Method for operating a servo motor driven turning station of a stacking tool for a punch press

Abstract

A method for operating a servo motor (10) driven turning station (5, 6, 7) of a stacking tool for a punch press includes the following steps: determining a target turning acceleration curve of the turning station (5, 6, 7) in the acceleration phase (A) of the turning increment (D); carrying out a reference acceleration run of the turning station (5, 6, 7); determining during the reference acceleration run the reference angular velocity (ref) of the turning station (5, 6, 7); determining from the target turning acceleration curve the target angular velocity (soll); calculating a target drive torque of the servo motor, at which the target angular velocity (soll) results, from the relationship, known from the reference acceleration run; and accelerating the turning station (5, 6, 7) with the servo motor (10) in the acceleration phase (A).

Claims

1. Method A method for operating a servo motor driven turning station of a stacking tool for a punch press, comprising the steps of: a) determining a target rotational acceleration curve of the turning station in the acceleration phase (A) of the turning increment (D); b) carrying out a reference acceleration run of the turning station while providing a certain reference drive torque by the servo motor or while supplying the servo motor with a certain reference supply current; c) determining one or more of the following reference parameters of the reference acceleration run: c1) the reference turning acceleration of the turning station or of the servo motor achieved over a certain turning range; c2) the reference angular velocity (.sub.ref) of the turning station or of the servo motor when a certain turning angle is reached; c3) the reference turning time (t.sub.ref) elapsed until a certain turning angle is reached; c4) the reference turning angle after a certain turning time has elapsed; d) determining one or more of the following target parameters from the target turning acceleration curve: d1) the target turning acceleration, which is to be present in a certain turning range; d2) the target angular velocity (.sub.soll), which should be present when a certain turning angle is reached; d3) the target turning time (t.sub.soll) which is to be present when a certain turning angle is reached; d4) the target turning angle, which should be present when a certain turning time is reached; e) calculating a target drive torque and/or a target supply current of the servo motor, at which the target turning acceleration, the target angular velocity (.sub.soll), the target turning time (t.sub.soll) and/or the target turning angle results, from the relationship, known from the reference acceleration run, between the reference turning acceleration, the reference angular velocity (.sub.ref), the reference turning time (t.sub.ref) and/or the reference turning angle and the drive torque of the servo motor and/or the supply current of the servo motor; and thereafter f) accelerating the turning station with the servo motor in normal production operation in the acceleration phase (A) of the turning increment (D) while providing the target drive torque by the servo motor or while supplying the servo motor with the target supply current.

2. The method according to claim 1, wherein a target turning acceleration curve is determined, according to which the turning station is accelerated substantially uniformly in the acceleration phase (A) of the turning increment (D).

3. The method according to claim 1, wherein the reference acceleration curve is performed while providing the nominal drive torque of the servo motor as the reference drive torque or while supplying the servo motor with the nominal supply current as the reference supply current.

4. The method according to claim 1, wherein the turning angle of the turning station is determined per turning increment (D) and the reference acceleration run is performed over a certain part of the turning angle, in particular over half the turning angle.

5. The method according to claim 1, wherein the available turning time per turning increment (D) is determined and the reference acceleration run is performed over a certain part of the turning time, in particular over half the available turning time.

6. The method according to claim 5, wherein the available turning time per turning increment (D) is determined in such a way that a theoretically available turning time per turning increment is reduced by a time period (t.sub.idle) which is provided at the end of the turning movement for a stabilization of the system.

7. The method according to claim 5, wherein the available turning time per turning increment (D) or the theoretically available turning time per turning increment (D) is determined as a function of the target stroke rate of the press or as a function of the current stroke rate of the press.

8. The method according to claim 1, wherein the available turning time per turning increment (D) and the turning angle of the turning station per turning increment (D) are determined and a target turning acceleration curve is defined, according to which half the turning angle is reached at the end or after the end of half the available turning time.

9. The method according to claim 8, wherein a target turning acceleration curve is defined, according to which the acceleration phase of the turning increment (D) is completed when the half of the turning angle is reached or after it is reached.

10. The method according to claim 1, wherein the target turning acceleration curve of the turning station is defined over the entire turning increment (D), in particular in such a way that the deceleration phase (B) starts directly after the acceleration phase (A).

11. The method according to claim 10, further comprising the steps of: a) determining a target turning deceleration which should be present in the deceleration phase (B) according to the target turning acceleration curve; b) calculating a target braking torque and/or a target braking supply current of the servo motor, at which the target turning deceleration results, from the relationship, known from the reference acceleration run, between the reference turning acceleration, the reference angular velocity (.sub.ref), the reference turning time (t.sub.ref) and/or the reference turning angle and the drive torque of the servo motor and/or the supply current of the servo motor; and c) decelerating the turning of the turning station with the servo motor in the deceleration phase (B) of the turning increment (D) with provision of the target braking torque by the servo motor or with supply of the servo motor with the target braking supply current.

12. The method according to claim 11, wherein the friction loss braking torque of the turning station and/or or a supply current corresponding to the friction loss is calculated before calculating the target braking torque and/or a target braking supply current of the servo motor and is taken into account in the calculation of the target braking torque and/or the target braking supply current of the servo motor.

13. The method according to claim 10, wherein, in particular prior to the determination of the target turning acceleration curve of the turning station, the friction loss braking torque of the turning station and/or a supply current corresponding to the friction loss braking torque is determined and is taken into account in the determination of the target turning acceleration curve of the turning station, in particular in such a way that, as a result of the friction loss braking torque during the transition from the acceleration phase (A) to the deceleration phase (B) of the turning increment (D) as a result of the friction loss braking torque, there is a sudden drop in angular velocity.

14. The method according to claim 13, wherein the friction loss braking torque of the turning station and/or the supply current corresponding to the friction loss braking torque is determined with a test run, during which the turning station is turned by the servo motor with in particular uniform angular velocity, in particular is turned back and forth, in particular by a turning angle which corresponds to half the turning angle of the turning station per turning increment (D).

15. The method according to claim 10, wherein the target turning acceleration curve of the turning station is determined in such a way that the target turning deceleration in the deceleration phase (B) of the turning increment (D) is numerically smaller than the target turning acceleration in the acceleration phase of the turning increment (D).

16. A punch press with a stacking tool with a turning station driven by a servo motor, wherein the punch press has a control for operating the turning station in accordance with the method according to claim 1.

17. The punch press according to claim 16, wherein the control for operating the turning station is integrated into the press control.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further preferred embodiments of the invention are apparent from the dependent claims and from the description, which now follows with reference to the figures. Thereby it is shown in:

(2) FIG. 1 a simplified illustration of the lower part of a progressive progressive die cutting tool for the production of three different sheet metal stacks for an electric motor;

(3) FIG. 2 a top view of the three sheet stacks produced with the progressive die cutting tool according to FIG. 1.

(4) FIG. 3 a vertical section transverse to the band travel direction through the progressive die cutting tool from FIG. 1 in the area of one of the turning stations;

(5) FIG. 4 the defined target turning acceleration curves in the form of the angular velocity of the turning stations over the entire turning increment;

(6) FIG. 5 the curves of the angular velocities of the turning stations over time during the reference acceleration runs;

(7) FIG. 6 the curves of the friction loss braking torques of the turning stations over time during the test runs to determine them;

(8) FIG. 7 the angular velocity of the defined target turning acceleration curve of the first turning station 5 over the entire turning increment, taking into account the determined friction loss braking torque;

(9) FIG. 8 the angular velocity of the defined target turning acceleration curve of the second turning station 6 over the entire turning increment when the determined friction loss braking torque is taken into account; and

(10) FIG. 9 the angular velocity of the defined target turning acceleration curve of the third turning station 7 over the entire turning increment, taking into account the determined friction loss braking torque.

DETAILED DESCRIPTION

(11) FIG. 1 shows a simplified illustration of the lower part of a progressive progressive die cutting tool 1 for producing the three different sheet metal stacks 2, 3, 4 for an electric motor, which are shown in FIG. 2 in top view. The first sheet metal stack 2 forms the rotor of the motor, the second sheet metal stack 3 forms the stator star of the motor and the third sheet metal stack 4 forms the stator ring of the motor.

(12) The progressive progressive die cutting tool 1 has three turning stations, which are designated by the reference numbers 5, 6 and 7. In the present case, the band travel direction A through the tool 1 runs from left to right.

(13) The production sequence in tool 1 starts with the smallest part. Accordingly, the rotor sheet metal stacks 2 are stacked in the first turning station 5, the stator star sheet metal stacks 3 in the second turning station 6 and the stator ring sheet metal stacks 4 in the third turning station 7.

(14) The connection of sheet metal to sheet metal is achieved here using the so-called clinching process, which is known to the person skilled in the art and therefore does not need to be described in more detail here. Alternatives to this would be joining the individual sheets by means of laser welding, baking varnish or glue.

(15) FIG. 3 shows a vertical section transverse to the band travel direction through the progressive progressive die cutting tool 1 in the area of the third turning station 7.

(16) The sheet stacks 2, 3, 4 must be turned during stacking because differences in sheet thickness can exist across the width of the sheet strip to be processed and these would always lead to skewed sheet stacks when stacked at the same point. With the turning of the sheet stacks, the presumed sheet metal thickness differences move in a circle and the result is a cylindrical stack.

(17) The rotor sheet stack 2 has a pitch of 10. This results in a turning angle of 36 per turning increment D for this sheet stack 2. The stator star has 12 beams, which results in a turning angle of 30 per torsion increment D for the stator star laminated core 3 and the associated stator ring laminated core 4. The turning stations 5, 6, 7 are each rotated by means of servo motors 10 via a toothed belt drive. The servo motors 10 each have, for example, a power of 3000 W and a nominal torque of 19.1 Nm. The stack height is monitored and controlled by counting the individual sheets and the measured band thickness. If the stack is high enough, switchable punches are used to cut out the interleavings for the clinching process so that a gap is created before the next stack is started to be stacked. The finished stacksin the situation shown in FIG. 3 these are stator ring sheet metal stacks 4fall downwards onto conveyor belts 8, which guide them away from the tool 1 at right angles to the band travel direction.

(18) The turning stations 5, 6, 7 also serve as sheet stack brakes. They must provide the necessary resistance when the individual sheets are joined. An important quality feature of the finished sheet stacks 2, 3, 4 is their holding force. This is checked repeatedly in random samples during the production process.

(19) In the present case, the progressive die-cutting tool 1 is mounted on an automatic die-cutting machine which is operated at 480 strokes per minute. A window over a crank angle of 300 is available for turning the turning stations 5, 6, 7. Accordingly, a theoretical turning time t of 104 ms is available for each turning increment D of 36 or 30. To ensure that at the end of the turning movement there is still sufficient time for demagnetizing or switching the current of the drive motor 10 and for any oscillations to subside, so that one or more catch pins can carry out the fine adjustment of the turning station, the theoretically available turning time t per turning increment D of 104 ms is shortened by a time span t.sub.idle of 4 ms, and an available turning time t per turning increment D of 100 ms is assumed for the determination of the target acceleration curves of the turning stations 5, 6, 7.

(20) The servo motors 10 must accelerate different external mass inertias in wide ranges. These depend on the outer radii of the turning stations to the fourth power.

(21) To determine the target parameters, the target turning acceleration curves of the turning stations 5, 6, 7 are set accordingly. In order to achieve the most energy efficient and material-saving turning of the sheet metal stacks possible with the turning stations 5, 6, 7, the available turning time t of 100 ms is evenly divided between the acceleration phase A and the deceleration phase B of the turning increment D in such a way that they immediately follow one another. In other words, acceleration is to take place over the first half of the respective turning angle per turning increment D and deceleration over the second half. In this way, unnecessarily strong accelerations and decelerations are avoided.

(22) The target turning acceleration curves thus determined for the turning stations 5, 6, 7 are shown in FIG. 4 on the basis of the angular velocity .sub.soll (s.sup.1) over the turning time t, t.sub.soll (ms). As can be seen, the acceleration time to is 50 ms, the deceleration time t.sub.B is also 50 ms, and the settling time t.sub.idle is 4 ms. As can also be seen, at the first turning station 5 for the rotor sheet packs 2, after a turning time of 50 ms or after a turning angle of 18, an angular velocity .sub.soll of 12.6 s.sup.1 must be achieved, while at the second turning station 6 for the stator star sheet metal stacks 3 and at the third turning station 7 for the stator ring sheet metal stacks 4, identical angular velocities .sub.soll of 10.5 s.sup.1 must be achieved in each case after a turning time of 50 ms or after a turning angle of 15. The acceleration and deceleration at the first turning station 5 for the rotor-sheet stacks 2 must be correspondingly greater. This is due to the larger turning angle per turning increment of 36 instead of 30. Since the specified target turning acceleration curves are symmetrical with respect to the acceleration A and deceleration B phases, the target parameters for the deceleration B phases are the reverse of those for the acceleration A phases.

(23) The turning stations 5, 6, 7, each of which is fully equipped and completely filled with sheet packs 2, 3, 4, perform a reference acceleration run over a reference turning angle which corresponds to half the turning angle of the turning station per turning increment D. Accordingly, the reference turning angle for the first turning station 5 is 18 and for the second turning station 6 and the third turning station 7 it is 15 in each case. The servo motors 10 drive each of the turning stations 5, 6, 7 with the nominal torque of 19.1 Nm, and the reference angular velocities .sub.ref and reference turning times t.sub.ref are recorded when the reference turning angles are reached.

(24) The reference acceleration curves determined in this way for the turning stations 5, 6, 7 are shown in FIG. 5 using the angular velocity .sub.ref (s.sup.1) over the turning time t.sub.ref (ms).

(25) As can be seen, the first turning station 5 for the rotor ring sheet metal stacks 2 reaches the reference turning angle after a reference turning time t.sub.ref of 8.6 ms and has a reference angular velocity .sub.ref of 73.1 s.sup.1 at the reference turning angle, while the second turning station 6 for the stator ring sheet metal stacks 3 requires a reference turning time t.sub.ref of 34.6 ms and reaches a reference angular velocity .sub.ref of 15.1 for this, and the third turning station 7 for the stator ring sheet metal stacks 3 requires a reference turning time t.sub.ref of 40.7 ms and achieves a reference angular velocity .sub.ref of 12.9 s.sup.1.

(26) Using the relationships between the reference angular velocities .sub.ref or the reference turning times t.sub.ref of the turning stations 5, 6, 7 and the reference drive torques of the associated servo motors 10 of 19.1 Nm, the target drive torques of the servo motors 10 are then calculated, which result in the respective target angular velocities .sub.soll and target rotation times t.sub.soll.

(27) For this purpose, the respective target parameters .sub.soll, t.sub.soll and reference parameters .sub.ref, t.sub.ref are set in relation to each other and the reference drive torque is multiplied by this ratio, which is shown below for the first turning station 5 by way of example.

(28) The target angular velocity .sub.soll determined for the turning station 5 after a turning angle of 18 is 12.6 s.sup.1. The reference angular velocity .sub.ref determined with the reference acceleration run of this turning station 5 after a turning angle of 18 is 73.1 s.sup.1. The ratio between the determined target angular velocity .sub.soll and the determined reference angular velocity .sub.ref is a factor of 0.172. Multiplying this by the reference drive torque of the servo motor 10 of 19.1 Nm results in a target drive torque for the first turning station 5 for the rotor sheet metal stacks 2 of 3.28 Nm. The same result is obtained if the reference turning time t.sub.ref of 8.6 ms determined for the first turning station 5 is related to the determined target turning time t.sub.soll of 50 ms for a turning angle of 18, which results in a ratio of 0.172, and the reference drive torque of the servo motor 10 of 19.1 Nm is multiplied by this number.

(29) For the second turning station 6 of the stator star sheet metal stacks 3, this calculation results in a target drive torque of the servo motor 10 of 13.23 Nm and for the third turning station 7 of the stator ring sheet metal stacks 4, a target drive torque of the servo motor 10 of 15.54 Nm. The calculated target drive torques for the acceleration phases A also represent the target braking torques for the deceleration phases B, simply with the direction of force reversed.

(30) In a variant of the teach-in operation described above, in addition to the reference acceleration runs, further test runs are carried out to determine the friction loss braking torques (frictional torques) M (Nm) of the individual turning stations 5, 6, 7 and are taken into account when determining the target turning acceleration runs of the turning stations 5, 6, 7.

(31) For this purpose, the turning stations 5, 6, 7 with their servo motors 10 are each slowly rotated back and forth by half the turning angle. The frictional torque M is determined by detecting the supply current or the drive torque of the servo motor. If the supply current is detected, the drive torque or friction torque is determined from the known relationship between the supply current and the drive torque of the servo motor 10.

(32) FIG. 6 shows the curves of the friction loss braking torques M (Nm) of the turning stations 5, 6, 7 determined during the test runs over time t (s).

(33) The friction torques M determined in this way, namely 0.5 Nm for the first turning station 5, 1.4 Nm for the second turning station 6 and 1.2 Nm for the third turning station 7, are now each subtracted twice from the acceleration torques and used accordingly as deceleration torques. Using the relationships known from the reference acceleration runs, these deceleration torques can be converted into angular velocities for the definition of a target rotational acceleration curve according to FIG. 4 and deducted accordingly in the deceleration phases B.

(34) FIGS. 7 to 9 show the target turning acceleration curves of the individual turning stations 5, 6, 7 over the entire turning increment D determined in this way, taking into account the determined friction loss braking torques M. As can be seen, with these target turning acceleration curves the deceleration phase B is even smoother than with those shown in FIG. 4. When calculating the respective target braking torque for deceleration phase B, the respective friction loss braking torque M is taken into account accordingly by assuming a target angular velocity .sub.soll reduced by twice the angular velocity component determined in each case at the transition from acceleration phase A to deceleration phase B.

(35) The process steps described above are carried out automatically by the control system of the automatic punching press when a corresponding teach-in function is called up. During regular operation of the automatic punching press, the turning stations 5, 6, 7 of the progressive die cutting tool 1 are then controlled in such a way that the servo motors 10 provide the respective target drive torques and target braking torques for the turning of the turning stations 5, 6, 7.

(36) It is also envisaged that, after the actual teach-in, the turning time t available per turning increment D, which is dependent on the number of strokes of the presses, is continuously determined, the target turning acceleration curves are adjusted accordingly and new target drive torques and target braking torques are calculated with the parameters known from the reference acceleration runs and used for control. In this way, the turning stations 5, 6, 7 can be automatically operated optimally at any stroke rate of the punch press.

(37) While preferred embodiments of the invention are described in the present application, it should be clearly noted that the invention is not limited to these and may be carried out in other ways within the scope of the claims which now follow.