Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21D24/00—Special deep-drawing arrangements in, or in connection with, presses
  • B21D24/10—Devices controlling or operating blank holders independently, or in conjunction with dies

Definitions

• the invention relates to a method for controlling and regulating servo-electric die cushion to forming presses according to the preamble of patent claim 1 and an apparatus for performing the method according to the preamble of patent claim. 6
• Press discloses, wherein the servo drive is connected via a gear and rack with the cushion plate.
• the servo drive is connected via a gear and rack with the cushion plate.
• mechanically coupled servo drives act on a common pressure cheek or a servo drive acts independently of others on each a pressure cheek element of a multi-part pressure cheek.
• Servo motors are controlled by a numerical control with the required for the generation of the pulling force position and
• Controlled torque signals wherein, if necessary, within a control loop, a feedback of the actual values of Servomotor or belonging to the drawing device cushion plate can be done.
• JP 04172200 A a control for the pre-acceleration of hydraulic die cushion is described in which the pre-acceleration is started at a certain press angle and the target position is specified by an arithmetic unit.
• a further device for a combined pneumatic and hydraulic die cushion in which between the phase of the pre-acceleration and the drawing operation, a change from position to pressure control by means of a position-dependent switching signal. Apart from the pre-acceleration phase, no further closed-loop phases are disclosed with attitude control. Since the position control loop for the phase of the pre-acceleration is closed only via the feedback of the actual path, the control quality of the adjustment of the speed of the die cushion is limited to the speed of the plunger. Due to the position-dependent switching signal for switching from position to force control process-dependent fluctuations can affect the reproducibility of the pressure build-up at the start of drawing.
• each separate control devices for the servo-valves assigned to the separate hydraulic actuators are necessary for the phase of pre-acceleration and the drawing process. Furthermore, the control of force setpoint profiles for the possibility of varying during the drawing process
• the individual pressure points on the one hand allow a mutually differentiated force setting during the drawing process and on the other hand to avoid tilting of the pressure cheek due to off-center loading, known from the prior art synchronous coupling of the pressure points with each other is unsuitable ,
• the movement of the pulling device is synchronized by means of electrical waves on the one hand between the plunger and the pulling device and on the other hand between a plurality of servomotors belonging to the pulling device.
• the required pulling force can be adjusted by changing the engine torque during the deep-drawing process.
• the device required for this purpose and the process steps required for the control are not disclosed.
• Movement of the press pusher is detected as a guide shaft by one or two position encoders and controlled the axes of movement of the parts transport device in function of the Leitwellenposition for precalculated motion functions.
• the advantage of this principle is the possibility of position synchronization on the one hand between press pusher and parts transport device and on the other hand between the individual axes of movement within the multi-axis part transport device.
• the invention has for its object to provide a method and apparatus for controlling and regulating servo-electric die cushion on presses, in which by means of a simple structure of the control and regulation and a small number of steps in the control or regulation flow a stable and precise sequence on the one hand in the phase of force-controlled drawing process and on the other hand is made possible in all phases of the position-controlled movement of the pad.
• the object is achieved by a method for
• Claims 1 to 7 takes place with a device with the
• the method and the device are aimed not only at servo-electric drives but also at servo-hydraulic drives for drawing cushions in forming presses, wherein the drawing cushions are used on the one hand as the die cushion acting on the lower die in the table and on the other hand as the die cushion acting on the upper tool in the tappet.
• the die cushions can be designed as single-point or multi-point drawing cushions.
• the core idea of the invention is that, for controlling and regulating the die cushion, the principle of the guide shaft-controlled electronic cam control is combined with the force control so that all movement phases of the die cushion, which take place without mechanical contact with the press ram, are controlled by electronic position cam disks during the movements with contact to the press ram via a force control with a path-dependent controlled force setpoint profile done.
• An advantage of this principle is the complete synchronism of the movement of the die cushion to the plunger movement, which is maintained even with speed changes and emergency stops of the plunger movement, without special Control functions are necessary. The same applies to the
• Synchronicity of the pressure points of multi-point die cushion with each other and for the synchrony of the die cushion movement to an as needed existing part transport device It is essential to be able to perform the switching between position control and force control with simple control engineering means.
• the switching can be done on the one hand via a limit value switch, which evaluates a control deviation, for example, when placing the plunger on the die cushion and activates a switching device to force control.
• the change of position and force control can be determined only by the course of the position cam relative to the position of the plunger. For example, if the cam extends above the plunger position, the pad position is enforced by the movement of the plunger.
• FIG. 1 Structure of a multi-point die cushion Fig. 2a device in a first embodiment of the
• Fig. 2b apparatus in a second embodiment for controlling servo-hydraulic die cushion
• Fig. 3 step sequence of the method for controlling servo-controlled die cushion
• Fig. 4a exemplary movement of a die cushion in the operating mode "with blocking" in the lower layer
• FIG. 5 block diagram for the die cushion control with electronic cam and partial changeover to force control in a first embodiment with rotary guide shaft
• FIG. 6 block diagram for the die cushion control with electronic cam and partial switching to force control in a second embodiment with linear encoder on the plunger and two cams 7
• FIG. 1 shows the structure of a servo-electric die cushion 8 designed as a multipoint cushion in one
• Electric cylinders 21 are in
• the spindle nut 23 connected to the pressure cheek 2 is non-rotatable and axially synchronous with the pressure cheek 2 movable.
• the associated spindle 3 is axially fixed in
• Press table 20 rotatably mounted.
• the remote from the spindle nut 23 end of the spindle 3 is connected via a coupling 24 with a servo motor 5 in operative connection.
• the power is transmitted from the electric cylinders 21 via the pressure cheek 2 and pull pins 25 on the blank holder 22 in the press tool.
• the die cushion 8 may also be used instead of electric cylinders 21 with hydraulic cylinders 3a as a servo-hydraulic die cushion
• the movement functions such as pre-acceleration, blocking in a defined position, if necessary retreat, lifting and run-up of the die cushion 8 take over.
• Fig. 2a shows the basic structure of the device with a schematically illustrated and described in Fig. 1 servo-electric die cushion 8, with which the method can be implemented.
• the servomotors 5 are each equipped with an encoder 6, via which the position and speed detection takes place.
• the cushion force is detected by a respective force transducer 4 for each pressure point.
• the force transducers 4 may be, for example, piezoelectric or resistive strain transducers.
• the cushion force can be detected indirectly via the motor current of the servo motors 5.
• the NC control device 59 includes, for each pressure point of the die cushion 8, an axis control device 58 which controls the position, speed and force of the pressure point takes over and generates the power to control the servomotor 5 or hydraulic cylinder 3a. Both devices are controlled by a Leitwelle, the Leitwelle either by real position encoder on the press ram, press drive or the drive of a parts transport system within the press or by a " virtual "Leitwellensignal example from the control of a servo press can be displayed.
• the cam disk control device 56 generates reference position values for the axis control devices 58 depending on the control shaft.
• the principle of the electronic cam is used, with each pad position being assigned a pad position by a control table or a mathematical function.
• the force setpoint control device 57 generates force setpoint profiles for the force control in the axis control devices 58. Depending on the application or part-specific requirement, this may be a constant value or a position-dependent controlled force profile for the pull region and, if required, additional values for the cushion run-up in the operating mode "Without Blocking "act.
• FIG. 2b It can be seen from FIG. 2b how a servo-hydraulic drawing pad 9 can be controlled by the method.
• the movable pressure cheek 2 is driven by two hydraulic cylinders 3a.
• the pressure in the hydraulic cylinders 3a is controlled by servo or proportional valves 5a.
• the position detection is carried out by linear displacement sensor 6a on the pressure cheek 2 and the force measurement is realized by pressure sensor 4a on the hydraulic cylinders 3a. From the arrangement of the signal interface (dotted
• Fig. 3 the proposed method is shown in the form of a sequence of steps.
• the controller calculates a so-called electronic position cam 12, which includes the desired course of the pad position 13 in dependence on the plunger position 11.
• the controller calculates a force setpoint profile that includes the force curve as a function of the plunger and / or cushion position 11, 13.
• the position cam 12 and the force command value profile are stored in the form of a table, a mathematical function or a combination of both in the controller.
• the pad position 13 is influenced by a position control, which receives its desired value from the position corresponding to the current plunger position 11 position cam 12. Due to the course of the position cam 12, the die cushion 8, 9 is initially held in its upper position and thensuingvantt shortly before the impingement of the plunger.
• the ram when the ram is placed on the die cushion 8, 9, it switches over to force or torque control with a first switchover condition 38.
• the first switching condition 38 can be met by reaching a certain plunger position 11, a defined control deviation or by a defined course of the position cam 12 in conjunction with a force limiting control.
• the associated embodiments are described in Figures 5 and 7.
• step 35 takes place from placement of the plunger on the die cushion 8, 9 until the end of the common movement of plunger and die 8, 9 a force or torque control, the setpoint from the according to the current pillow or plunger position 13, 11 read Force setpoint profile receives.
• step 36 takes place depending on the preselected
• Switching condition 39 can either by reaching a certain plunger or cushion position 11, 13 of a defined deviation or by a specific
• Course of the position cam 12 can be met in conjunction with a force limiting control.
• the cyclic motion sequence is continued with the first method step 33. Due to the course of the position cam 12 depending on the selected operating mode of the die cushion 8, 9, the movement functions locks or retreat in the lower position, lifting the part, cushion run-up and cushioning 19 executed with subsequent rest in the upper position.
• FIG. 4a shows a typical movement sequence of the die cushion 8, 9 in the "blocked" mode in connection with the proposed method.
• the cushion run-up does not take place immediately after passing through the lower reversal point of the tappet but the movement of the die cushion 8, 9 is initially blocked and the run-up takes place with a time delay relative to the plunger movement
• the plunger position 11, the cushion position 13 and a position cam 12 are shown as time- or crank angle-dependent course.
• the position control takes place with electronic position cam 12, wherein the pad position 13 of the position cam 12 follows and the rest in the upper position and the pre-acceleration of the die cushion 8, 9 controls. This corresponds to the first method step 33 according to FIG. 3.
• the subsequent third phase 16 includes the movement functions pillow retraction and blocking in the lower layer, lifting the part, cushion run-up, cushioning and rest in the upper position.
• the sequence is repeated cyclically with the first phase 14 described above.
• the said movement functions are contained in the course of the position cam 12 and are performed by the position control in dependence on the serving as a guide shaft tappet position 11.
• a typical movement sequence of the die cushion 8, 9 in the "without blocking" mode of operation in connection with the proposed control method is shown in Fig. 4b.
• the plunger position 11, the cushion position 13 and a position cam 12 are shown as time or crank angle dependent course.
• Force setpoint profile one or more additional values that are dimensioned so that the die cushion 8, 9 of the
• Figures 5, 6 and 7 show application examples and advantageous embodiments of the proposed die cushion control with electronic cam and partial switching to force control in the form of block diagrams.
• the first embodiment according to FIG. 5 includes a cam control function 41 for calculating, storing and monitoring shaft-dependent read-out of position cam disks 12, a force setpoint control function 42 for calculating, storing and position-dependent readout of force setpoint profiles and an axis controller 58 which consists of the three control loops position controller 43, speed controller 44 and force regulator 45 and the switching device for Controller setpoint 49 and the power amplifier 46 is.
• All three control loops are closed by returning the corresponding actual values.
• the actual position value is supplied by the encoder 6.
• the actual speed value is generated by a differentiator 47 from the actual position value and the actual force value is detected by the force transducer 4.
• the functional sequence is controlled by the guide shaft i, which here corresponds to the crank angle of the press, as follows:
• position values are continuously transferred to the position controller 43 by the cam control function 41.
• the position controller 43 is followed by the speed controller 44, which in turn controls the force controller 45 via the switching device 49.
• the three cascaded controllers operate as position control, so that the servo motor 5 controlled via a power amplifier 46 and the actively connected pressure cheek 2 follow the position cam 12. In this way, the first movement phase of the die cushion 8, 9, consisting of locking in the upper layer and pre-acceleration is controlled.
• the function unit for government switching 55 is effective, which consists in this embodiment of limit value switch 48 and switching device for controller setpoint 49.
• limit value switch 48 which evaluates a deviation in the impact point 17, switched by means of switching means 49 to force control.
• position and speed controller 43, 44 are ineffective and the force controller 45 receives its setpoint values from the force setpoint control function 42. This continuously generates setpoints by ram or pillow position-dependent readout of the stored Power setpoint profile. This is the second phase
• FIG. 6 shows a second embodiment of the die cushion control which uses a linear position sensor 7 on the press ram as a guide shaft.
• a distinction between downward and upward movement is no longer possible directly by the guide wave signal.
• two cams are used, each with a position cam 50 for the control function down and a position cam 51 for the control function up.
• Switching is effected by a switching device 53, which is controlled via a switching cam 52 generated by the rotary position sensor 1.
• the switching can also take place by means of a virtual guide shaft, a device for direction detection or a control signal from the sequence control for the slide movement.
• the another mode of operation corresponds to the first embodiment according to FIG. 5.
• a device for dynamic force limitation 54 is used as a functional unit for regulating changeover 55.
• This device limits the output signal of the speed controller 44 to a dynamically predefinable maximum value, which is generated by the force setpoint control function 42. In this way, the change between position control and force control is determined only by the course of the position cam 12 relative to the plunger position 11.
• the force limitation is not effective and the system is in position control, so that the die cushion 8, 9 follows the cam. If, on the other hand, the position cam 12 runs above the tappet position 11, the cushion position 13 is forced by the movement of the press tappet. In this case, the output signals of the position and speed controller become so large that the force limitation is effective. Thus, the system is in force control and the force setpoint profile is effective.
• Switching device for controller setpoints 50 position cam for the control function downwards

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• 2005
  • 2005-03-19 DE DE102005012876A patent/DE102005012876A1/de not_active Withdrawn
• 2006
  • 2006-03-17 AT AT06722642T patent/ATE416859T1/de active
  • 2006-03-17 ES ES06722642T patent/ES2317509T3/es active Active
  • 2006-03-17 WO PCT/DE2006/000486 patent/WO2006099845A1/fr not_active Application Discontinuation
  • 2006-03-17 JP JP2008502240A patent/JP5185809B2/ja not_active Expired - Fee Related
  • 2006-03-17 DE DE502006002334T patent/DE502006002334D1/de active Active
  • 2006-03-17 CN CN2006800089521A patent/CN101146630B/zh not_active Expired - Fee Related
  • 2006-03-17 EP EP06722642A patent/EP1861214B1/fr not_active Revoked

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