DEVICE FOR PERFORMING A MAGNETORHEOLOGICAL LIQUID WITH A MAGNETIC FIELD, SYSTEM AND METHOD FOR MACHINING A WORKPIECE BY MEANS OF THE MAGNETORHEOLOGICAL LIQUID

Description

[0001] The present application relates to a device for applying a magnetic field to a magnetorheological fluid. It further relates to a system and a method for machining a workpiece and / or tool using the magnetorheological fluid.

[0002] Microelectronic and mechanical systems (MEMS) have become prevalent in almost all technical fields, manufactured using microfabrication. Micromilling is a key component of microfabrication. It is a machining process with a geometrically defined cutting edge. Micromilling enables the production of precision components with high geometric diversity and a wide range of materials. Due to the requirements for dimensional and geometric accuracy of the generated components, special tool preparation is necessary for reliable machining. A central aspect of this tool preparation is the preparation of the cutting edges of micromilling tools. A variety of preparation methods are used for targeted cutting edge preparation, such as brushing, abrasive blasting, laser ablation, magnetic finishing, or immersion lapping.

[0003] Both the cutting edge preparation of micro-milling tools and micro-deburring share the challenge of preparing workpiece edges in a defined and reproducible manner. Due to the complex interrelationships of influencing factors such as motion kinematics, machining medium, and engagement conditions, achieving precise and requirement-compliant edge preparation has thus far been only partially successful.

[0004] From WO 94 / 04313 A1, a device and a method for polishing a workpiece using a magnetorheological fluid are known. Further devices and methods using magnetic or magnetorheological fluids are known from DE 102 44 867 A1, US 2018 / 200862 A1, US 2017 / 352460 A1, US 2 787 854 A, US 2013 / 273816 A1 and US 2 735 231 A.

[0005] The object of the present invention is therefore to propose a device that enables alternative, preferably improved, micromachining compared to the prior art, in particular improved cutting edge preparation. Furthermore, it is an object of the present invention to propose a corresponding system and a corresponding method that enables alternative, preferably improved, workpiece or tool machining. In particular, it may be an object of the present invention to improve the preparation of tools with diameters of 100 µm ≤ D ≤ 1,000 µm.

[0006] According to the invention, this problem is solved by a device, a system, and a method with the features of the corresponding independent claims. Possible embodiments and further developments are described in the dependent claims and the following description.

[0007] The proposed device is used to apply a magnetic field to a magnetorheological fluid. This allows a tool or workpiece located in the magnetorheological fluid to be machined.

[0008] The device comprises a container for receiving a magnetorheological fluid, having a preferably upwardly directed opening for at least partial immersion of the workpiece and / or tool into the magnetorheological fluid, a plurality of electromagnets arranged on the container for applying a magnetic field to the container, wherein each electromagnet comprises a magnetic conductor and a coil wound around the conductor as well as at least one power source electrically connected to the coils.

[0009] The device may be particularly suitable for being installed in or on a machine tool for the manufacture or processing of workpieces with functional characteristics in the micrometer range or tools with functional characteristics in the micrometer range.

[0010] The container is typically at least partially filled with a magnetorheological fluid. This is, in particular, an abrasive magnetorheological fluid. The magnetorheological fluid may, in particular, comprise a carrier oil, especially polyalphaolefin oil, and an abrasive medium, especially diamond, corundum, and / or silicon carbonate. Furthermore, the magnetorheological fluid may comprise stabilizing additives, for example, thixotropic agents, wetting and dispersing additives, and / or oxidation inhibitors. The magnetorheological fluid used may be enriched with abrasive diamond particles with a volume particle concentration of up to CA = 15%.

[0011] The container can be cuboid or cube-shaped. An interior space of the cube or cuboid is typically hollow to hold the magnetorheological fluid. In particular, an upper face of the cuboid or cube is open or contains an opening. In another embodiment, the container is rotationally symmetrical about its longitudinal axis and, in particular, has the shape of a hollow cylinder. This can have a circular base and be open at the top. In particular, an upper face of the cylinder or hollow cylinder is open or contains an opening.

[0012] The container walls can have a constant thickness or varying material thicknesses. The base plate of the container can have the same thickness as the wall thickness or a different thickness. Preferably, the container comprises PVC and / or another diamagnetic or paramagnetic material.

[0013] The wall thickness or base thickness of the container can be at least 0.5 mm, preferably at least 2 mm, particularly preferably at least 3 mm and / or can be at most 5 mm, preferably at most 4.5 mm, particularly preferably at most 4 mm.

[0014] The container can have a height, width, length, and / or base plate diameter of, in particular, at least 10 mm, preferably at least 20 mm, and particularly preferably at least 30 mm, and / or can have a height, width, length, and / or base plate diameter of, in particular, at most 200 mm, preferably at most 150 mm, and particularly preferably at most 120 mm. For example, the container can have a height, width, length, and / or base plate diameter of, in particular, 100 mm.

[0015] The device comprises a plurality of electromagnets. The electromagnets are typically identical in design. The electromagnets can be arranged on the container, preferably on the outside. At least one, some, or all of the plurality of electromagnets can be arranged on an exterior surface, in particular on an outer wall or several outer walls of the container. The electromagnet(s) can, for example, be glued and / or screwed to an outer wall or several outer walls of the container. Other fixing methods, such as clamps, are also conceivable. The outer walls, or the outer wall of the container, can have projections, in particular integral ones, which serve to hold the electromagnets, onto which the electromagnets can, for example, be attached. Preferably, the electromagnets are rigidly connected to the container.The respective coil of the electromagnets of the majority of electromagnets can be connected to the power source or to another power source.

[0016] The plurality of electromagnets comprises a first number of electromagnets in a first plane. The first plane is arranged perpendicular to the longitudinal axis of the container. In an example not covered by the invention, the first plane may also be arranged at an acute or obtuse angle to the longitudinal axis of the container. A second number of electromagnets is arranged in a second plane perpendicular to the longitudinal axis of the container. The second plane may be arranged parallel to the first plane. In an example not covered by the invention, the first and second planes may also intersect in a straight line. A third number of electromagnets is arranged in a third plane perpendicular to the longitudinal axis of the container. The third plane may be arranged parallel to the first and / or second plane. Further planes with electromagnets may be provided. Preferably, each plane comprises at least one pair of coils.

[0017] In one embodiment, at least one electromagnet is provided per level. More than one electromagnet can be provided, for example, at least two, three, four, five, or ten electromagnets per level. A large number of electromagnets per level can be provided, in particular up to 100, 50, 30, or 20 electromagnets per level. The number of electromagnets can be even or odd.

[0018] The system can have 1 to X levels of electromagnets, where X is a natural number. Specifically, it can have at least three, four, five, or ten levels of electromagnets. It can also have a maximum of 100, 80, 50, or 20 levels of electromagnets. The more levels of electromagnets there are, the more levels of the magnetorheological fluid can be individually controlled. The electromagnets within a level can be individually controlled. They can also be controlled with different or identical pulses. It is also possible for some electromagnets within a level to be controlled with one pulse and others with a second pulse.

[0019] According to the invention, a first combination of electromagnets can be subjected to a first pulse, while another combination of electromagnets can be subjected to a second pulse. Further combinations of electromagnets, subjected to further pulses, are possible. The combinations of electromagnets can each be located in the same plane and / or in different planes. For example, the first combination can comprise electromagnets arranged one above the other in different planes.

[0020] The majority of electromagnets can be arranged rotationally symmetrically around the longitudinal axis of the container. In particular, the electromagnets of one plane, for example the first and / or the second and / or the third plane, can be arranged rotationally symmetrically around the longitudinal axis of the container.

[0021] In one embodiment, the electromagnets of one plane are arranged one above the other and / or offset from the electromagnets of another plane. The electromagnets of one plane can be arranged one above the other and offset from the electromagnets of another plane. The first set of electromagnets and / or the second set of electromagnets and / or the third set of electromagnets can be arranged one above the other. The first set of electromagnets and / or the second set of electromagnets and / or the third set of electromagnets can be arranged offset from each other.

[0022] According to the invention, the current source for controlling the magnetic flux density is adjustable. The current source is configured to regulate an excitation frequency. The current source can be configured such that excitation frequencies of at least 5 Hz, at least 10 Hz, at least 20 Hz, or at least 30 Hz, preferably at least 40 Hz, and excitation frequencies of at most 150 Hz are adjustable. According to the invention, a frequency range of the excitation frequencies from 5 Hz ≤ f ≤ 150 Hz is adjustable.

[0023] It may be provided that the frequency ranges for each electromagnet are individually adjustable. For example, more than one adjustable power source may be provided for this purpose. One electromagnet can be connected to one power source. A second electromagnet can be connected to a second power source. Further electromagnets can each be connected to a power source. It may also be provided that one power source is connected to more than one electromagnet. A second power source can be connected to one or more further power sources. The power source(s) can each be adjustable as described above.

[0024] Controlling the excitation frequency of one or more electromagnets enables pulsed operation of the electromagnet(s). Pulsing can be used to reorient the abrasive media. This can increase machining efficiency and / or reduce flow dead zones. Pulsing can also or alternatively increase the fluid density or abrasive density at the machining point. Additionally or alternatively, pulsing can optimize chip removal and / or lead to improved material removal rates. Pulsing can also or alternatively improve the removal of worn carbonyl iron particles.

[0025] In one embodiment, the electromagnets of a plane can all be connected to a controllable current source. Alternatively, the electromagnets of a plane can each be connected to a different current source. Additionally or alternatively, at least one electromagnet of a plane can be connected to a current source and / or at least one electromagnet of the same plane can be connected to at least one other current source.

[0026] The electromagnets can be switched individually and with time delays. They can also be switched at different frequencies. This can have the advantage of achieving a locally specific and directed pressure change in the magnetorheological fluid.

[0027] At least one permanent magnet can also be arranged on the container, preferably on an outside of the container. The magnetorheological fluid can be subjected to a magnetic field by the permanent magnet. The magnetic fields of the electromagnet(s) and / or the permanent magnet(s) can superimpose.

[0028] The device is particularly suitable for use in a machine tool, for example a micro-milling machine tool.

[0029] The present application further relates to a system for machining a workpiece and / or tool, preferably a workpiece with functional features in the micrometer range, hereinafter referred to as a micro-workpiece, or a tool with functional features in the micrometer range, hereinafter referred to as a micro-tool, by means of a magnetorheological fluid.

[0030] The dimensions of a micro-workpiece and / or micro-tool can be characterized, in particular, by having an extent, for example along a longitudinal axis and / or along an axis perpendicular to the longitudinal axis, of a maximum of 10,000 µm, preferably a maximum of 5,000 µm, and particularly preferably a maximum of 2,000 µm. An extent, for example along a longitudinal axis and / or along an axis perpendicular to the longitudinal axis, can be a minimum of 50 µm, preferably a minimum of 80 µm, and particularly preferably a minimum of 100 µm. The maximum extent of the micro-workpiece or micro-tool along a straight line can be a maximum of 2,000 µm, preferably a maximum of 1,500 µm, and particularly preferably a maximum of 1,000 µm, and / or a minimum of 50 µm, preferably a minimum of 80 µm, and particularly preferably a minimum of 100 µm.

[0031] The system typically comprises a device as described above. Furthermore, the system includes a workpiece holder for receiving a workpiece and / or tool to be machined, in particular a micro-workpiece and / or micro-tool. The workpiece holder can be moved between a first and a second position such that the workpiece and / or tool is arranged in a first position outside an interior of the container, hereinafter referred to as the container interior, and in at least a second position is arranged partially within the container interior, in particular at least partially within a magnetorheological fluid arranged therein. The tool holder can also be moved to further positions.Preferably, the further positions are located such that in the further positions the workpiece and / or tool is partially located in the interior of the container, in particular at least partially in a magnetorheological fluid arranged therein.

[0032] The system can have at least one additional workpiece holder for simultaneously inserting two tools and / or workpieces into the interior of the container.

[0033] At least one workpiece holder can be moved along one axis, preferably along two axes, and particularly preferably along three axes. The axes can be perpendicular to each other. Additionally or alternatively, at least one or the same tool holder can be rotated about at least one axis and / or about at least two axes and / or about at least three axes.

[0034] In one embodiment, the system comprises a multi-axis robot, preferably a five-axis or six-axis robot. In particular, the workpiece holder, or at least one of the workpiece holders, can be arranged on the multi-axis robot. The multi-axis robot can, for example, be designed as an industrial robot comprising a robot arm.

[0035] Furthermore, the application relates to a method for machining a workpiece and / or tool, preferably a micro-workpiece or micro-tool, using a magnetorheological fluid.

[0036] The procedure comprises the following steps, which are preferably carried out in the following order. I. Providing a previously described system, II. Inserting, in particular clamping, a workpiece and / or tool into the workpiece holder, III. Moving the workpiece holder with the inserted workpiece and / or tool into a second position in which the workpiece and / or tool is at least partially immersed in the magnetorheological fluid, IV. Applying a magnetic field to the magnetorheological fluid arranged in the container, in particular by supplying at least one electromagnet with current via the power source.

[0037] In the first step, the container is preferably at least partially filled with a magnetorheological fluid. However, the container can also be filled with the magnetorheological fluid only after the second step.

[0038] In the second step, the workpiece holder is preferably located in a first position outside the container.

[0039] The workpiece / tool ​​can be moved within the container to create a relative velocity and thus material separation.

[0040] By applying a magnetic field to the magnetorheological fluid, the workpiece and / or tool located in the magnetorheological fluid can be machined.

[0041] The workpiece / tool ​​can be guided through the switched magnetorheological fluid, i.e., fluid subjected to a magnetic field. This allows for material separation. The magnetic field causes the magnetic particles in the magnetorheological fluid, such as iron particles, to align themselves along the magnetic field lines. These particles can then "hold" the abrasive particles in place. The switched magnetorheological fluid can remain stationary during this process.

[0042] Alternatively, the magnetorheological fluid and / or abrasive particles contained therein can be moved by applying the magnetic field, so that at least partial removal of a workpiece and / or tool surface is effected.

[0043] In one embodiment, the magnetorheological fluid can be subjected to a homogeneous or inhomogeneous magnetic field in the fourth process step. A homogeneous magnetic field can have the advantage of ensuring homogeneous material separation and thus homogeneous processing.

[0044] In one embodiment, step IV comprises changing the magnetic flux density of the magnetic field. In particular, the magnetic flux density can be changed by altering the applied current supplying the at least one electromagnet. Additionally or alternatively, different electromagnets of the plurality of electromagnets can be supplied with current simultaneously or sequentially. Preferably, at least two electromagnets are operated simultaneously as a coil pair. Different coil pairs can be operated sequentially.

[0045] In step IV, at least one electromagnet of the first and / or second and / or third level can be operated simultaneously. Preferably, at least two electromagnets of the first and / or second and / or third level can be operated simultaneously.

[0046] Depending on the requirements of the workpiece or tool being processed, different magnetic flux densities can be achieved, resulting in corresponding material removal or separation at the workpiece and / or tool surface. Depending on the intensity of the magnetic flux density, the surface of the workpiece and / or tool can be locally subjected to varying degrees of material removal and / or separation.

[0047] In one embodiment, the electromagnets in step IV can be operated in a pulsed manner, so that the magnetic field changes over time. This allows the magnetorheological fluid to be subjected to an inhomogeneous magnetic field, enabling the adjustment of a variable processing pressure PB depending on the immersion depth t of the workpiece or tool immersed in the magnetorheological fluid.

[0048] In one embodiment, particularly while the magnetorheological fluid is subjected to a magnetic field, the workpiece and / or tool can be guided through the magnetorheological fluid. This allows, for example, the immersion depth of the workpiece and / or tool to be varied. The workpiece and / or tool can be guided through the magnetorheological fluid along one or more translational axes. For example, it can be guided along a helical path. Additionally or alternatively, the workpiece and / or tool can be rotated in the magnetorheological fluid about at least one axis. The rotational speed in revolutions per minute (rpm) can be at least 10, preferably at least 100, particularly preferably at least 1,000 and / or at most 100,000, preferably at most 50,000, and particularly preferably at most 10,000.

[0049] In one version, an angle between a workpiece longitudinal axis and / or a tool longitudinal axis and the container longitudinal axis can be set before step IV is performed. Additionally or alternatively, an angle between a workpiece longitudinal axis and / or a tool longitudinal axis and the container longitudinal axis can be changed during step IV. This allows for targeted control of the material separation.

[0050] By moving the workpiece and / or tool within the magnetorheological fluid and / or varying the immersion depth and / or immersion angle, the prevailing pressure and flow conditions within the magnetorheological fluid can be influenced. This allows for the machining of individual edges.

[0051] In addition to or as an alternative to the geometric variation of the workpiece and / or tool's trajectory, the rheological properties of the magnetorheological fluids can be influenced by controlling the magnetic flux density B using the adjustable current source. This allows for pulsed machining, which can improve the machining result. The advantages of pulsed machining include shorter machining times and / or lower surface roughness.

[0052] To remove the tool or workpiece, the workpiece holder with the inserted workpiece and / or tool can be moved to a position outside the container, in particular to the first position.

[0053] The application possibilities of the process, the system, and the device include cutting edge preparation and virtually all machining operations requiring geometrically defined cutting edges. Cutting edge preparation is used in almost all technical fields, including dental and medical technology, the electrical industry, the optical industry, and mold and tool making. For example, the cutting edges of milling tools can be prepared for machining graphite tool electrodes. The resulting precision injection molds can then be used to manufacture highly complex and microstructured plastic components, such as endoscope lenses and micro gears. In addition to cutting edge preparation, another application is the deburring of the manufactured microcomponents.Both micro-machining and micro-injection molding result in fine burrs or injection points that must be removed for the component to function flawlessly. This can also be achieved with the described method, fixture, and / or system. Furthermore, post-processing of additively manufactured components is possible. Due to their layered structure, these components exhibit a higher average surface roughness (Ra) than conventionally manufactured components. The described method, fixture, and / or system can be used to smooth the surface and achieve a defined rounding of the edges.

[0054] The present application comprises several embodiments. The following detailed description shows and describes further exemplary embodiments of the invention. Accordingly, the drawings and the detailed description are to be considered illustrative and not limiting. Embodiments not covered by the claims below are intended to provide a better understanding of the invention.

[0055] They show Fig. 1 a system for machining a workpiece and / or tool using a magnetorheological fluid, Fig. 2 a schematic cross-sectional view through the container of the system Figure 1 , Fig. 2 schematic longitudinal section view through the container of the system of Figure 1 with micro-milling tool shown, Fig. 2c a schematic longitudinal section view through the container of the system of Figure 1with a micro-milling tool shown, as well as a comparison to immersion lapping, Fig. 3 a cross-sectional view of a device for applying a magnetic field to a magnetorheological fluid, and Fig. 4 the device according to Figure 3 in a longitudinal section.

[0056] Figure 1 Figure 100 shows a system for machining a workpiece and / or tool using a magnetorheological fluid 1. The system 100 is shown schematically, so dimensions and dimensional ratios may differ from actual dimensions. Furthermore, the individual components are not necessarily depicted realistically, but are essentially schematic for the purpose of explaining the function. The system 100 includes a device 10 for applying a magnetic field to the magnetorheological fluid.

[0057] For this purpose, the device 10 has a container 2 for receiving the magnetorheological fluid 1. The container 2 has a longitudinal axis L. Figure 1 The container 2 is shown in a section along its longitudinal axis L. The container 2 is essentially cuboid in shape, comprising side walls 21 and a base 22. The container 2 is open at the top, i.e., it has an opening 23 that corresponds essentially to the area of ​​the base 22. The side walls 21 and the base 22 define an interior space 24, which is at least partially filled with the magnetorheological fluid 1. The magnetorheological fluid 1 comprises a carrier oil, in this case a polyalphaolefin oil, with an abrasive medium 11, in this case diamond. The magnetorheological fluid 1 fills approximately 80% of the interior space 24 of the container.

[0058] An electromagnet 3 is arranged on the outside of the container. The electromagnet 3 comprises a magnetic conductor 31 and a coil 32 wound around the magnetic conductor 31. The magnetic conductor 31 comprises 11Smn30. The coil 32 comprises copper. The coil 32 typically has between 300 and 1,000 turns. The coil 32 is electrically connected to a power source 4. The power source 4 is adjustable, so the magnetic flux density of the electromagnet 3 can be controlled. Excitation frequencies f from 50 Hz to 150 Hz can be set using the adjustable power source 4.

[0059] Furthermore, the system 100 comprises a movable workpiece holder 5 in which a workpiece, in this case a micro milling tool 6, is clamped. The workpiece holder 5 is, in this case, a tool spindle of a 5-axis milling machine.

[0060] Recurring features are marked with the same reference symbols in the following figures for better clarity and comprehensibility.

[0061] In Figure 2a The container 2 is shown in a cross-section perpendicular to the longitudinal axis I. The container 2 is filled with the magnetorheological fluid 1. A path of motion 7 is schematically represented by arrows, showing how the micro-milling tool can be moved through the magnetorheological fluid 1 for cutting edge preparation. The movement along the path of motion 7 is achieved by moving the tool holder 5 along at least some of the five axes of the 5-axis milling machine. Furthermore, the micro-milling tool 6 is rotated about a longitudinal axis of the micro-milling tool 6 at a speed n S. In the example shown, the speed is, for instance, 10,000 rpm.

[0062] In Figure 2a Is container 2 the Figure 1 and 2ain a longitudinal section along the in Figure 2a The micro-milling tool 6 is shown on the line AA. It is positioned at an angle αE relative to the longitudinal axis L of the container. In this example, the angle is 45°, but it can be varied. In particular, the angle can also be varied during the cutting edge preparation process. Furthermore, the plunge depth TE is varied, so that in addition to the one shown in Figure 2a The depicted path of motion 7 in the horizontal plane corresponds to the path of motion 7' ​​in the vertical plane as shown in Fig. 2b The process is shown.

[0063] During the preparation of the micro milling cutter 6, it can be clamped directly into the spindle of the machine tool 5. This eliminates the need for subsequent tool re-clamping and saves a process step. The tool, in this case the micro milling cutter 6, is then moved within the magnetorheological fluid 1 using the drive axes of the machine tool, enabling even highly complex motion strategies. Furthermore, depending on the geometry of the workpiece being machined, the movement can be modified by varying the immersion depth TE and the immersion angle α E, thus influencing the prevailing pressure and flow conditions. This also allows for the machining of individual edges.In addition to geometrically varying the trajectory, the rheological properties of magnetorheological fluids can be influenced by controlling the magnetic flux density B using a variable current source. This allows for pulsed processing, significantly improving the processing result. Excitation frequencies in the range of 50 Hz ≤ f ≤ 150 Hz are achievable with the variable current source.

[0064] With the device 10 or the system 100 and the method, individual cutting edges or surfaces of a workpiece can be machined to varying degrees. This allows for precise adjustment of the cutting edge radius rβ and the edge rounding on microcomponents being machined. This is achieved through the anisotropic rheological properties of the magnetorheological fluid, since the maximum yield strength τ and thus the process forces FP occur orthogonally to the magnetic flux Φ. Compared to immersion lapping, this results in increased material separation, especially on surfaces and edges that are at an angle αE between 60° and 90° to the magnetic field lines.

[0065] In Figure 2cOn the left (I) the magnetorheological fluid 1 with the abrasive particles 11 is shown, and on the right (II) a classic lapping medium 1', here Al₂O₃, is shown. The machined edges 6' are highlighted by thicker lines. Magnetic field lines 8 of the electromagnet 3 are shown on the left (I).

[0066] In addition to targeted machining, the controllable yield stress τo allows for higher machining pressures pB than in the conventional immersion lapping process, thus significantly reducing the machining time t. The magnetic flux density B enables individual adjustment of the machining pressure pB, allowing for material- and geometry-specific machining. Furthermore, this process also allows the use of abrasive particles 11 with very small grain sizes d, e.g., diamond particles with a grain size of 5 µm < dK < 500 µm. Therefore, even sensitive components with functional characteristics in the micrometer range, hereinafter referred to as microcomponents, can be machined precisely and with a high surface finish by adjusting the yield stress τo.

[0067] Figure 3 Figure 10 shows another exemplary device for applying a magnetic field to a magnetorheological liquid.

[0068] The container 2 is hollow cylindrical with an upward-facing opening. A magnetorheological fluid 1 is arranged in the container. A microtool 6 is immersed in the magnetorheological fluid 1. A magnetic conductor 31 is arranged circularly and coaxially to the longitudinal axis L of the container. Projections 31' of the magnetic conductor 31 extend towards the container and are located on an outer wall of the container. The projections 31' are wound with coils 32, which are electrically connected to an adjustable power source (not shown). Electromagnets 3 comprising the electrical conductor 31' and the coils are arranged rotationally symmetrically about the longitudinal axis of the container 2. Figure 3It is evident that in a first layer six electromagnets 3, marked by capital letters A, B, C, D, E, F, are arranged. Electromagnets A and D are arranged opposite each other. Electromagnets C and F are arranged opposite each other. Electromagnets B and E are arranged opposite each other. From Figure 4 Figure 2, showing a section along the longitudinal axis L of container 2, clearly shows that further electromagnets 3 are arranged in two additional planes, marked by indices 2 and 3. The electromagnets A, B, C, D, E, and F of the three planes are arranged one above the other. In other embodiments, the electromagnets A1, A2, and A3 can also be arranged offset from each other. This also applies, of course, to electromagnets B, C, D, E, F, or any other possible electromagnets.

[0069] Based on the Figures 3 and 4The following section explains the procedure for machining a workpiece, in this example a microtool 6. First, the workpiece 6 to be machined is clamped into the machine tool or preparation machine 5 (not shown here). For cutting edge preparation, for example, a 5-axis milling machine is used, in whose tool spindle the micromilling tool to be machined is clamped.

[0070] The workpiece 6 is then immersed in the container 2 filled with abrasive magnetorheological fluid 1 (see in particular Fig. 4During immersion, the abrasive magnetorheological fluid 1 is preferably not yet subjected to a magnetic field to prevent undesired preparation effects. In the next step, the abrasive magnetorheological fluid is subjected to a magnetic field. For this purpose, electromagnets 3 are supplied with current from the power source (not shown). Only some of the electromagnets can be supplied with current. For example, electromagnets A and C are supplied with current to achieve the magnetic flux 9 shown as an example for machining the cutting edges of the workpiece 6.

[0071] In the preparation performed, a homogeneous magnetic field with a magnetic flux density of 0.5 T is selected. This can be achieved by means of targeted control and a multi-coil setup, as described in Figures 3 and 4The magnetic field can be modified three-dimensionally by controlling different electromagnets, even in different planes. Additionally, a temporal change of the magnetic field is also possible. The workpiece 6 is guided through the abrasive magnetorheological fluid 1, as shown, for example, in relation to... Fig. 2a and 2b as described. Of course, other movement patterns besides those of the Figures 2a and 2b possible.

[0072] Complex motion kinematics can be implemented within the MRF using the 5-axis milling machine. These can be specifically adapted to the external geometry of the workpiece being machined. In the example process shown, a helical path was selected in combination with a spindle speed of nS = 10,000 rpm and a total machining time of tB = 9 min. In other processes, the machining time can be up to 20 min, preferably up to 15 min, and / or at least 2 min, preferably at least 5 min.

[0073] Once the processing time has elapsed, the electromagnets can be disconnected from the power supply. The workpiece is moved to its starting position, specifically outside the container, and can be removed. In the exemplary process, an increase in the cutting edge rounding of 58% to rβ = 5.1 µm was achieved.

Claims

1. A device for applying a magnetic field to a magnetorheological liquid (1), comprising - a container (2) for receiving a magnetorheological liquid (1), having a preferably upwardly directed opening (23) for at least partially immersing the workpiece and / or tool into the magnetorheological liquid (1), - a plurality of electromagnets (3), arranged on the container (2), for applying a magnetic field to the container (2), wherein each electromagnet (3) comprises a magnetic conductor (31) and a coil (32) wound around the conductor (31), and at least one power source (4) electrically connected to the coils (32), wherein a first number of the electromagnets (3) is arranged in a first plane perpendicular to the longitudinal axis (L) of the container (2) and a second number of the electromagnets (3) is arranged in a second plane perpendicular to the longitudinal axis (L) of the container (2), and a third number of electromagnets (3) is arranged in a third plane perpendicular to the longitudinal axis (L) of the container (2), characterized in that a first pulse may be supplied to a first combination of the electromagnets and a second pulse may be supplied to a second combination of the electromagnets, wherein the power source is controllable for control of the magnetic flux density and is configured to control an excitation frequency, wherein excitation frequencies of at least 5 Hz to at most 150 Hz may be set.

2. The device according to claim 1, characterized in that the container (2) is filled at least partially with a magnetorheological liquid (1), in particular an abrasive magnetorheological liquid (1), wherein the magnetorheological liquid (1) comprises in particular a carrier oil, in particular polyalphaolefin oil, and carbonyl iron particles and an abrasive medium, in particular diamond, corundum and / or silicon carbonate.

3. The device according to claim 1 or 2, characterized in that the container (2) is cuboid or cube-shaped or is rotationally symmetrical about its longitudinal axis (L), in particular has the form of a hollow cylinder which has a circular base plate and is open upwardly.

4. The device according to any one of the preceding claims, characterized in that excitation frequencies of at least 50 Hz, preferably at least 60 Hz, in particular at least 70 Hz and / or excitation frequencies of at most 140 Hz, in particular at most 130 Hz, may be set.

5. A system for processing a workpiece and / or tool by means of a magnetorheological liquid (1), comprising - a device according to any one of the preceding claims, - a workpiece receptacle for receiving a workpiece and / or tool to be processed, wherein the workpiece receptacle is movable in such a way that the workpiece and / or the tool in a first position is arranged outside the container interior (24) and in at least a second position is arranged partially in the container interior (24), in particular at least partially in a magnetorheological liquid (1) arranged therein.

6. The system according to the preceding claims, characterized by at least one further workpiece receptacle, for simultaneously introducing two tools and / or workpieces into the container interior (24).

7. The system according to any one of claims 5 or 6, characterized in that at least one workpiece receptacle is movable along an axis, preferably along two axes, particularly preferably along three axes and / or is rotatable about at least one axis and / or about at least two axes and / or about at least three axes.

8. The system according to any one of claims 5 - 7, characterized by a multi-axis robot, preferably a five-axis robot or a six-axis robot, wherein the at least one workpiece receptacle is arranged on the multi-axis robot.

9. A method for processing a workpiece and / or tool, comprising the following steps I. providing a system according to any one of claims 5 to 8, wherein the container (2) is filled at least partially with a magnetorheological liquid (1), II. inserting, in particular clamping, a workpiece and / or tool in a workpiece receptacle, wherein the workpiece receptacle is in a first position arranged outside the container (2), III. moving the workpiece receptacle with inserted workpiece and / or tool into a second position, in which the workpiece and / or the tool is immersed at least partially into the magnetorheological liquid (1), IV. applying a magnetic field to the magnetorheological liquid (1) arranged in the container (2), in particular by energizing at least one electromagnet (3) with current by the power source.

10. The method according to the preceding claims, characterized in that step IV comprises changing the magnetic flux density of the magnetic field, in particular by changing the current for energizing the at least one electromagnet (3), and / or in that different electromagnets of the plurality of electromagnets (3) are operated in succession.

11. The method according to any one of the two preceding claims, characterized in that in step IV the electromagnets (3) are operated in a pulsating manner, so that the magnetic field changes over time.

12. The method according to any one of the three preceding claims, characterized in that - whilst a magnetic field is being supplied to the magnetorheological liquid (1) - the workpiece and / or tool is guided through the magnetorheological liquid (1), in particular is guided through the magnetorheological liquid (1) along one or more translational axes, in particular is guided along a helical path, and / or is rotated in the magnetorheological liquid (1) around at least one axis.

13. The method according to any one of claims 9 to 12, characterized in that before carrying out step IV, an angle between a workpiece longitudinal axis and / or a tool longitudinal axis and the container longitudinal axis (L) is set, and / or before carrying out step IV, an angle between a workpiece longitudinal axis and / or a tool longitudinal axis and the container (2) longitudinal axis (L) is changed.