EP3970914A1 - Device for applying a magnetic field to a magnetorheological fluid, system and method for processing a workpiece using the magnetorheological fluid - Google Patents

Abstract

The present invention relates to a device for applying a magnetic field to a magnetorheological fluid, comprising a container for receiving a magnetorheological fluid, having a preferably upward-facing opening for at least partially immersing the workpiece and/or tool in the magnetorheological fluid, at least one on the An electromagnet arranged in a container for applying a magnetic field to the container, the electromagnet comprising a magnetic conductor and a coil wound around the conductor, and a power source electrically connected to the coil. Furthermore, the invention relates to a system and a method for processing a workpiece and/or tool using the magnetorheological fluid.

Description

The present application relates to a device for applying a magnetic field to a magnetorheological fluid. Furthermore, it relates to a system and a method for processing a workpiece and/or tool using the magnetorheological fluid.

Microelectronic and mechanical systems (MEMS), which are manufactured using micro-manufacturing, have found their way into almost all technical areas. Micro-milling is a central component of micro-manufacturing. Micro-milling is a machining process with a geometrically defined cutting edge. Micro milling offers the possibility Being able to manufacture precision components with a high degree of geometric diversity in combination with a wide range of materials. Due to the requirements for shape and dimensional accuracy of the generated components, special tool preparation is required for process-reliable machining. A central part of this tool preparation is the cutting edge preparation of micro milling tools. A large number of preparation processes are used for the targeted preparation of cutting edges, for example brushing, blasting, laser ablation, magnet finishing or immersion sliding lapping.

Both the cutting edge preparation of micro milling tools and micro deburring combine the difficulty of preparing workpiece edges in a defined and reproducible manner. Due to the complex interrelationships of influencing factors such as movement kinematics, processing medium and engagement conditions, it has so far only been possible to make an accurate and requirement-oriented edge preparation insufficient.

It is therefore the object of the present invention to propose a device which, compared to this prior art, enables an alternative, preferably improved, micromachining, in particular an improved cutting edge preparation. Furthermore, it is an object of the present invention to propose a corresponding system and a corresponding method that enable alternative, preferably improved, workpiece or tool processing. In particular, it can be an object of the present invention to improve the preparation of tools with diameters of 100 μm≦D≦1000 μm.

The proposed device serves to apply a magnetic field to a magnetorheological fluid. A tool or workpiece located in the magnetorheological fluid can thus be processed.

The device comprises a container for receiving a magnetorheological fluid, having an opening, preferably pointing upwards, for at least partially immersing the workpiece and/or tool into the magnetorheological fluid, at least one electromagnet arranged on the container for applying a magnetic field to the container, the electromagnet comprising a magnetic conductor and a coil wound around the conductor and a power source electrically connected to the coil.

In particular, the device can be suitable for being installed in or on a machine tool for producing or machining workpieces with functional features in the micrometer range or tools with functional features in the micrometer range.

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

The container can be cuboid or cube-shaped. An interior of the cube or cuboid is typically hollow for containing the magnetorheological fluid. In particular, an upper side surface 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 plate and be open at the top. In particular, an upper side surface of the cylinder or hollow cylinder is open or contains an opening.

The container walls can have a constant thickness or different material thicknesses. The bottom plate of the container can be the same or have a thickness different from the wall thickness. The container preferably comprises PVC and/or another dia- or paramagnetic material.

A wall thickness or base thickness of the container can be in particular 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.

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

In one embodiment, the device includes a plurality of electromagnets. The electromagnets are typically designed like the at least one electromagnet described above. The electromagnets can - be arranged on the container - preferably outside. The electromagnet and/or at least some or all of the plurality of electromagnets can be arranged on an outside, in particular on an outside wall or on several outside walls of the container. The electromagnet or the electromagnets can, for example, be glued to an outer wall or to several outer walls of the container and/or screwed to it. Other fixation options, for example by means of clamps, are also conceivable. The outer walls or the outer wall of the container can have projections, in particular integral ones, which are used to hold the electromagnets, onto which the electromagnets can be plugged, for example. Preferably, the electromagnets are immovably connected to the container. The respective coil of the electromagnets of the plurality of electromagnets can be connected to the power source or to a further power source in each case.

The plurality of electromagnets may include a first number of electromagnets in a first level. The first plane is preferably perpendicular to the longitudinal axis of the container. The first plane can also be arranged at an acute or obtuse angle to the longitudinal axis of the container. A second number of electromagnets can be arranged in a second plane, preferably perpendicular to the longitudinal axis of the container. The second plane can be arranged parallel to the first plane. Provision can also be made for the first and the second plane to intersect in a straight line. A third number of electromagnets can be arranged in a third plane, preferably perpendicular to the longitudinal axis of the container. The third level can be arranged parallel to the first level and/or second level. Additional levels with electromagnets can be provided. Each level preferably comprises at least one pair of coils.

In one embodiment, at least one electromagnet is provided per level. There can be more than one electromagnet, for example at least two or at least three or at least four or at least five or at least 10 electromagnets per level. A large number of electromagnets can be provided per level, in particular up to 100 or up to 50 or up to 30 or up to 20 electromagnets can be provided per level. The number of electromagnets can be an even number or an odd number.

1 to X levels of electromagnets can be provided. X is a natural number. In particular, at least three or at least four or at least five or at least 10 levels of electromagnets can be provided. In particular, a maximum of 100 or a maximum of 80 or a maximum of 50 or a maximum of 20 levels of electromagnets can be provided.

The more levels of electromagnets are provided, the more levels of the magnetorheological fluid can be controlled individually. The electromagnets of one level can each be controlled individually. The electromagnets of one level can be controlled at different times. The electromagnets of a plane can be different or the same Pulses can be controlled. It can also be provided that some electromagnets of one plane can be controlled with one pulse and some electromagnets can be controlled with a second pulse.

In one embodiment, a first pulse can be applied to a first combination of electromagnets, while a second pulse can be applied to another combination of electromagnets. There can be further combinations of electromagnets that can be subjected to further pulses. The combinations of electromagnets can each lie in one plane and/or in different planes. For example, the first combination can include electromagnets that are arranged one above the other in different levels.

The plurality 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.

In one embodiment, the electromagnets of one level are arranged one above the other and/or offset from one another in relation to the electromagnets of another level. The electromagnets of one level can be arranged one above the other in relation to the electromagnets of another level and can be arranged offset in relation to the electromagnets of another level. The first number of electromagnets and/or the second number of electromagnets and/or the third number of electromagnets can/can be arranged one above the other. The first number of electromagnets and/or the second number of electromagnets and/or the third number of electromagnets can be offset from one another.

In one embodiment, the power source is adjustable to control the magnetic flux density. In particular, the power source can be designed to regulate an excitation frequency. The power source can be designed such that excitation frequencies of at least 1 Hz or at least 5 Hz or at least 10 Hz or at least 20 Hz or at least 30 Hz, preferably at least 40 Hz, particularly preferably at least 50 Hz and/or excitation frequencies of in particular at most 200 Hz or at most 190 Hz or at most 180 Hz or at most 170 Hz, preferably at most 160 Hz, in particular preferably 150 Hz can be set. A frequency range of 50 Hz≦f≦150 Hz can particularly preferably be set.

Provision can be made for the frequency ranges to be individually controllable for each electromagnet. For example, more than one controllable current source can be provided for this purpose. An electromagnet can be connected to a power source. A second electromagnet can be connected to a second power source. Additional electromagnets can each be connected to a power source. Provision can also be made for a power source to be connected to more than one electromagnet. A second power source may be connected to one or more other power sources. The power source(s) can each be controllable as described above.

Controlling an excitation frequency of one or more electromagnets enables pulsed operation of the electromagnet(s). The pulsing can be used to reorient the abrasives. In this way, an increase in the effectiveness of the processing and/or a reduction in dead areas in terms of flow technology can be achieved. The pulsing can additionally or alternatively serve to increase the fluid density or abrasive agent density at the processing point. The pulsing can additionally or alternatively optimize chip removal and/or lead to an improved removal rate. In addition or as an alternative, the pulsing can serve to improve the removal of worn carbonyl iron particles.

In one embodiment, the electromagnets of one level can all be connected to an adjustable power source. Alternatively, the electromagnets of one level can each be connected to a different power source. Additionally or alternatively, at least one electromagnet of one level can be connected to a power source and/or at least one electromagnet of the same level can be connected to at least one further power source.

The electromagnets can be switched individually and at different times. The electromagnets can be switched with different frequencies. This can have the advantage that a locally specific and directed pressure change in the magnetorheological fluid can be achieved.

At least one permanent magnet can also be arranged on the container, preferably on an outside of the container. With the permanent magnet, the magnetorheological fluid can be subjected to a magnetic field. The magnetic fields of the electromagnet or the electromagnets and/or the permanent magnet or the permanent magnets can overlap.

The device can be particularly suitable for being used in a machine tool, for example a machine tool for micro-milling.

The present application also 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 microtool, using a magnetorheological fluid.

The dimensions of a micro-workpiece and/or micro-tool can be characterized in particular by the fact that they have an extension, 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, particularly preferably a maximum of 2,000 μm. An extension, for example along a longitudinal axis and/or along an axis perpendicular to the longitudinal axis, can be at least 50 μm, preferably at least 80 μm, particularly preferably at least 100 μm. The maximum extent of the micro-workpiece or micro-tool along a straight line can be a maximum of 2000 μm, preferably a maximum of 1500 μm, particularly preferably a maximum of 1000 μm and/or a minimum of 50 μm, preferably a minimum 80 μm, particularly preferably at least 100 μm.

The system typically includes a device according to the above embodiment. 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 in such a way that the workpiece and/or the tool is/are arranged in a first position outside of an interior space of the container, hereinafter the interior space of the container, and in a second position at least partially in the interior space of the container, in particular at least partially in a magnetorheological fluid arranged therein. The tool holder can also be moved to other positions. The further positions are preferably localized in such a way that in the further positions the workpiece and/or tool is/are partially arranged in the interior of the container, in particular at least partially in a magnetorheological fluid arranged therein.

The system can have at least one additional workpiece holder for the simultaneous introduction of two tools and/or workpieces into the interior of the container.

At least one workpiece holder can be moved along one axis, preferably along two axes, particularly preferably along three axes. In particular, the axes can be perpendicular to one another. Additionally or alternatively, at least one or the same tool holder can be rotatable about at least one axis and/or about at least two axes and/or about at least three axes.

In one embodiment, the system has a multi-axis robot, preferably a five-axis robot or a 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 be designed, for example, as an industrial robot, comprising a robot arm.

The application also relates to a method for machining a workpiece and/or tool, preferably a micro workpiece or micro tool, using a magnetorheological fluid.

1. I. Bereitstellen eines zuvor beschriebenen Systems,
2. II. Einsetzen, insbesondere Einspannen, eines Werkstücks und/oder Werkzeugs in die Werkstückaufnahme,
3. III. Verfahren der Werkstückaufnahme mit eingesetztem Werkstück und/oder Werkzeug in eine zweite Position, in der das Werkstück und/oder das Werkzeug zumindest teilweise in die magnetorheologische Flüssigkeit eingetaucht ist,
4. IV. Beaufschlagen der in dem Behälter angeordneten magnetorheologischen Flüssigkeit mit einem Magnetfeld, insbesondere durch Versorgen von zumindest einem Elektromagneten mit Strom durch die Stromquelle.

The method comprises the following steps, which are preferably carried out in the following order.

1. I. Provision of a previously described system,
2. II. Insertion, in particular clamping, of a workpiece and/or tool in the workpiece holder,
3. III. Moving the workpiece holder with the workpiece and/or tool inserted into a second position in which the workpiece and/or the tool is at least partially immersed in the magnetorheological fluid,
4. IV. Applying a magnetic field to the magnetorheological liquid arranged in the container, in particular by supplying at least one electromagnet with current through the current source.

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

In the second step, the workpiece holder is preferably in a first position, arranged outside of the container.

The workpiece/tool can be moved in the container in order to generate a relative speed and thus a material separation.

The workpiece and/or tool arranged in the magnetorheological fluid can be machined by applying a magnetic field to the magnetorheological fluid.

The workpiece/tool can be guided through the switched, i.e. subjected to a magnetic field, magneto-rheological fluid. In this way, a material separation can be effected. By being subjected to the magnetic field, the magnetic particles in the magnetorheological fluid, for example iron particles, can align themselves along the magnetic field lines. These particles can "hold" the abrasive particles. The switched magnetorheological fluid can be at rest.

Alternatively, the magnetorheological fluid and/or the abrasive particles contained therein can be moved by being acted upon by the magnetic field, so that a workpiece and/or tool surface is at least partially removed.

In one embodiment, in the fourth method step, the magnetorheological fluid can be subjected to a homogeneous or inhomogeneous magnetic field. A homogeneous magnetic field can have the advantage that a homogeneous material separation and thus a homogeneous processing can be guaranteed.

In one embodiment, step IV includes changing the magnetic flux density of the magnetic field. In particular, the magnetic flux density can be changed by changing the current applied to power the at least one electromagnet. Additionally or alternatively, different electromagnets of the plurality of electromagnets can be supplied with current simultaneously or one after the other. At least two electromagnets are preferably operated simultaneously as a pair of coils. Different pairs of coils can be operated one after the other.

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

Depending on the requirements of the workpiece or tool to be machined, different magnetic flux densities can be implemented result in corresponding material removal or material separation on the workpiece and/or tool surface. Depending on the intensity of the magnetic flux density, the surface of the workpiece and/or workpiece can be locally removed to varying degrees and/or material can be separated.

In one embodiment, the electromagnets can be operated in a pulsating manner in step IV, so that the magnetic field changes over time. An inhomogeneous magnetic field can thus be applied to the magnetorheological fluid, as a result of which a variable processing pressure P _B can be set as a function of an immersion depth t of the workpiece or tool immersed in the magnetorheological fluid.

In one embodiment, the workpiece and/or tool can be guided through the magnetorheological fluid, in particular while the magnetorheological fluid is being subjected to a magnetic field. For example, an immersion depth of the workpiece and/or tool can be changed. The workpiece and/or tool can be guided through the magnetorheological fluid along one or more translatory axes. For example, it can be guided along a helical path. Additionally or alternatively, the workpiece and/or tool can be rotated about at least one axis in the magnetorheological fluid. A speed in 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, particularly preferably at most 10,000.

In one embodiment, an angle between a longitudinal axis of the workpiece and/or a longitudinal axis of the tool and the longitudinal axis of the container can be set before carrying out step IV. Additionally or alternatively, an angle between a longitudinal axis of the workpiece and/or a longitudinal axis of the tool and the longitudinal axis of the container can be changed while performing step IV. As a result, the material separation can be influenced in a targeted manner.

By moving the workpiece and / or tool in the Magnetorheological fluid and/or a variation of the immersion depth and/or the immersion angle can influence the prevailing pressure and flow conditions in the magnetorheological fluid. This makes it possible to process individual edges.

In addition or as an alternative to the geometric variation of the movement path of the workpiece and/or tool, the rheological properties of the magnetorheological fluids can be influenced by controlling the magnetic flux density B using the controllable current source. In this way, pulsed processing can be achieved, as a result of which the processing result can be improved. The advantages of pulsed processing are shorter processing times and/or lower surface roughness.

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

The application possibilities of the method, the system and the device can exist in the preparation of cutting edges and in almost all machining operations that require machining with a geometrically defined cutting edge. Cutting edge preparation is used in almost all technical areas. Among other things, in dental and medical technology, the electrical industry, the optical industry and in mold and tool making. For example, the cutting edges of milling tools for machining tool electrodes made of graphite can be prepared. The precise injection molds produced with it can be used to manufacture highly complex and microstructured plastic components, such as endoscope lenses and micro gears. In addition to cutting edge preparation, another area of application can be the deburring of the manufactured micro-components. Fine burrs or injection points occur in both micro-machining and micro-injection molding, which must be removed for the component to operate correctly. This can also be implemented with the described method or the device and/or the system. In addition, can post-processing of additively manufactured components may be possible. Due to the layered structure, these have a higher mean roughness value Ra than conventionally manufactured components. With the described method or the device and/or the system, a smoothing of the surface and a defined rounding of the edges can be realized.

The present application encompasses several embodiments. The following detailed description shows and describes further exemplary embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded in an illustrative rather than a restrictive sense.

Fig. 1

ein System zum Bearbeiten eines Werkstücks und/oder Werkzeugs mittels einer magnetorheologischen Flüssigkeit,

Fig. 2a

eine schematische Querschnittsansicht durch den Behälter des Systems der Figur 1,

Fig. 2b

eine schematische Längsschnittansicht durch den Behälter des Systems der Figur 1 mit eingezeichnetem Mikrofräswerkzeug,

Fig. 2c

eine schematische Längsschnittansicht durch den Behälter des Systems der Figur 1 mit eingezeichnetem Mikrofräswerkzeug sowie einen Vergleich zum Tauchgleitläppen,

Fig. 3

eine Querschnittansicht einer Vorrichtung zum Beaufschlagen einer magnetorheologischen Flüssigkeit mit einem Magnetfeld, und

Fig. 4

die Vorrichtung gemäß Figur 3 in einem Längsschnitt.

Show it

1

a system for processing a workpiece and/or tool using a magnetorheological fluid,

Figure 2a

a schematic cross-sectional view through the container of the system of FIG figure 1 ,

Figure 2b

a schematic longitudinal sectional view through the container of the system of figure 1 with marked micro milling tool,

Figure 2c

a schematic longitudinal sectional view through the container of the system of figure 1 with a micro-milling tool drawn in and a comparison to immersion sliding lapping,

3

a cross-sectional view of a device for applying a magnetic field to a magnetorheological fluid, and

4

the device according to figure 3 in a longitudinal section.

figure 1 shows a system 100 for processing a workpiece and/or tool using a magnetorheological fluid 1. The system 100 is shown schematically so that dimensions and dimensional relationships may deviate from real dimensions. Furthermore, the individual components are not necessarily shown realistically, but essentially schematically for the purpose of explaining the function. The system 100 includes a device 10 for applying a magnetic field to the magnetorheological fluid.

For this purpose, the device 10 has a container 2 for receiving the magnetorheological liquid 1 . The container 2 has a longitudinal axis L. In figure 1 the container 2 is shown in a section along the longitudinal axis L. The container 2 is essentially cuboid, having side walls 21 and a bottom 22 . The container 2 is open at the top, ie it has an opening 23 which essentially corresponds to the area of the bottom 22 . The side walls 21 and the bottom 22 define a container interior 24 which is at least partially filled with the magnetorheological fluid 1 . The magnetorheological fluid 1 shown 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.

An electromagnet 3 is arranged on the outside of the container. The electromagnet 3 includes a magnetic conductor 31 and a coil 32 wound around the magnetic conductor 31. The magnetic conductor 31 includes 11Smn30. The coil 32 comprises copper. The coil 32 typically has between 300 and 1000 turns. The coil 32 is electrically connected to a power source 4 . The power source 4 can be regulated, so that a magnetic flux density of the electromagnet 3 can be regulated. The controllable power source 4 can be used to set excitation frequencies f from 50 Hz to 150 Hz.

Furthermore, the system 100 includes a movable workpiece holder 5, in which a workpiece, in this case a micro-milling tool 6, is clamped. In the present case, the workpiece holder 5 is a tool spindle of a 5-axis milling machine.

Recurring features are used for clarity and Provided comprehensibility in the following figures with the same reference numerals.

In Figure 2a the container 2 is shown in a cross section perpendicular to the longitudinal axis l. The container 2 is filled with the magnetorheological liquid 1. A movement path 7 is shown schematically by means of arrows, which shows how the micro milling tool can be moved through the magnetorheological liquid 1 for the preparation of the cutting edge. The movement along the movement path 7 is realized 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 at a speed ns about a longitudinal axis of the micro-milling tool 6 . In the example shown, the speed is 10,000 rpm, for example.

In Figure 2a is the container 2 the figures 1 and 2a in a longitudinal section along the in Figure 2a shown line AA. The micro-milling tool 6 is set at an angle α _E relative to the longitudinal axis L of the container. In the present example, this is 45°, but can be varied. In particular, the angle can also be varied during the cutting edge preparation process. Furthermore, an immersion depth T _E is varied, so that in addition to the in Figure 2a illustrated trajectory 7 in the horizontal plane, the trajectory 7 'in the vertical plane as in Figure 2b shown runs.

When preparing the micro milling cutter 6 , it can thus be clamped directly into the spindle of the machine tool 5 . This means that later re-clamping of the tool becomes obsolete and one process step is saved. The tool, here the micro-milling tool 6, is then moved within the magnetorheological fluid 1 using the drive axles of the machine tool, so that highly complex movement strategies can also be implemented. Depending on the geometry of the workpiece to be machined, the movement can also be supplemented by varying the immersion depth T _E and the immersion angle α _E , thereby influencing the prevailing pressure and flow conditions. This also enables the processing of individual edges. In addition to the geometric variation of the trajectory, the control of the magnetic Flow density B by means of an adjustable power source, the rheological properties of the magnetorheological fluids are influenced. In this way, pulsed processing can be achieved, which significantly improves the processing result. Excitation frequencies in the range of 50 Hz ≤ f ≤ 150 Hz can be realized via the controllable power source.

With the device 10 or the system 100 and the method, individual cutting edges or edges and surfaces of a workpiece can be machined to different extents. As a result, precise setting of a cutting edge rounding r _β and an edge rounding on micro-components to be machined is possible. This can be achieved through anisotropic rheological properties of the magnetorheological fluid, since the maximum yield point τ and thus the process forces FP _occur orthogonally to the magnetic flux Φ. In comparison to immersion slide lapping, there is increased material separation, especially on surfaces and edges that are at an angle α _E between 60° and 90° to the magnetic field lines.

In Figure 2c on 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 Al ₂ O ₃ , is shown. The machined edges 6' are emphasized by heavier lines. Magnetic field lines 8 of the electromagnet 3 are shown on the left (I).

In addition to targeted processing, the controllable yield point τ _o means that higher processing pressures p _B can be achieved than in the classic slide lapping process, which significantly reduces the processing time t in comparison. Due to the level of the magnetic flux density B, an individual adjustment of the processing pressure p _B can thus take place, as a result of which material and geometry-specific processing can take place. In addition, this method also offers the use of abrasive particles 11 with very small grain sizes d, for example diamond particles with a grain size of 5 μm<d _K <500 μm. This means that even sensitive components with functional features in the micrometer range, hereinafter referred to as micro components, can be machined precisely and with a high surface quality by adjusting the yield point τ _o will.

figure 3 shows a further exemplary device 10 for applying a magnetic field to a magnetorheological fluid.

The container 2 is in the form of a hollow cylinder with an upwardly directed opening. A magnetorheological liquid 1 is arranged in the container. A micro tool 6 is immersed in the magnetorheological fluid 1 . A magnetic conductor 31 is circular and coaxial with the longitudinal axis L of the container. Projections 31' of the magnetic conductor 31 protrude toward the container and are arranged on an outer wall of the container. The projections 31' are wound with coils 32 which are electrically connected to a controllable power source (not shown). Electromagnets 3 comprising the electrical conductor 31 ′ and the coils are arranged rotationally symmetrically around the longitudinal axis of the container 2 . In figure 3 it can be seen that six electromagnets 3, marked by capital letters A, B, C, D, E, F, are arranged in a first level. The electromagnets A and D are arranged opposite each other. The electromagnets C and F are arranged opposite each other. The electromagnets B and E are arranged opposite each other. the end figure 4 , showing a section along the longitudinal axis L of the container 2, it becomes clear that further electromagnets 3 are arranged in two further planes, marked by indices 2, 3. The electromagnets A, or B, or C, or D, or D or E or F of the three levels are each arranged one below the other. In other exemplary embodiments, the electromagnets A ₁ , A ₂ and A ₃ can also be offset from one another. Of course, this also applies to the electromagnets B, C, D, E, F or possible other electromagnets.

Based on Figures 3 and 4 the method for machining a workpiece, in the present example a microtool 6, is explained below. First, the workpiece 6 to be machined is clamped into the machine tool or preparation machine 5 (not shown here). A 5-axis milling machine, for example, is used for cutting edge preparation, in whose tool spindle the micro-milling tool to be machined is clamped.
Then the workpiece 6 is in the magnetorheological with abrasive Liquid 1 filled container 2 immersed (see in particular 4 ). During immersion, the abrasive magnetorheological liquid 1 is preferably not yet exposed to a magnetic field in order to prevent undesired preparation effects. In the next step, a magnetic field is applied to the abrasive magnetorheological fluid. For this purpose, electromagnets 3 are supplied with power from the power source (not shown). Only some of the electromagnets can be powered. For example, the electromagnets A and C are supplied with current in order to achieve the magnetic flux 9 shown as an example for machining the cutting edges of the workpiece 6 .

A homogeneous magnetic field with a magnetic flux density of 0.5 T is selected for the preparation carried out. This can be done by means of a targeted control and a multi-coil structure, as in Figure 3 and 4 shown, can be changed three-dimensionally by controlling different electromagnets, also in different levels. In addition, a change in the magnetic field over time is also possible. The workpiece 6 is passed through the abrasive magnetorheological fluid 1, such as with reference to FIG Figures 2a and 2b was described. Of course, other trajectories than those of the Figures 2a and 2b possible.

Using the 5-axis milling machine, complex movement kinematics can be realized within the MRF. These can be specifically adapted to the outer geometry of the workpiece to be 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 processing time of t _B = 9 min. In other methods, the processing time can be up to 20 minutes, preferably up to 15 minutes, and/or at least 2 minutes, preferably at least 5 minutes.

After the processing time has expired, the electromagnets can be disconnected from the power supply. The workpiece is moved to the starting position, in particular outside the interior of the container, and can be removed. In the exemplary process, the rounding of the cutting edges was increased by 58% to r _β = 5.1 µm.

Claims (15)

Device for applying a magnetic field to a magnetorheological liquid (1), comprising - a container (2) for receiving a magnetorheological fluid (1), having a preferably upward-facing opening (23) for at least partially immersing the workpiece and/or tool in the magnetorheological fluid (1), - at least one electromagnet (3) arranged on the container (2) for applying a magnetic field to the container (2), the electromagnet (3) having a magnetic conductor (31) and a coil (32) wound around the conductor (31) includes and - A power source (4) electrically connected to the coil (32). Device according to claim 1, characterized in that the container (2) is at least partially filled with a magnetorheological liquid (1), in particular an abrasive magnetorheological liquid (1), the magnetorheological liquid (1) 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. 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 shape of a hollow cylinder which has a circular base plate and is open at the top. Device according to one of the preceding claims, characterized by a plurality of electromagnets (3) which - preferably outside - are arranged on the container (2) and are preferably immovably connected to the container (2), the respective coil (32) of the electromagnets (3) of the plurality of electromagnets (3) being connected to the power source (4) or to each another power source (4) is connected. Device according to claim 4, characterized in that the plurality of electromagnets (3) comprises a first number of electromagnets (3) in a first plane perpendicular to the longitudinal axis (L) of the container (2) and/or a second number of electromagnets (3 ) in a second plane perpendicular to the longitudinal axis (L) of the container (2) and/or a third number of electromagnets (3) in a third plane perpendicular to the longitudinal axis (L) of the container (2). Device according to one of the preceding claims, characterized in that the power source for controlling the magnetic flux density can be regulated, in particular is designed to regulate an excitation frequency, in particular excitation frequencies of at least 50 Hz, preferably at least 60 Hz, particularly preferably at least 70 Hz and/or or excitation frequencies of in particular at most 150 Hz, preferably at most 140 Hz, particularly preferably 130 Hz, can be set. System for processing a workpiece and/or tool by means of a magnetorheological fluid (1), comprising - a device according to any one of the preceding claims, - a workpiece holder for receiving a workpiece and/or tool to be machined, the workpiece holder being movable in such a way that the workpiece and/or the tool is arranged in a first position outside of the interior of the container (24) and in at least a second position partially in the Container interior (24), in particular at least partially in a magnetorheological liquid (1) arranged therein. System according to the preceding claim, characterized by at least one further workpiece holder for the simultaneous introduction of two tools and/or workpieces into the container interior (24). System according to one of the preceding claims, characterized in that at least one workpiece holder can be moved along one axis, preferably along two axes, particularly preferably along three axes and/or about at least one axis and/or about at least two axes and/or about at least three Axes can be rotated. System according to one of the preceding claims, characterized by a multi-axis robot, preferably a five-axis robot or a six-axis robot, the at least one workpiece holder being arranged on the multi-axis robot. Method for machining a workpiece and/or tool, comprising the following steps I. Providing a system according to any one of claims 10 to 13, wherein the container (2) is at least partially filled with a magnetorheological fluid (1), II. Insertion, in particular clamping, of a workpiece and/or tool in a workpiece holder, the workpiece holder being in a first position outside of the container (2), III. Moving the workpiece holder with the workpiece and/or tool inserted into a second position in which the workpiece and/or the tool is at least partially immersed in the magnetorheological fluid (1), IV. Applying a magnetic field to the magnetorheological liquid (1) arranged in the container (2), in particular by supplying at least one electromagnet (3) with current through the current source. Method according to one of 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 supplying the at least one electromagnet (3) and/or in that different electromagnets of the plurality of electromagnets (3 ) operate. Method according to one of the 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. Method according to one of the preceding claims, characterized in that - while the magnetorheological fluid (1) is subjected to a magnetic field - the workpiece and/or tool is guided through the magnetorheological fluid (1), in particular along one or more translational axes through the magnetorheological fluid (1) is guided, in particular along a helical path, and/or is rotated about at least one axis in the magnetorheological fluid (1). Method according to one of the preceding claims, characterized in that before step IV is carried out, an angle is set between a longitudinal axis of the workpiece and/or a longitudinal tool axis and the longitudinal axis of the container (L) and/or that during the implementation of step IV an angle between a workpiece longitudinal axis and/or a tool longitudinal axis and the container (2) longitudinal axis (L) is changed.

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