Method and machine tool for producing a dressing tool, and dressing tool

Abstract

The invention proposes a method for producing a dressing tool (102). The method comprises selecting a dressing tool specification in dependence on requirements in terms of profile complexity and profile accuracy of a grinding wheel to be dressed, selecting a wire material and a wire diameter of an eroding wire (112) in dependence on the selected dressing tool specification, defining eroding parameters of the eroding wire (112) in dependence on the selected dressing tool specification, defining a movement profile of the eroding wire (112) in dependence on the selected dressing tool specification, rotating the dressing tool (102) about an axis of rotation (106), moving an eroding wire (112) at least in a first direction (120) parallel to the axis of rotation (106) and in a second direction (122) perpendicular to the axis of rotation (106) in dependence on the defined movement profile, and applying an electrical voltage to the eroding wire (112) in dependence on the defined eroding parameters. The invention also proposes a machine tool (100) for producing a dressing tool (102). In addition, there are systematic strategies for setting the profiling conditions in dependence on the requirements of the grinding process (profile shape and accuracy).

Description

[0001] METHOD AND MACHINE TOOL FOR PRODUCING A DRESSING TOOL AND DRESSING TOOL

[0002] Technical area

[0003] The present invention relates to a method and a machine tool for producing a dressing tool.

[0004] Technical background

[0005] The increasing demand for high-precision parts and cutting tools is leading to a high demand for profiled grinding wheels as the most efficient machining tools for precision machining. Diamond dressing tools are known as productive tools for conditioning grinding wheels. Diamond dressing tools consist of bonded diamond abrasive grains in a metallic bond matrix. This constellation of components is also evident in metal-bonded grinding tools. However, the key distinguishing features between diamond dressing tools and metal-bonded grinding tools lie in the grain sizes and specifications used, the required manufacturing tolerances, and the specific manufacturing processes for the production of dressing tools, which differ from those for grinding tools.Accordingly, the corresponding objects, grinding tools and dressing tools, must be clearly defined and distinguished from one another in technical terms. Even with conventional methods based primarily on sintering and vacuum brazing technology, the manufacturing methods of both objects differ, and it is precisely these differences that determine the significantly different application requirements and market values ​​of a grinding tool compared to a dressing tool. The conventional production of diamond dressing tools is accordingly associated with high costs and processing times. The workpiece quality and the efficiency of the grinding process are directly dependent on the dressing tool used in the process, as the surface topography of the grinding wheel, grinding wheel wear, and grinding forces and temperatures are all related to this. Furthermore, the profile accuracy of the dressing tool determines the dimensional and geometric tolerances of the workpiece.Various methods for manufacturing diamond dressing tools have been presented in the literature, with mechanical machining being the most commonly used method in industry.

[0006] The machining of dressing tools depends on the geometry of the desired profile and the dresser's specifications. A wide variety of profiles is required in the industry. The machining of dressing tools is an extremely time-consuming and costly process, which also results in extreme wear and tear on the tools used.

[0007] Depending on the profile shape, grit size, and concentration of the diamond dressing tool, a profile deviation occurs between the profile on the dressing tool and the workpiece. This can lead to shape and dimensional inaccuracies of the workpiece and may need to be compensated. In mechanical machining, compensating for the profile deviation is very time-consuming and requires considerable effort to achieve the desired profile with the required tolerances on the dressing tool. This process involves several measuring and machining cycles, which are predominantly implemented and controlled manually.

[0008] Despite the numerous advantages of state-of-the-art machine tools and methods for manufacturing dressing tools, they still have potential for improvement. For example, there are many challenges in conditioning superabrasive grinding wheels, which cause high wear on the dressing tools. Therefore, the development of a new generation of dressing tools has recently been promoted. Dressing tools with diamond grains, PCD or CVD segments, or a mixture of diamond grains with PCD or CVD inserts in a metallic or hybrid bond are examples of such dressing tools. Although the use of this generation of dressing tools leads to a reduction in dressing tool wear, machining such tools (with the usual accuracy requirements) is a major challenge.This results in high demands on an efficient process for the production of form and profile rollers (form dressing wheels). Diamond form and profile rollers are traditionally manufactured using infiltration, negative, or positive electroplating processes. However, these manufacturing processes have significant disadvantages, including long development and delivery times and considerable costs.

[0009] Object of the invention

[0010] It would therefore be desirable to design a metal-bonded diamond dressing tool, as well as to provide a corresponding machine tool and an alternative method for manufacturing this dressing tool, which at least largely avoid the disadvantages of known machine tools and a method for mechanically manufacturing a dressing tool. In particular, the invention is intended to enable the productive manufacture of diamond dressing tools (stationary and rotating) with high profile accuracy (a few pm) and wear resistance. Among other things, the invention enables users to independently implement the development steps, at least for the development phase of a grinding product, which generally corresponds to a multitude of adjustment and compensation cycles, with a significant reduction in production time and costs.Furthermore, diamond grinding tools with metallic or hybrid-metallic bond, medium grain size and high concentration, which are commercially available and cheaper as dressing tools, can be used as the basis for the dressing tool to be developed.

[0011] General description of the invention

[0012] This problem is addressed by a novel dressing tool in combination with a machine tool and a method having the features of the independent patent claims. Advantageous further developments, which can be implemented individually or in any combination, are presented in the dependent claims. The term "novel" refers to the innovative methodology used to manufacture the dressing tool with the application-specific specifications (grain size, concentration, and profile shape).

[0013] In the following, the terms "have", "have", "comprise" or "include" or any grammatical variations thereof are used in a non-exclusive manner. Accordingly, these terms can refer both to situations in which, apart from the features introduced by these terms, no further features are present, or to situations in which one or more further features are present. For example, the expression "A has B", "A has B", "A comprises B" or "A includes B" can refer both to the situation in which, apart from B, no further element is present in A (i.e., a situation in which A consists exclusively of B), and to the situation in which, in addition to B, one or more further elements are present in A, for example element C, elements C and D, or even further elements.

[0014] Furthermore, it should be noted that the terms "at least one" and "one or more," as well as grammatical variations of these terms, when used in connection with one or more elements or features and intended to express that the element or feature may be provided singly or multiple times, are generally used only once, for example, when the feature or element is first introduced. When the feature or element is subsequently mentioned again, the corresponding term "at least one" or "one or more" is generally no longer used, without limiting the possibility that the feature or element may be provided singly or multiple times.

[0015] Furthermore, the terms “preferably”, “in particular”, “for example” or similar terms are used hereinafter in connection with optional features, without limiting alternative embodiments. Thus, features introduced by these terms are optional features, and these features are not intended to limit the scope of the claims and in particular the independent claims. Thus, as those skilled in the art will recognize, the invention can also be carried out using other embodiments. Similarly, features introduced by “in one embodiment of the invention” or by “in an embodiment of the invention” are understood to be optional features, without limiting alternative embodiments or the scope of the independent claims.Furthermore, these introductory expressions are intended to leave untouched all possibilities of combining the features introduced thereby with other features, whether optional or non-optional.

[0016] In a first aspect of the present invention, a method for manufacturing a dressing tool is proposed. The method comprises the following steps:

[0017] Selecting a dressing tool specification for a grinding wheel to be dressed depending on the requirements for shape and profile complexity and accuracy,

[0018] - Selecting a wire material and a wire diameter of an EDM wire depending on the selected dressing tool specification - Defining EDM parameters of the EDM wire depending on the selected dressing tool specification,

[0019] - Defining a movement profile of the EDM wire depending on the selected dressing tool specification,

[0020] - Rotating the dressing tool around a rotation axis,

[0021] - moving the eroding wire at least in a first direction parallel to the rotation axis and in a second direction perpendicular to the rotation axis depending on the defined movement profile, and

[0022] - Applying an electrical voltage to the erosion wire depending on the defined erosion parameters.

[0023] In other words, the dressing tool specification is first selected. The dressing tool specification is selected based on the requirements for the shape or profile complexity and accuracy of a grinding wheel to be dressed using the dressing tool. This involves a design and material selection for the dressing tool to be manufactured, which are based on the profile shape and profile accuracy of the grinding wheel to be dressed using the dressing tool. Next, a wire material and wire diameter are selected, the erosion conditions and parameters are set and programmed, and feed strategies are developed based on the dressing tool specification and profile requirements.Finally, the dressing tool is manufactured according to the selected dressing tool specification, using EDM parameters and feed strategies. The EDM wire follows a predefined movement profile and is operated with respect to the level and duration of the applied electrical voltage. This provides a productive process for manufacturing dressing tools (stationary and rotating) with high profile accuracy (to within a few microns). This invention facilitates the production of dressing tools, allowing profiles with complex geometries to be manufactured with high precision. This invention is suitable for all conductive bond materials of dressing tools. This invention overcomes the obstacles inherent in mechanical manufacturing.Furthermore, this invention makes it possible to produce a new generation of precise dressing tools with high adaptability and flexibility, low wear rates, and high profile accuracy. Wire electrical discharge (WED) profiling can significantly reduce machining time compared to mechanical processes. WED profiling offers an excellent opportunity to achieve optimal grain protrusion and microtopography on the surface of the dressing tools. The EDM wire can be oriented essentially perpendicular to the rotation axis. The components are arranged so that WED sparks can be supplied and the wire can be moved perpendicular to the rotation axis over the dressing tool. The choice of WED parameters and conditioning strategy depends on the topography requirements and profile specifications.This method allows the production of various profiles and small radii (depending on the wire diameter for the interior). A substantially perpendicular orientation of the EDM wire to the rotation axis is defined as an orientation that deviates from a perfectly perpendicular orientation by no more than 15°.

[0024] The method may further comprise synchronizing and controlling the rotation of the dressing tool and the movement of the EDM wire. Thus, the method allows for automated production of the dressing tool.

[0025] The method may further comprise moving the EDM wire according to at least one predetermined movement profile. This allows the dressing tool to be specifically manufactured with a desired profile.

[0026] The movement profile can be adapted to the profile of the dressing tool to be produced. Thus, the movement of the EDM wire follows the desired profile shape.

[0027] The method may further include varying a relative angle to the dressing tool. This allows for targeted control of the material removal.

[0028] The method may further comprise rotating the dressing tool in a dielectric bath, which may be filled with a liquid dielectric, and at least partially moving the EDM wire in the dielectric bath. Such a dielectric prevents excessive heating of the dressing tool.

[0029] The dielectric used is preferably a specially formulated hydrocarbon- or deionized water-based fluid with specifically adjusted conductivity values ​​between 2 and 50 pS / cm at 20°C. These properties optimize the discharge conditions and improve the material removal rate.

[0030] Preferably, the machine tool is equipped with a program-controlled dielectric flow system, which can be adjusted between 0.5 and 50 rpm depending on the machining phase. This contributes to significantly improving the profile accuracy and service life of the dressing tools.

[0031] The liquid dielectric can be deionized water or an EDM oil. The different dielectrics influence the properties of the WED conditioning. In water-bath WED machines, only the conductive bonding material can be directly influenced by an electrical discharge. In contrast, the discharge in oil-bath WED machines affects the diamond grains. The advantage of this process is the high profile accuracy for dressing tools with large grain sizes. Oil-bath machines can reduce the height difference between the grains to achieve high profile accuracy. Achieving the same profile accuracy in a water-bath WED machine is difficult.

[0032] Alternatively, the method may further comprise rotating the dressing tool in a gas atmosphere and at least partially moving the EDM wire in the gas atmosphere.

[0033] With this type of dry EDM, vibration of the EDM wire is minimal due to the negligible process reaction force. Furthermore, the gap distance is smaller than with conventional machine tools that use a liquid dielectric bath, and there is no corrosion of the workpiece. Thus, high EDM accuracy can be achieved.

[0034] The process may further include adapting the diameter of the EDM wire to the dressing tool, and in particular to the desired profile of the dressing tool. WED conditioning thus offers an excellent opportunity to achieve optimal grain projection and microtopography on the surface of the dressing tools, as well as sharp-edged inner contours up to an inner radius of 20 μm.

[0035] The dressing tool can comprise electrically non-conductive diamond grains, electrically conductive diamond grains, PCD segments, and / or doped CVD segments. The new generation of dressing tools comprises a cylindrical body with built-in CVD and PCD inserts in the outer diameter in the radial direction. The key advantage of this tool is its high profile retention (low wear). However, profiling the dressing tool in question is also challenging. The invention can also be used for profiling and reprofiling these dressing tools. WED conditioning results in a high-precision profile with sharp cutting edges for the PCD or doped CVD segments. Electrically conductive PCD or CVD segments can also be machined.WED conditioning can significantly reduce machining time compared to mechanical processes for both metal- and hybrid-bonded diamond dressing tools, as well as for dressing tools with CVD / PCD inserts. This new process enables the production of more complex dressing tools. The greatest wear on dressing tools occurs at the sharp outer radii or corners. The PCD or CVD inserts on the outer corners of the profile or edges increase the wear resistance of the dressing tool. These dressing tools can be manufactured using WED conditioning.

[0036] The procedure can be computer-implemented. This allows the procedure to be carried out under computer control, reducing costs by eliminating personnel costs.

[0037] According to a further aspect of the present invention, a machine tool for producing a dressing tool is proposed. The machine tool has a clamping device for holding a dressing tool. The clamping device is designed to rotate the dressing tool about a rotational axis. The machine tool further has a wire feed device. The wire feed device has an erosion wire and a movement device for moving the erosion wire at least in a first direction parallel to the rotational axis and in a second direction perpendicular to the rotational axis. The machine tool further has a voltage source for applying an electrical voltage to the erosion wire. The machine tool further has a controller.The controller is designed to define a movement profile of the erosion wire as a function of a selected dressing tool specification, to define a movement profile of the erosion wire as a function of the selected dressing tool specification, to move the erosion wire at least in the first direction and in the second direction as a function of the defined movement profile, and to control the electrical voltage applied to the erosion wire as a function of the defined erosion parameters.

[0038] This machine tool enables a productive process for the manufacture of dressing tools (stationary and rotating) with high profile accuracy (to within a few microns). This invention facilitates the production of dressing tools, allowing profiles with complex geometries to be produced very precisely and very quickly. This invention is suitable for all conductive bond materials for dressing tools. This invention overcomes the obstacles inherent in mechanical manufacturing. Furthermore, it makes it possible to produce a new generation of precise dressing tools with low wear rates and high profile accuracy. Wire EDM profiling can significantly reduce machining time and costs compared to mechanical processes. WED conditioning offers an excellent opportunity to achieve optimal grain protrusion and microtopography on the surface of the dressing tools.

[0039] The clamping device is preferably a high-precision clamping device that allows the dressing tool to be fixed rotationally symmetrically with a radial runout of less than 2 pm. This ensures precise machining and prevents form errors that could arise from misalignment.

[0040] The control system is preferably an advanced wire control system for highly concentrated superabrasive grains. The machine tool features a wire feed device with adaptive wire tension control between 1 N for roughing or small wire diameters of 30 μm and 20 N for finishing or large wire diameters of 250 μm to minimize wire vibration during EDM. This enables effective machining of dressing rolls with grain concentrations above CI 75 without the need for a wire guide system.

[0041] The machine tool allows for the use of specially optimized EDM parameters for highly concentrated superabrasive grains. The machine preferably uses adaptive discharge energy adjustment: 10 pJ for finishing or fine wire diameters of 30 pm - 8 mJ for roughing or coarse wire diameters of 250 pm, and pulse durations between 0.1 and 2 ps to prevent diamond grains from falling out of the metal matrix. This enables subsequent reprofiling of dressing rolls with minimal material loss.

[0042] The machine tool allows for automated process monitoring. The machine tool is preferably equipped with a closed-loop control system that measures and adjusts the machining parameters in real time.

[0043] The clamping device can have a spindle that defines the rotational axis. In this case, a WED (Wire Electrical Discharge) machine is equipped with a rotary axis. To achieve the highest profile accuracy on the grinding product and avoid the positioning errors associated with reclamping the dressing tool, the rotary axis can have the same standard grinding interface (HSK, etc.) as the grinding machine's dressing spindle. Accordingly, the dressing tool can be transferred directly from the EDM system to the grinding machine on its mounting fixture.

[0044] The EDM wire can be oriented essentially perpendicular to the rotational axis. The components are arranged to allow WED sparks to be applied and the wire to be moved perpendicular to the rotational axis over the dressing wheel. The choice of WED parameters and conditioning strategy depends on the dressing tool specifications, topographical requirements, and profile specifications. This method allows for the production of various shapes and profiles, including small radii (depending on the wire diameter for the internal area).

[0045] The control system can be configured to control the movement device. This allows the machine tool to allow automated conditioning of the dressing tool.

[0046] The control system can be CNC. The use of high-precision CNC-controlled WED machines that follow the profile path eliminates the need for complex profile evaluation and compensation. Furthermore, the process guarantees high profile accuracy of the dressing tools due to the constant wire feed, which ensures virtually wear-free tools.

[0047] The control system can be designed to synchronize and control the clamping device and the movement device. This allows the movements of the holding device and the movement device to be precisely coordinated.

[0048] The movement device can be designed to move the EDM wire according to at least one predetermined movement profile. This allows the dressing tool to be specifically conditioned with a desired profile.

[0049] The movement profile can be adapted to the profile of the dressing tool to be produced. Thus, the movement of the movement device follows the desired profile shape.

[0050] The movement device can be designed to vary a relative angle to the dressing tool. This allows for targeted control of the material removal.

[0051] The machine tool can further comprise a dielectric bath. The dielectric bath can be filled with a liquid dielectric. The clamping device can be designed to rotate the dressing tool in the dielectric bath. The movement device can be designed to at least partially move the EDM wire in the dielectric bath. Such a dielectric ensures the generation of electrical sparks and prevents excessive heating of the dressing tool.

[0052] The liquid dielectric can be deionized water or an EDM oil. The different dielectrics influence the properties of the WED conditioning. In water-bath WED machines, only the conductive bonding material can be directly influenced by an electrical discharge. In contrast, the discharge in oil-bath WED machines affects the diamond grains. The advantage of this process is the high profile accuracy for dressing tools with large grain sizes. Oil-bath machines can reduce the height difference between the grains to achieve high profile accuracy. Achieving the same profile accuracy in a water-bath WED machine is difficult.

[0053] Alternatively, the clamping device can be designed to rotate the dressing tool in a gas atmosphere. The movement device can be designed to at least partially move the EDM wire in the gas atmosphere.

[0054] The diameter of the EDM wire can be adapted to the dressing tool and, in particular, to the desired profile of the dressing tool. WED conditioning thus offers an excellent opportunity to achieve optimal grain protrusion and microtopography on the surface of the dressing tools.

[0055] The dressing tool can comprise electrically non-conductive diamond grains, electrically conductive diamond grains, and / or PCD (polycrystalline diamond) segments and / or doped CVD (chemical vapor deposition) segments. The new generation of dressing tools comprises a cylindrical body with built-in CVD and PCD inserts in the outer diameter in the radial direction. The key advantage of this tool is its high profile retention (low wear). However, profiling the dressing tool in question is also challenging. The invention can also be used for profiling and reprofiling these dressing tools. WED conditioning results in a high-precision profile with sharp cutting edges on the PCD or CVD segments. Electrically conductive PCD or CVD segments can also be machined.WED conditioning can significantly reduce machining time compared to mechanical processes for both metal-bonded diamond dressing tools and dressing tools with CVD / PCD inserts. This new process enables the production of more complex dressing tools. The greatest wear on dressing tools occurs at the sharp outer radii or corners. The PCD or CVD inserts on the outer corners of the profile or edges increase the wear resistance of the dressing tool. These dressing tools can be manufactured using WED conditioning. Currently, no mechanical profiling methods are known for the reliable and cost-effective design of such innovative dressing tools, and existing products are largely still in the development phase.

[0056] The term "machine tool," as used herein, is a broad term to which its ordinary and customary meaning should be given, as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can refer, without limitation, in particular to a machine for conditioning dressing tools. The machine tool can, in particular, be designed as a wire-cutting machine, which can also be referred to as a WED machine.

[0057] The term "profiling," as used herein, is a broad term that should be given its usual and common meaning as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can refer, without limitation, in particular to the introduction of a predetermined profile into a dressing tool.

[0058] The term "dressing tool," as used here, is a broad term to which its usual and common meaning should be given, as understood by one skilled in the art. The term is not limited to a specific or adapted meaning. The term can, without limitation, refer in particular to a tool for dressing grinding wheels. Such a dressing tool can be a diamond dressing tool. Diamond dressing tools are used for the economical dressing of grinding wheels in various bond systems. Diamond dressing tools are used, for example, as single-point diamonds, multi-point diamonds, or diamond-studded dressing rolls, so-called diamond form rolls and diamond profile rolls. Dressing must be carried out under constant cooling, as diamonds are very heat-sensitive. Optimal cooling of the dresser and the dressing holder is therefore essential for a favorable dressing process.However, sudden cooling should be avoided due to the diamonds' susceptibility to cracking. Ideally, diamond dressing tools are mounted on the machine table, as this achieves the highest accuracy and eliminates the need for additional axes to control the tool. Diamond profile rollers are also used in mass production. These diamond dressing tools are produced in sintered or electroplated bond. Dressing ensures precise concentricity and a correct geometric shape of the grinding wheel. Dressing also serves to profile or re-profile a grinding wheel. It also serves to break out impurities and dull abrasive grains from the grinding wheel, thus exposing sharp abrasive grains. This reduces heat development during the grinding process and keeps the stock removal rate constant.Diamond dressing tools feature different diamond designs. Natural diamonds and synthetic diamonds are used. Synthetic diamonds are increasingly being used today. The materials used are MCD, doped CVD, and PCD. Their defined shape ensures consistent and reproducible quality throughout their entire service life.

[0059] The term "dressing tool specification," as used herein, is a broad term to which its ordinary and common meaning should be given, as understood by one skilled in the art. The term is not limited to a specific or adapted meaning. The term can, without limitation, refer in particular to selectable properties of the dressing tool. The selectable properties include, in particular, the material of the dressing tool, the grain size of the dressing tool, the grain concentration of the dressing tool, the shape or profile geometry of the dressing tool, and the dimensions of the dressing tool.

[0060] The term "erosion wire," as used herein, is a broad term to which its ordinary and customary meaning should be given, as understood by those skilled in the art. The term is not limited to any specific or adapted meaning. The term can refer, without limitation, in particular to a thin wire used in wire-cutting. In wire-cutting, the erosion wire is wound on a spool. From there, the wire is guided to the upper wire guide via deflection rollers and brake rollers, the so-called wire feed.Wire erosion (also known as wire cutting, spark erosion, or wire cutting) is a high-precision shaping manufacturing process (cutting method) for electrically conductive materials. It works according to the principle of spark erosion: A sequence of electrical voltage pulses generates sparks that transfer material from the workpiece (anode) to a continuous thin wire (cathode) and into the separating medium, the dielectric. The wire is then disposed of. The accuracy of the process is based on the fact that the spark always jumps at the point where the distance between the workpiece and wire is minimal. The erosion wire is wound on a spool and from there is guided via deflection rollers and the brake roller to the upper wire guide.The wire is pulled through the lower wire guide by two opposing drive rollers at a defined wire tension in the range of 5 to 25 Newtons and a speed of up to 25 m / min relative to the workpiece and then disposed of. The wire guides above and below the workpiece guide and support the wire and suppress vibrations. Furthermore, the wire guides serve to provide a defined deflection point during conical cutting. The workpieces are cut in a liquid dielectric. This usually consists of deionized water. However, some special machines also use EDM oil. Through constant flushing, the dielectric removes the resulting EDM waste from the cutting gap and cools the wire, which must absorb a high current due to its small cross-section. The wire must be positively polarized and the workpiece negatively polarized.This causes electromigration away from the workpiece, which is also relevant for material removal (metal ions are positively charged). In the subsequent cuts, the polarity can also be different or alternating. This depends on the technology of the respective machine manufacturer. If the EDM wire approaches the workpiece at a very close distance, an electric field forms at the point of the closest distance, in which positively and negatively charged ions are strongly accelerated. These ions form an ionized channel between the workpiece and electrode that conducts electricity. The ions now collide in the discharge channel, resulting in a visible spark. At the same time, a gas bubble forms from the evaporating dielectric and material (electrode and workpiece). The pressure in the gas bubble increases evenly, and plasma forms. The bubble expands until it is spatially bounded by the electrode and workpiece.The current is now interrupted by the initiation of the pulse pause, and the bubble implodes. The implosion tears molten material from the workpiece and also from the electrode. If the pulse pause is initiated too late (pulse duration too long), an arc can occur, which leads to a wire break. Brass is the most commonly used wire material. However, copper, tungsten, and steel are also increasingly being used. To increase cutting performance and precision, EDM wires are coated with zinc and other materials and / or thermally treated. The standard diameter is 0.25 mm in Europe and 0.2 mm in Asia. Due to the low tolerance (1 pm to 2 pm), EDM wires are available in the range 0.02 mm to 0.33 mm. The latest developments allow the use of two different wire diameters in one machining operation.The term "wire feed device" as used here is a broad term which should be given its ordinary and customary meaning as understood by a person skilled in the art. The term is not limited to a specific or adapted meaning. The term can, without limitation, refer in particular to a device which feeds an EDM wire relative to a workpiece. The EDM wire is wound on a spool and from there is guided via deflection pulleys and the brake pulley to the upper wire guide of the wire feed device. The wire is pulled relative to the workpiece by two opposing drive pulleys at a defined wire tension in the range of 5 to 25 Newtons and a speed of up to 25 m / min, through the lower wire guide and is then disposed of. The wire guides above and below the workpiece guide and support the wire and suppress vibrations.

[0061] Furthermore, within the scope of the present invention, a computer program is proposed which, when run on a computer or computer network, executes the method according to the invention in one of its embodiments.

[0062] Furthermore, within the scope of the present invention, a computer program with program code means is proposed for carrying out the inventive method in one of its embodiments when the program is executed on a computer or computer network. In particular, the program code means can be stored on a computer-readable data carrier and / or a computer-readable storage medium.

[0063] The terms "computer-readable medium" and "computer-readable storage medium," as used herein, may refer in particular to non-transitory data storage devices, such as a hardware data storage medium on which computer-executable instructions are stored. The computer-readable medium or the computer-readable storage medium may, in particular, be or include a storage medium such as a random-access memory (RAM) and / or a read-only memory (ROM).

[0064] Furthermore, within the scope of the present invention, a data carrier is proposed on which a data structure is stored which, after being loaded into a working and / or main memory of a computer or computer network, can execute the method according to the invention in one of its embodiments. Furthermore, within the scope of the present invention, a non-transient computer-readable medium is proposed, comprising instructions which, when executed by one or more processors, cause the one or more processors to carry out the method according to one of the embodiments described above or below, or to have it carried out, in particular by means of a controller.

[0065] Also proposed within the scope of the present invention is a computer program product with program code means stored on a machine-readable carrier in order to carry out the method according to the invention in one of its embodiments when the program is executed on a computer or computer network.

[0066] A computer program product is understood as a tradable product. It can, in principle, exist in any form, for example, on paper or a computer-readable data carrier, and can, in particular, be distributed via a data transmission network.

[0067] Finally, within the scope of the present invention, a modulated data signal is proposed which contains instructions executable by a computer system or computer network for carrying out a method according to one of the described embodiments.

[0068] With regard to the computer-implemented aspects of the invention, one, several, or even all method steps of the method according to one or more of the embodiments proposed here can be performed by means of a computer or computer network. Thus, in general, any of the method steps, including the provision and / or manipulation of data, can be performed by means of a computer or computer network. In general, these steps can comprise any of the method steps, excluding the steps that require manual work, for example, the provision of samples and / or certain aspects of performing actual measurements.

[0069] In summary, without limiting further possible embodiments, the following embodiments are proposed:

[0070] Embodiment 1: Method for producing a dressing tool, comprising selecting a dressing tool specification depending on requirements for profile complexity and accuracy of a grinding wheel to be dressed,

[0071] - Selecting a wire material and a wire diameter of an EDM wire depending on the selected dressing tool geometry,

[0072] - Defining the erosion parameters of the erosion wire depending on the selected dressing tool specification,

[0073] - Defining a movement profile of the EDM wire depending on the selected dressing tool specification,

[0074] - Rotating the dressing tool around a rotation axis,

[0075] - moving the eroding wire at least in a first direction parallel to the rotation axis and in a second direction perpendicular to the rotation axis depending on the defined movement profile, and

[0076] Applying an electrical voltage to the EDM wire depending on the defined EDM parameters.

[0077] Embodiment 2: Method according to the preceding embodiment, wherein the eroding wire is oriented substantially perpendicular to the axis of rotation.

[0078] Embodiment 3: Method according to one of the two preceding embodiments, further comprising synchronizing and controlling the rotation of the dressing tool and the movement of the erosion wire.

[0079] Embodiment 4: Method according to one of the preceding embodiments, further comprising moving the eroding wire according to at least one predetermined movement profile.

[0080] Embodiment 5: Method according to the preceding embodiment, wherein the movement profile is adapted to the profile of the dressing tool to be produced.

[0081] Embodiment 6: Method according to one of the preceding embodiments, further comprising varying a relative angle to the dressing tool.

[0082] Embodiment 7: Method according to one of the preceding embodiments, further comprising rotating the dressing tool in a dielectric bath, wherein the dielectric bath is filled with a liquid dielectric, and at least partially moving the eroding wire in the dielectric bath.

[0083] Embodiment 8: Method according to the preceding embodiment, wherein the liquid dielectric is deionized water or an erosion oil.

[0084] Embodiment 9: Method according to one of embodiments 1 to 6, further comprising rotating the dressing tool in a gas atmosphere and at least partially moving the eroding wire in the gas atmosphere.

[0085] Embodiment 10: Method according to one of the preceding embodiments, further comprising adapting a diameter of the eroding wire to the dressing tool and in particular to the profile of the dressing tool to be produced.

[0086] Embodiment 11: Method according to one of the preceding embodiments, wherein the dressing tool comprises electrically non-conductive diamond grains, electrically conductive diamond grains, PCD segments and / or doped CVD segments.

[0087] Embodiment 12: Method according to one of the preceding embodiments, wherein the method is computer-implemented.

[0088] Embodiment 13: A machine tool for producing a dressing tool, comprising a clamping device for receiving a dressing tool, wherein the clamping device is designed to rotate the dressing tool about a rotational axis, a wire feed device, wherein the wire feed device comprises an erosion wire and a movement device for moving the erosion wire at least in a first direction parallel to the rotational axis and in a second direction perpendicular to the rotational axis, a voltage source for applying an electrical voltage to the erosion wire, and a controller, wherein the controller is designed to define a movement profile of the erosion wire depending on a selected dressing tool specification,for moving the erosion wire at least in the first direction and in the second direction depending on the defined movement profile, and for controlling the electrical voltage applied to the erosion wire depending on the defined erosion parameters.

[0089] Embodiment 14: Machine tool according to the preceding embodiment, wherein the clamping device has a spindle, wherein the spindle defines the axis of rotation.

[0090] Embodiment 15: Machine tool according to one of embodiments 13 to 14, wherein the eroding wire is oriented substantially perpendicular to the axis of rotation.

[0091] Embodiment 16: Machine tool according to one of embodiments 13 to 15, wherein the controller is designed to control the movement device.

[0092] Embodiment 17: Machine tool according to one of embodiments 13 to 15, wherein the controller is a CNC controller.

[0093] Embodiment 18: Machine tool according to one of embodiments 13 to 17, wherein the controller is designed to synchronize and control the clamping device and the movement device.

[0094] Embodiment 19: Machine tool according to one of embodiments 13 to 18, wherein the controller is configured to independently control the clamping device and the movement device. Embodiment 20: Machine tool according to one of embodiments 13 to 18, wherein the movement device is configured to move the EDM wire according to at least one predetermined movement profile.

[0095] Embodiment 21: Machine tool according to the preceding embodiment, wherein the movement profile is adaptable to the profile of the dressing tool to be produced.

[0096] Embodiment 22: Machine tool according to one of embodiments 13 to 21, wherein the movement device is designed to vary a relative angle to the dressing tool.

[0097] Embodiment 23: Machine tool according to one of embodiments 13 to 22, further comprising a dielectric bath, wherein the dielectric bath is filled with a liquid dielectric, wherein the clamping device is designed to rotate the dressing tool in the dielectric bath, wherein the movement device is designed to at least partially move the eroding wire in the dielectric bath.

[0098] Embodiment 24: Machine tool according to the preceding embodiment, wherein the liquid dielectric is deionized water or an erosion oil.

[0099] Embodiment 25: Machine tool according to one of embodiments 13 to 22, wherein the clamping device is designed to rotate the dressing tool in a gas atmosphere, wherein the moving device is designed to at least partially move the eroding wire in the gas atmosphere.

[0100] Embodiment 26: Machine tool according to one of embodiments 13 to 25, wherein a diameter of the eroding wire is adaptable to the dressing tool and in particular to the profile of the dressing tool to be produced.

[0101] Embodiment 27: Machine tool according to one of embodiments 13 to 26, wherein the dressing tool can be produced from a commercially available and cheaper than dressing tools metal- or hybrid-metal-bonded diamond grinding tool with a medium grain and a high concentration, in particular as a starting form

[0102] Embodiment 28: Machine tool according to one of embodiments 13 to 27, wherein the dressing tool comprises electrically non-conductive diamond grains, electrically conductive diamond grains, PCD segments and / or doped CVD segments.

[0103] Short description of the characters

[0104] Further details and features will become apparent from the following description of exemplary embodiments, particularly in conjunction with the subclaims. The respective features can be implemented individually or in combination with one another. The invention is not limited to the exemplary embodiments. The exemplary embodiments are illustrated schematically in the figures. The same reference numerals in the individual figures designate identical or functionally identical elements, or elements that correspond to one another in terms of their functions.

[0105] In detail:

[0106] Figure 1 shows a machine tool for conditioning a dressing tool according to the present invention;

[0107] Figure 2 shows an exemplary functional representation of a functioning of the machine tool;

[0108] Figure 3 shows an exemplary comparison of a surface topography of a dressing tool produced according to the invention and a conventionally produced dressing tool before operation;

[0109] Figure 4 shows an exemplary comparison of a surface topography of a dressing tool produced according to the invention and a conventionally produced dressing tool after operation; and

[0110] Figure 5 shows an exemplary comparison of different surface values ​​of a dressing tool produced according to the invention and a conventionally produced dressing tool after profiling and after dressing.

[0111] Description of the embodiments

[0112] Figure 1 shows a machine tool 100 for producing a dressing tool 102 according to the present invention. The dressing tool 102 is, in particular, a cylindrical dressing roll. The dressing tool 102 can be produced from a commercially available and cheaper than dressing tools, metal- or hybrid-metal-bonded diamond grinding tool with a medium grain size and a high concentration (as a starting form). The dressing tool 102 can further comprise electrically non-conductive diamond grains, electrically conductive diamond grains, PCD segments, and / or doped CVD segments that are oriented radially with respect to an axis of symmetry of the dressing tool. The machine tool 100 has a clamping device 104 for holding the dressing tool 102. The clamping device 104 is designed to rotate the dressing tool 102 about a rotation axis 106. The clamping device 104 has a spindle 108.The dressing tool 102 can be arranged and held on the spindle 108. The spindle 108 defines the rotation axis 106.

[0113] The machine tool 100 further comprises a wire feed device 110. The wire feed device 110 comprises an erosion wire 112. The erosion wire 112 is wound on a spool (not shown in detail). From there, the erosion wire 112 is guided via deflection rollers and brake rollers of a lower wire guide 114 to an upper wire guide 116. The erosion wire 112 is oriented substantially perpendicular to the axis of rotation 106. A diameter of the erosion wire 112 can be adapted to the dressing tool 102 and, more precisely, to the profile of the dressing tool 102 to be produced. The wire feed device 110 further comprises a movement device 118 for moving the erosion wire 112 at least in a first direction 120 parallel to the axis of rotation 106 and in a second direction 122 perpendicular to the axis of rotation 106. The movement device 118 is designed in particular to move the eroding wire 112 according to at least one predetermined movement profile.The movement profile can be adapted to the profile of the dressing tool 102 to be produced. The movement device 118 is further configured to vary a relative angle to the dressing tool 102. The machine tool 100 further comprises a voltage source 124. The voltage source 124 is configured to apply an electrical voltage to the erosion wire 112. The electrical voltage can be applied to the erosion wire such that the workpiece in the form of the dressing tool 102 acts as the anode and the erosion wire acts as the cathode. The machine tool 100 can be manufactured, for example, by converting or retrofitting a conventional erosion machine with the clamping device 104 and the spindle 108.

[0114] The machine tool 100 further comprises a controller 126. The controller 126 is configured to define a movement profile of the EDM wire depending on a previously selected dressing tool specification. The controller 126 is further configured to define a movement profile of the EDM wire 112 depending on the selected dressing tool specification. The controller 126 is further configured to move the EDM wire 112 at least in the first direction and in the second direction depending on the defined movement profile. Furthermore, the controller 126 is configured to control the electrical voltage applied to the EDM wire 112 depending on the defined EDM parameters. In particular, the controller 126 is configured to control the movement device 118. The controller 126 is, in particular, a CNC controller 124.The controller 126 is configured to synchronize and control the clamping device 104 and the movement device 118. The controller 126 is configured to control the clamping device 104 and the movement device 118 independently of one another. In other words, the clamping device 104 and the movement device 118 can be controlled separately and independently, but synchronously.

[0115] The machine tool 100 further includes an optional dielectric bath 130. The dielectric bath 130 is filled with a liquid dielectric. The liquid dielectric is deionized water or an EDM oil. The clamping device 104 is configured to rotate the dressing tool 102 in the dielectric bath 130. The movement device 118 is configured to at least partially move the EDM wire 112 in the dielectric bath 130. Alternatively, the machine tool 100 can be configured for dry EDM. For example, the clamping device 104 can be configured to rotate the dressing tool 102 in a gas atmosphere, and the movement device 118 can be configured to at least partially move the EDM wire 112 in the dielectric bath 130.In a method for manufacturing the dressing tool 102, a dressing tool specification is first selected depending on the profile complexity and accuracy requirements of a grinding wheel to be dressed. In other words, it is previously determined which profile, material, grain, etc. the dressing tool to be manufactured must have in order to be able to produce a desired profile geometry and profile accuracy of a grinding wheel to be dressed. Then, erosion parameters of the erosion wire 112 are defined depending on the selected dressing tool specification. Furthermore, a movement profile of the erosion wire 112 is defined depending on the selected dressing tool specification. The definitions are made in and / or by the controller 126.In other words, the erosion conditions and parameters, as well as feed strategies, are set and programmed depending on the dressing tool specification and profile requirements in order to subsequently realize the profile complexity and accuracy of the grinding wheels using the dressing tool 102. The erosion parameters include, in particular, the erosion duration, the movement or feed speed of the erosion wire 112, the level of the electrical voltage applied to the erosion wire 112, the duration of the electrical voltage applied to the erosion wire 112, and the orientation of the erosion wire 112.

[0116] Furthermore, the dressing tool 102 is arranged on the spindle 108 of the clamping device 104 and held there. The dressing tool 102 is then rotated about the axis of rotation 106. The erosion wire 112 is oriented substantially perpendicular to the axis of rotation 106. In parallel, the erosion wire 112 is moved at least in a first direction 120 parallel to the axis of rotation 106 and in a second direction 122 perpendicular to the axis of rotation 106 depending on the defined movement profile. The movement of the erosion wire 112 thus takes place according to at least one predetermined movement profile that is adapted to the profile of the dressing tool 102 to be produced. During this process, an electrical voltage is applied to the erosion wire 112 depending on the defined erosion parameters. The resulting spark discharge leads to material removal on the dressing tool 102 at the point closest to the erosion wire 112.The rotation of the dressing tool 102 and the movement of the erosion wire 112 are synchronized and controlled by the controller 126. Depending on the profile to be produced, a relative angle to the dressing tool 102 can be varied. The rotation of the dressing tool 102 takes place in the dielectric bath 130. In addition, the erosion wire 112 is at least partially moved in the dielectric bath 130. Figure 2 shows an exemplary functional representation of a mode of operation of the machine tool 100. The axis of rotation 106 of the clamping device 104 is shown with a direction of rotation 132 indicated by way of example. The dressing tool 102 and the erosion wire 112 oriented relative thereto are also shown. By means of the erosion wire 112 moved relative to the dressing tool 102, a desired or target profile 134 of the dressing tool 102 is to be formed. The target profile 134 may, for example, comprise tooth-shaped or wave-shaped depressions 136.For this purpose, the erosion wire 112 is moved parallel to the rotational axis 106 and perpendicular to the rotational axis 106, as indicated, for example, by a wire path 138, i.e., a path along which the erosion wire 112 is moved. Initially, a coarse material removal can occur on the dressing tool 102, as indicated by a coarsely eroded region 140. Finally, a fine material removal can occur.

[0117] Figure 3 shows an exemplary comparison of the surface topography of a dressing tool 102 manufactured according to the invention and a conventionally manufactured dressing tool prior to operation. The left part of Figure 3 shows an exemplary surface topography 142 of a dressing tool 102 manufactured according to the invention. The right part of Figure 3 shows an exemplary surface topography 144 of a conventionally manufactured dressing tool 146. Both dressing tools 102, 146 have a wave-shaped profile 148. However, due to the conditioning of the dressing tool 102 according to the invention by means of wire erosion, a surface 150 of the dressing tool 102 produced according to the invention is provided with significantly smaller grains 152 of a few pm in size before operation than the surface 154 of the conventionally produced dressing tool 146, which has larger grains 156 of more than 400 pm in size.

[0118] Figure 4 shows an exemplary comparison of a surface topography of a dressing tool produced according to the invention and a conventionally manufactured dressing tool after operation. The left part of Figure 4 shows an exemplary surface topography 142 of a dressing tool 102 produced according to the invention. The right part of Figure 4 shows an exemplary surface topography 144 of a conventionally manufactured dressing tool 146. Both dressing tools 102, 146 have a wave-shaped profile 148. Due to the inventive production of the dressing tool 102 by wire EDM, a surface 150 of the dressing tool 102 produced according to the invention is provided, even after operation, with significantly smaller grains 152 of a few pm in size than the surface 154 of the conventionally manufactured dressing tool 146, which has larger grains 156 of more than 400 pm in size.A comparison of Figures 3 and 4 shows that the conventional roller dressing tools 146 have larger grain sizes. Wear of the conventional dressing tools 146 is lower after use than that of the dressing tool 102 manufactured according to the invention. However, the dressing tool 102 manufactured according to the invention can be very easily resharpened after changes in topography (wear).

[0119] Figure 5 shows an exemplary comparison of different surface values ​​of a dressing tool produced according to the invention and a conventionally produced dressing tool after profiling and after dressing.

[0120] The left part of Figure 5 shows the surface values ​​for a dressing tool 102 manufactured according to the invention after profiling or conditioning and after dressing or after a grinding operation. The right part of Figure 5 shows the surface values ​​for a conventionally manufactured dressing tool 146 after profiling and after dressing. Curve 158 represents the surface values ​​after profiling for a dressing tool eroded according to the invention. Curve 160 represents the surface values ​​after dressing for a dressing tool eroded according to the invention. Curve 162 represents the surface values ​​after profiling for a conventional dressing tool. Curve 164 represents the surface values ​​after dressing for a conventional dressing tool.

[0121] The surface values ​​are given on the y-axis in pm. The surface values ​​are Sa, Sk, Spk, and Svk.

[0122] Sa denotes the mean arithmetic height. This parameter is the extension of the line roughness parameter Ra (arithmetic mean) into the area. It is the magnitude of the height difference of each point compared to the arithmetic mean of the surface. This parameter is generally used to assess surface roughness.

[0123] Sk denotes the core height. This parameter is calculated as the difference between the heights at the areal material fraction values ​​of 0% and 100% on the equivalence line. Specifically, it is a value obtained by subtracting the minimum height from the maximum height of the core surface. Spk denotes the reduced peak height. This parameter represents the average height of the peaks above the core surface.

[0124] Svk denotes the reduced valley height. This parameter expresses the arithmetic mean of the reduced groove depth of the area-to-material ratio curve. This can be used, for example, to quantify the depth of the area where a liquid applied to the surface collects.

[0125] Figure 5 shows how the surface parameters of the surface topography of the dressing tool 102 are specifically changed with the method according to the invention compared to conventional dressing tools 146. While conventional dressing tools 146 have approximately identical surface values ​​Sa, Sk, Spk, and Svk after profiling and dressing, it can be seen that with the dressing tool 102 according to the invention, the surface values ​​Sa, Sk, Spk, and Svk become significantly smaller after dressing.

[0126] List of reference symbols

[0127] machine tool

[0128] Dressing tool

[0129] clamping device

[0130] axis of rotation

[0131] spindle

[0132] Wire feed device

[0133] Eroding wire lower wire guide upper wire guide

[0134] Movement device first direction second direction

[0135] Voltage source

[0136] steering

[0137] CNC control

[0138] Dielectric bath

[0139] Direction of rotation

[0140] Target profile

[0141] Deepenings

[0142] Wire path roughly eroded area

[0143] Surface topography of the dressing tool manufactured according to the invention

[0144] Surface topography conventionally manufactured dressing tool conventionally manufactured dressing tool wave-shaped profile

[0145] Surface dressing tool manufactured according to the invention smaller grains

[0146] Surface conventionally manufactured dressing tool larger grains

[0147] Surface values ​​after profiling of dressing tools eroded according to the invention

[0148] Surface values ​​after dressing with dressing tool eroded according to the invention

[0149] Surface values ​​after profiling with conventional dressing tool Surface values ​​after dressing with conventional dressing tool Sa mean arithmetic height

[0150] Sk core height

[0151] Spk peak height

[0152] Svk reduced valley height

Claims

Claims 1. A method for producing a dressing tool (102), comprising Selecting a dressing tool specification depending on the requirements for profile complexity and accuracy of a grinding wheel to be dressed, Selecting a wire material and a wire diameter of an EDM wire (112) depending on the selected dressing tool specification, Defining erosion parameters of the erosion wire (112) depending on the selected dressing tool specification, Defining a movement profile of the erosion wire (112) depending on the selected dressing tool specification, Rotating the dressing tool (102) about a rotation axis (106), Moving an eroding wire (112) at least in a first direction (120) parallel to the rotation axis (106) and in a second direction (122) perpendicular to the rotation axis (106) depending on the defined movement profile, and Applying an electrical voltage to the erosion wire (112) depending on the defined erosion parameters.

2. Method according to the preceding claim, wherein the eroding wire (112) is oriented substantially perpendicular to the axis of rotation (106).

3. Method according to one of the two preceding claims, further comprising synchronizing and controlling the rotation of the dressing tool (102) and the movement of the EDM wire (112).

4. Method according to one of the preceding claims, further comprising moving the EDM wire (112) according to at least one predetermined movement profile.

5. Method according to the preceding claim, wherein the movement profile is adapted to the profile of the dressing tool (102) to be produced.

6. Method according to one of the preceding claims, further comprising varying a relative angle to the dressing tool.

7. Method according to one of the preceding claims, further comprising rotating the dressing tool (102) in a dielectric bath (130), wherein the dielectric bath (130) is filled with a liquid dielectric, in particular deionized water, or an erosion oil, and at least partially moving the erosion wire (112) in the dielectric bath (130).

8. The method according to any one of claims 1 to 6, further comprising rotating the dressing tool (102) in a gas atmosphere and at least partially moving the eroding wire (112) in the gas atmosphere.

9. Method according to one of the preceding claims, further comprising adapting a diameter of the eroding wire (112) to the dressing tool and in particular to the profile of the dressing tool (102) to be produced.

10. Method according to one of the preceding claims, wherein the dressing tool comprises electrically non-conductive diamond grains, electrically conductive diamond grains, PCD segments and / or CVD segments.

11. Method according to one of the preceding claims, wherein the method is computer-implemented.

12. A machine tool (100) for producing a dressing tool (102), comprising a clamping device (104) for receiving the dressing tool (102), wherein the clamping device (104) is designed to rotate the dressing tool (102) about a rotational axis (106), a wire feed device (110) comprising an erosion wire (112) and a movement device (118) for moving the erosion wire (112) at least in a first direction (120) parallel to the rotational axis (106) and in a second direction (122) perpendicular to the rotational axis (106), a voltage source (124) for applying an electrical voltage to the erosion wire (112), and a controller (126) configured to define a movement profile of the erosion wire (112) depending on a selected dressing tool specification, move the erosion wire (112) according to the defined movement profile at least in the first and second directions, and control the electrical voltage applied to the erosion wire (112) depending on defined erosion parameters.

13. A diamond dressing tool (102) manufactured or producible by a method according to any one of claims 1 to 11.

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