FINE BLANKING PRESS AND METHOD FOR OPERATING THE SAME

Abstract

The disclosure pertains to a fine blanking press comprising a first press unit comprising a first press drive for driving the first press unit in a first driving movement during a fine blanking process step, and a second press unit wherein the second press unit is driven in a second driving movement at least partially during the first driving movement of the first press unit, and wherein a force control unit exerts a counter force against a force exerted by the first press unit during its first driving movement, and wherein the force control unit comprises at least one sensor and a controller operative to receive measuring data collected by the at least one sensor, and wherein the controller is configured to carry out a closed loop control on basis of the received measuring data. The disclosure further pertains to a method for operating a fine blanking press.

Claims

1. A fine blanking press comprising: a first press unit configured to drive a first press drive unit in a first driving movement during fine blanking process step, a second press unit configured to drive a second press drive unit in a second driving movement at least partially while driving the first press unit in its first movement, and configured such that: a force control unit exerts a counter force against a primary force exerted by the first press unit during its first driving movement, and in that the force control unit comprises at least one sensor operative to generate measuring data; and a controller for receiving the measuring data collected by the at least one sensor and configured to perform a closed-loop control analysis on the basis of received measuring data.

2. The fine blanking press according to claim 1, wherein the first press drive includes a hydraulic cylinder, and the force control unit includes at least one proportional control valve, which is configured to connect the barrel side and/or the piston side of the hydraulic cylinder to each other.

3. The fine blanking press according to claim 2, wherein each of the barrel and/or piston sides are pressurized before, and/or during, the first driving movement of the first press unit.

4. The fine blanking press according to claim 1 wherein at least one sensor comprises at least one position sensor configured for measuring the position of the first press unit, and wherein the controller is configured to carry out a closed loop control of the position of the first press unit on basis of the measured position data.

5. The fine blanking press according to claim 1 wherein the first press drive is configured to drive the first press unit in different movement steps, including: (i) an approach step, during which the first press unit approaches the process material to be fine blanked, (ii) a fine blanking step, during which the process material is fine blanked, and (iii) a return step, during which the first press unit returns to its initial position before the initial approach step, and wherein the controller is configured to carry out the closed loop control such that the first press unit is driven at a constant speed at least during the fine blanking step.

6. The fine blanking press according to claim 1 wherein the at least one sensor comprises at least one force sensor measuring the force exerted by the first press unit and/or the counter force controlled by the force control unit, and wherein the controller is configured to carry out a closed loop control of one of the forces exerted by the first press unit and the counter force controlled by the force control unit on basis of the measured force data.

7. The fine blanking press according to claim 1, wherein the force control unit is configured to control a force exerted by the second press unit as a counter force against the force is exerted by the first press unit during its first driving movement.

8. The fine blanking press according to claim 7 wherein the force control unit is configured to control a force exerted by the second press unit independently from the force exerted by the first press unit during its first driving movement.

9. The fine blanking press according to claim 7, wherein the second press unit is driven in the second driving movement at least partially by the first driving movement of the first press unit.

10. The fine blanking press according to claim 7, wherein the second press unit comprises a second press drive comprising a hydraulic cylinder, and a force control unit comprising at least one proportional control valve configured to connect the barrel side and/or the piston side of the hydraulic cylinder to the tank for hydraulic fluid.

11. The fine blanking press according to claim 10 wherein the barrel and/or piston sides are pressurized before and/or during the second driving movement of the second press unit.

12. The fine blanking press according to claims 10 wherein the barrel and/or piston sides are connected to each other by the control valve.

13. A method for operating a fine blanking press wherein a first press unit is driven in a first driving movement during a fine blanking process step, and a second press unit is driven in a second driving movement at least partially during the first driving movement of the first press unit, wherein during the first driving movement of the first press unit a counter force is exerted against a force exerted by the first press unit, and at least one sensor collects measuring data, wherein a closed loop control is carried out on the basis of the measuring data.

14. The method according to claim 13 wherein the at least one sensor comprises at least one position sensor measuring the position of the first press unit, and wherein a closed loop control of the position of the first press unit is carried out on the basis of the measured position data.

15. The method according to claim 13 wherein the first press unit is driven during a fine blanking process step in one of various movement steps, including: (i) an initial approach step, during which the first press unit approaches the process material to be fine blanked, (ii) a fine blanking step, during which the process material is fine blanked, and (iii) a return step, during which the first press unit returns to its initial position before the initial approach step, and wherein the closed loop control is carried out such that the first press unit is driven at a constant speed at least during the fine blanking step.

16. The method according to one of claim 13 wherein the at least one sensor comprises at least one force sensor measuring one of the forces exerted by the first press unit and/or the counter force controlled by the force control unit, and wherein a closed loop control of the forces exerted by one of the first press unit and/or the counter force controlled by the force control unit is carried out on basis of the measured force data.

17. The method according to claim 13 wherein in that the second press unit is driven in the second driving movement at least partially by the first driving movement of the first press unit.

18. The method according to claim 13 wherein a counter force is exerted by a first press drive of the first press unit.

19. The method according to claim 13 wherein a counter force is exerted by the second press unit.

20. The method according to claim 19 wherein the counter force exerted by the second press unit is controlled such that it blocks the driving movement of the second press unit over a part of the first driving movement of the first press unit.

21. The method according to claim 13 wherein a force exerted by the second press unit during its second driving movement is controlled independently from the force exerted by the first press unit during its first driving movement.

22. The method according to claim 21 wherein the force exerted by the second press unit during its second driving movement is controlled such that it is constant over at least a part of the first driving movement of the first press unit.

23. The method according to claim 22 wherein the force exerted by the second press unit during its second driving movement is controlled such that it follows an array of different forces during the first driving movement of the first press unit.

24. The method according to claim 22 wherein the force exerted by the first press unit during its first driving movement is controlled such that the force is constant during the beginning of the first driving movement until reaching a maximum value and decreases for the remaining part of the first driving movement of the first press unit and the force starts the first driving movement with a maximum value and decreases over the remainder of the first driving movement of the first press unit.

25. The method according claim 24 wherein the force exerted by the second press unit during its second driving movement is controlled such that it is reduced to zero over at least a part of the first driving movement of the first press unit.

26. The method according to claim 25 wherein the force exerted by the second press unit during its second driving movement is controlled such that it is inverted over at least a part of the first driving movement of the first press unit.

27. The method according to claim 26 wherein the second press unit carries out an opposite movement, in particular a synchronized movement, with regard to the first press unit during the first driving movement of the first press unit and after the first press unit has finished its first driving movement.

28. The method according to claim 27, wherein the second press unit carries out a movement in the direction of the first driving movement of the first press unit until at least the first press unit contacts the second press unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Embodiments of the disclosure are explained in more detail in the following by reference to schematic drawings.

[0052] FIG. 1. shows an inventive fine blanking press,

[0053] FIG. 2. shows an embodiment of an inventive force control unit of an inventive fine blanking press in a first operating condition,

[0054] FIG. 3. shows the force control unit of FIG. 2 in a second operating condition,

[0055] FIG. 4. shows a further embodiment of an inventive force control unit of an inventive fine blanking press,

[0056] FIG. 5. shows a force exerted by a second press unit according to an embodiment,

[0057] FIG. 6. shows a force exerted by a second press unit according to a further embodiment,

[0058] FIG. 7. shows a force exerted by a second press unit according to a further embodiment, and

[0059] FIG. 8. shows a force exerted by a second press unit according to a further embodiment.

[0060] In the drawings the same reference numerals refer to identical or functionally identical parts.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0061] The fine blanking press according to the disclosure shown in FIG. 1 comprises a press ram 10, constituting a first press unit, and a working table 12 arranged opposite the blanking ram 10. A first press drive not further shown in FIG. 1 is provided for driving the press ram 10 in a first driving movement during a fine blanking process step, in FIG. 1 upwards and downwards. Integrated into the press ram 10 and the working table 12 are cushions 68, 70, which are connected to a blanking tool arranged between the press ram 10 and the working table 12 through transfer pins 72, 74. The blanking tool further comprises press punch 14, which may be positionally fixed together with the working table 12, and die 16, and moves together with the press ram 10. The blanking tool further comprises ejectors 76, 78, set plates 80, 82, press plate 84 and a tool guiding 86. Punch 14 and die 16 blank parts out of a sheet metal 18 fed to the process zone between the press ram 10 and the working table 12 by a feeding unit 20, in the example shown in FIG. 1 in a direction from left to right. A chopping unit 22 is provided downstream of the process zone for chopping scrap process material after the fine blanking process. In the shown example, the feeding unit 20 comprises two rotationally driven feeding rollers 24, 26 arranged on opposite sides of the process material 18. Of course also other feeding units are possible, for example gripper feeders or other feeders. The chopping unit 22 comprises axially driven cutters 28, 30 arranged on opposite sides of the process material 18 for chopping the scrap process material. An impingement ring 32, like a V-ring, is further shown schematically for securely holding the process material 18 during the fine blanking process. The impingement ring 32 may in particular be provided on the press plate 84 of the blanking tool driven by one of the cushions. This general design of a fine blanking press is known to the skilled person and shall not be explained in more detail.

[0062] FIG. 1 shows the open condition of the fine blanking press in which the process material 18 can be fed into the process zone. Subsequently, the press ram 10 can be moved upwards against the working table 12. The process material 18 is thus clamped by the blanking tool between the press ram 10 and the working table 12 and securely held in place by the impingement ring 32. Subsequently, the press ram 10 can be further driven against the working table 12, punch 14 and die 16 thus blanking a part out of the process material 18. The working table 12 may exert a counter force against the press drive of the blanking ram 10, for example through a cushion, in particular for clamping the impingement ring 32 into the process material 18 to improve clamping of the process material 18. After the explained movements the press ram 10 can be moved downwards and the fine blanking press is opened again to eject the produced part. This operation of a fine blanking press is also generally known to the skilled person.

[0063] In the following embodiments of inventive force control units shall be explained which may be incorporated into the fine blanking press shown in FIG. 1.

[0064] In FIG. 2 a hydraulic cylinder is shown having a first cylinder cavity CV1, forming a piston side, and a second cylinder cavity CV2, forming a barrel side. The first cylinder cavity CV1 is connected via a hydraulic line S1 to a controller SM and through the controller SM via a return pressure control module RPCM to a tank TNK. The second cylinder cavity CV2 is connected via hydraulic line S2 and return pressure control module RPCM to the tank TNK. The controller SM represents at least a control valve which is directly connected to cylinder cavities CV1 and CV2 while connecting both cavities CV1 and CV2 between themselves or any or both of them directly to the tank TNK according to the process requirements in terms of pressures, fluid flow, fluid viscosity, fluid temperature and any other relevant parameters during the fine blanking cycle while depending on the needed hydraulic design they can also be connected to an external additional return pressure control module RPCM or integrated inside the same valve the RPCM module, being this valve a controlled valve, being preferably a high dynamic proportional valve, or a servo valve, or a proportional piezoelectric valve, or any other type of valve. The inventive force control can be applied to any forces exerted during the fine blanking process by means of the controller SM together with suitable valves or by the controller SM acting as a control valve, as explained. T0 and T2 denote tank lines. A position sensor EN1, for example an encoder, is provided for detecting the position of the cylinder piston. The hydraulic cylinder shown in FIG. 2 is connected to a first press unit and/or a second press unit of the fine blanking press, such as one of the cushions 68, 70, which is driven in a second driving movement by the first driving movement of a first press unit, in the shown example the press ram 10 exerting the main blanking force. The second driving movement of the second press unit displaces the cylinder piston of the hydraulic cylinder, as visualized in FIGS. 2 and 3 by arrow 100. Data from the position sensor EN1 is fed to the controller SM which may carry out a closed-loop control on basis of the sensor measuring data. The position sensor of the second press unit may be connected to the controller SM and the position sensor of the first press unit may be connected to the controller SM. A closed loop control may then be based on the position of the first press unit, e.g. a press ram. The complete press cycle may be managed according to the position of the first press unit. However, also other press units may serve as reference for a position control. Of course the SM controller could also be connected to other external sensors not shown in FIG. 2, or the SM controller may incorporate internally position sensors or other needed sensors. Possible sensors include for example pressure sensors, viscosity sensors, flow sensors, temperature sensors and any other needed sensors depending on the design configuration. Data from such sensors may then be fed again to controller SM which may carry out a closed-loop control on basis of the sensor measuring data. As explained the fine blanking press may have more than one first press unit and more than one second press unit. Thus, all or some sensors from all or some press units may be connected to corresponding controllers, for example controller SM or the below explained main control module CM. In case there is more than one controller the controllers may communicate between themselves where it is needed for the proper control.

[0065] When the piston is pushed in by the press ram movement, as shown in FIG. 3, the volume of the second cylinder cavity CV2 is reduced and the volume of the first cylinder cavity CV1 is increased. The amount of volume change is known to the controller SM through the sensor data of the position sensor EN1. On this basis the controller SM can control the return pressure control module RPCM, which comprises at least a control valve, for example a proportional control valve, such that it can provide a desired volume flow between the hydraulic cylinder and the tank TNK. In this manner for example pressure PR4a and PR4b in the second cylinder cavity CV2 can be maintained at a constant value despite the movement effected between FIGS. 2 and 3. Therefore, a counter force exerted via the hydraulic cylinder by the second press unit against the force exerted by the press ram 10 can also be kept constant. Hydraulic pressures PR4a and PR4b can for example be unequal to hydraulic pressure PR5, in particular higher than hydraulic pressure PR5.

[0066] A corresponding force diagram is shown in FIG. 5, where the force is shown over the stroke, in this case between the operating condition shown in FIG. 2, denoted by stroke position S1, and the operating position shown in FIG. 3, denoted by stroke position S2. R1 denotes a start ramp building up the constant force Fc and R2 denotes an exit ramp building down the constant force Fc. Between the ramps R1 and R2 the force is held constant at force value Fc.

[0067] In the same way a force between stroke positions 51 and S2, as shown in FIG. 6, can be realized. In this case the force is built more slowly up to force value Fc and after reaching force value Fc is decreased towards the end position S2 of the stroke.

[0068] The return pressure control module RPCM can also comprise a pump for pumping hydraulic fluid from the tank TNK to the first and/or second cylinder cavity CV1, CV2. The pump can also be controlled by controller SM, as well as corresponding valves for feeding hydraulic fluid from tank TNK to the first cylinder cavity CV1 or the second cylinder cavity CV2. For example by feeding hydraulic fluid from the tank TNK to the second cylinder cavity CV2 during the press ram movement, a counter force exerted by the second press unit can be increased substantially. With such an embodiment, the force exerted by the second press unit can be controlled variably and with great flexibility. Examples of possible force profiles between stroke positions Si and S2 are shown in FIGS. 7 and 8. In FIG. 7 the counter force exerted by the second press unit is first increased in a ramp to a force Fc1, subsequently to a force Fc2, subsequently to a higher force Fc3 and is after that reduced sharply to a force Fc4 and finally Fc5. In the embodiment according to FIG. 8 the force is first increased in a ramp to a force Fc2, which is maintained constant for a first time interval, subsequently the force is increased to a blocking force Fc1 blocking further movement of the second press unit, e.g. one of the cushions 68, 70, thus inverting the function of the cushion 68, 70 to the function of a second ram, and is subsequently reduced again to force Fc2, where it is kept constant for the remaining cycle of the stroke until an exit ramp, thus inverting the function of a second ram to a cushion function again.

[0069] By referring to FIG. 4 a further detailed embodiment of an inventive force control unit of the inventive fine blanking press shall be explained.

[0070] FIG. 4 shows a further enhanced force control unit based on components already explained with regard to FIGS. 2 and 3. More specifically, TABLE I below summarizes the various components shown in FIG. 4.

TABLE-US-00001 TABLE I TNK: Fluid tank PMP: Pump PMC: Pump module control CM: Main control module SM: Control module CLC: Cleanness control sensor RPCM: Return Pressure control module PLCNCD: PLC or CNC control device VS: Viscosity sensor P0 . . . P2 . . .: Pressure lines T0 . . . T2 . . .: Tank lines CMM1 . . . CMM3 . . .: Communication channels CV1: Cylinder cavity no1 CV2: Cylinder cavity no2 PT0 . . . PT5 . . .: Pressure transducers OT.1 . . . OT.7 . . .: Temperature sensors EN.1 . . . EN.3 . . . Position sensors FC.1 . . . FC.8 . . .: Flow control sensors S1 . . . S2 . . .: Hydraulic lines PR0 . . . PR2 . . .: Fluid pressures

[0071] The sensors shown in FIG. 4 are used for a closed loop control carried out by the main control module CM. The PLC or CNC control device is used for introducing process parameters by a press operator. The main control module controls the force control system on this basis. Pump PMP is connected to tank TNK, wherein pump PMP is controlled by pump module control PMC which is also connected to the main control module CM by communication channels CMM. The main control module is further connected to hydraulic cylinder cavities CV1 and CV2. This could be done directly or through an additional return pressure control module RPCM connected to tank TNK. At the same time the main control module is connected to the control module SM which is also directly connected to cylinder cavity CV1 and CV2, and connected to tank TNK through the return pressure control module RPCM. Control Module SM represents at least a control valve which is directly connected to cylinder cavities CV1 and CV2, while connecting both cavities CV1 and CV2 between themselves or any or both of them directly to the tank TNK according to the process requirements in terms of pressures, fluid flow, fluid viscosity, fluid temperature and any other relevant parameters during the fine blanking cycle. Depending on the needed hydraulic design it can also be connected to an external additional return pressure control module RPCM or integrated inside the same valve the RPCM module, being this valve a controlled valve, being preferably a high dynamic proportional valve, or a servo valve, or a proportional piezoelectric valve, or any other type of valve.

[0072] As indicated the main control module CM receives process data introduced by the press operator from the PLC or CNC control device PLCNCD. On this basis the main control module CM establishes an initial pump fluid pressure and flow taking in consideration measuring data on hydraulic fluid temperature, fluid viscosity, fluid cleanness for example. It may also consider further factors such as valve reaction times (delay times), in order to compensate such delays in advance and to make the force control unit follow very precisely the process parameters introduced into the PLCNCD device by the press operator. As part of the closed-loop control the main control module CM monitors all system sensors and adjusts all system components according to the system status. To this end the main control module CM is connected via communication channels CMM to the relevant system components and sensors.

[0073] Control module SM and return pressure control module RPCM are both directly controlled by the main control module CM such that the desired hydraulic fluid pressure values are at all times maintained in cylinder cavities CV1 and CV2. As explained, hydraulic cylinder with cylinder cavities CV1 and CV2 may for example be connected to one of the cushions 68, 70 and during a first driving movement of the press ram 10 may for example exert a desired counter force, including for example an impingement force, such as a V-ring force. This control is effected, as explained above with regard to FIGS. 2 and 3, by a controlled leaking of hydraulic fluid from cylinder cavity CV2 through control module SM and return pressure control module RPCM to tank TNK while at the same time for example press ram is pushing in the cylinder piston and forcing the fluid to leak to the tank, as visualized in FIG. 4 again by arrow 100.

[0074] For example main control module CM considers position changes of the cylinder piston through measuring data from position sensor EN.1 as well as pressure PR1 inside cylinder cavity CV2 through pressure sensor PT1. Based on this measuring data main control module CM controls control module SM such that the desired force is exerted by the second press unit, such as a cushion 68, 70. As explained, in this manner force profiles such as shown in FIGS. 5 to 8 can be realized.

[0075] While in the above explained mode the cushion 68, 70 is a passive cushion, the embodiment of FIG. 4 also allows implementing an active cushion 68, 70. To this end, main control module CM can adjust the pump fluid pressure PRO monitored by pressure sensor PT0 and fluid flow monitored by flow control sensor FC.1 through pump control module PMC and pump PMP to achieve a desired pressure PR1 monitored by pressure sensors PT1 and PT4 and desired flow monitored by flow control sensors FC.3 and FC.6 to achieve the desired force. This force, which can in particular be a counter force, including an impingement force or V-ring force, is maintained before the press ram 10 begins its first driving movement and thus before it starts to push in the cylinder piston. In this way the cushion 68, 70 is preloaded. Once the press ram 10 begins its driving movement pressure PR1 will increase sharply while at the same time position sensor EN.1 will detect piston movement. Based on measuring data of the corresponding sensors PT4, PT1 and EN.1 the main control module CM will control pump module control PMC and thus pump PMP to reduce the pressure and fluid flow to a minimum or even zero while at the same time controlling control module SM and thus return pressure control module RPCM to open a corresponding valve connecting cylinder cavity CV1 and CV2 and to leak the desired amount of fluid to tank TNK, as explained above, to obtain the desired force profile.

[0076] Due to the closed-loop control any change of any monitored parameters will be detected and can be addressed immediately by the main control module CM which will readjust the force control system correspondingly.

[0077] Once the press ram 10 has achieved its final blanking position and the press ram movement starts to reverse to open the blanking tool, the main control module CM can apply corresponding fluid flow and pressure to cylinder cavity CV2 to fully extend cylinder piston. To that end main control module CM can close return fluid line T0 to tank TNK by closing the controlled valve inside return pressure control module RPCM and flushing hydraulic fluid from cavity CV1 to CV2 at the same time, controlled by control module CM, which will introduce new fluid under pressure PR1 into cavity CV2 through pressure line P1, controlled by pressure sensor PT1 and as safety redundant controlled by pressure sensor PT4, as well as control of piston movement by position sensor EN.1.

[0078] In addition control module SM and main control module CM may have a second safety tank line T1 connecting pressure lines P1, P2 and P0 to tank TNK through return pressure control module RPCM. In this manner cylinder damage in case of a valve or sensor failure can be avoided due to a second safety fluid tank line.

REFERENCE NUMERAL LIST

[0079] 10 press ram [0080] 12 working table [0081] 14 press punch [0082] 16 die [0083] 18 sheet metal [0084] 20 feeding unit [0085] 22 chopping unit [0086] 24 feeding rollers [0087] 26 feeding rollers [0088] 28 cutters [0089] 30 cutters [0090] 32 impingement ring [0091] 68 cushions [0092] 70 cushions [0093] 72 transfer pins [0094] 74 transfer pins [0095] 76 ejectors [0096] 78 ejectors [0097] 80 set plates [0098] 82 set plates [0099] 84 press plate [0100] 86 tool guiding [0101] 100 arrow