EP1646462B1 - Method for shaping a workpiece - Google Patents

Description

The invention relates to a method for forming a workpiece. Such a method is from the US-A-5 587 633 known.

Numerous methods and devices are available for forming workpieces. In press machines, the workpieces are brought into engagement with suitable tools which provide the forces necessary for the operation. The presses generally differ in off, force and work-linked presses. Of particular interest in this connection are the work-connected forming devices or pressing machines, in particular the spindle presses. The determining characteristic of these work-connected pressing machines is the working capacity E, which is fully implemented at every working cycle.

In a screw press, the spindles are driven by a positive or non-positive connected flywheel or directly by motor. The rotary motion is converted via a steep-going multiple thread in a straight-line plunger movement. The sudden impact of the ram on the workpiece, the kinetic energy of the flywheel, spindle and ram is completely converted into useful and lost work. The energy conversion is characterized by the impact efficiency ηs. (Lexicon Production Technology Process Engineering, Ed. Heinz M. Hiersig, VDI-Verlag).

As drive for the spindle or the flywheel usually an electric drive motor, preferably an asynchronous motor is used. In order to obtain optimum operating behavior, ie drive power, current consumption, efficiency, flexible application possibilities and short stroke times, it is desirable to control and regulate the screw press or the ram stroke accordingly.

In the publication DE 34 44 240 C2 is a screw press disclosed in which the speed and thus the speed of the plunger in wide areas can be controlled, and thus also forming work with relatively little work capacity such as edge dipping can be performed. The screw press comprises a flywheel with its own drive, which has a pre-rotation speed at the beginning of the ram stroke, which is connectable via a disc clutch with the drive pulley and the spindle comes to a standstill at the end of the forming process and is uncoupled from the spindle. The spindle including spindle drive pulley also has its own drive, which also serves to return the ram. For the working stroke, the spindle is now accelerated by means of the spindle drive, preferably maximum, and then downshifted to the speed required for the coupling with the flywheel at the end of the idle stroke.

If the majority of the ram stroke at higher speed, with still separate clutch drive through, so can be with the in DE 34 44 240 revealed spindle press achieve short cycle times. However, in this embodiment, two high power drive motors are necessary. which can lead to a high power requirement. If the speeds are not precisely controlled, energy can also be lost through the coupling process.

DE 38 41 852 A1 describes a drive arrangement for driving a threaded spindle of a screw press, wherein the coupling of the threaded spindle takes place on a constantly rotating drive pulley via a differential or superposition gear. For coupling, a shaft of the gearbox is braked. Through appropriate control and regulation of the braking speed and torque and thus pressing force and stroke speed can be varied during the cycle. In addition, the braking energy can be tapped and made available, for example, for the ram return stroke.

The disadvantage of this design is that a constantly rotating drive pulley is necessary, resulting in higher energy consumption. Another disadvantage is the large speed difference between the spindle and drive pulley when coupling, which means energy consumption and clutch wear.

A directly driven screw press is in DE 195 45 004 A1 disclosed. Here, an optimal operating behavior is achieved in that a variable-speed drive consisting of a three-phase asynchronous motor and a frequency controller or power converter is used to improve the energy balance and for a more accurate control of the path-time course. The required forming energy is adjusted by varying the speed. The speed-time profile of the spindle can be varied by a device for controlling or regulating the drive.

By varying the speed-time curve, relatively short stroke times can be achieved to achieve the respectively desired forming energy. However, tolerances caused by the mechanism, for example during the return stroke of the ram or tolerances in the workpieces, are disregarded, which on the one hand affects the accuracy of the forming process and on the other hand can also lead to energy loss.

Another directly driven screw press is described in the Lasco company magazine "Upgrade" (issued December 2000). As an example, a forming process with low deformation energy is shown. The drive motor with frequency converter accelerates the moving masses, ie the flywheel and the coupled spindle, to a speed corresponding to the maximum energy. The plunger is thereby driven at maximum speed until shortly before the beginning of the forming process, and then, as a generator, brakes at the preselected speed to begin the forming process. The return stroke is carried out by reversing the drive. About half return stroke height is in turn braked as a generator and the drive elements are delayed so that the mechanical brake at top dead center only works as a parking brake.

In this previously described screw press can be as in the in DE 195 45 004 A1 revealed spindle press to achieve the respectively desired forming energy realize relatively short stroke times. However, tolerances caused by the mechanism, for example during the return stroke of the ram or tolerances in the workpieces, are also disregarded because the speed of the ram or the speed of the drive motor and the position of the plunger in which it is braked, depending on the workpiece are fixed.

It is an object of the invention to provide a method for forming a workpiece, in which the aforementioned disadvantages of the prior art are at least partially overcome or at least reduced.

This object is achieved with regard to the method for forming a workpiece with the features of patent claim 1 and with regard to the forming device with the features of claim 29.

In the method for forming at least one workpiece, a striking tool impacts during a striking movement from a predetermined or predeterminable starting position with a predetermined or predeterminable impact velocity on the workpiece located on a support and the speed of the striking tool during the impact movement is dependent on the position of the impact tool and controlled or regulated depending on the given impact speed.

The impact movement is the preferably axial movement of the impact tool (or: plunger) in the direction of the workpiece and that from a starting position until it collides with the workpiece. The difference in height which the impact tool undergoes during the impact movement from the initial position to the impact on the workpiece is the stroke of the impact tool, hereinafter also referred to as the working stroke or impact stroke. After the forming process, the impact tool is usually returned to a predetermined end position. The height difference which the striking tool undergoes during this return movement is also referred to below as the return stroke.

The velocity of the impact tool during the impact movement is a measure of the available kinetic energy (E). The kinetic energy is proportional to the product of the mass (m) of the impact tool and the square of the velocity (v) of the impact tool (E = ½mv ² ). Since the mass of the impact tool is constant during the impact movement, the velocity of the impact tool or the initial position or the working stroke and the acceleration (equations of motion) of the striking tool play a decisive role for the kinetic energy available on impact. The kinetic energy during the impact, which results from the impact velocity of the striking tool, is also referred to below as forming energy.

The forming energy is largely converted to useful work upon impact with the workpiece, thereby deforming the workpiece. The loss energy or the resulting loss work is introduced among other things in the recoil of the impact tool.

A core idea of the invention is now that the speed of the impact tool during the impact movement can be controlled or regulated depending on the position of the impact tool in order to achieve a desired or predetermined impact velocity. In other words, this means that the instantaneous velocity (v (t)) of the impact tool is a function of the momentary position (x (t)) of the impact tool (v (t) = v (x (t)) The impact velocity of the impact tool is a constant, the However, their value can be chosen arbitrarily. Accordingly, the impact tool is accelerated or decelerated, depending on which position (or position) it is currently in, in order finally to reach the predetermined impact speed.

In this case, the initial position (x (t ₀ )) of the impact tool depending on the predetermined impact velocity, for example, when the impact movement is to be performed at a constant speed or a constant acceleration, or depending on the requirements of the workflow can be determined and set.

The method according to the invention thus has the advantage that a desired impact speed or the resulting deformation energy can be achieved in a predetermined by the physical laws frame, regardless of the initial position set, and that equally, within certain limits, a desired starting position can be set can, regardless of the given impact speed. As a result, the forming process is very flexible.

In order to determine the speed during the striking movement as a function of the position of the striking tool, in an advantageous embodiment at least one position of the striking tool can be measured or determined. With the value of the at least one position of the impact tool and the predetermined impact speed, the speed values during the impact movement can then be calculated.

The position of the impact tool is preferably determined by a suitable position measuring device which transmits the position value to a control and regulation unit for controlling or regulating the impact tool. This makes it possible, for one thing, to determine a specific position, for example the initial position, and then to calculate the necessary or optimal or optimal speed profile for achieving the predetermined impact speed. The impact tool is then controlled or controlled during the impact movement to these speed values. On the other hand, a control or regulation can be done in real time by always measured during the impact movement, the current situation or is determined and the speed is then calculated in accordance with the measured instantaneous attitude values, preferably by numerical differentiation, and controlled or regulated.

The fact that the position of the impact tool according to the invention within the forming device is known at all times has the further advantage that it enables repeatable working. It is particularly advantageous if, for example, by means of the position measuring device, the initial position of the impact tool and / or the position after a return movement of the impact tool is measured or determined. If, for example, too great a tolerance occurs during the return movement of the impact tool, i. the actual return stroke is greater or smaller than the predetermined height difference, this is detected by the position measuring device and used to determine the speed curve of a subsequent power stroke, so that the impact tool in turn bounces with exactly the predetermined impact velocity on the workpiece.

In the case of repeated bouncing of the impact tool on the same workpiece, it is advantageous if the position of the impact tool is measured or determined after the deformation of the workpiece by the impact. Thus, with repeated machining of a workpiece in the apparatus, the height of the workpiece as a result of the deformation can be detected and the subsequent working stroke can be extended by this distance, for example, so that the deformation energy transmitted to the workpiece is always constant.

In a particularly advantageous embodiment, the striking tool is accelerated from the starting position to the predetermined impact speed. To achieve an impact speed lower than a maximum impact velocity, it may be advantageous if the starting position is set lower than a maximum starting position.

The percussion tool can usually pass through a maximum working stroke predetermined by the shaping device during its impact movement from a maximum initial position, after which the maximum or maximum impact velocity and thus the maximum deformation energy is achieved. Due to the possible position detection of the impact tool of the But ram or the impact tool but also be driven from any position or position within the maximum power stroke, so that a working stroke is smaller than the maximum stroke. In this case, the highest attainable impact velocity or deformation energy is then less than the maximum impact velocity or deformation energy.

This is particularly advantageous in applications with flat workpieces and / or low deformation energy required. When accelerating from the starting position, the desired impact velocity or deformation energy is then just reached upon impact with the workpiece. The short working stroke brings very short stroke times with it, which can be achieved very short cycle times, on the other hand, thereby energy can be saved.

It is also particularly advantageous if the impact tool is accelerated from the initial position and braked when reaching a predetermined position between the starting position and the workpiece in order to achieve the predetermined impact velocity. The speed is thus varied over the stroke length so that, for example, even from a high starting position and at a large working stroke, the generation of low impact speeds or forming energies is possible. In order nevertheless to achieve a short working stroke time, the impact tool is first accelerated, if possible, with a maximum starting acceleration to a maximum speed, which is achieved in the predetermined position between the starting position and the workpiece, from which the impact tool is then decelerated to the desired impact speed, the lower than the maximum speed.

In practice, for example, when machining the front side of very large or long workpieces, a very high starting position can now be selected in order to facilitate the insertion of the workpiece into the carrier. Even with the use of automatic feeders for the workpieces, such as robots with grippers or automatic gripping tools, a high initial position of the impact tool may be advantageous to facilitate the feed. From this high starting position can then at the process according to the invention, depending on the requirement, both high and very low forming energies are generated.

Furthermore, it is particularly advantageous if the speed of the striking tool is controlled or regulated during the striking movement in such a way that the shortest possible working stroke time is achieved at any starting position. This can be realized by means of the control and regulating device, which optimizes the speed profile of the impact tool depending on the position and the predetermined impact velocity of the striking tool so that as far as possible the shortest stroke time is achieved.

The control and regulation of the speed of the impact tool is preferably carried out with a control and regulating device which controls and regulates a variable-speed drive motor of a drive device for the impact tool.

As a control and regulating device preferably a frequency converter unit is used, which controls the speed and the direction of rotation of the drive motor and controls. It is particularly advantageous if the Ftequenzumrichtereinheit determined by means of a microprocessor, the speed profile of the drive motor during the impact movement in response to a predetermined impact velocity and a predetermined starting position and / or determined by a position measuring device location.

In a particularly advantageous embodiment of the method according to the invention, the impact tool is lifted back after the impact by a return movement in a predetermined or predeterminable end position. The return movement into the end position is preferably carried out in the reverse direction of rotation of the drive motor. However, other methods are conceivable to bring the impact tool in the final position. Thus, for example, the impact tool can be lifted by means of telescopic rods hydraulically or pneumatically. The pressure required for this purpose can be generated, for example, during the impact movement of the plunger by compressing a liquid or a gas in a suitable chamber.

It is particularly advantageous if the speed of the striking tool is controlled and regulated during the return movement into the end position as a function of the position of the striking tool. An optimal control and regulation of the speed of the impact tool is given by the Ftequenzumrichtereinheit whose microprocessor determines the speed curve during the stroke in dependence on the predetermined end position and / or determined by the position measuring device location. This control and regulation option can be used when retrieving the impact tool by means of the drive motor.

It is particularly useful if the initial position of the impact tool is selected for the working stroke as the end position of a return stroke. Especially when several identical workpieces are to be processed one after the other, the optimum stroke time and forming energy are always achieved. However, it is also possible to drive the impact tool in any other end position. This can be advantageous if different workpieces are to be processed one after the other. The end position of the return stroke can then be selected in particular depending on the workpiece to be machined and / or the desired impact velocity in the subsequent impact movement.

In a particularly advantageous embodiment, the impact tool is accelerated away during the return movement into the end position of the workpiece or carrier and braked upon reaching a predetermined position between the workpiece or the carrier on the one hand and the end position on the other hand by means of the drive motor. Upon reaching the end position, the impact tool is then completely decelerated by a mechanical braking device. This control and regulation of the speed during the return movement has the advantage that the impact tool can be driven very accurately in the end position, but at the same time reached this end position very quickly. Furthermore, the risk is reduced that the mechanical braking device wears quickly or that the overflow or the tolerance of the return stroke is too large, as it may be the case at too high speed of the impact tool when reaching the end position.

This precise speed control during the return stroke or the resulting exact end position of the impact tool is for example particularly advantageous when the workpiece is driven with the impact tool up to the end position and removed in the end position. The workpiece can then always with high accuracy by means of a discharge device, such as a gripping tool, removed and removed.

In a particularly expedient embodiment, the impact tool is accelerated during acceleration with a predetermined constant starting acceleration. Preferably, the impact tool is decelerated even during braking with a predetermined constant braking acceleration. This achieves high accuracy and at the same time an energy-saving mode of operation. The amount of the constant starting acceleration and the constant braking acceleration, for example, depending on the direction of movement of the impact tool, that is, depending on whether it performs a striking movement or a return movement, are selected. In this case, for example, the effect of gravity on the impact tool can be considered and the acceleration can be selected accordingly.

It is especially advantageous if the drive motor is switched to the workpiece without torque prior to the impact of the impact tool and / or uncoupled in the drive device. As a result, loads for the engine and the control and regulating device are avoided, which can be generated by occurring current and voltage peaks. The drive motor can usually be switched momentarily via the frequency inverter unit. The instantaneous switching or uncoupling takes place, for example, on a signal of the position measuring device shortly before the impact, so that as far as possible no forming energy is lost.

In a particularly advantageous embodiment of the method according to the invention, the drive motor is operated as a generator during deceleration of the striking tool by means of the drive motor. The energy gained during deceleration by the generator can then be fed back into the power grid.

The position of the impact tool in the forming device is preferably determined by means of at least one, in particular non-contact position sensor, in particular an optical or magnetic or inductive and preferably incremental position sensor. The advantage of this method is that the measurement can be carried out without contact and the measuring device can thus be mounted in a safe position in the machine.

In an advantageous embodiment of the method according to the invention, a Umformvortichtung is used, which is designed as a screw press, and wherein the drive motor operates in the drive device of the screw press. The drive motor then preferably directly drives a flywheel, which in turn displaces a spindle coupled thereto in rotation. The spindle cooperates with the impact tool, preferably via a thread, that this is moved by the rotation of the spindle depending on the direction of rotation to the workpiece or carrier out or away.

The forming device designed in particular for use in the method or for carrying out the method according to the present invention comprises at least one support for the workpiece, at least one impact tool, at least one drive device for moving the impact tool relative to the support and at least one position measuring device for determining the position of the Impact tool within the forming device, wherein for the forming of the workpiece, a starting position of the striking tool is adjustable or adjusted and wherein a control and regulating device is provided which controls the speed of the percussion tool during a working stroke depending on the position and controls, so that a predetermined or predetermined Impact speed on the workpiece is achieved.

The forming device is preferably a screw press. However, it is also conceivable to form the forming device as another work-bound forming machine or pressing machine, for example a hammer, or as a force-bonded pressing machines such as a hydraulic press. The forming devices then differ substantially in the concrete Design of the driving device. A large number of possible drives can be controlled and regulated by suitable means so that the speed can be varied via the stroke. By using the position measuring device that is then also possible from any starting position out.

If now a forming device for carrying out the method according to the invention is designed as a screw press, then the drive device preferably comprises a variable-speed drive motor, wherein in particular an asynchronous motor can be used. Furthermore, the drive device comprises a flywheel, which is coupled to a spindle and is driven by the drive motor.

In a particularly advantageous embodiment of the forming device, a frequency converter unit is used as a control and regulating device, which controls and regulates the drive motor speed and possibly also the direction of rotation of the drive motor. The frequency converter unit preferably comprises a microprocessor. Among other things, the desired values for the respective starting position and the speed can be entered into a memory associated with the microprocessor. The values detected by the position measuring device are also transmitted as a signal to the microprocessor. From these values, the processor then determines or calculates the necessary or most favorable speed profile during a striking movement.

For the return movement of the impact tool from the workpiece or carrier preferably also an end position for the impact tool is adjustable or adjusted. The end position is also stored in the memory associated with the microprocessor, so that the processor can also calculate the course of the return movement. The return movement is preferably carried out by changing the direction of rotation of the drive motor.

It is particularly advantageous if a mechanical braking device is provided for holding the striking tool in the end position. The mechanical brake device or brake then acts upon reaching the end position for example, on the flywheel and holds this, whereby the impact tool is stopped in its movement.

The position measuring device preferably comprises a conventional and in particular non-contact position sensor, in particular an optical, magnetic or inductive and preferably incremental position sensor.

The invention will be further elucidated on the basis of exemplary embodiments and with reference to the accompanying drawings.

FIG 1a

eine vereinfachte Darstellung einer Ausführungsform des Verfahrens gemäß der Erfindung,

FIG 1b

das Verfahren gemäß FIG 1a bei durchgeführter Schlagbewegung,

FIG 2

ein Geschwindigkeits-Zeit-Diagramm, das theoretische Geschwindigkeits-Zeit-Verläufe bei konstanter Anfahrbeschleunigung darstellt,

FIG 3

ein Geschwindigkeits-Zeit-Diagramm, das theoretische Geschwindigkeits-Zeit-Verläufe bei konstanter Anfahrbeschleunigung und anschließender konstanter Abbremsung auf eine konstante Auftreffgeschwindigkeit aus unterschiedlichen Ausgangslagen darstellt,

FIG 4

ein Geschwindigkeits-Zeit-Diagramm, das theoretische Geschwindigkeits-Zeit-Verläufe zum Erreichen verschiedener Auftreffgeschwindigkeiten aus einer konstanten Ausgangslage darstellt,

FIG 5

ein Geschwindigkeits-Zeit-Diagramm, das reale, gemessene Geschwindigkeits-Zeit-Verläufe bei dem Verfahren gemäß der Erfindung darstellt,

FIG 6

eine vorteilhafte Ausführungsform einer Umformvorrichtung zur Durchführung des Verfahrens gemäß der Erfindung.

Shown schematically in each case:

FIG. 1a

a simplified representation of an embodiment of the method according to the invention,

FIG. 1b

the method according to FIG. 1a when carried out impact movement,

FIG. 2

a velocity-time diagram representing theoretical velocity-time curves with constant acceleration of start,

FIG. 3

a speed-time diagram representing theoretical speed-time curves with constant acceleration of acceleration and subsequent constant deceleration to a constant impact velocity from different starting positions,

FIG. 4

a velocity-time diagram representing theoretical velocity-time profiles for achieving different impact velocities from a constant starting position,

FIG. 5

a velocity-time diagram illustrating real, measured velocity-time profiles in the method according to the invention,

FIG. 6

an advantageous embodiment of a forming device for Implementation of the method according to the invention.

Corresponding parts and sizes are in the 1 to 6 provided with the same reference numerals.

In FIG. 1a and FIG. 1b the forming process according to the invention is shown greatly simplified. To illustrate FIG. 1a and FIG. 1b a simple forming device with a percussion tool, in particular a plunger 1, a drive device 2 and a support 3, on which a workpiece 4 is arranged. The position of the plunger is determined by a position sensor (not shown here, cf. FIG. 6 ). The plunger 1 is accelerated by the drive device 2 from an initial position H _0a, H _0b, H _0c, H _0d (H _0a = H _0d> H _0b> H _0c) out ( FIG. 1a ). The initial velocities of the plunger v _0a , v _0b , v _0c , v _0d are in all associated starting positions H _0a , H _0b , H _0c , H _0d equal to 0 m / s. The plunger 1 moves in the device down to the befindliches on the carrier 3 workpiece 4. When the ram 1 has reached the workpiece 4, it collides with an impact velocity v _Aa , v _Ab , v _Ac , v _Ad ( _FIG . FIG. 1b ).

The starting position H _0a , H _0b , H _0c , H _{0d of} the plunger 1 can be set arbitrarily. Thus, for example, two different sized or high workpieces with the same impact velocity v _A , which results from the same stroke ΔH, edited or by accelerating from the different starting positions H _0a , H _0b , H _0c , H _0d different impact _velocities v _Aa , v _Ab , v _Ac , v _{Ad are} reached. The maximum working stroke ΔH _a is reached from the starting position H _0a and, with continuous acceleration, leads to a maximum impact velocity v _Aa and the associated maximum forming energy. It is also possible to set arbitrarily lower initial positions H _0b , H _0c . However, the lower the starting position is chosen, the lower is the maximum achievable impact velocity (v _Ab > v _Ac ) with continuous acceleration.

In the method according to the invention, it is likewise possible first to accelerate the plunger 1 in the direction of the workpiece 4 from a starting position H _od and after a predetermined first partial working stroke ΔH _d1 or in a predetermined height or position H _d , hereinafter also referred to as Abbremslage slow for a predetermined second Teilarbeitshub ΔH _d2 , so that an impact velocity v _Ad set or the resulting deformation energy is generated, the smaller the from the starting position H _{0d is the} maximum possible.

The plunger 1 can preferably be accelerated with constant starting acceleration and constant braking acceleration, which can each have different amounts of acceleration. However, the method is not limited to this variant since starting acceleration and deceleration do not necessarily have to be constant.

In FIG. 1a is the partial strokes ΔH _d1 and ΔH _d2 and the braking position H _d between Anfahrbeschleunigungs- and braking only from the maximum starting position (H _0a = H _0d ) shown. But the plunger 1 can also from all other starting positions (H _0b , H _0c = H _0d ) first accelerated and from a predetermined and normally to the in FIG. 1a be braked different position H _d .

A speed course with acceleration and deceleration process is advantageous in practice, for example, when large or long workpieces have to be inserted into the machine and therefore a lot of space must be available below the ram. The plunger 1 is then moved, for example, in the maximum starting position H _0a = H _0d and after the insertion of the workpiece 4 is first accelerated and then decelerated to the desired impact velocity v _Ad . If flat workpieces 4 are processed, the impact velocity v _Aa , v _Ab , v _{Ac is} usually generated simply by accelerating from the respectively required starting position H _0a , H _0b , H _0c .

The speed profile over the ram stroke, both working stroke and return stroke is determined by a control and regulating unit, preferably a microprocessor unit in a frequency converter unit (not shown here) which is housed in the drive device 2.

In this case, at least the starting position H _0a H _0b , H _0c , H _0d , and the desired impact velocity v _Aa , v _Ab , v _Ac , v _Ad pretend. Furthermore, the amount of the starting acceleration and the braking acceleration can be specified or predefined or preset. The control and regulation device then calculates the speed profile over the height of the working stroke or sub-hubs ΔH _a , ΔH _b , ΔH _c and ΔH _d1 and ΔH _d2 , so that overall to achieve the desired impact velocity v _Aa , v _Ab , v _{Ac ,} v _Ad at the given values for the starting acceleration and the braking acceleration, as far as possible the shortest stroke time results. In this case, the result may be a speed course with continuous acceleration of approach or the control and regulation device determines a braking position H _d , from which the plunger 1 is decelerated until impact.

The return stroke is in the FIGS. 1a and 1b indicated only by the arrow. After the impact on the workpiece 4, the plunger 1 is returned by means of the drive means 2 back to its initial position H _0a , H _0b , H _0c , H _0d or in any other end position. For this purpose, it is first accelerated and decelerated in a likewise determined by the control unit and control position H _d , so that it has in its final position approximately the speed 0 m / s. The position H _d , from which the plunger 1 is braked, is dependent on the desired end position and possibly also on the recoil of the plunger. 1

FIG. 2 shows theoretical speed-time curves at constant starting acceleration from different starting position H _0a , H _0b , H _0c . The ram is accelerated at a constant starting acceleration from the starting position H _0a , H _0b , H _0c to the maximum impact velocity v _Aa , v _Ab , v _Ac for a maximum forming energy (100%). This maximum impact velocity v _Aa , v _Ab , v _Ac is _denoted in the diagram by v _E100% (H _0a ), v _E100% (H _0b ), v _E100% (H _0c ). The time span until the maximum impact velocity v _{E100% is} reached corresponds to the total duration of the working stroke t _Ges from the respective initial position H _0a , H _0b , H _0c , where t _{0 is} always equal to 0 s. From the diagram it can be seen that from the different starting positions H _0a , H _0b , H _0c at constant starting acceleration respectively different high maximum impact _velocities v _E100% (H _0a ), v _E100% (H _0b ), v _E100% (H _0c ) can be achieved The higher the initial position, the higher the impact velocity. The total duration of the working stroke t _Ges longer with increasing starting position H _0a , H _0b , H _0c .

FIG. 3 shows theoretical speed-time curves with constant starting acceleration and subsequent constant deceleration to a constant impact velocity. It should now from the same starting positions H _0a H _0b , H _0c as in FIG. 2 a constant Auftxeffgeschwindigkeit V _{A are} generated, resulting in the example, only 10% of the maximum deformation energy, ie v _A equals v _E10% (H _0a , H _0b , H _0c ). With a known constant acceleration acceleration and deceleration, known impact velocity and known starting position can be at any starting position on the equations of motion, the total duration of the working stroke t _ges and determine the working stroke t ₁ , or the braking position to which the deceleration must occur. The result of such an idealized velocity-time curve is in FIG. 3 shown. The maximum velocities v _max (H _0a ), v _max (H _0b ), v _max (H _0c) are reached after the working stroke _times t ₁ (H _0a ), t ₁ (H _0b ), t ₁ (H _0c ) the ram brakes with the brake acceleration and, after the total duration of the working stroke t _Ges (H _0a ), t _Ges , (H _0b ), t _Ges (H _0c ), hits the workpiece at the speed v _E10% FIG. 3 is apparent, the higher the starting position H _0a , H _0b , H _{0c is} selected, the longer ist.die total duration of the working stroke t _Ges until reaching the predetermined impact velocity v _E10% Furthermore, extended with increased starting position H _0a , H _0b , H _0c also the working stroke time (H _0a ), t ₁ (H _0b ), t ₁ (H _0c until the deceleration process is initiated and the maximum speed of the plunger v _max (H _0a ) v _max (H _0b ), v _max (H _0c ) increases.

The method according to the invention now also makes it possible to generate different impact speeds from a constant starting position as required. In FIG. 4 are three theoretical speed-time curves to achieve each different Aufueffgeschwindigkeiten from a constant starting position shown. The starting position corresponds to the maximum starting position H _0a . In order to achieve the impact speed v _E100% corresponding to the maximum deformation energy, the plunger is constantly accelerated out of the initial position H _0a , out until impact with the workpiece. The duration of this working stroke is indicated in the diagram as t _Ges (100%). Should now from the same starting position H _0a , only one impact velocity V _E50% can be achieved, which corresponds to 50% of the maximum forming energy, the plunger is first accelerated to v _max (50%) and from a predetermined position or time to the predetermined impact velocity v _E50% braked. It can be seen from the diagram that this process lasts longer (t _tot (50%)) than the acceleration to 100% of the transformation energy. The third curve shows the approach of an impact velocity v _B10% , which corresponds to only 10% of the maximum deformation energy, also from the starting position H _0a . The maximum velocity v _max (10%) is in this case lower than when generating the 50% forming energy and the total duration of the working stroke t _Ges (10%) is even longer. The relationship between transformation energy E and velocity v can ideally be given as E = ½mv ² . The velocity v is therefore proportional to the root of E.

FIG. 5 shows three real, measured speed-time courses of the method according to the invention, with the in FIG. 4 shown theoretical speed-time courses are comparable. The working stroke or the starting position can be assumed to be the same for all curves A, B, C. For the forming processes, however, different impact velocities or different forming energies were chosen, which are denoted by 100%, 50%, and 10% and are assigned to the curves A, B, C. In addition, the speed-time curves each of the force impulse α, β, γ superimposed upon impact of the plunger on the workpiece at the respective impact time.

The curve A (100%) shows the speed-time curve for an acceleration to the maximum speed to reach the maximum deformation energy. The plunger is accelerated from the starting position via the curve section K1 until it reaches the maximum possible impact velocity v _E100% in the curve section K2. The curve section K3 illustrates the deceleration of the plunger by the energy loss during impact. Part of the energy is introduced into the forming process. The remaining energy is at least partially converted into a recoil of the plunger (K4). The remainder of the speed in the curve A (100%) is due to this recoil.

Subsequently, the plunger is driven by means of the drive motor, which is usually switched on or coupled again only after the impact and recoil in the direction of the end position. In this case, the plunger is first accelerated to a predetermined position, which shows the curve section K5. Upon reaching the predetermined position of the plunger is braked by means of the motor. This position or the associated time, by which it is represented in this and the following curves, and the maximum speed reached at this time is described by the curve section K6. After reaching the predetermined position of the plunger is slowed down by means of the drive motor until it reaches a very low speed (K7). If the plunger arrived in the predetermined end position additionally engages a mechanical brake, which is evident from curve section 8. The mechanical brake decelerates the ram to exactly 0 m / s and holds it in the end position. By gripping the mechanical brake, the amount of braking acceleration is changed, which is represented in K8 as a small bulge in the curve.

The force pulse α occurs exactly at the time when the plunger impacts the workpiece. In the illustration, this can be seen from the fact that the maximum of α is at a time shortly after reaching the desired impact speed. This also applies to the power surges β and γ in the other curves.

The curve B (50%) shows the velocity-time curve for an acceleration to a speed to reach 50% of the maximum forming energy at constant stroke. This means that the plunger is first accelerated (K1) until a predetermined position with a predetermined maximum speed v _{max is} reached (K9) and then decelerated to the desired impact speed v _B50% , (K2). The reduction in the speed during the deceleration process is shown in curve section K10. In curve section K2, the desired impact velocity v _{B50% is again} achieved. The further course of curve B (50%) corresponds to the course of curve A (100%). The ram is slowed down by the impact (K3) and pushed back (K4). Subsequently, the drive motor engages and guides the plunger by accelerating (K5, K6) and braking (K7) to the end position, in which the mechanical brake brings the plunger to a standstill (K8).

The curve C (10%) shows the speed-time curve for an acceleration to a speed to reach 10% of the maximum forming energy with a likewise constant working stroke. The curve is comparable to that of B (50%). However, the desired impact velocity v _E10% is lower, so that first to a lower maximum velocity v _max than B (50%) is accelerated (K1, K9) and decelerated over a longer period of time (K10). The total duration of the working stroke is thus insignificantly longer compared to B (50%).

In FIG. 6 a forming device is shown, which is particularly suitable for carrying out the method according to the invention. The plunger 1 is driven by a spindle 5. For this purpose, the spindle 5 has a steep-threaded thread 9 in which a ram 8 attached to the ram 1 runs. The spindle 5 is coupled to a flywheel 6, which is directly driven by a drive motor 7, usually a variable speed variable in its direction of rotation asynchronous motor. The flywheel 6 and the spindle 5 coupled thereto are now set in rotation via the drive motor. The rotational speed of flywheel 6 and spindle 5 is adjusted via the rotational speed of the drive motor 7. For controlling the speed and a frequency converter unit with a microprocessor (not shown) is provided. The rotation of the spindle 5 is transmitted via the spindle nut 8 on the plunger 1 and this moves in the direction of the carrier 3 to or away from this. The speed of the drive motor 7 is a measure of the speed of the plunger. 1

On the carrier 3, a workpiece (not shown here) may be applied, so that the plunger impacts with a predetermined impact speed. Shortly before the impact of the drive motor 7 is turned off, so that the control and regulating device is protected from damage or interference from voltage and current peaks that may occur during impact. After the impact or recoil of the plunger 1 of the drive motor 7 again turned on and the plunger 1 lifted back to its end position.

The position of the plunger 1 is determined without contact, preferably by means of a magnetic, incremental position sensor 10 or measured. The measured values can be transmitted to the frequency converter unit and to an external control device. The measured values are used by the frequency converter unit in order to determine, for example, the speed or the speed profile of the plunger 1, which is necessary for an optimum forming process or for reaching the predetermined end position.

LIST OF REFERENCE NUMBERS

1

tappet

2

driving means

3

carrier

4

workpiece

5

spindle

6

flywheel

7

drive motor

8th

spindle nut

9

thread

10

locator

H _0a , H _0b , H _0c , H _0d

starting position

ΔH _a , ΔH _b , ΔH _c ,

stroke

H _d

Abbremslage

ΔH _d1, ΔH _d2

Teilarbeitshub

v ₀ , v _0a , v _0b , v _0c

initial velocity

v _A , V _Aa , v _Ab , v _Ac , v _Ad

impact velocity

v _E100% , v _E50% , v _E10%

Impact velocity at 100%, 50%, 10% strain energy

V _max , v _maxd

maximum speed

t ₀ , t ₁ , t _Gcs

Arbeitshubzeit

α, β, γ

power Blast

K1 to K10

curve sections

Claims (8)

1. A method of shaping at least one work piece (4) wherein

   (a) a striking tool (1) bounces against the work piece (4) located on a work piece holder (3) during a striking movement from a predetermined or predeterminable initial position (H_0a, H_0b, H_0c) at a predetermined or predeterminable impact velocity (V_Aa, V_Ab, V_Ac, V_Ad), and

   (b) wherein the velocity of said striking tool (1) is controlled or regulated during the striking movement as a function of the position of said striking tool (1) and in dependence on the predetermined impact velocity (v_Aa, v_Ab, V_Ac, V_Ad),

   (c) with the instantaneous position of said striking tool (1) during the striking movement being permanently measured and with the values of the instantaneous position of said striking tool (1) as measured and said predetermined impact velocity (v_Aa, v_Ab, v_AC, v_Ad) being used to compute the velocity values during the striking movement,

   (d) wherein said striking tool (1) is accelerated out of the initial position (H_0d) and is decelerated when a predetermined position (H_d) between said initial position (H_0d) and said work piece (4) is reached in order to achieve said predetermined impact velocity (v_Ad)

   (e) wherein said striking tool (1) is elevated and returned into a predetermined or predeterminable final position by a returning movement after the impact,

   (f) wherein the velocity of said striking tool (1) is controlled or regulated during the returning movement into said final position as a function of the position of said striking tool (1), and

   (g) wherein the final position of the returning stroke is different from the initial position of the previously performed striking movement and wherein the final position is selected as a function of the work piece (4) to be processed and/or the desired impact velocity (v_Aa, v_Ab, v_Ac, v_Ad) during the subsequent striking movement.
2. The method according to Claim 1,
   wherein at least one position of said striking tool (1), in particular the initial position (H_0a, H_0b, H_0c, H_0d) of said striking tool (1) and/or the position after a returning movement of said striking tool (1) or the position of said striking tool (1) after shaping of said work piece (4) is measured or determined by the impact and the velocity values are computed by using said at least one positional value of said striking tool (1) and said predetermined impact velocity (v_Aa, V_Ab, V_Ac, V_Ad) during the striking movement.
3. The method according to Claim 2,
   wherein the positional value of said striking tool (1) is transmitted to a control and regulator unit for control or regulation of said striking tool (1), and wherein the control and regulation of the velocity of said striking tool (1) is performed by means of said control and regulator unit that controls and regulates a speed-variable driving motor (7) in a driving means (2) for said striking tool, and wherein a frequency converter unit is employed as control and regulator unit, which controls and regulates the rotational speed and the sense of rotation of said driving motor (7), with said driving motor (7) being preferably switched without momentum and/or decoupled in said driving means (2) prior to the impact of said striking tool (1) on said work piece (4), and/or with said driving motor (7) being operated as generator by means of said driving motor (7) during deceleration of said striking tool (1) while the energy produced during deceleration by said generator is fed back into the mains supply network.
4. The method according to any of the preceding Claims,
   wherein the speed of said striking tool (1) is accelerated from said initial position (H_0a, H_0b, H_0c) to said predetermined impact velocity (V_Aa, V_Ab, _VAc, V_Ad) and wherein said initial position (H_0b, H_0c) is set to a level lower than a maximum initial position (H_0a) for achieving an impact velocity (V_Ab, V_Ac) lower than a maximum impact velocity (v_Aa)_.
5. The method according to Claim 5,
   wherein the velocity of said striking tool (1) during the striking movement is controlled or regulated in such a manner that the shortest working stroke cycle possible (t_Ges) will be achieved with any initial position (H_0a, H_0b, H_0c, H_0c) possible.
6. The method according to any or several of the preceding Claims,
   wherein said striking tool (1) is accelerated during the returning movement into said final position away from said tool or tool holder and, when a predetermined position (H_d) between said work piece (4) or said tool holder (3), on the one hand, and said final position, on the other hand, is reached, is decelerated by a generator function by means of said driving motor (7), and/or is completely decelerated by a mechanical braking means when said final position is reached.
7. The method according to any or several of the preceding Claims,
   wherein said striking tool (1) is accelerated at a predetermined constant starting acceleration and/or is decelerated in braking at a predetermined constant braking acceleration.
8. The method according to any or several of the preceding Claims,
   wherein a shaping device is employed which is a screw press, and wherein said driving motor (7) operates in the driving means (2) of said screw press and drives a flywheel (6) directly that causes a spindle (5) to rotate which is coupled to said flywheel.

Images