Method for controlling a ceramic or metal powder press, and ceramic or metal powder press

Abstract

The invention relates to a method of controlling a ceramic and/or metal powder press (1) for pressing a compressible material (6), wherein at least one electromotive drive (15, 16; 20, 21), which adjusts at least one punch (5; 4) along a pressing direction, is controlled in such a manner that the drive (15, 16; 20, 21) moves the punch (5; 4) along a setpoint positioning path (as1) and the drive is readjusted if it deviates from the setpoint positioning path (as1), wherein a measured force (F11, F12) acting on the compressible material (6), the punch (4) or its supporting components (17-19), is used as at least one control variable for readjustment. The invention also relates to a ceramic and/or metal powder press (1) configured to carry out the method.

Claims

1. A method of controlling a ceramic and/or metal powder press for pressing a compressible material, the ceramic and/or metal powder press including a drive that adjusts a punch supported by one or more supporting components along a pressing direction, the method comprising: moving, with the drive, the punch along a predetermined position path; measuring a force acting on the compressible material, the punch, or the one or more supporting components of the punch; determining a deviation between a position of the punch at a first time and a position of the predetermined position path corresponding to the first time based on a difference between the measured force at the first time and a setpoint force corresponding to the first time; determining a setpoint control variable for position control of a controller of the drive based on the difference between the measured force and the setpoint force corresponding to the first time; readjusting the position of the punch with the drive based on the determined setpoint control variable.

2. The method according to claim 1, wherein the readjusting is carried out with respect to the predetermined position path as a function of the measured force.

3. The method according to claim 2, wherein the predetermined position path is predefined as a function of the setpoint force.

4. The method according to claim 1, wherein predetermined positions of the punch are calculated and/or controlled as a function of the measured force.

5. The method according to claim 1, wherein the predetermined position path is calculated as a function of the measured force.

6. The method according to claim 5, wherein the predetermined position path comprises a predetermined position path of a servo axis or a plurality of servo axes.

7. The method according to claim 5, wherein the predetermined position path is calculated as a function of the measured force in such a manner that a tool axis or the punch follows the setpoint force.

8. The method according to claim 1, wherein the drive is attached to a spindle, and wherein the method further comprises determining the setpoint control variable based on a spindle pitch of the drive and/or a machine-specific modulus of elasticity of the ceramic and/or metal powder press.

9. The method according to claim 1, wherein the punch is adjusted as part of a floating axis.

10. The method according to claim 1, wherein the drive is configured as a servo-motive drive and/or drives a spindle on a side of the punch that is opposite the compressible material.

11. A ceramic and/or metal powder press for pressing a compressible material, comprising: a drive, which adjusts a punch along a pressing direction; at least one force-measuring device, which is arranged for measuring a pressing force acting on the compressible material, the punch, or supporting components of the punch; a controller, which is adapted to: move the punch with the drive along a predetermined position path of the punch, determine a deviation between a position of the punch at a first time and a position of the predetermined position path corresponding to the first time based on a difference between the pressing force measured by the at least one force-measuring device at the first time and a setpoint force corresponding to the first time, determine a setpoint control variable for a position control of the drive based on the difference between the measured force and the setpoint force corresponding to the first time, and readjust the punch with the drive based on the determined setpoint control variable.

12. The press according to claim 11, wherein the punch is part of a floating axis.

13. The press according to claim 11, wherein the drive moves the punch relative to at least one other punch arranged laterally thereto at least in a pressing position.

14. The press according to claim 11, wherein the punch is arranged to be adjustable by two or more drives simultaneously, and wherein the setpoint control variable determined from the measured force is applied to the drives.

15. The press according to claim 14, wherein the setpoint control variable comprises a single setpoint control variable.

16. The press according to claim 11, wherein the controller is adapted to control the drive such that the drive is readjusted with respect to the predetermined position path as a function of the measured force, and wherein the predetermined position path is predefined as a function of the setpoint force.

17. The press according to claim 11, wherein the drive is configured as a servo-motive drive and/or drives a spindle on a side of the punch that is opposite the compressible material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An exemplary embodiment will be described in the following with reference to the drawings, wherein:

(2) FIG. 1 shows individual components of a ceramic and/or metal powder press and a diagram to illustrate the pressing sequence.

DETAILED DESCRIPTION

(3) As shown in FIG. 1, a ceramic and/or metal powder press 1 comprises a frame 2, in which various further components are accommodated. Some of the further components are fixedly connected to the frame 2, and some are adjustable with respect to the latter and relative to each other, in particular along a pressing direction.

(4) A central component is a die 3, having a die opening, in which one or more punches 4, 5 are inserted, in particular from below. Compressible material 6 is able to be filled into the die opening above the punches 4, 5, in particular. One or more further punches 7 are insertable from above into the die opening filled with the compressible material 6, in order to shape the compressible material 6 to a compact. The compressible material 6 is a metallic and/or ceramic powdery and/or granular material, in particular.

(5) The for example only one top punch 7 is attached at the bottom to a punch carrier 8, in particular in the shape of a plate. The punch carrier 8 and the punch 7 are adjustable in and against the pressing direction by means of an electromotive drive 10, which comprises, in particular, a servo motor and a spindle 9.

(6) A force-measuring device 11 is arranged in the area of the top frame 2 shown in the FIGURE, on which the drive 10 and the punch 7 are mounted or arranged. The force-measuring device 11 can be installed, for example, as a load cell, between two of the components arranged between the frame 2 and the punch 7. The force-measuring device 11 is used to measure a compressive force exerted between these components and/or exerted on the compressible material 6 by means of the punch 7, and to output it as a measured force F3.

(7) A central punch 5, for example, and a punch for surrounding the former in an annular manner, are shown below the die 3, which enable pressing of a contoured compact.

(8) The central second punch 5 is arranged on a punch carrier 12, in particular in the shape of a plate. The punch carrier 12 is adjustable relative to a bottom section of the frame 2, for example, by means of two electromotive drives 15, 16 along the pressing direction. The two drives 15, 16 in turn each comprise a motor and a spindle 13, 14 driven by the latter. In the range extending from the frame 2 to the punch 5, force-measuring devices 24, 25 are arranged to measure a current pressing force acting via the drives 15, 16 and to output corresponding measuring values as the measured forces F21 and F22, respectively.

(9) The central lower, first punch 4 is arranged on a punch carrier 17, in particular in the shape of a plate. The punch carrier 17 is adjustable relative to a lower section of the frame 2 by means of, for example, two electromotive drives 20, 21 along the pressing direction. The two drives 20, 21 in turn each comprise a motor and a spindle 18, 19 driven by the latter. In the range extending from the frame 2 to the punch 4, force-measuring devices 22, 23 are arranged to measure a current pressing force acting via the drives 20, 21 and to output corresponding measuring values as measured forces F11 and F12, respectively.

(10) A controller C serves to control and monitor functions of the press 1. In particular, the controller C also serves to control the drives 10, 15, 16, 20, 21. In the case of servo motors or servo drives having their own control circuits, the controller C provides the servo drives or their control circuits with control signals for the setpoint movement to be adjusted. For this purpose the controller C provides, in particular, setpoint position control variables s3, s11, s12, s21 and s22 as control signals for the drives 10, 15, 16, 20 and 21, respectively. The setpoint position control variables s3, s11, s12, s21 and s22, respectively, can be, for example, continuously applied signals or temporary difference or control values, in particular.

(11) The measured forces F3, F11, F12, F21, F22 are thus supplied to the controller C to be considered during a current pressing method.

(12) To carry out a preferred pressing method the controller C takes a predetermined pressing sequence into consideration. The pressing sequence is based on pressing forces which are to be exerted by the punches 4, 5, 7 during a time sequence of the pressing process on the compressible material 6.

(13) This is shown in a position-time diagram below the illustrated components. Curves are shown above the time sequence t, which show a momentary position a. The momentary position a can be an actual position of a surface of a punch 4, 5, 7 contacting the compressible material. For reasons of easier manageability, basically any other, in particular, a sufficiently precisely measurable or determinable position a along the distance from the punch 4, 5, 7 to its drives 13, 16, 20, 21, 10, can be used, in particular also a position determinable by the drive itself.

(14) For simplification, only one setpoint positioning path as3 of the top punch 7 and the setpoint positioning path as1 of the first, bottom punch 5 are shown. For a press having a greater number of punches above and/or below the die opening, a greater number of such setpoint positioning paths are suitably used. In particular, the number of such setpoint positioning paths will depend on the number of axes or punches 4, 5, 7, which are to be controlled.

(15) The setpoint positioning paths as1, as3 are determined as a function of pressing forces required by each of the punches 4, 5, 7 over the time sequence t.

(16) It is shown, for example, during continuous lowering of the top punch 7 that the first bottom punch 5 is initially moved upwards and then slightly lowered from a predetermined position. In particular, a so-called floating movement is to be executed by the bottom punch 5, wherein it yields when the pressing force acting on the compressible material 6 from above is too great. It can also be provided that the bottom punch 5 moves upwards in a readjusting movement if the pressing force acting on the compressible material 6 from above is too weak.

(17) In the cycle of the pressing method shown, it is assumed that the momentary position a1m of the bottom punch 5 temporarily deviates upwards from the momentary setpoint position as1m provided at this moment. Based on the measured forces F21, F22 of the corresponding force-measuring devices 24, 25 associated with said bottom punch 5, the controller C determines a control deviation K(21) if the measured force F21 of one of the force-measuring devices 25 deviates, for example, from a setpoint force Fs for the measured force value of this force-measuring device 25, in particular. Therefore, a control signal, or setpoint position control variable s21, which controls readjustment as a function of the control deviation K(21), is applied to the associated drive 16.

(18) The control deviation K(21) and thus the setpoint position control variable s21 are thus force-dependent open- or closed-loop control variables, which depend directly on one or also on a plurality, as the case may be, of the measured forces F21.

(19) As the setpoint positioning paths as1, as3 are determined, and also as the setpoint position control variables s3, s11, s12, s21, s22 are determined for the quantities influencing each momentary position a of the corresponding punches 4, 5, 7, preferably also further quantities influencing the pressing process, such as a machine-specific modulus of elasticity E, a spindle pitch and also momentary positions of further punches 4, 5, 7, as the case may be, are also taken into consideration.

(20) During the execution of a pressing method each control deviation K(21) and/or the momentary setpoint position control variables s3, s11, s12, s21, s22 can be determined in various ways. Basically, a table look-up or a calculation are possible.

(21) In the case of a table look-up, in a table comprising setpoint positions to be reached over time as a function of setpoint forces, the knowledge of a person skilled in the art or a person operating the plant, on a stiffness of the structure, contours and material properties of the compact could also be considered.

(22) Since it is very cumbersome to model all components in the force flow of each of the axes, to obtain the best possible model as a basis for determining correct data for the table, calculation is preferred. In particular, a simplified model can be the basis of calculation. The deviations of the real object from the model are considered in the calculation via the setpoint-actual force difference.

(23) To this end, in the controller C governing the servo controllers, in particular, a setpoint path is calculated using the force, according to the controller clock. If the setpoint force is set in relation to the actual force in operation, this will result in the control deviation EK of the measured force under consideration. This control deviation, together with the spindle pitch and a machine-specific modulus of elasticity is converted to a setpoint position controllable by the position controller of the servo axis, or the drive. If the tool axis or its drive control now follows the calculated path, the provided force profile will automatically be realized on the axis.

LIST OF REFERENCE NUMERALS

(24) 1 ceramic and/or metal powder press 2 frame 3 die 4 punch 5 punch 6 compressive material 7 punch 8 punch carrier, in particular in the shape of a plate 9 spindle 10 electromotive drive 11 force-measuring device 12 punch carrier, in particular in the shape of a plate 13 spindle 14 spindle 15 electromotive drive 16 electromotive drive 17 punch carrier, in particular in the shape of a plate 18 spindle 19 spindle 20 electromotive drive 21 electromotive drive 22 force-measuring device 23 force-measuring device 24 force-measuring device 25 force-measuring device a position along pressing direction as3 setpoint positioning path of third, top punch a1m momentary position of first, bottom punch as1 setpoint positioning path of first, bottom punch as1m momentary setpoint position of first, bottom punch C controller E machine-specific modulus of elasticity K(21) control deviation F3 measured force as measured quantity F11 measured force as measured quantity F12 measured force as measured quantity F21 measured force as measured quantity F22 measured force as measured quantity Fs setpoint force s3 setpoint position control variable s11 setpoint position control variable s12 setpoint position control variable s21 setpoint position control variable s22 setpoint position control variable t time sequence of a pressing method