EP2903811B1 - Method for controlling a ceramic or metal powder press, and ceramic or metal powder press - Google Patents

Description

The invention relates to a method with the features of claim 1 for controlling a ceramic and / or metal powder press for pressing a material to be pressed. The invention also relates to a ceramic and / or metal powder press controlled in this way for pressing a pressed material according to claim 7. There are ceramic and / or metal powder presses in which a so-called floating of individual axes, ie in particular of, during a pressing process Press stamp and these (s) supporting components, is required during the molding process. Floating means that the axis can be pushed out of its position by at least one other, in particular opposite, axis. However, it holds against the force programmed in the tool program for the axis against the axis that displaces it, which is more clearly comparable, for example, to a spring action. Another application is a force-controlled reduction of the pressing force on the upper, force-carrying axis in particular. The term float can therefore also be described as floating, controlled yielding or controlled readjusted.

In particular in the case of servo-motorized powder presses, in particular multi-plate presses, there is a particular problem in comparison with, for example, hydraulic powder presses in the case of spindle presses which have a spindle drive. A conventional torque limitation provided by a drive control or drive regulation as a function of the servo controller is not able to limit the force on such axes with absolute precision. The reason is that the rotational movement of the servo motor is converted into a translatory movement with the help of a spindle. The efficiency of this spindle depends on several physical variables, including the temperature, and is therefore to be classified as a quasi-unknown variable. If a double drive is used for such a tool axis, the torque limitation is unusable. With a double drive, two servo motors, each with a spindle, drive a tool axis. Due to the efficiency problems of the spindles, synchronous operation of the two servo axes cannot be guaranteed. From a procedural point of view, the tolerance for the synchronous deviations is in particular less than 0.01 mm.

Servo controllers that can be used in such screw presses consist of current, speed and position controllers. In principle, force control is not possible with these controllers.

An example is from US 6 074 584 A a ceramic powder and / or metal powder press known.

The object of the invention is to improve a ceramic and / or metal powder press and a method for controlling a ceramic and / or metal powder press for pressing a material to be pressed using at least one electromotive drive so that more reliable operation is made possible , in particular a force control with at least one floating axis or a floating press ram is made possible. In particular, the process should be applicable to such a press, which is equipped with a servo spindle drive.

This object is achieved by the method with the features of claim 1 or the ceramic and / or metal powder press with the features of claim 7.

Advantageous refinements are the subject of dependent claims.

A particularly preferred embodiment consists in a method for controlling a ceramic and / or metal powder press for pressing a pressed material, in which at least one electromotive drive, which adjusts at least one pressing die along a pressing direction, is controlled in such a way that the drive drives the pressing die along a target position path in particular to a respectively current target position of the press ram and the drive is readjusted in the event of a deviation from the position target path, with a measured force acting on the material to be pressed, the press ram or components carrying it as at least one manipulated variable for the readjustment , is used.

In other words, target positions of at least one press ram are regulated via its at least one electromotive drive as a function of a measured force. Regulation can also be implemented by readjustment using various control and regulating devices which are interconnected.

The force of the tool axis, that is to say in particular the measured force on one of the components from the press ram to its fixed point relative to a frame and possibly relative to other tool axes, is measured in the sensor using suitable sensors or a suitable force measuring device Translational movement measured during an ongoing press cycle.

Such a regulation can be implemented for only one press ram of a multiplicity of press rams of such a press or of a tool correspondingly used in such a press. However, such a regulation can also be implemented for several or all press rams of such a press or of such a tool.

A further embodiment consists in that the position target path is readjusted as a function of the at least one measured force, the position target path being predefined as a function of a target force according to a further development.

Here, too, force values are transferred to position values. A further development is that each axis can evaluate the respective force independently and regardless of the overall network and can initiate a readjustment.

One embodiment consists in that target positions of at least one press ram are calculated and / or regulated as a function of at least one such measured force.

It is also an embodiment that, based on the measured force, the nominal position path is calculated, in particular for one servo axis or several servo axes, in particular calculated such that a tool axis or, in particular, its press stamp follows the programmed force.

In particular, the position is thus not directly controlled via a direct manipulated variable of a drive, for example a voltage applied to the drive, an applied current or an oil pressure applied to the hydraulic cylinder. Instead of the setpoint position itself is changed so that a controlled setpoint or setpoint position is applied to a drive control and then the drive control in turn carries out a control or preferably regulation of the actuating variables of the drive depending on the applied regulated setpoint position. It is therefore preferably a double control chain with two controls connected in series or, in particular, controls.

It is provided according to the invention that the deviation is a force-control deviation between the measured force and the target force is converted into a target position control variable that can be implemented for a position controller of the control device of at least one drive.

In other words, a force control deviation is determined and from this a target position control variable is determined, which is used to control the electromotive drive. One embodiment of this is that a spindle pitch of the drive and / or a machine-specific modulus of elasticity is additionally converted into the desired position control variable that can be implemented for the position controller of the at least one drive.

It is also possible to take into account further variables which are dependent on the prevailing temperatures or variable or model-specific geometric and more constructive or material-dependent variables, in particular of the press and in its environment. In particular, the machine-specific modulus of elasticity can refer to individual or all components in the force flow between the side of the press die facing the material to be pressed and the drive or the frame element carrying the drive. Can also be used for different axes or force flows of different modulus of elasticity can be provided.

In particular, it is an embodiment that the at least one press ram is adjusted as part of a floating, that is to say in particular floating or controlled, yielding or readjusted axis.

A particularly preferred embodiment consists in a ceramic and / or metal powder press for pressing a material to be pressed with at least one electromotive drive which adjusts at least one pressing die along a pressing direction, a control device which is designed to control the drive in such a way that the drive drives the Press ram is moved along a nominal position path to a respective current nominal position of the press ram and the drive adjusts if there is a deviation from the nominal position path, with at least one force measuring device in the press which is used to measure a pressing force that is applied to the material to be pressed, the press stamp or this Components acts, is arranged and wherein the pressing force thus measured forms at least one manipulated variable for the readjustment for the control device.

The control device can be an independent component or a control device integrated in the respective drive or its motor, in whole or in part, as in e.g. a servo drive.

The one or more drives and force measuring devices can be assigned to one or more press rams or axes which are arranged on a side of the die opening opposite the main pressing force acting on them. A main pressing force can be achieved by an electric motor drive, but optionally also by mechanical, pneumatic or hydraulic drives can be applied. The main pressing force acts in particular via one or more rams, which are arranged on the side of the material to be pressed that is opposite the press ram thus regulated and act on the material to be pressed. However, a press ram that is entirely or partially subordinate to the main press force, or together with other press rams, can also be regulated in this way, in particular if a plurality of press rams that are adjustable relative to one another by means of electromotive drives are arranged on the side of such a main press force. This also includes the fact that, in the case of an electromotive main pressing force, the axis transmitting this force is also designed as a servo motor and with a spindle drive and can be regulated in such a way that it floats.

One configuration of the press is that the press ram is part of a floating axis.
Another embodiment of the press is that the drive moves a press ram relative to at least one press ram arranged at least laterally in the press position.
In other words, a plurality of press rams are arranged on one side of the die opening, these plurality of press rams being adjustable independently of one another along the pressing direction. In particular, only one, several or all of the press rams can be regulated in such an arrangement.

According to the invention, it is provided that a single press stamp of this type is arranged so that it can be adjusted by two or more drives at the same time, a correction value determined, in particular, from the measured force being applied to the drives.

For example, such a press stamp is arranged on a so-called plate as a stamp carrier, the plate being adjustable within the framework or tool by means of two or more drives along the pressing direction. A control deviation determined from one or more measured force values can be used to determine a common target position control variable for all affected drives. According to a further development, the drives can also be regulated independently of one another, in particular depending on individually determined measured forces, in order to prevent the plate or the stamp carrier from tilting by means of suitable regulation.

An embodiment consists in such a press, in which the control device is designed to control at least one drive by means of a method described in this way. In other words, a press equipped with corresponding components is operated using the method for regulating the target positions of at least one press ram depending on at least one measured force.

It is also an embodiment of such a press or of such a method that the drive is designed as a servo-motor drive and / or drives a spindle upstream of the press ram.

Depending on the measured force values, press rams, which are adjustable depending on the position, can also be regulated, in particular with electromotive servo spindle drives.

According to a development, a nominal position path of one or more servo axes is calculated based on a measured force such that the tool axis or in particular the press stamp of which follows the programmed force.

Fig. 1

einzelne Komponenten einer Keramik- und/oder Metallpulver-Presse und ein Diagramm zur Veranschaulichung eines Pressablaufs.

An embodiment is explained below with reference to the drawing. It shows:

Fig. 1

individual components of a ceramic and / or metal powder press and a diagram to illustrate a pressing process.

How from Fig. 1 As can be seen, a ceramic and / or metal powder press 1 comprises a frame 2, in which various other components are accommodated. In some cases, the further components are connected to the frame 2 in a stationary manner, in some cases they can be adjusted relative to this and relative to one another, in particular along a pressing direction.

The central component is a die 3, in the die opening of which one or more plungers 4, 5 are immersed, in particular from below. A material to be pressed 6 can be filled into the die opening in particular above the press punches 4, 5. One or more further press punches 7 can be inserted from above into the die opening filled with pressed material 6 in order to deform the pressed material 6 into a pressed body. The pressed material 6 is in particular a metallic and / or ceramic powdery and / or granular material.

The exemplary only one punch 7 is on the underside of an in particular plate-shaped punch holder 8. By means of an electric motor drive 10, which in particular has a servo motor and a spindle rod 9, the punch holder 8 and the press punch 7 can be adjusted back and forth in the pressing direction.

A force measuring device 11 is arranged in the area of the illustrated upper frame 2, on which the drive 10 is fastened or arranged, and the press ram 7. The force measuring device 11 can sit, for example, as a load cell on the route between the frame 2 and the press ram 7 between two of the components. The force measuring device 11 is used to measure a pressure force acting between these components and / or a pressing force acting on the pressed material 6 via the press ram 7 and to output it as a measured force F3.

On the underside of the die 3, a central press ram 5 and a press ram 4 surrounding it in an annular manner are shown by way of example, which enable a contoured press body to be pressed.

The central second press stamp 5 is arranged on a plate carrier 12, which is in particular plate-shaped. The stamp carrier 12 is adjustable relative to a lower section of the frame 2 by means of two electromotive drives 15, 16, for example, along the pressing direction. The two drives 15, 16 each have a motor and a spindle rod 13, 14 driven thereby. Force measuring devices 24, 25 are arranged in the area from the frame 2 to the press ram 5 in order to measure an instantaneous pressing force acting via the drives 15, 16 and to output corresponding measured values as the respectively measured force F21 or F22.

The central lower, first press ram 4 is arranged on a plate carrier 17, which is in particular plate-shaped. The stamp carrier 17 is adjustable relative to a lower section of the frame 2 by means of two electromotive drives 20, 21, for example, along the pressing direction. The two drives 20, 21 each have a motor and a spindle rod 18, 19 driven thereby. Force measuring devices 22, 23 are arranged in the area from the frame 2 to the press ram 4 in order to measure an instantaneous pressing force acting via the drives 20, 21 and to output corresponding measured values as the respectively measured force F11 or F12.

A control device C serves to control and monitor functions of the press 1. In particular, the control device C serves, among other things, to control the drives 10, 15, 16, 20, 21. In particular in the case of servomotors or servo drives with their own control loops, the control device C serves to supply the servo drives or their control loops with control signals for desired movements to be driven. For this purpose, the control device C provides control signals s3, s11, s12, s21 and S22 in particular as control signals for the drives 10, 15, 16, 20, 21. The target position control variables s3, s11, s12, s21 and S22 can be, for example, continuously applied signals or, in particular, temporary difference or control values.

Correspondingly, the measured forces F3, F11, F12, F21, F22 are applied to the control device C to be taken into account when the pressing method is running.

To carry out a preferred pressing method, the control device C takes into account a predetermined pressing sequence. The pressing process is based on pressing forces which are to act on the pressing material 6 from the pressing dies 4, 5, 7 during a time course of the pressing process.

This is shown in a position-time diagram below the components outlined. Above the temporal Curves t are each represented by curves which represent a current position a. The current position a can be an actual position of a surface of one of the punches 4, 5, 7 touching the material to be pressed. For reasons of easier handling, however, any other position a, in particular, which can be measured or determined in a sufficiently precise manner, can in principle also be used along the distance from the press rams 4, 5, 7 to their drives 13, 16, 20, 21, 10, in particular also one position determined by the drive itself.

For the sake of simplicity, only one target position path as3 of the upper press ram 7 and one position target path as1 of the first, lower press ram 5 are shown, for example. In the case of a press with a larger number of press rams above and / or below the die opening, more such positions are appropriate -Sollbahnen used. In particular, the number of such nominal target tracks depends on the number of axes or press rams 4, 5, 7 which are to be regulated.

The nominal position paths as1, as3 are determined as a function of the press forces required for the respective press rams 4, 5, 7 over the course of time t.

It is shown as an example that during a continuous lowering of the upper press ram 7, the first lower press ram 5 is initially moved upwards and is moved somewhat downwards again from a predetermined position. In particular, a so-called floating movement is to be carried out by the lower press ram 5, in which the latter gives downwards when the pressing force acting on the material to be pressed 6 from above is too great. It can also be provided that if the level is too low from above Pressing force 6 acting press force readjustment of the lower ram 5 upwards.

In the cycle of the pressing process shown, it is assumed that the current position a1m of the lower press ram 5 in the meantime deviates upwards from the current target position as1m provided at this time. On the basis of the measured forces F21, F22 of the force measuring devices 24, 25 assigned according to this lower press ram 5, the control device C determines a control deviation εK (21) if, for example, the measured force F21 of one of the force measuring devices 25 has a desired force Fs for in particular the measured force value of this force measuring device 25 deviates. Correspondingly, a control signal or a target position control variable s21 is applied to the assigned drive 16, which controls readjustment as a function of the control deviation εK (21).

The control deviation εK (21) and thus the target position control variable s21 are thus force-dependent control variables which depend directly on one or possibly more of the measured forces F21.

When determining the target position paths as1, as3 and correspondingly when determining the target position control variables s3, s11, s12, s21, s22, the variables influencing the respective current position a of the corresponding press punches 4, 5, 7 also preferably become additional variables variables influencing the pressing process, such as, in particular, a machine-specific modulus of elasticity E, a spindle pitch and, if appropriate, also current positions of other press punches 4, 5, 7 are taken into account.

The respective control deviations εK (21) and / or the current target position control variables s3, s11, s12, s21, s22 can be determined in different ways during an ongoing pressing process. In principle, a table comparison or a calculation are possible.

In the case of a table comparison, the knowledge of the specialist or system operator about, for example, a rigidity of the structure, contours and material properties of the tester could also be taken into account in a table with target positions to be moved over time depending on target forces.

Since it is very complex to model all components in the power flow of the respective axes in order to create a model that is as perfect as possible as the basis for determining correct data for the table, a calculation is preferred. In particular, a simplified model can be used as the basis for a calculation. The deviations of the real object from the model are coupled into the calculation via the target / actual force difference.

For this purpose, a target path over the force is calculated in the control device C, which is in particular superimposed on servo controllers. If the setpoint force is set in relation to the actual force during operation, the control deviation εK of the measured force considered in each case is obtained. Together with the spindle pitch and a machine-specific modulus of elasticity, this control deviation is converted into a target position that can be controlled by the position controller of the servo axis or the drive. If the tool axis or its drive control follows the calculated path, the intended force profile is automatically realized on the axis.

Reference symbol list:

1

Ceramic and / or metal powder press

2nd

frame

3rd

die

4th

Press stamp

5

Press stamp

6

Press material

7

Press stamp

8th

in particular plate-shaped stamp carrier

9

Spindle rod

10th

electric motor drive

11

Force measuring device

12th

in particular plate-shaped stamp carrier

13

Spindle rod

14

Spindle rod

15

electric motor drive

16

electric motor drive

17th

in particular plate-shaped stamp carrier

18th

Spindle rod

19th

Spindle rod

20th

electric motor drive

21

electric motor drive

22

Force measuring device

23

Force measuring device

24th

Force measuring device

25th

Force measuring device

a

Position along the pressing direction

as3

Position target path third, upper stamp

a1m

current position of the first, lower stamp

as1

Position target path first, lower stamp

as1m

Current target position of the first, lower stamp

C.

Control device

E

machine-specific modulus of elasticity

εK (21)

Control deviation

F3

measured force as a measurand

F11

measured force as a measurand

F12

measured force as a measurand

F21

measured force as a measurand

F22

measured force as a measurand

Fs

Target force

s3

Target position control variable

p11

Target position control variable

p12

Target position control variable

p21

Target position control variable

p22

Target position control variable

t

chronological course of a press process

Claims (11)

1. Method for controlling a ceramic and/or metal powder press (1) for pressing a compressible material (6), in which

   - at least one electric-motor drive (15, 16; 20, 21), which adjusts at least one press plunger (5; 4) along a pressing direction, is configured as a servo-motor drive and/or drives a spindle (13, 14; 18, 19) connected in front of the press plunger (5; 4), is activated in such a way that

   - the drive (15, 16; 20, 21) moves the press plunger (5; 4) along a desired position path (as1) and

   - the drive is readjusted in the event of a deviation from the desired position path (as1),

   - wherein a measured pressing force (F11, F12) which acts on the compressible material (6), the press plunger (4) or components (17 - 19) carrying the latter is used as at least one actuating variable for the readjustment,

   - at least one press plunger (5; 4) is adjustd along the pressing direction by means of at least two drives (15, 16; 20, 21),

   - in each case an instantaneous pressing force (F21, F22; F11, F12) acting via the drives (15, 16) is measured and corresponding measured values are output as respectively measured pressing forces (F21, F22; F11, F12), and in that

   - as the deviation, a force-control deviation (2K(21)) between the measured pressing force (F11, F12) and the desired force (Fs) is transformed into a desired position control variable (sll, s12) for a position controller of the control device (C) of the at least one drive (20, 21).
2. Method according to Claim 1, in which readjustment with respect to the desired position path (as1) is carried out as a function of the at least one measured force (F11, F12), wherein in particular the desired position path (as1) is predefined as a function of a desired force (Fs).
3. Method according to Claim 1 or 2, in which desired positions of at least one press plunger are calculated and/or controlled as a function of at least one such measured force (F11, F12).
4. Method according to a preceding claim, in which the desired position path (as1) for a servo axis or multiple servo axes is calculated by using the measured force (F11, F12), such that a tool axis or its press plunger follows the programmed force.
5. Method according to a preceding claim, in which, in addition, a spindle pitch of the drive (18 - 21) and/or a machine-specific modulus of elasticity constant (E2) is transformed into the desired position control variable (sll, s12) for the position controller.
6. Method according to a preceding claim, in which the press plunger (4; 5) is adjusted as a constituent part of a floating axis.
7. Ceramic and/or metal powder press (1) for pressing a compressible material (6), comprising

   - at least one electric-motor drive (15, 16; 20, 21), which adjusts at least one press plunger (5; 4) along a pressing direction, is configured as a servo-motor drive and/or drives a spindle (13, 14; 18, 19) connected in front of the press plunger (5; 4),

   - a control device (C), which is designed to activate the drive (15, 16; 20, 21) in such a way that

   - the drive (15, 16; 20, 21) moves the press plunger (5; 4) along a desired position path (as1) of the press plunger (5; 4) and

   - the drive readjusts in the event of a deviation from the desired position path (as1),
   characterized by

   - at least one force measuring device (22, 23; 24, 25; 11), which is arranged to measure a pressing force (F11, F12) which acts on the compressible material (6), the press plunger (4) or components (17 - 19) carrying the latter,

   - wherein, for the control device (C), the measured pressing force (F11, F12) forms at least one actuating variable for the readjustment, wherein

   - as the deviation, a force-control deviation (2K(21)) between the measured force (F11, F12) and the desired force (Fs) is transformed into a desired position control variable (sll, s12) for a position controller of the control device (C) of the at least one drive (20, 21), and wherein

   - an individual such press plunger (5; 4) is arranged to be simultaneously adjustable by two or more drives (15, 16; 20; 21), wherein a correction value determined from the measured force (F11, F12) is applied to the drives (15, 16; 20; 21).
8. Press (1) according to Claim 7, in which the press plunger (4; 5) is a constituent part of a floating axis.
9. Press (1) according to Claim 7 or 8, in which the drive (15, 16; 20; 21) moves a press plunger (4; 5) relative to at least one press plunger (5; 4) arranged laterally thereto, at least in the pressing position.
10. Press according to one of Claims 7 to 9, wherein a single correction value from the measured force (F11, F12) is applied to the drives (15, 16; 20; 21) .
11. Press according to one of Claims 7 to 10, in which the control device (C) is designed to activate the drive (15, 16; 20, 21) by means of a method according to one of Claims 1 to 5.

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