EP2072182A1 - Grinding machine with a device for conditioning a grinding machine and procedure for it - Google Patents

Abstract

The machine has a conditioning device (11) for profiling, sharpening and cleaning abrasive surfaces (7, 8) of a grinding wheel (2), where the conditioning device consists of a single tool that is designed as a cup-shaped electrode (12). The electrode is rotatably supported on a carriage (14) around a central axis (13), where the carriage adjusts an adjustable working gap (23) between machining surfaces of the electrode and the abrasive surfaces. A spark-erosive discharge occurs in the working gap by application of spark voltage by a spark generator (17). The electrode is made of aluminum. An independent claim is also included for a method for conditioning a cup-shaped grinding wheel in a grinding machine.

Description

The present invention relates to a grinding machine for grinding a workpiece, comprising a machine frame, a bearing mounted on the machine frame and guides movable bearing means in which a cup-shaped grinding wheel is rotatably driven and electrically insulated around a grinding wheel axis, which is constructed of electrically conductive material and a first abrasive region with an annular abrasive coating and second abrasive regions with jacket surface abrasive coatings, each consisting of an electrically conductive bonding material and abrasive grains incorporated therein, which abrasive disc is electrically connected to a generator, means for holding the workpiece to be ground, a device for conditioning the Grinding wheel with at least one movable electrode, which is also electrically connected to the generator and means for supplying a cooling lubricant to the El ektrode and the workpiece.

Such grinding machines are known. With such grinders, for example, indexable inserts can be ground, which must be done with high precision, including the grinding wheel must be kept in an optimal condition with respect to accuracy and sharpness. To ensure this quality of the grinding wheel, it must be prepared and conditioned accordingly. In this case, essentially three processes are used, namely the profiling, the sharpening and the cleaning of the grinding wheel.

The profiling process, with which the grinding wheel is brought into the desired shape, is usually carried out at each new grinding wheel, a profiling is also carried out when the grinding wheel has been in use for a long time. In known manner, such a profiling is performed with a Siliziumcarbidscheibe, which is adjustable to the grinding wheel in the grinding machine or on which the grinding wheel can be employed in the grinding machine. Here, in addition to the grinding wheel material and silicon carbide Dressing disc removed, this silicon carbide enters the coolant circuit and must, as this material is very aggressive, be removed as quickly as possible from the cooling lubricant medium. For this purpose, the corresponding complex equipment is required.

In the sharpening operation of a grinding wheel, the binding material of the abrasive pad is reset to improve the projection of the abrasive grains over the bonding material. It is known to carry out the sharpening operation of a grinding wheel for metal-bonded grinding wheels by means of electrochemical processes, in which by means of an electrode and a supplied electrolyte, an electrochemical separation of the conductive bonding material of the abrasive coating of the grinding wheel. The detached material must then be laboriously filtered out of the working as a cooling lubricant electrolytic medium, including expensive devices are required.

The cleaning of the grinding wheel with which the chips resulting from the grinding operation, which settle in the unevennesses of the abrasive coating, can be carried out in a known manner with a corundum disk, but it can also be carried out by means of the previously described electrochemical process In both methods, the disadvantages described above occur.

An object of the present invention is therefore to design a grinding machine for grinding a workpiece so that both the profiling, the sharpening and the cleaning of the grinding wheel can be carried out in a simple manner with a single tool and the cleaning of the cooling lubricant can be carried out in a simple manner.

According to the invention, the object is achieved in that the device for profiling, sharpening and cleaning is formed from a single designed as a cup-shaped electrode tool which is equipped at least with an annular processing surface, which pot-shaped electrode mounted to rotate about its central axis drivable on a carriage is, by means of which one between the respective processing surface the pot-shaped electrode and the respective abrasive coating existing working gap is adjustable, in which upon application of an ignition voltage by the generator spark erosive discharge occurs.

This electroerosive discharge in the working gap erodes the bonding material, depending on how wide the working gap is, how large the discharge energy is selected and which discharge frequency is used. As a result, the grinding wheel can be profiled, sharpened and cleaned, which can be carried out in a very simple manner by the single electrode used for this purpose. The sharpening and cleaning of the grinding wheel can be carried out easily during the grinding of a workpiece, whereby the efficiency of the machining operations, since no interruption arises, is optimal. In addition, it is ensured that the grinding wheel constantly has an optimum grinding quality, this also increases the efficiency, the machining of the workpieces is very accurate. The removed by the spark erosive discharge material is carried away by the introduced into the working gap cooling lubricant, a cleaning of this cooling lubricant is possible in a simple manner, as is also carried out in corresponding spark erosion machines.

Advantageously, the axis of the pot-shaped electrode is aligned parallel to the grinding wheel axis and perpendicular to the working surface of the grinding wheel. As a result, the working surface is ideally perfectly planed and conditioned perpendicular to the axis of rotation of the grinding wheel.

Advantageously, the axis of the pot-shaped electrode is mounted electrically isolated in the carriage, which carriage is held on a linear guide on the bearing device and controlled in the direction of the axis along the linear guide is displaceable. As a result, the pot-shaped electrode can be switched on and off in an optimal and simple manner to the grinding wheel or the processing surface to be conditioned.

A further advantageous embodiment of the invention is that the carriage is designed as a cross slide, so that the electrode with respect to the grinding wheel is substantially axially and radially movable, and that the electrode is equipped with a further, substantially mantle-shaped processing surface. Thus, not only the annular abrasive coating of the cup-shaped grinding wheel but also a coat surface-shaped abrasive coating of this grinding wheel can be conditioned accordingly with this electrode, whereby the possible applications for grinding processes are increased.

In an advantageous manner, the mantle surface-shaped processing surface of the electrode is of cylindrical design and the two carriages designed as cross slide are pivotable relative to each other about an axis perpendicular thereto. This can also be used to condition a surface-shaped abrasive coating with this electrode if it has a so-called clearance angle with respect to the annular abrasive coating.

The mantle surface-shaped processing surface of the electrode can also be formed frusto-conical, whereby a mantle surface-shaped abrasive coating can also be conditioned if this has a so-called clearance angle with respect to the annular abrasive coating by both carriages are moved simultaneously.

The spark erosion generating generator is a capacitive discharge spark generator, which allows for optimal spark discharge, and is disposed on the cup-shaped grinding wheel storage apparatus, resulting in the shortest possible spark discharge discharge lines, which has a positive effect thereon ,

Advantageously, the means for supplying the cooling lubricant from nozzles attached to supply lines are formed, via which nozzles the cooling lubricant in the machining gap and the Workpiece can be fed, which has an optimal conditioning and optimal cooling and lubrication result.

A further advantageous embodiment of the invention is that the cooling lubricant is an oil-based dielectric, whereby an optimal cooling and lubrication during the grinding process is achieved, and an optimal environment for the spark erosive discharge for conditioning the grinding wheel is obtained.

Advantageously, the electrode is made of aluminum, whereby it is easy to work, and also in connection with the oil-based based dielectric optimal spark erosive discharge can be achieved.

Advantageously, a control device is provided for controlling and regulating the work processes, whereby these can be optimally coordinated with the grinding operations to be performed.

A further object of the invention is to provide a method for conditioning a cup-shaped grinding wheel with which it can be profiled, sharpened and cleaned in an optimum manner, which is achieved according to the invention by conditioning a cooling lubricant for conditioning the grinding surfaces of the grinding wheel in the working gap an ignition voltage is applied across the generator across the working gap and the electrode is moved towards the grinding wheel at a feed rate until a predetermined threshold of mean voltage, measured across the working gap, and / or average current flow, as measured by the discharge lines , is passed through that then the ignition voltage across the working gap, the discharge energy, the discharge frequency and the feed rate to a given value for profiling, sharpening or cleaning the grinding wheel are set and the ents Pre-emptive process is carried out by spark erosive discharge.

Advantageously, a discharge energy of about 10 to 100 mJ and a discharge frequency of about 1 to 100 kHz is selected for profiling the grinding wheel, resulting in an optimum removal performance.

The profiling operation is carried out until the average stress, measured across the working gap, and / or the average flow of current, as measured by the discharge conduits, is substantially constant, indicating that the abrasive coating to be profiled is optimally formed.

For pre-sharpening the grinding wheel, a discharge energy of about 0.5 to 5 mJ and a discharge frequency of about 10 kHz to 1 MHz are selected, a corresponding discharge energy and discharge frequency is also selected for sharpening and cleaning the grinding wheel, wherein the sharpening and cleaning of the grinding wheel during the Editing a workpiece can be performed.

After a grinding operation, it may be necessary to restore the optimum sharpness state of the abrasive coating in use by means of an additional secondary sharpening function. This re-sharpening function lasts for a predetermined time while not being ground, and works with parameters similar to sharpening and cleaning the grinding wheel while machining a workpiece.

Optimum machining of the abrasive wheel by the electrode is achieved when the advancing speed of the electrode is adjusted by a regulator located within the controller within a selectable bandwidth due to the average voltage measured across the working gap and the average current flow as measured by the discharge lines.

Advantageously, the discharge energy and the discharge frequency during sharpening and cleaning of the grinding wheel by an optimization algorithm arranged in the control within a selectable bandwidth due to the maximum contact pressure, the average contact pressure during the spark, the ratio of Power of the drive motor to the contact force and the disc wear, measured during the previous and completed grinding operations set. This gives a simpler operation of the procedure.

Advantageously, for sharpening the grinding wheel between two grinding operations, a discharge energy of about 0.1 to 5 mJ and a discharge frequency of about 10 kHz to 1 MHz is selected, and this resharpening operation is performed during a selectable re-sharpening time, whereby a large process stability is achieved.

By adjusting the discharge energy and the discharge frequency during sharpening of the grinding wheel, as well as the re-sharpening time by an optimization algorithm within a selectable bandwidth due to the maximum contact pressure, the average contact force during sparking, the ratio of the power of the drive motor to the contact pressure and the disk wear measured during the preceding and completed grinding operations is set to achieve further ease of operation.

An embodiment of the device according to the invention and of the method according to the invention for conditioning a grinding wheel will be explained in more detail below by way of example with reference to the attached drawing.

• Fig. 1 in räumlicher Darstellung die Lagereinrichtung für die rotierend antreibbare topfförmige Schleifscheibe mit der aufgesetzten Vorrichtung zum Profilieren, Schärfen und Reinigen der Schleifscheibe;
• Fig. 2 eine räumliche Darstellung der Einrichtung gemäss Fig. 1 im Schnitt;
• Fig. 3 in schematischer Darstellung die Vorrichtung zum Konditionieren der topfförmigen Schleifscheibe, dargestellt in einer ersten Position zum Konditionieren des ringförmigen Schleifbelags der Schleifscheibe;
• Fig. 4 in schematischer Darstellung die Vorrichtung zum Konditioneren der topfförmigen Schleifscheibe, dargestellt in einer zweiten Position zum Konditionieren des mantelflächenförmigen Schleifbelags der Schleifscheibe;
• Fig. 5 in schematischer Darstellung die Vorrichtung beim Konditionieren des mantelflächenförmigen Schleifbelags der Schleifscheibe, bei welcher die topfförmige Elektrode eine kegelstumpfförmige Aussenfläche aufweist und der mantelflächenförmige Schleifbelag mit einem Freiwinkel ausgestattet ist; und
• Fig. 6 in schematischer Darstellung die Vorrichtung beim Konditionieren eines mit Freiwinkel versehenen mantelflächenförmigen Schleifbelags mit zylindrischer topfförmiger Elektrode.

It shows,

• Fig. 1 in a spatial representation of the bearing device for the rotating drivable cup-shaped grinding wheel with the attached device for profiling, sharpening and cleaning the grinding wheel;
• Fig. 2 a spatial representation of the device according to Fig. 1 on average;
• Fig. 3 a schematic representation of the apparatus for conditioning the cup-shaped grinding wheel, shown in a first position for conditioning the annular abrasive coating of the grinding wheel;
• Fig. 4 a schematic representation of the device for conditioning the cup-shaped grinding wheel, shown in a second position for conditioning the mantle-shaped abrasive covering of the grinding wheel;
• Fig. 5 a schematic representation of the device during conditioning of the mantle-shaped abrasive covering of the grinding wheel, wherein the cup-shaped electrode has a frusto-conical outer surface and the mantle-shaped abrasive coating is provided with a clearance angle; and
• Fig. 6 a schematic representation of the device in the conditioning of a provided with clearance angle coat surface-shaped abrasive coating with cylindrical pot-shaped electrode.

Out Fig. 1 is the storage device 1 can be seen, which is placed in a known manner, not shown directly on the machine frame of a grinding machine or inserted between bearing device 1 and machine frame carriage assembly. In this bearing device 1, a pot-shaped grinding wheel 2 is rotatably mounted about a grinding wheel axis 3. The rotating drive of this grinding wheel 2 via an electric motor 4, which is arranged on the bearing device 1.

The pot-shaped grinding wheel 2 consists of a grinding cup 5, on which a slip ring 6 is placed, which has an annular abrasive coating 7 and a mantle-shaped abrasive coating 8. With this grinding wheel 2, a workpiece 9 can be ground, for example an indexable insert, which is held in a known manner by means 10 for holding the workpiece 9 to be ground, arranged in the grinding machine.

For conditioning the abrasive coatings 7, 8 of the cup-shaped grinding wheel 2, a device 11 is provided, which has a cup-shaped electrode 12 which is mounted for rotation about its central axis 13 drivable in a carriage 14 which on the bearing device 1 in the direction of the central axis thirteenth is held displaceable. The displacement of the carriage 14 on the bearing device 1 via a ball screw drive 15, the drive motor 16 is mounted on the bearing device 1.

Also on the storage device 1, a generator 17 is arranged. This generator 17 is connected via lines 18 to the power supply of the grinding machine. The generator 17 is connected via a discharge line 19 with the cup-shaped grinding wheel 2 and via a further discharge line 20 with the cup-shaped electrode 12, as will be seen below. The communication with the known, not shown machine control via the line 35, which can meet a variety of specifications such as Ethernet, Profibus or RS 232.

In the area of the workpiece 9 to be ground, a nozzle 21 is attached in known manner, which is connected to a feed line, not shown, via which a cooling lubricant can be introduced into the grinding area. A further nozzle 22 is arranged in a known manner in the region of the electrode, via which the cooling lubricant can be introduced into the working gap 23 between the cup-shaped electrode 12 and the slip ring 6 of the grinding wheel 2 via a feed line, not shown.

How out Fig. 2 it can be seen, the spindle 24 of the cup-shaped grinding wheel 2 is mounted in electrically insulated bearings 25. The electric motor 4 is electrically isolated from the spindle 24 in a known manner. On the spindle 24, a slip ring 26 is mounted, which cooperates with a contact 27, to which the discharge line 19 (FIG. Fig. 1 ) connected. Thus, the cup-shaped grinding wheel 2 via the spindle 24, the slip ring 26, the contact 27 and the corresponding discharge line to the generator 17 (FIG. Fig. 1 ) connected.

Like also out Fig. 2 can be seen, the pot-shaped electrode 12 is flanged onto an electrode spindle 28, which is electrically isolated in a corresponding manner in the carriage 14 (FIG. Fig. 1 ) Is mounted and about the spindle 28 electrically isolated motor 29 arranged around the central axis 13 can be driven. On the electrode spindle 28, in turn, a slip ring 30 is mounted, which cooperates with a contact 31, which contact 31 via the discharge line 20 (FIG. Fig. 1 ) is electrically connected to the generator 17.

The grinding wheel cup 5 of the cup-shaped grinding wheel 2 is made of an electrically conductive material. The patch on the grinding wheel pot 5 slip ring 6 consists of a base made of aluminum, bronze or steel. On this body, the abrasive coatings 7, 8 are applied, which consist of a bond in which the abrasive grains are incorporated. The binding material consists of a metal alloy, synthetic resin or ceramic, which are also electrically conductive. In this electrically conductive bonding material, the abrasive grains are embedded in a known manner, which may consist of diamond or another correspondingly suitable material.

The cup-shaped electrode 12 is also made of an electrically conductive material, preferably of aluminum. However, this pot-shaped electrode 12 may also consist of copper, graphite or another conductive suitable material.

The cooling lubricant used is preferably an oil-based dielectric, for example the cooling lubricant marketed on the market under the name "lonogrind" by the company Oelheld GmbH, Stuttgart, Germany. The generator 17 used here is a spark generator with capacitive discharge, as it is for example in U.S. Patent No. 4,710,603 the company Fanuc Ltd. is described.

For conditioning the abrasive coatings 7, 8 of the cup-shaped grinding wheel 2, an ignition voltage is applied by the generator 17 via the working gap 23, whereby between the pot-shaped electrode 12th and the cup-shaped grinding wheel 2 forms an ion channel in the dielectric cooling lubricant and a discharge can take place. The working gap 23 must be large enough so that the released binding material but also the dissolved abrasive grains can be washed away without damaging the pot-shaped electrode 12 or the abrasive coatings 7, 8 of the cup-shaped grinding wheel 2. For a 25 micron diameter metal-bonded diamond grinding wheel, the working gap 23, ie, the distance between the bottom of the bonding material of the abrasive pad of the grinding wheel 2 and the cup-shaped electrode 12, should be between 50 and 100 microns. To achieve this, an ignition voltage across the working gap 23 of 300 to 500 volts, preferably 400 volts, is required. With a smaller ignition voltage, there is a risk that the working gap is too small and the leaching of the bonding material and the abrasive grains violate the surface of the cup-shaped electrode 12.

As already mentioned, the generator 17 is arranged on the bearing device 1, which means that the electrical discharge lines 19 and 20 (FIG. Fig. 1 ) can be kept very short, whereby an optimal conditioning process of the grinding wheel can be achieved by means of spark erosion.

Fig. 3 shows a schematic representation of the position of the cup-shaped electrode 12 to the cup-shaped grinding wheel 2 when the annular abrasive coating 7 of the cup-shaped grinding wheel 2 is to be conditioned. The central axis 13 of the pot-shaped electrode 12 is in this case aligned exactly parallel to the grinding wheel axis 3. The cup-shaped electrode 12 is formed in a hollow cylindrical shape, and has an annular processing surface 32, which is exactly flat. The cup-shaped grinding wheel 2 rotates around the grinding wheel axis 3, wherein the peripheral speed of the grinding wheel is about 15 to 25 meters per second, if it is a metal-bonded diamond grinding wheel, this can be increased up to 63 meters per second for grinding wheels with CBN grains.

This also corresponds to the speed of the grinding wheel for grinding a workpiece. The pot-shaped electrode rotates around the central Axis 13 at a slower speed. By rotating the electrode 12, a very accurate flatness of the electrode 12 and the abrasive coating 7 is achieved.

Before the spark erosion discharge conditioning operation can be carried out, the cup-shaped electrode 12 must be placed at the correct distance from the abrasive linings 7, 8 to be conditioned. The conditioning operations described below are carried out with a cup-shaped grinding wheel with a diameter of 400 mm, a pad width of 10 mm and a grain size of 25 microns. The discharge energy at the generator is adjusted, the cup-shaped electrode 12 is moved via the carriage 14 along the central axis 13 to the grinding wheel 2, wherein the speed can be 10 to 100 micrometers per minute. Once the average voltage across the working gap 23, which is measured in a known manner and / or the average current flowing through the electrical discharge lines 19 and 20 ( Fig. 1 ) flows, which is also measured in a known manner, pass a predetermined limit, can be started with the conditioning by spark discharge. For profiling the annular abrasive pad 7, a high discharge energy, typically 10 to 100 mJ, and a low discharge frequency, typically 1 to 100 kHz, are selected. The feed rate of the cup-shaped electrode 12 is set at a rate of typically 0.5 to 5 microns per minute. This feed rate is controlled during spark erosion processing within a given bandwidth due to the measured average voltage across the working gap 23 and the average current flowing through the two discharge lines.

The profiling process is terminated when the average voltage across the working gap and / or the average current flowing through the discharge lines remain substantially constant, ie not more than 10% during one rotation of the grinding wheel 2 and the electrode 12, respectively. In this profiling an absolutely flat annular abrasive coating 7 is obtained, which lies in a plane perpendicular to the grinding wheel axis 3 level. It would also be conceivable that annular tapered machining surface 32 of the electrode and align the central axis 13 is not parallel to the grinding wheel axis 3, one would then receive an annular abrasive coating 7, which would be at an angle with respect to the plane perpendicular to the grinding wheel axis 3.

The profiling can be shortened by the grinding wheel 2 with the corresponding abrasive coating 7, 8 and the electrode 12 are hired with the corresponding surface to each other, the generator 17 remains off. The grinding wheel 2 and the electrode 12 are driven in rotation. The grinding wheel 2, which is usually delivered in a relatively precisely profiled state, thereby aligns the electrode 12 by a grinding operation. The profiling process can then be completed by the previously described dressing process.

With this dressing method, there is a risk that the electrode will be unnecessarily abraded too much. In order to avoid this, the generator 17 can be switched on to carry out the dressing process. A medium voltage is applied. Thereafter, grinding wheel 2 and electrode 12 are moved against each other until grinding wheel 2 and electrode 12 abut one another. It creates a short-circuit voltage. The advancing movement of the grinding wheel 2 or the electrode 12 is stopped, it can be waited until an equilibrium sets in the discharge discharge.

For pre-sharpening the annular abrasive coating 7 of the cup-shaped grinding wheel 2, a discharge energy of typically 0.1 to 5 mJ and a discharge frequency of typically 10 kHz to 1 MHz are selected. The advancing movement of the cup-shaped electrode 12 is brought to a low speed of typically 0.1 to 0.4 microns per minute. The feed rate is optimally adjusted within a certain bandwidth due to the measured average voltage across the working gap 23 and the average current flowing through the discharge lines by means of a regulator in the controller. The pre-sharpening process can be considered complete when a feed distance of 20 to 50 microns is reached, this Feed distance corresponds approximately to the grain diameter. As a result, thermally stressed grains are eliminated.

For sharpening and cleaning the annular abrasive covering 7 of the cup-shaped grinding wheel 2 during the grinding process (inprocess), the advancing movement of the cup-shaped electrode 12 is set to a maximum speed of 0.4 micrometers per minute. Discharge energies of 0.1 to 5 mJ and discharge frequencies of 10 kHz to 1 MHz are typically selected. The feed rate is optimally adjusted within a certain bandwidth due to the measured average voltage across the working gap 23 and the average current flowing through the discharge lines by means of the controller in the controller.

During the grinding of a workpiece 9, the pressing force with which the workpiece 9 is pressed against the grinding wheel 2 and the power of the electric motor 4 for the grinding wheel can be measured in a known manner. In particular, the maximum contact pressure, the average contact force during sparking and the ratio of the power of the electric motor to the contact force are calculated. At the end of each grinding operation, the disc wear is estimated in a known manner. From these measured values, or from the data prepared accordingly in a computer and control device, the sharpness state of the abrasive coating 7, 8 of the grinding wheel 2 in use can be quantified in a known manner.

The discharge energy and discharge frequency for sharpening and cleaning are advantageously adjusted within a certain range due to the sharpness state of the abrasive pad 7, 8 of the grinding wheel 2 in use during the preceding and completed grinding operations.

For re-sharpening the annular abrasive coating 7 of the cup-shaped grinding wheel 2 between two grinding operations, the advancing movement of the cup-shaped electrode 12 to a speed set at a maximum of 0.4 microns per minute. Discharge energies of 0.1 to 5 mJ and discharge frequencies of 10 kHz to 1 MHz are typically selected. The feed rate is optimally adjusted within a certain bandwidth due to the measured average voltage across the working gap 23 and the average current flowing through the discharge lines by means of the controller in the controller. This process can be considered complete after a certain re-sharpening time.

The discharge energy, the discharge frequency and the re-sharpening time are advantageously set within a certain range due to the sharpness state of the abrasive pad 7, 8 of the grinding wheel 2 in use during the preceding and completed grinding operations.

As already mentioned, the values described above for conditioning a pot-shaped grinding wheel with a diameter of 400 mm, which has a pad width of 10 mm and a grain size of 25 microns apply. For larger paving widths, the feed rate would have to be reduced accordingly, depending on the ablatable volume per unit of time. For other grain sizes, different feed distances apply accordingly.

Like from the Figures 3 and 4 it can be seen, the carriage 14 on which the conditioning device 11 are arranged, be placed on a perpendicular thereto further carriage 33 so that the cup-shaped electrode 12 can be moved not only in the direction of the central axis 13 on the cup-shaped grinding wheel 2 but also across it. It can thereby be achieved that a jacket-shaped abrasive coating 8 of the cup-shaped grinding wheel 2 can also be processed with this conditioning device 11.

How out Fig. 4 it can be seen, the pot-shaped electrode 12 is moved so that its lateral surface 34 is adjacent to the jacket-shaped abrasive coating 8. The working gap 23 thus arises between jacket-shaped Abrasive coating 8 and lateral surface 34 of the pot-shaped electrode 12. To condition this mantelfächenförmigen abrasive coating 8, the further carriage 33 is moved transversely to the central axis 13 of the cup-shaped electrode 12, the cup-shaped electrode 12 but during the machining operation in the direction of the central axis 13 is oscillating , so that the entire lateral surface 34 is stressed evenly.

How out Fig. 5 it can be seen here has the cup-shaped electrode 12, which is inserted into the device 11 for conditioning the abrasive coatings 7, 8 of the cup-shaped grinding wheel 2, the shape of a truncated cone. The device 11 is placed on the cross slide 14, 33. For conditioning the surface-shaped abrasive coating 8, which has a clearance angle with respect to the annular abrasive coating 7, which corresponds to the truncated cone angle of the electrode 12, the lateral surface 34 of the cup-shaped electrode 12 by appropriate method of the two carriages 14 and 33 in the region of the mantle surface-shaped abrasive coating. 8 brought until the desired working gap 23 is formed. During the conditioning process of the surface-shaped abrasive covering 8 of the cup-shaped grinding wheel 2, the electrode 12 rotates about the axis 13, simultaneously the two carriages 14, 33 are moved such that the electrode performs a superimposed movement in the direction of the clearance angle, represented by arrow 37, and in FIG This direction is moved oscillating, whereby here the lateral surface 34 of the electrode 12 is claimed evenly.

With the embodiment of the device 11 according to Fig. 6 can also be a coat surface-shaped abrasive coating 8 of a cup-shaped grinding wheel 2 are conditioned, which has a clearance angle with respect to the annular abrasive coating 7. The pot-shaped electrode 12 used here in the device 11 has a cylindrical outer shape. The carriage 14 is pivotable and adjustable in a known manner about a perpendicular to the directions of movement of the two carriages 14, 33 axis 36. To condition the surface-shaped abrasive coating 8 of the grinding wheel 2, the carriage 14 is pivoted relative to the carriage 33 by an angle which corresponds to the clearance angle. By moving the carriage 33 of the working gap 23 is set, the cup-shaped electrode 12 is moved during the machining process in the direction of the central axis 13 oscillating, so that the entire surface 34 is uniformly stressed.

With this inventive device and the inventive method, a pot-shaped grinding wheel can be conditioned in a most optimal manner, the sharpening and cleaning operations can be easily performed even during the grinding of workpieces. The grinding wheel always has an optimal condition, which increases efficiency.

Claims (20)

Grinding machine for grinding a workpiece (9), comprising a machine frame, a bearing mounted on the machine frame and guides movable storage device (1), in which a pot-shaped grinding wheel (2) about a grinding wheel axis (3) rotatably driven and electrically isolated, the electrically conductive material is constructed and has a first grinding area with an annular abrasive coating (7) and second grinding areas with coat-shaped abrasive coatings (8), each consisting of an electrically conductive bonding material and abrasive grains embedded therein, which grinding wheel (2) with a generator (17) electrically connected, means (10) for holding the workpiece to be ground (9), a device (11) for profiling, sharpening and cleaning the abrasive coatings (7, 8) of the grinding wheel (2) with at least one movable electrode (12), which is also electrically connected to the generator (17) i St, and means (21, 22) for supplying a cooling lubricant to the electrode (12) and the workpiece (9), characterized in that the device (11) for profiling, sharpening and cleaning of a single cup-shaped electrode (12) formed Tool which is equipped at least with an annular processing surface (32), which cup-shaped electrode (12) is rotatably mounted on a carriage (14) for rotation about its central axis (13), by means of which a between the respective processing surface (32, 34) of the pot-shaped electrode (12) and the respective abrasive coating (7, 8) existing working gap (23) is adjustable, in which upon application of an ignition voltage by the generator (17) a spark discharge occurs. Grinding machine according to claim 1, characterized in that the axis (13) of the pot-shaped electrode (12) is aligned parallel to the grinding wheel axis (3) and perpendicular to the annular processing surface (32). Grinding machine according to claim 1 or 2, characterized in that the axis (13) of the cup-shaped electrode (12) is mounted electrically insulated in the carriage (14), which carriage (14) via a Linear guide on the bearing device (1) held and controlled in the direction of the axis (13) along the linear guide is displaceable. Grinding machine according to one of claims 1 to 3, characterized in that the carriage is designed as a cross slide (14, 33), so that the electrode (12) with respect to the grinding wheel (2) is substantially axially and radially movable, and that the electrode (12) is equipped with a further, substantially mantle-shaped working surface (34). Grinding machine according to claim 4, characterized in that the mantle surface-shaped processing surface (34) of the electrode (12) is cylindrical and in that the two formed as cross slide carriages (14, 33) about an axis perpendicular thereto (36) are mutually pivotable. Grinding machine according to claim 4, characterized in that the mantle surface-shaped processing surface (34) of the electrode (12) is frusto-conical. Grinding machine according to one of claims 1 to 6, characterized in that the generator (12) is a spark generator with capacitive discharge, which is arranged on the bearing device (1). Grinding machine according to one of claims 1 to 7, characterized in that the means for supplying the cooling lubricant consist of nozzles (21, 22) attached to supply lines, via which nozzles (21, 22) the cooling lubricant into the working gap (23) and to the workpiece (9) is deliverable. Grinding machine according to one of claims 1 to 8, characterized in that the cooling lubricant is an oil-based dielectric. Grinding machine according to one of claims 1 to 9, characterized in that the electrode (12) consists of aluminum. Grinding machine according to one of claims 1 to 10, characterized in that a control device is provided for controlling and regulating the work processes. Method for conditioning a cup-shaped grinding wheel (2) in a grinding machine with a device (11) for profiling, sharpening and cleaning the grinding pads (7, 8) of the grinding wheel (2) according to one of claims 1 to 11, characterized in that for conditioning the grinding pads (7, 8) of the grinding wheel (2) into the working gap (23) a cooling lubricant is supplied, via the generator (17) over the working gap (23) an ignition voltage is applied and the electrode (12) against the grinding wheel (2 ) is traversed at a feed rate until a predetermined limit value of the average voltage, measured across the working gap (23), and / or the average current flow, measured through the discharge lines (19, 20), is passed, that then the ignition voltage above the Working gap, the discharge energy, the discharge frequency and the feed rate to a given value for profiling, sharpening or Rei nigen the grinding wheel (2) are set and the corresponding operation is carried out by spark erosive discharge. A method according to claim 12, characterized in that for profiling the grinding wheel (2) a discharge energy of about 10 to 100 mJ and a discharge frequency of about 1 to 100 kHz is selected. A method according to claim 13, characterized in that the profiling is carried out until the average voltage, measured across the working gap (23), and / or the average current flow, measured by the discharge lines, is substantially constant. A method according to claim 12, characterized in that for pre-sharpening the grinding wheel (2) a discharge energy of about 0.1 to 5 mJ and a discharge frequency of about 10 kHz to 1 MHz is selected. A method according to claim 12, characterized in that for sharpening and cleaning the grinding wheel (2) a discharge energy of about 0.1 to 5 mJ and a discharge frequency of about 10 kHz to 1 MHz is selected and that the sharpening and cleaning of the grinding wheel (2 ) is performed while machining a workpiece (9). Method according to one of claims 12 to 16, characterized in that during the processing operation of the grinding wheel (2) by the electrode (12) the feed rate by a controller arranged in the controller within a selectable bandwidth due to the average voltage, measured over the working gap ( 23) and the average current flow measured by the discharge lines. Method according to one of claims 12 to 17, characterized in that the discharge energy and the discharge frequency during the sharpening and cleaning of the grinding wheel (2) by an optimization algorithm arranged in the control within a selectable bandwidth due to the maximum contact pressure, the average contact force during the spark , the ratio of the power of the drive motor to the contact pressure and the disc wear measured during the preceding and completed grinding operations. A method according to claim 12, characterized in that for re-sharpening the grinding wheel (2) between two grinding operations a discharge energy of about 0.1 to 5 mJ and a discharge frequency of about 10 kHz to 1 MHz is selected, and that this resharpening operation during a selectable Nachschärfzeit is performed. Method according to one of claims 12 to 19, characterized in that the discharge energy and the discharge frequency during re-sharpening of the grinding wheel (2), as well as the re-sharpening time, by an optimization algorithm arranged in the control within a selectable bandwidth due to maximum contact force, the average contact force during sparking, the ratio of the power of the drive motor to the contact pressure and the disc wear measured during the preceding and completed grinding operations.

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