Patent Application
20230294244
The present invention relates to a method for producing a green body and to a method for further processing a green body to form a machining segment.
Machining tools, such as core drill bits, saw blades, abrasive disks and cut-off grinding chains, comprise machining segments that are attached to a tubular, disk-shaped or annular basic body, the machining segments being connected to the basic body by welding, brazing or adhesive bonding. Depending on the machining method of the machining tool, machining segments that are used for core drilling are referred to as drilling segments, machining segments that are used for sawing are referred to as sawing segments, machining segments that are used for abrasive removal are referred to as abrading segments and machining segments that are used for cut-off grinding are referred to as cut-off grinding segments.
Machining segments for core drill bits, saw blades, abrasive disks and cut-off grinding chains are produced from a matrix material and hard material particles, where the hard material particles can be randomly distributed or are arranged according to a defined particle pattern in the matrix material. In the case of machining segments with randomly distributed hard material particles, the matrix material and the hard material particles are mixed, and the mixture is poured into a suitable mold and further processed to form the machining segment. In the case of machining segments with hard material particles arranged in a defined manner, a green body is built up in layers from matrix material, in which the hard material particles are arranged according to the defined particle pattern. In the case of machining segments that are to be welded to the basic body of the machining tool, the structure comprising a machining zone and a neutral zone has proven to be successful, since some combinations of matrix material and basic body cannot be welded. The machining zone is built up from a first matrix material and the neutral zone is built up from a second matrix material, which is different from the first matrix material and can be welded to the basic body.
Machining tools which can be designed as a core drill bit, saw blade, abrasive disk or cut-off grinding chain and are intended for the wet machining of concrete materials are only suitable to a limited extent for the dry machining of concrete materials. In the wet machining of concrete materials, an abrasive concrete sludge is produced, which is conducive to the machining process and leads to a self-sharpening of the machining segments during the machining. The matrix material is removed by the abrasive concrete sludge and new hard material particles are exposed. In the dry machining of concrete materials, no abrasive concrete sludge that could be conducive to the machining process can form. The hard material particles quickly become dull and the machining rate drops. Due to the lack of concrete sludge, the matrix material wears too slowly and deeper-lying hard material particles cannot be exposed.
For the dry machining of concrete materials, machining segments in which the first hard material particles on the upper side have a projection with respect to the first matrix material are required. It applies here that the machining rate that can be achieved with the machining segment is all the higher, the greater the projection of the first hard material particles. European patent application EP 3 670 041 relates to a method for producing a machining segment from a first matrix material and first hard material particles, which are arranged according to a defined first particle pattern. The method is distinguished by the fact that a green body in which the first hard material particles on the upper side have a projection with respect to the first matrix material is produced. The green body is further processed with a special press punch, which has depressions in a pressing region, the arrangement of the depressions corresponding to the defined first particle pattern of the first hard material particles.
The known method for producing a machining segment has the disadvantage that a special press punch with depressions in the pressing region is required for further processing the green body to form the machining segment that is used for compacting or hot pressing. A special press punch is required for each defined first particle pattern according to which the first hard material particles are arranged.
It is an object of the present invention to provide a method for producing a green body for a machining segment with which machining segments which have a projection of the hard material particles on the upper side can be produced. Conventional tool components are intended to be used both in the production of the green body and in the further processing of the green body to form the machining segment; it is intended to avoid the use of special tool components.
The method for producing a green body for a machining segment from a powdered or granular first matrix material and first hard material particles is characterized according to the invention by the following steps:
The method according to the invention for producing a green body is distinguished by the fact that the green bodies are built up upright, i.e. the building-up direction runs parallel to the vertical direction between the underside and upper side of the machining segment. The projection of the first hard material particles on the upper side of the machining segments is created by means of the powdered or granular supporting material, the supporting material being different from the first matrix material.
The term “supporting material” covers all materials for building up machining segments in which hard material particles can be embedded. The supporting material is in a powdered or granular form and is different from the first matrix material; it serves for embedding the hard material particles completely in powdered or granular material.
Green bodies which are produced by means of the method according to the invention for producing a green body can be further processed by means of known methods for further processing the green body to form machining segments. The known methods for further processing include compacting the green body by cold pressing or hot pressing to form a compact body, which is further processed to form the machining segment by free-form sintering or hot pressing, or further processing the green body by free-form sintering or hot pressing to form the machining segment.
Green bodies are further processed under the influence of temperature by free-form sintering or hot pressing to form the finished machining segment, the sintering temperature of the first matrix material, up to which temperature the green bodies or compact bodies must be heated, being set. The supporting material can retain its powdered or granular state (first variant) during the further processing of the green body to form the machining segment or it can support the sintering process as an infiltrate (second variant).
In a first variant, a supporting material with a melting temperature which is higher than the sintering temperature of the first matrix material is applied. If the melting temperature of the supporting material is higher than the sintering temperature of the first matrix material, the supporting material 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.
In a second variant, a supporting material with a melting temperature which is lower than the sintering temperature of the first matrix material is applied. If the melting temperature of the supporting material is lower than the sintering temperature of the first matrix material, the supporting material changes its powdered or granular state when it is heated up and liquefies before the first matrix material is sintered. The liquid supporting material can distribute itself in the first matrix material and support the sintering process as an infiltrate.
The invention also relates to a method for further processing a green body produced by the method for producing a green body to form a machining segment, which is connected by an underside to a basic body of a machining tool. In the case of a green body produced by the method according to the invention for producing a green body, the first hard material particles on the upper side have a projection with respect to the first matrix material.
In a first embodiment, the green body is compacted into a compact body under the action of pressure and the compact body is then further processed to form the machining segment. The green body is compacted into the compact body under the action of pressure between a first press punch, which forms the underside of the machining segment, and a second press punch, which forms the upper side of the machining segment.
It is particularly preferred for the compact body to be further processed to form the machining segment by free-form sintering or hot pressing. Since the first hard material particles in a green body produced according to the invention have been completely embedded in the powdered or granular supporting material, a conventional second press punch can be used for hot pressing, in order to form the upper side of the machining segment.
In a second embodiment, the green body is further processed to form the machining segment by free-form sintering or hot pressing. Since the first hard material particles in a green body produced according to the invention have been completely embedded in powdered or granular supporting material, a conventional second press punch can be used for hot pressing, in order to form the upper side of the machining segment.
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.
In the drawing:
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.
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.
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.
The drilling shaft 12A, 12B in the exemplary embodiment of
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
The properties of the supporting material 63, in particular the melting temperature Tmelt, determine the behavior of the supporting material 63 during further processing. If the melting temperature Tmelt of the supporting material 63 is lower than the sintering temperature Tsinter 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 Tmelt of the supporting material is higher than the sintering temperature Tsinter 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.
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 (
The machining segment 71 differs from the machining segment 51 of
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.
In the case of the machining segment 71 shown in
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
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.
The green body 71 shown in
The green body 72 is produced in a number of steps: in a first step, the supporting material 83 is applied (
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 Tmelt, determine the behavior of the supporting material 83 during further processing. If the melting temperature Tmelt of the supporting material 83 is lower than the sintering temperature Tsinter 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 Tmelt of the supporting material 83 is higher than the sintering temperature Tsinter 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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20181949.7 | Jun 2020 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/065614 | 6/10/2021 | WO |
