EP2319636B1 - Press assembly for a tool machine - Google Patents

Description

• mit einem Pressantrieb,
• mit einem ersten Druckelement, dem eine erste Antriebseinheit des Pressantriebs zugeordnet ist und mittels dessen die Werkzeughalterung mit einer durch die erste Antriebseinheit des Pressantriebs bereitgestellten Presskraft beaufschlagbar ist, indem das erste Druckelement den Stößel beaufschlagt sowie
• mit einem zweiten Druckelement, dem eine zweite Antriebseinheit des Pressantriebs zugeordnet ist und mittels dessen die Werkzeughalterung mit einer durch die zweite Antriebseinheit des Pressantriebs bereitgestellten Zusatz-Presskraft beaufschlagbar ist, indem das zweite Druckelement den Stößel beaufschlagt,
• wobei die Werkzeughalterung und das zweite Druckelement relativbeweglich sind, wenn nur das erste Druckelement die Werkzeughalterung beaufschlagt und
• wobei Mittel zur Hemmung, insbesondere zur Aufhebung der Relativbeweglichkeit von Werkzeughalterung und zweitem Druckelement vorgesehen sind, so dass die Werkzeughalterung bei Beaufschlagung zunächst ausschließlich durch das erste Druckelement im Bedarfsfall durch das zweite Druckelement mit einer Zusatz-Presskraft beaufschlagbar ist.

The invention relates to a press drive arrangement of a machine tool for generating a working stroke of a tool holder provided on a plunger, in which a workpiece can be acted upon by a tool mounted on the tool holder,

• with a press drive,
• with a first pressure element, which is associated with a first drive unit of the press drive and by means of which the tool holder can be acted upon by a pressing force provided by the first drive unit of the press drive by the first pressure element acts on the plunger and
• with a second pressure element, which is associated with a second drive unit of the press drive and by means of which the tool holder can be acted upon by an additional pressing force provided by the second drive unit of the press drive by the second pressure element acting on the push rod,
• wherein the tool holder and the second pressure element are relatively movable when only the first pressure element acts on the tool holder and
• wherein means for inhibiting, in particular for canceling the relative mobility of the tool holder and the second pressure element are provided, so that the tool holder is initially acted upon by the second pressure element with an additional pressing force when acted upon exclusively by the first pressure element.

A press drive arrangement of the above type is known from JP 2001-150191 A , The prior art relates to a press drive arrangement with a main drive and with an auxiliary drive. The main drive is a hydraulic piston / cylinder drive, the hydraulic piston acts on the workpiece machining provided with a processing tool holder tool. The auxiliary drive is arranged above the main drive and comprises a plunger and an electromotive spindle drive provided for this purpose. By the latter, the plunger of the auxiliary drive can be lowered into the hydraulic cylinder of the main drive, there to increase the oil pressure to increase the available pressing force on the tool holder.

In workpiece machining, the tool holder and the processing punch of the previously known press drive arrangement are initially moved only by the main hydraulic drive in the direction of the workpiece to be machined. After placing the processing stamp on the workpiece is determined by means of a sensor, whether the force applied by the hydraulic main drive pressing force for the workpiece machining sufficient or if an additional pressing force is needed. Optionally, the plunger of the auxiliary drive is lowered into the hydraulic cylinder of the main drive and thereby generates the required additional pressing force by means of the auxiliary drive.

Another press drive arrangement is disclosed in U.S. Patent No. 5,347,054 JP 2001-009538 A , This press drive arrangement comprises a first impact part, by means of which a tool arrangement mounted in an upper tool turret can be acted upon is. Upon being acted upon by the first impact part, a tool mounted on the tool arrangement is moved along a lifting axis in the direction of a metal sheet to be processed. The first impact member is driven by a first piston-cylinder drive. In addition, a second impact member is provided on the turret punch press, by means of which the tool assembly is additionally acted upon. The second impact member is driven by a second piston-cylinder unit.

The object of the present invention is to provide a press drive arrangement of the type mentioned above with a space-saving design.

According to the invention, this object is achieved by the press drive arrangement according to claim 1.

In the case of the invention, one of the drive units of the press drive is formed by a spindle drive with a drive spindle, which has an axial receptacle. In the axial recording of the drive spindle provided with the tool holder plunger is arranged to save space.

It is possible to apply the tool holder initially exclusively by the first pressure element. Only in case of need, ie when the pressing force provided by the first pressure element is not sufficient to perform the desired workpiece processing, a second pressure element can be added, which acts on the tool holder with an additional pressing force. The connection of the second pressure element is effected by the relative mobility of the tool holder and the second pressure element is inhibited, in particular is canceled. The second pressure element is only used if it proves to be actually necessary. Due to the relative mobility of the tool holder and the second pressure element, the second pressure element, as long as it is not for pressing force is needed, the work stroke is not or at least slower than the tool holder to be moved. Unnecessary acceleration of the second pressure element is avoided. Consequently, the mass to be moved or accelerated is only as large as actually required. In this way, on the one hand, the energy consumption of the press drive arrangement can be reduced, on the other hand, the dynamics can be increased with the same drive power of the press drive arrangement.

In particular, the drive units can be designed very differently. For example, the first drive unit can be provided with a particularly high dynamic range (eg a maximum acceleration of up to 100 m / s ² ) but with a relatively low maximum force (eg a maximum force of 40 kN). The second drive unit can be designed to provide higher forces (eg a maximum force of 160 to 250 KN) but lower acceleration values (eg a maximum acceleration up to 10 m / s ² ). Overall, this results in a highly dynamic press drive which can also provide high pressing forces.

As long as only a relatively low pressing force is required, as in the stamping of relatively thin metal sheets, the working strokes can be generated exclusively by means of the highly dynamic drive unit. In this case, for example, with a pitch of 1 mm, i. H. between two strokes, the metal sheet is shifted by 1 mm with respect to the tool, lifting speeds of 1500 strokes per minute can be achieved. Only in case of need, z. As when punching relatively thick metal sheets, an additional pressing force is initiated by the second drive unit.

The tool holder is provided on a plunger on which attack the pressure elements for pressing force introduction. This can be the connection the pressure elements take place in the immediate vicinity of the drive units and there are favorable conditions for the introduction of the pressing force.

Advantageous embodiments of the invention according to claim 1 emerge from the dependent claims 2 to 11.

According to claim 2 is provided in a preferred embodiment of the invention that the plunger is arranged in the axial receptacle of the drive spindle of the spindle drive and at the end facing away from the tool holder end opposite the drive spindle axially projecting and acted upon by one of the pressure elements section.

In the case of a construction of the invention according to claim 3, the second pressure element and the tool holder are relatively movable along a working stroke axis along which the working stroke of the tool holder can be generated by means of the press drive arrangement. Thus, while the tool holder is moved in the stroke only in the stroke direction along the Arbeitshubachse by the first pressure element, the second pressure element in the stroke direction are moved slower than the tool holder. In particular, the second pressure element can remain unmoved in the stroke direction. The energy saving options already mentioned above are particularly significant.

In addition, the second pressure element even at a caused by the first pressure element working stroke of the tool holder even contrary the stroke direction to be moved. In this way, it can be transferred to a starting position for a subsequent power stroke before the power stroke is completed. Since the press drive arrangement is thus ready for the next working stroke faster after completion of a working stroke, the process time is shortened.

In a construction of the invention according to claim 4, the tool holder is acted upon by the second pressure element with an additional pressing force by the relative mobility of the tool holder and the second pressure element is inhibited or canceled only in one direction. In order to initiate an additional pressing force, the relative mobility is inhibited or canceled at least in a pressing force introduction direction, in which the second pressure element acts on the tool holder with an additional pressing force. In the opposite direction remains according to claim 4, the relative mobility but also obtained at force introduction by the second pressure element. The motion coupling of tool holder and second pressure element is therefore only to the extent necessary.

Advantageously, the relative mobility of the tool holder and the second pressure element is inhibited or canceled by a Zuschaltthub, in which a relative movement of the tool holder and the second pressure element is carried out according to claim 5. In the event that the second pressure element is moved toward the tool holder in the stroke direction in the stroke direction, the second pressure element can be accelerated in the stroke direction before introducing an additional pressing force. If the movement of the accelerated pressure element is then inhibited or canceled, the drive power applied to the second pressure element is largely available for acceleration or for loading the tool holder in the stroke direction. The proportion of drive power, which is required for an acceleration of the second pressure element after its connection is reduced.

Advantageously, the stroke length of the Zuschaltthubes is dimensioned so that the second pressure element can be accelerated during Zuschaltthub to a desired pressing speed in the stroke direction. The drive power is then completely available for loading the tool holder.

According to claim 6, the relative mobility of the tool holder and the second pressure element can be canceled by a Zuschlagthub a contact surface on the second pressure element comes with a tool holder side contact surface to the plant. The result is a robust and reliable version of the force and motion coupling.

By the first pressure element along the Arbeitshubachse immovably connected to the tool holder (claim 7), the first pressure element can constantly initiate pressing force into the tool holder without time delay. In addition, the fixed connection of the first pressure element to the Werkzeughalterung along the working stroke axis that the tool holder can be moved by means of the first pressure element in a following on the working stroke return stroke. The need for additional return means, eg. B. return springs, provide deleted.

For the drive units different drive types are considered. For the first drive unit, a gearless piezo drive is advantageous due to its high dynamics. A disadvantage of gearless piezoelectric drives but their relatively short stroke lengths. By a particularly high dynamics and relatively long stroke lengths, however, is characterized by an inductive linear drive, in particular a so-called "tube motor" from. If the second drive unit is furthermore designed as an electric spindle drive unit, overall results in an electrically driven Pressantriebsanordnung (claim 8). On hydraulic drive technology can be omitted in this case.

The embodiment of the invention according to claim 9 is characterized by a particularly advantageous construction of a press drive arrangement.

According to claim 10, an embodiment of the invention is provided with a rotary drive unit, by means of which the tool holder is rotatable about the working stroke axis. Due to the rotational adjustability of the tool holder, a tool mounted in the tool holder for workpiece machining can be rotated relative to the workpiece in a desired orientation. In a particularly compact design acts z. As a rotary valve with the second pressure element together to take the tool storage to the working stroke axis. Alternatively, however, the rotary valve can also be arranged separately from the second pressure element, which results in design possibilities of the press drive arrangement, which can be advantageous in particular with regard to the stability of the press drive arrangement.

The press drive arrangement can be designed in such a way that automatically an additional pressing force occurs when a certain pressing force introduced into the tool holder by the first pressure element is exceeded is introduced by the second pressure element in the tool holder.

In a type according to claim 11, detection means are provided, by means of which a need for the initiation of an additional pressing force during the workpiece loading can be determined. The detection means may be formed by displacement and / or force sensors. In a cost-effective variant without additional sensors, only the current is consumed, which is consumed by the electric first drive unit. Since the power consumption is a measure of the power provided by the drive, it can be concluded when exceeding a predetermined limit of the power consumption that a connection of the second pressure element is required. As soon as a need is identified, the press drive arrangement is controlled so that the second pressure element is switched on for the introduction of the pressing force.

Figur 1:

eine Seitenansicht einer Stanz-/Umformmaschine mit einer Pressantriebsanordnung;

Figur 2:

eine Schnittdarstellung einer Pressantriebsanord- nung erster Bauart;

Figuren 3a bis 3c:

die Pressantriebsanordnung nach Figur 2 bei der Stanzbearbeitung einer dünnen Blechtafel;

Figuren 4a bis 4c:

die Pressantriebsanordnung nach Figur 2 bei der Stanzbearbeitung einer dicken Blechtafel;

Figur 5:

Verfahrensschritte eines Bearbeitungsverfahrens mit Hilfe einer Pressantriebsanordnung nach Figur 2;

Figur 6:

eine Schnittdarstellung einer Pressantriebsanord- nung zweiter Bauart und

Figuren 7 bis 9:

Geschwindigkeiten von Antriebsspindeln der Press- antriebsanordnung nach Figur 5 im Verlauf von drei unterschiedlich gesteuerten Werkstückbear- beitungen.

Preferred embodiments of the invention are shown schematically in the drawings and are explained in more detail below with reference to the figures. Show it:

FIG. 1:

a side view of a stamping / forming machine with a Pressantriebsanordnung;

FIG. 2:

a sectional view of a press drive arrangement of the first type;

FIGS. 3a to 3c:

the Pressantriebsanordnung after FIG. 2 during punching of a thin metal sheet;

FIGS. 4a to 4c:

the Pressantriebsanordnung after FIG. 2 in the punching of a thick metal sheet;

FIG. 5:

Process steps of a machining method using a Pressantriebsanordnung after FIG. 2 ;

FIG. 6:

a sectional view of a Pressantriebsanord- tion of the second type and

FIGS. 7 to 9:

Speeds of drive spindles of the press drive arrangement according to FIG. 5 in the course of three differently controlled workpiece machining operations.

FIG. 1 is a machine tool in the form of a punching / forming machine 1 can be seen, which has a C-shaped machine frame 2, in the pharynx 3 a coordinate guide 4 of conventional design is arranged, on which a metal sheet to be machined 5 can be fixed. A processing unit 6 arranged on the upper frame limb of the machine frame 2 comprises a press drive arrangement 7, a tool holder 8 and a processing tool 9 mounted in the tool holder 8.

For processing a metal sheet 5 by means of the punching / forming machine 1, the point to be machined of the metal sheet 5 is arranged by the coordinate guide 4 under the processing tool 9. The tool holder 8 together with the processing tool 9 is then lowered by the press drive arrangement 7 with a working stroke along a working stroke axis 10 in a stroke direction 11 onto the metal sheet 5.

The metal sheet processing, z. As a punching, is carried out by the machining tool 9, which the metal sheet 5 with a pressing force or punching force is applied, wherein the machining tool 9 during machining with a arranged on the opposite side of the metal sheet 5 second machining tool (not shown) cooperates. After completion of the working stroke, the machining tool 9 is raised along the working stroke axis 10 in a return stroke direction 12.

By means of the press drive arrangement 7, the tool holder 8, together with the machining tool 9, is also rotatable about the working stroke axis 10.

As editing tools can in the tool holder 8 in addition to punching tools and forming tools, such as embossing, bending and beading tools, etc., are changed.

All drives of the punching / forming machine are controlled by a numerical control unit 13.

In detail, the press drive arrangement 7 of the punching / forming machine 1 FIG. 2 refer to. The tool holder 8 is immovably connected to an elongate plunger 14 whose longitudinal axis coincides with the working stroke axis 10.

At the end of the plunger 14 remote from the tool holder 8, a first drive unit in the form of a highly dynamic linear motor 15 is provided which forms part of a press drive of the press drive arrangement 7. Within an annular primary part 16 of the linear motor 15 which revolves about the working axis 10, a likewise secondary secondary part 17 of the linear motor 15 is arranged. By means of a measuring device 18, the current required by the linear motor 15 is measurable.

The secondary part 17 is provided with a plate-shaped pressure element 19 which is rotatably connected to the plunger 14 by an axial pivot bearing 20 about the working stroke 10, but axially immovable. In an alternative design, a damping element may additionally be provided between pressure element 19 and plunger 14.

In a further alternative design, a linear motor in the form of a so-called "tube motor" can be used instead of the linear motor 15 shown. A "tube motor" is characterized by a cylindrical structure, which makes it possible that the secondary part of the motor relative to the primary part is fully rotatable about the lifting axis and can perform a highly dynamic stroke in each relative rotational position. Advantageously, therefore, can be dispensed with the use of a "tube motor" on the pivot bearing 20.

Furthermore, the press drive arrangement 7 has, as part of the press drive, a second drive unit in the form of an electric rotary / lifting drive, which is formed by an electric spindle drive 21. The spindle drive 21 is designed to be less dynamic than the linear motor 15, but can provide a significantly higher pressing force.

The spindle drive 21 comprises a drive spindle 22 whose spindle axis coincides with the working stroke axis 10. The drive spindle 22 is provided with two external threads 23 and 24. Both external threads 23 and 24 have the same thread pitch, but are formed in opposite directions. A first drive nut 25 is seated on the first external thread 23, a second drive nut 26 is seated on the second external thread 24. The rotational positions of the drive nuts 25 and 26 about the working stroke axis 10 can be determined by means of sensors 27.

A torque motor 28, which is associated with the first drive nut 25, has a frame-fixed stator 29 and a rotor 30 which is formed circumferentially about the working axis 10 and gearless with the drive nut 25 is connected. The stator 29, the rotor 30 and the drive nut 25 overlap each other at least partially along the working stroke axis 10. The second drive nut 26 is associated with a torque motor 31, which is of the same type as the torque motor 28. It has a stator fixed to the stator 32 and a rotor 33 immovably connected to the drive nut 26.

The drive spindle 22 is provided with an axial receptacle 34, in which the plunger 14 is arranged. In particular, the plunger 14 projects axially through the drive spindle 22.

The axial receptacle 34 of the work spindle 22 has a portion of smaller diameter to form a cylindrical shoulder 39. On the inner circumference of the cylindrical shoulder 39 is provided with two radially opposite axial guide grooves 36. The guide grooves 36 extend within the cutting plane according to FIG. 2 ie FIG. 2 shows the inner diameter of the cylindrical shoulder 39 in the peripheral region of the guide grooves 36. In the peripheral region outside the guide grooves 36, the inner diameter of the cylindrical shoulder 39 corresponds approximately to the outer diameter of the plunger 14 (off FIG. 2 not apparent). Two driving wings 35 immovably connected to the plunger 14 project into the axial guide grooves 36 on the inner circumference of the cylindrical shoulder 39.

In a modified (not shown) type of a press drive, the guide grooves 36 may also be provided in a separate from the cylindrical shoulder 39 axial portion of the receptacle 34, for example in FIG. 2 be arranged offset upwards. Accordingly are in this alternative, the driving wings 35 compared to the in FIG. 2 shown ratios higher up. Since the driver vanes 35 are guided in this case in the guide grooves 36 of the work spindle 22 with a greater radial distance from each other, there is a variant with a more stable mutual guidance of the work spindle 22 and plunger 14th

Furthermore, the cylindrical shoulder 39 in the in FIG. 2 shown pressing drive 7 on its tool holder side end face a circumferential bearing surface 37. Axially opposite the abutment surface 37 of the plunger 14 is provided with a circumferential inlet surface 38, which is formed by a radial shoulder of the plunger 14.

A sensor 39a is used to determine the axial position of the plunger 14 or the tool holder 8 relative to the machine frame 2 and the rotational position of the plunger 14 and the tool holder 8 about the working stroke axis 10th

In the following, the general mode of operation of the press drive arrangement 7 will be described, before subsequently the individual motion sequences in the case of different workpiece machining operations on the basis of FIG FIGS. 3a to 3c and 4a to 4c be explained.

In order to raise or lower the plunger 14 together with the tool holder 8 and the machining tool 9 mounted therein by means of the linear motor 15 along the working stroke axis 10, the secondary part 17 of the linear motor 15 performs a corresponding lifting or lowering movement along the working stroke axis 10 relative to the frame-fixed Primary part 16 of the linear motor 15 off. The lifting movement of the secondary part 17 is transmitted via the pressure element 19 and via the axial pivot bearing 20 on the plunger 14. In the same way is one through the Linear motor 15 generated force in the lifting and return stroke 11 and 12 in the plunger 14 introduced.

During the lifting movement of the plunger 14 by the linear motor 15, the wings 35 on the drive spindle 22 and the axial guide grooves 36 form an anti-rotation device for the plunger 14.

Furthermore, the plunger 14 is rotationally adjustable by means of the spindle drive 21 about the working stroke axis 10. The spindle drive 21 consequently forms a rotary drive unit, by means of which the tool holder 8 provided on the plunger 14 can be adjusted in rotation about the working stroke axis 10. In order to move the plunger 14 together with the tool holder 8 in a rotational position about the working stroke axis 10, the work spindle 22 is rotated about the working stroke axis 10. The wings 35 serve as a rotary valve, by means of which the plunger 14 is rotated together with the tool holder 8 during the rotational movement of the drive spindle 22 about the working stroke axis 10. The rotational movement of the drive spindle 22 results without the drive spindle 22 also executing a lifting movement along the working stroke axis 10 by the drive nuts 25 and 26 are rotated at the same speed and in the same direction by the torque motors 28 and 31.

In addition, the plunger 14 can be lowered by means of the spindle drive 21 in the stroke direction 11 or acted upon with an (additional) pressing force in the stroke direction 11. For this purpose, the drive spindle 22 is lowered in the lifting direction 11. The lowering of the drive spindle 22 results without the drive spindle 22 is rotated simultaneously by the drive nuts 25 and 26 are rotated by the torque motors 28 and 31 at the same speed but in opposite directions. When the abutment surface 37 on the cylindrical shoulder 39 is pressed in the stroke direction 11 onto the insertion surface 38 on the plunger 14, a (additional) pressing force generated by means of the spindle drive 21 can be introduced into the plunger 14.

Consequently, the cylindrical shoulder 39 serves as a pressure element, which can act on the plunger 14 and consequently also the tool holder 8 with an (additional) pressing force provided by the spindle drive 21.

The FIGS. 3a to 3c show three different operating states of the press drive assembly 7 in the punching of a relatively thin metal sheet FIGS. 3a to 3c Punching shown the required pressing force or punching force is generated exclusively by the linear motor 15.

FIG. 3a shows the Pressantriebsanordnung 7 in an operating condition in which the tool holder 8 assumes a starting position before a power stroke. Starting from the starting position, the tool holder 8 is moved together with the machining tool 9 in the lifting direction 11 on the metal sheet 5. The axial movement of the machining tool 8 is effected by the linear motor 15. The spindle drive 21, in particular the drive spindle 22 together with the radial shoulder 39, remains during the stroke movement. As a result, the tool holder 8 moves based on the proportions in FIG FIG. 3a in the lifting direction 11 of the cylindrical shoulder 39 away. The tool holder 8 and the cylindrical shoulder 39 perform a relative movement along the working stroke axis 10.

FIG. 3b the conditions can be seen when the machining tool 9 just touches the metal sheet 5. The section of the working stroke at which the machining tool 9 only approaches the metal sheet 5 is finished. Since the drive spindle 22 in the same position stopped at the beginning of the working stroke ( FIG. 3a Was arranged), the axial distance between the abutment surface 37 and the inlet surface 38 has increased due to the lowering movement of the plunger 14.

In the following punching processing applied to the processing tool 9, the metal sheet 5 in the lifting direction 11 with a pressing force. The pressing force or punching force with which the machining tool 9 acts on the metal sheet 5 is provided by the linear motor 15. For this purpose, the pressure element 19 connected to the secondary part 17 of the linear motor 15 acts on the plunger 14 with the pressing force. About the plunger 14 and the tool holder 8, the pressing force is finally applied to the machining tool 9. Since it is a relatively thin metal sheet 5 in the case shown, the maximum of the linear motor 15 to be provided pressing force (about 40 KN) is sufficient to durchzustanzen the metal sheet 5.

In Figure 3c the operating state of the press drive assembly 7 is shown after the processing tool 9 has punched through the metal sheet. Starting from this state, the plunger 14 by means of the linear motor 15 back to the starting position according to FIG. 3a moved with a return stroke. The spindle drive 21 remains stationary during the working stroke and during the return stroke.

Due to the high dynamics of the linear motor 15, the punching machining described above can be carried out in a very short time, so that in particular in the thin sheet metal range with the help of the press drive assembly 7 at a pitch of 1 mm stroke numbers up to 1500 strokes / min can be achieved.

The FIGS. 4a to 4c show three different operating states of the press drive arrangement 7 when punching a relatively thick metal sheet. 5

FIG. 4a the conditions can be seen when the processing tool 9 just touches the metal sheet 5. The conditions in FIG. 4a therefore correspond to the circumstances FIG. 3b , The pressing force with which the machining tool 9 acts on the metal sheet 5 is initially provided exclusively by the linear motor 15. Accordingly, the plunger 14 and thus also the tool holder 8 is acted upon only by the plate-shaped pressure element 19 with a pressing force.

However, the maximum force that can be generated by the linear motor 15 is not sufficient to punch through the relatively thick metal sheet 5. The need for an additional pressing force is determined by the current required by the linear motor 15 by means of the measuring device 18 (FIG. FIG. 2 ) is measured and the measured values are constantly transmitted to the numerical control unit 13. In an evaluation part of the control unit 13, the measured current is compared with a current limit, which corresponds to the current that is consumed by the linear motor 15 at the maximum pressure to be provided by him. If the measured current reaches the predetermined limit value, the numerical control unit 13 evaluates this as necessary for the introduction of an additional pressing force by means of the spindle drive 21. The measuring device 18 and the above-mentioned evaluation part of the numerical control unit 13 thus constitute detection means by means of which the need for initiation an additional pressing force is determined.

In addition, the numerical control unit 13 triggers a Zuschaltthub, in which the drive spindle 22 moves together with the cylindrical shoulder 39 in the lifting direction 11 by means of the torque motors 28 and 31 becomes. The stroke length of the Zuschaltthubes is sufficient so that the spindle drive 21 can accelerate together with the cylindrical shoulder 39 during the Zuschalthubes to a speed at which the subsequent workpiece machining is performed (press speed).

The Zuschaltthub is completed when the contact surface 37 rests against the inlet surface 38. The cylindrical shoulder 39 and the tool holder 8 can not approach further along the working stroke axis 10. The relative mobility of the cylindrical shoulder 39 and the tool holder 8 is thus canceled along the working stroke axis 10 in one direction. It results in the FIG. 4b shown relationships.

In the subsequent workpiece machining, an additional pressing force is introduced into the tool holder 8 via the introduction surface 38 on the tappet 14, which is generated by the spindle drive 21. Since the spindle drive 21, together with the cylindrical shoulder 39, has already been accelerated to the pressing speed before the abutment surface 37 encounters the introduction surface 38, the spindle drive 21 no longer has to be accelerated further. Its drive power is thus completely available for the acceleration of the plunger 14, the tool holder 8 and the machining tool 9 and for applying the same with an additional pressing force available.

The pressing force provided by the linear motor 15 and the additional pressing force provided by the electric spindle drive 21 add up. The sum of the pressing forces is sufficient to punch through the relatively thick metal sheet 5. The conditions after punching the metal sheet 5 are Figure 4c refer to.

After the working stroke, the processing tool 9 is returned to its original position with a return stroke (FIG. FIG. 3a ) raised by the linear motor 15 and the spindle drive 21 simultaneously moved in the return stroke 12. Under these circumstances, the speed of the machining tool 9 during the return stroke is limited by the speed of the slower spindle drive 21.

However, conditions may also arise in which the direction of movement of the spindle drive 21 can be reversed before completion of the working stroke. By way of example, a workpiece machining is to be mentioned in which in a lower portion of the power stroke only a pressing force is required, which is smaller than the maximum to be provided by the linear motor 15 pressing force. In this case, can use a retraction of the slower spindle drive 21 before completion of the working stroke. Consequently, the speed of the machining tool 9 is determined during the later return stroke only by the faster linear motor 15. The machining tool 9 can thus be moved back faster and the time for the return stroke is shortened.

For completeness, it should be noted that the connection of the spindle drive 21 can be made not only at the time to which a machining tool on the metal sheet 5, but also in the course of the entire workpiece machining or the working stroke.

In FIG. 5 are again the three main steps in the context of the FIGS. 4a to 4c summarized punching process summarized. First, the tool holder 8 is acted upon exclusively by the first, plate-shaped pressure element 19 under the introduction of a pressing force ( FIG. 4a ). If necessary, the second pressure element, in this case the cylindrical shoulder 39, is switched on by a Zuschaltthub relative to the tool holder 8 for initiating an additional pressing force. Finally, the tool holder 8 through the second Pressure element under introduction of an additional pressing force applied ( FIG. 4b ).

The numerical control unit 13 of the punching / forming machine 1 makes it possible to operate the press drive assembly 7 in two different control modes. In a basic control mode, the press drive assembly is operated according to the procedure described above, i. the processing tool 9 is always lowered only by means of the linear motor 15 on the metal sheet 5 to be processed. Only in case of need an additional pressing force is then initiated by the spindle drive 21.

But is it z. B. on the basis of the thickness of the metal sheet to be processed 5 already clear in advance that the producible by the linear motor 15 pressing force is not sufficient to edit the metal sheet 5, a thick plate control mode can be adjusted. In the thick sheet control mode, the spindle drive 21 is moved from the front. In this way, the time loss caused by the Zuschlthub is avoided.

An alternative type of press drive assembly 40 is FIG. 6 refer to. According to FIG. 6 the press drive assembly 40 assumes its home position prior to a power stroke. The tool holder 41 is provided on a ram 42 extending along the working stroke axis 10. The plunger 42 is rotatable together with the tool holder 41 and a machining tool 43 by means of a rotary drive unit forming a rotary motor 44 about the working stroke axis 10. For this purpose, the rotary motor 44 on a rotating rotor 45, which is gearless connected to the plunger 42. The rotor 45 is arranged within a frame-fixed stator 46.

To generate pressing force and to generate the lifting movement of the tool holder 41 along the working stroke axis 10 serve two electric spindle drives 47 and 48. The first spindle drive 47 has a supported on the machine frame 2 stator 49, within which a rotating rotor 50 is provided. The rotor 50 is directly connected to a drive nut 51 which engages with a drive spindle 52. The spindle axis of the drive spindle 52 coincides with the working stroke axis 10. The drive spindle 52 is provided on the tool holder side with a pressure washer 53, which is connected via a thrust bearing 54 with the drive spindle 52.

The second spindle drive 48 is arranged on an axial attachment of the drive spindle 52. It has a higher dynamics than the first spindle drive 47, but can only produce a relatively low force. The spindle drive 48 comprises a stator 55, which is supported on the drive spindle 52 of the first spindle drive 47. Furthermore, the second spindle drive 48 has a rotor 56 rotating around the working axis 10. The rotor 56 is gearless connected to a drive nut 57 which engages with a drive spindle 58. The spindle axis of the drive spindle 58 also coincides with the working stroke axis 10.

The drive spindle 58 is connected to the plunger 42 via a plate spring 59 and an axial pivot bearing 60. The plate spring 59 is biased in the lifting direction 11 with a spring force which is slightly smaller than the maximum axial force to be provided by the spindle drive 48. Overall, a successive arrangement of the two spindle drives 47 and 48 results.

The axial pivot bearing 60 and the disk spring 59 form a first pressure element, which the plunger 42 at its in an axial receptacle 61st Actuate the drive spindle 52 disposed end. The pressure disk 53 forms a second pressure element.

The operation of the press drive assembly 40 will be described below with reference to FIGS FIGS. 7 to 9 described. The FIGS. 7 to 9 show the axial velocity of the drive spindle 52 relative to the machine frame 2 (dashed line) and the axial velocity of the drive spindle 58 relative to the drive spindle 52 (dash-dotted line) in the course of various exemplary workpiece machining operations.

For workpiece machining according to FIG. 7 At the beginning, the machining tool 43 is lowered exclusively by means of the highly dynamic spindle drive 48. At a time t ₁ , the work spindle 58 and at the same time the processing tool 43 reaches a constant speed v ₁ . At the time t ₂ , the processing tool 43 hits the metal sheet 5 to be processed. The processing tool 43 now loads the metal sheet 5 with a pressing force provided by the spindle drive 48. This pressing force is transmitted from the drive spindle 58 of the spindle drive 48 via the plate spring 59 and the pivot bearing 60 on the plunger 42.

At the in FIG. 7 As shown, the axial force generated by the spindle drive 48 exceeds the spring force with which the plate spring 59 is biased. However, since the pressing force applied to the machining tool 43 is insufficient to further lower the machining tool 43 placed on the metal sheet 5 by deforming the metal sheet 5, the plunger 42 together with the tool holder 41 and the machining tool 43 stored therein temporarily stops. In the further lowering movement of the drive spindle 58, the plate spring 59 is therefore compressed.

The numerical control unit 13 recognizes, as has already been explained with reference to the first type of press drive assembly 7, z. B. by measuring the current required by the spindle drive 48 that the spindle drive 47 must be switched to initiate an additional pressing force. Immediately, ie, almost at time t ₂ , the numerical control unit 13 triggers a Zuschaltthub, in which the drive spindle 52 is lowered together with the pressure plate 53 in the stroke direction 11. With the drive spindle 52 and the spindle drive 48 in the stroke direction 11 on the (still) standing plunger 42 is moved, whereby the plate spring 59 is compressed by a further. At the same time, however, the lowering movement of the drive spindle 58 of the spindle drive 48 is decelerated until the drive spindle 58 finally stands relative to the drive spindle 52 (time t ₃ ). Subsequently, the drive spindle 58 is moved relative to the drive spindle 52 by means of the spindle drive 48 in the return stroke direction 12 until it reaches its starting position relative to the work spindle 52 FIG. 6 occupies (time t ₄ ).

The stroke length of the Zuschaltthubes is sufficient so that the spindle drive 47 can accelerate during the Zuschaltthubes to a speed at which the subsequent workpiece processing is carried out (pressing speed v _p ).

The Zuschaltthub is completed when the pressure plate 53 in the stroke direction 11 abuts on the plunger 42 (time t ₅ ). The thrust washer 53 and the plunger 42 can not approach further along the working stroke axis 10. Consequently, the relative mobility of the pressure plate 53 and the plunger 42 and thus also the tool holder 41 is repealed in a direction along the working stroke axis 10. The spindle drive 47 now passes via the drive spindle 52 and the pressure plate 53 directly an additional pressing force in the plunger 42 and further into the tool holder 41 a. After completion of the working stroke (time t ₆ ), the drive spindle 52 is raised in the return direction 12. As a result, the spindle drive 48 mounted on the drive spindle 52 is also moved together with the plunger 42 in the return stroke direction 12. The return stroke is completed at time t ₇ . The press drive assembly 40 is again in the operating state according to FIG. 6 ,

FIG. 8 shows the velocity profiles of the drive spindles 52 and 58 in a second, exemplary workpiece machining. In the case shown, the spindle drive 47 serves to extend the working stroke of the machining tool 43 generated by the highly dynamic spindle drive 48. For reasons of cost or to achieve the highest possible dynamic drive, the stroke of the machining tool 43 that can be generated by the spindle drive 48 is relatively short, eg. B. 5 mm. In the case according to FIG. 8 The stroke of the highly dynamic spindle drive 48 is not sufficient, so that in addition the spindle drive 47 must be moved (time t ₈ ). The stroke of the machining tool 43 is extended, since the travel paths of the drives 47 and 48 add up. The return stroke can be carried out at least partially by simultaneous operation of both spindle drives 47 and 48 (time period t ₉ to t ₁₀ ).

In the workpiece machining according to the FIGS. 7 and 8 For example, the press drive assembly 40 operates in a standard mode. Deviating from this, the press drive arrangement 40 can also be operated in a high-dynamics mode. FIG. 9 the speeds of the drive spindles 52 and 58 can be seen in the course of an exemplary workpiece machining in the high dynamic mode. Also shows FIG. 9 the resulting speed of the machining tool 43 (solid line). For reasons of comparison, the resulting speed of the machining tool 43 is also shown in sections, if it would perform a stroke of about the same length, but only using the low-dynamic drive 47 (line of crosses).

In high dynamic mode, the spindle drives 47 and 48 are operated by means of the numerical control unit 13 such that both accelerate and decelerate both drives 47 and 48 during acceleration and deceleration of the machining tool 43. In this way, the fact is made use of that due to the successive arrangement of the spindle drives 47 and 48 whose accelerations add up to a total acceleration of the machining tool 43.

According to FIG. 9 Accordingly, the highly dynamic spindle drive 48 is used primarily in the acceleration and deceleration processes. In particular, the spindle drive 48 remains during the working stroke and the return stroke even a short time (time t ₁₁ to t ₁₂ and time t ₁₃ to t ₁₄ ). In the case of workpiece machining after FIG. 9 The required pressing force does not exceed the biasing force of the plate spring 59. At time t ₁₅ , the Pressantriebsanordnung 40 is back to its original position.

Based on the sectionally indicated speed profile of the machining tool 43 in the case of machining using only the slower spindle drive 47 (FIG. Fig. 9 , Line of crosses), the time gain due to the high dynamic mode is particularly clear. While thanks to the high dynamic mode at the time t _15, the return stroke is already completed, the machining tool 43 has been accelerated at use only the spindle drive 47 at this time only to a constant Rückhubgeschwindigkeit.

On the part of the numerical control unit 13 results in the high-dynamics mode by z. B. both spindle drives 47 and 48, the same desired positions or the same desired speeds of the machining tool 43 in the course of workpiece machining can be specified, the spindle drives 47 and 48 follow the setpoint specification with different gain factors. In addition, the setpoint specification takes place on condition that the machining tool 43 does not have to be moved faster than the maximum possible speed of the slower spindle drive 47.

Regardless of the possibility to initiate an additional pressing force, if necessary, only by the successive arrangement of the spindle drives 47 and 48 and the ability to operate the spindle drives 47 and 48 in high dynamic mode, an advantageous Pressantriebsanordnung, which is characterized by a high dynamics distinguished.

Incidentally, a highly dynamic Pressantriebsanordnung can result in an analogous manner when using other drive types. Decisive is only that a first drive is provided which drives an actuator in a stroke direction on which a second drive is supported to drive a plunger or a tool holder in the same stroke direction. In addition, control means must be provided which allow the operation of the press drive assembly in a high dynamic mode in which a power stroke is generated by simultaneously accelerating and / or decelerating both drives.

In the press drive arrangement 40, in conjunction with the possibility of connecting the spindle drive 47 in the high dynamic mode, there is the additional advantage that the switchover stroke does not have to be triggered by the numerical control unit 13. Rather, the Zuschalthub results automatically. In high dynamic mode, the drive spindle 52 becomes common moved in the stroke direction 11 with the pressure disk 53 during the entire working stroke. When the machining tool 43 abuts the metal sheet 5 with a pressing force exceeding the spring force of the plate spring 59, the plate spring 59 springs. The processing tool 43 together with the plunger 42 stops for a short time. However, since the drive spindle 52 is already moved in the stroke direction 11, the drive spindle 52 with the pressure disk 53 immediately approaches the stationary plunger 42 in the stroke direction 11 until the pressure disk 53 bears against the plunger 42. This results in a Zuschalthub.

The Einfederungsweg, by which the plunger 42 springs against the drive spindle 52 can be determined for example by means of a measuring device. In order to move the machining tool 43 into an exact position along the working stroke axis 10, the currently measured deflection travel is taken into account on the control side.

Claims (11)

1. A press drive arrangement of a machine tool for generating a working stroke of a tool holder (8, 41) provided on a ram (14, 42), in which a workpiece (5) can be processed by a tool (9, 43) mounted on the tool holder (8, 41),

   • comprising a press drive,

   • comprising a first pressure element (19, 60), which is assigned a first drive unit (15, 48) of the press drive and by means of which the tool holder (8, 41) can be loaded with a pressing force provided by the first drive unit (15, 48) of the press drive, as a result of the first pressure element (19, 60) loading the ram (14, 42), and

   • comprising a second pressure element (39, 53), which is assigned a second drive unit (21, 47) of the press drive and by means of which the tool holder (8, 41) can be loaded with an additional pressing force provided by the second drive unit (21, 47) of the press drive, as a result of the second pressure element (39, 53) loading the ram (14, 42),

   • wherein the tool holder (8, 41) and the second pressure element (39, 53) can be moved relative to one another if only the first pressure element (19, 60) loads the tool holder (8, 41), and

   • wherein means for inhibiting, in particular for cancelling, the relative mobility of the tool holder (8, 41) and the second pressure element (39, 53) are provided, so that when the tool holder (8, 41) is initially loaded exclusively by the first pressure element (19, 60), the tool holder (8) can be loaded if required with an additional pressing force by the second pressure element (39, 53),

   characterised in that the ram (14, 42) is arranged at least partially in an axial seat (34, 61) of a drive spindle (22, 52) of a spindle drive (27, 47), which forms one of the drive units (15, 21, 47, 48) of the press drive.
2. A press drive arrangement according to claim 1, characterised in that the ram (14) is arranged in the axial seat (34) of the drive spindle (22) of the spindle drive and in that the ram (14) comprises at the end remote from the tool holder (8) a portion which protrudes axially with respect to the drive spindle (22) and at which the ram can be loaded by one of the pressure elements (19, 39, 53, 60).
3. A press drive arrangement according to anyone of the preceding claims, characterised in that the second pressure element (39, 53) and the tool holder (8, 41) are movable relative to one other along a working stroke axis (10), along which the working stroke of the tool holder (8, 41) can be generated by means of the press drive arrangement (7, 40).
4. A press drive arrangement according to anyone of the preceding claims, characterised in that the tool holder (8, 41) can be loaded with an additional pressing force by the second pressure element (39, 53) by inhibiting or cancelling the relative mobility of the tool holder (8, 41) and the second pressure element (39, 53) in only one direction.
5. A press drive arrangement according to anyone of the preceding claims, characterised in that the tool holder (8, 41) can be loaded with an additional pressing force by the second pressure element (39, 53) by inhibiting or cancelling the relative mobility of the tool holder (8, 41) and the second pressure element (39, 53) by an activatable stroke, in the course of which a relative movement of the tool holder (8, 41) and the second pressure element (39, 53) is effected.
6. A press drive arrangement according to anyone of the preceding claims, characterised in that the tool holder (8, 41) can be loaded with an additional pressing force by the second pressure element (39, 53) by cancelling the relative mobility of the tool holder (8, 41) and the second pressure element (39, 53) by an activatable stroke, in the course of which a bearing surface (37) on the second pressure element (39, 53) and a lead-in surface (38) on the tool holder (8, 41) are pressed together along the working stroke axis (10).
7. A press drive arrangement according to anyone of the preceding claims, characterised in that the tool holder (8, 41) and the first pressure element (19, 60) are fixedly joined to one another along the working stroke axis (10).
8. A press drive arrangement according to anyone of the preceding claims, characterised in that at least one drive unit (21, 47, 48) is in the form of an electric spindle drive and/or in that one drive unit (15) is in the form of an inductive linear drive.
9. A press drive arrangement according to anyone of the preceding claims, characterised in that the ram (14, 42) can be loaded by a pressure element (39, 60) at a portion arranged in the axial seat (34, 61) of the drive spindle (22, 52).
10. A press drive arrangement according to anyone of the preceding claims, characterised in that a rotary drive unit (21, 44) is provided, by means of which the tool holder (8, 41) can be rotatably adjusted around the working stroke axis (10).
11. A press drive arrangement according to anyone of the preceding claims, characterised in that sensing means (18, 13) are provided, by means of which when the tool holder (8, 41) is loaded exclusively by the first pressure element (19, 60) it is possible to determine whether it is necessary to load the tool holder (8, 41) with an additional pressing force by the second pressure element (39, 53).

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