring differs from the machining segment 51 by its annular structure. The machining segments can differ from one another in the dimensions and in the curvatures of the surfaces. The structure of the machining segments is explained on the basis of the machining segment 51 and applies to the machining segments 11A, 21A, 21B, 31, 41.

[0049] The machining segment 51 comprises the first hard material particles 57, which are arranged in the first matrix material 56. “First hard material particles” refer to those hard material particles of the machining segment 51 that machine a substrate, the number of the first hard material particles 57 and the defined first particle pattern according to which the first hard material particles 57 are arranged in the first matrix material 56 being adapted to the requirements of the machining segment 51. The first hard material particles 57 generally originate from a particle distribution which is characterized by a minimum diameter, a maximum diameter and an average diameter.

[0050] The machining segment 51 is connected by an underside 61 to the basic body of the machining tool. In the case of machining segments for core drilling and in the case of machining segments for abrasive removal, the underside of the machining segments is generally formed as planar, whereas the underside in the case of machining segments for sawing has a curvature in order to be able to fasten the machining segments to the curved end face of the annular or disk-shaped basic bodies. In the case of the machining segment 51 shown in FIG. 5C, the first hard material particles 57 have a projection A with respect to the first matrix material 56 on an upper side 62 opposite from the underside 61.

[0051] The green body 52 is built up in the upright structure from the first matrix material 56, the first hard material particles 57, the second matrix material 59 and a powdered supporting material 63. The supporting material 63 is different from the first matrix material 56 and serves for protecting the first hard material particles 57 on the upper side 62.

[0052] The green body 52 is compacted under the action of pressure between a first press punch 64, which forms the underside 61 of the machining segment 51, and a second press punch 65, which forms contacts the supporting material 63 to form the upper side 62 of the machining segment 51. The pressing direction of the first press punch 64 and the second press punch 65 runs parallel to the building-up direction of the green body 52. Examples of suitable methods for achieving an action of pressure on the green body 52 are cold-pressing methods or hot-pressing methods. In the case of cold-pressing methods, the green body 52 is exclusively subjected to an action of pressure, while in the case of hot-pressing methods the green body 52 is subjected not only to the action of pressure but also to an action of temperature up to temperatures of about 200° C.

[0053] The compact body 53 is further processed to form the machining segment 51 by free-form sintering or hot pressing. In the case of free-form sintering, there is an action of temperature on the compact body 53 and in the case of hot pressing there is an action of pressure and temperature. If the compact body 53 is further processed by free-form sintering, the green body 52 is compacted until the compact body 53 has substantially the final geometry of the machining segment 51. If the compact body 53 is further processed by hot pressing, the compact body 53 is shaped further during hot pressing.

[0054] The properties of the supporting material 63, in particular the melting temperature T.sub.melt, determine the behavior of the supporting material 63 during further processing. If the melting temperature T.sub.melt of the supporting material 63 is lower than the sintering temperature T.sub.sinter of the first matrix material 56, the supporting material 63 changes its powdered or granular state when it is heated up and liquefies before the first matrix material 56 is sintered; the liquid supporting material 63 can distribute itself in the first matrix material 56 during the sintering process and support the sintering process as an infiltrate. If the melting temperature T.sub.melt of the supporting material is higher than the sintering temperature T.sub.sinter of the first matrix material 56, the supporting material 63 remains in its powdered or granular state when it is heated up and can be removed from the finished machining segment without any problem after the sintering process.

[0055] FIGS. 6A-D show the production of the green body 52 by means of the method according to the invention for producing a green body. The green body 52 is built up from the first matrix material 56, the first hard material particles 57, the second matrix material 59 and the supporting material 63.

[0056] The green body 52 is produced in a number of steps: in a first step, a supporting layer 66 of the supporting material 63 is applied (FIG. 6A), it being possible for the supporting material 63 to be applied in one layer or in a number of layers. In a second step, the first hard material particles 57 are arranged in the supporting material 63 according to the defined first particle pattern (FIG. 6B), the first hard material particles 57 not being completely embedded in the supporting material 63 but having a projection with respect to the supporting material 63. In a third step, a first matrix layer 67 of the first matrix material 56 is applied to the supporting material 63 and the first hard material particles 57 (FIG. 6C), it being possible for the first matrix material 56 to be applied in one layer or in a number of layers. In a fourth step, a second matrix layer 68 of the second matrix material 59 is applied to the first matrix material 56 and the first hard material particles 57 (FIG. 6D), it being possible for the second matrix material 59 to be applied in one layer or in a number of layers. In the production of a green body for a machining segment without a neutral zone, there may be no need to apply the second matrix material 59.

[0057] FIGS. 7A, B show a further machining segment 71 produced by the method according to the invention for producing a green body and the method for further processing the green body to form the machining segment. The machining segment 71 is in this case produced in two stages: In a first stage, a green body 72 is produced (FIG. 7A) and, in a second stage, the green body 72 is further processed to form the machining segment 71 (FIG. 7B).

[0058] The machining segment 71 differs from the machining segment 51 of FIG. 5C by the fact that the machining segment 71 is built up from a machining zone 74 and does not have a neutral zone. The machining zone 74 is built up from a powdered or granular first matrix material 76, first hard material particles 77, which are arranged according to a defined first particle pattern, and second hard material particles 78.

[0059] Depending on the wear properties of the first matrix material 76, increased wear of the first matrix material 76 on the side surfaces of the machining segment 71 can occur during the machining of a substrate with the machining segment 71 as a result of friction with the substrate. This wear can be reduced by the second hard material particles 78.

[0060] In the case of the machining segment 71 shown in FIG. 7B, the second hard material particles 78 were arranged according to the defined second particle pattern in the first matrix material 76. Alternatively, the second hard material particles 78 may be admixed with the first matrix material 76 as randomly distributed particles.

[0061] The first hard material particles 77 and second hard material particles 78 generally originate from particle distributions which are characterized by a minimum diameter, a maximum diameter and an average diameter. In the exemplary embodiment of FIGS. 7A, B, the first hard material particles 77 originate from a first particle distribution with a first average diameter and the second hard material particles 78 originate from a second particle distribution with a second average diameter, the first average diameter being greater than the second average diameter. Alternatively, the first hard material particles 77 and second hard material particles 78 may originate from the same particle distribution and have the same average diameter.

[0062] The machining segment 71 is connected by an underside 81 to the basic body of a machining tool. A substrate is machined by first hard material particles 77, which are arranged on an upper side 82 opposite from the underside 81.

[0063] The green body 71 shown in FIG. 7A is built up in an upright manner from the first matrix material 76, the first hard material particles 77, the second hard material particles 83 and a powdered or granular supporting material 83. The supporting material 83 is different from the first matrix material 76 and serves for covering the first hard material particles 77 on the upper side 82. The state of the supporting material 83 is adapted to the state of the first matrix material 76, i.e. in the case of a powdered first matrix material 76 a powdered supporting material 83 is used and in the case of a granular first matrix material 76 a granular supporting material 83 is used.

[0064] The green body 72 is produced in a number of steps: in a first step, the supporting material 83 is applied (FIG. 7A), it being possible for the supporting material 83 to be applied in one layer or in a number of layers. In a second step, the first hard material particles 77 are arranged in the supporting material 83 according to the defined first particle pattern (FIG. 7B), the first hard material particles 77 not being completely embedded in the supporting material 83 but having a projection with respect to the supporting material 83. The production of the green body 72 ends with a sequence of a third and a fourth step, the sequence being carried out once or a number of times: in the case of the green body 72 of FIG. 7A, the sequence of the third and fourth steps is carried out three times. In the third step, the first matrix material 76 is applied and in the fourth step the second hard material particles 78 are arranged in the first matrix material 76 according to the defined second particle pattern.

[0065] The green body 72 is further processed to form the machining segment 71 by free-form sintering or hot pressing. In the case of free-form sintering, the green body 71 is subjected to a temperature effect, and in the case of hot pressing there is an effect of pressure and temperature. The properties of the supporting material 83, in particular the melting temperature T.sub.melt, determine the behavior of the supporting material 83 during further processing. If the melting temperature T.sub.melt of the supporting material 83 is lower than the sintering temperature T.sub.sinter of the first matrix material 76, the supporting material 83 changes its powdered or granular state when it is heated up and liquefies before the first matrix material 76 is sintered; the liquid supporting material 83 can distribute itself in the first matrix material 76 during the sintering process and support the sintering process as an infiltrate. If the melting temperature T.sub.melt of the supporting material 83 is higher than the sintering temperature T.sub.sinter of the first matrix material 76, the supporting material 83 remains in its powdered or granular state when it is heated up and can be removed from the finished machining segment without any problem after the sintering process.