AT507257A2 - Controller for handling device i.e. three-axis linear robot, of injection molding machine, has memory storing data of path for end piece of handling device, where path is calculated by characteristics of injection molding part or component - Google Patents

Abstract

The controller (1) has a computer unit (4) comprising an electronic processor unit and an electronic memory (5) for storing data of a target path for a motor-driven end piece of a handling device (2), where the target path is calculated by using elastic characteristics of an injection molding part or a component of the handling device. The processor unit and the memory are connected with one another, where the characteristics of the part or component are detected by a sensor (11) that is arranged at the handling device. An independent claim is also included for a method for moving injection molding parts by a handling device of an injection molding machine.

Description

The invention relates to a control unit for a handling device of an injection molding machine, wherein the handling device is a motor-driven end piece in the form of a receiving or. Transfer head comprises, which serves for moving an injection-molded part, and wherein the control unit comprises an electronic memory in which the data of a desired trajectory for the tail are stored, along which the tail is movable by means of the control unit.

In the field of injection molding machines, handling devices, for example in the form of robots, are generally used for removing and subsequently depositing injection molded parts from the injection molding machine. However, such handling devices can also be suitably used for manipulation tasks in other fields of application. Examples of such areas of application are the parts manipulation on machine tools or in palletizing stations, as they are integrated in logistics systems. For use in the removal and storage of such handling devices can be additionally equipped with hand axes for rotary and pivotal movements. In this case, such a handling device in production cells for various handling activities, such as insertion, removal, storage, stacking, transfer to post-processing, etc. are used. In order to reduce the cycle times, the activities such as the removal and storage should be carried out as quickly as possible. At the same time, however, the activities must be carried out with a high degree of precision, for example in order to accurately approach the removal or storage positions. Precise and rapid positioning is necessary, especially when removing and depositing, without the injection molded part brought into contact with the handling device being subjected to vibrations.

In the prior art, some possibilities are already mentioned, which are intended to reduce vibrations of the handling device, which can be transferred to the injection molding machine.

In DE 198 48 420 an injection molding machine with handling device for removal and for feeding of workpieces is shown. To reduce shocks resulting from the movement of the handling device, a guide frame with respect to the injection molding machine has the same degree of freedom as the handling device with respect to the guide frame. In DE 198 48 419, in turn, a mechanical coupling 63855 35 / hn 2 of certain parts of the injection molding machine with the handling device is mentioned as a possible solution to the same problem at least for a certain period of time. '• .htm

In EP 1 306 868 a robot control is shown which optimizes the path behavior by means of an algorithm in order to optimize the force distribution and, concomitantly, to minimize oscillations of the object to be moved. The weight and the moment of inertia of the object to be moved are measured beforehand or are known. The active axes of the handling system are controlled according to the planned path, so that in particular for a palletizing robot, the load to be traversed does not tip over and essentially only normal forces occur between the gripping tool and the object to be moved.

A disadvantage of the above-mentioned disclosures that the aid for damping or the pre-planned desired trajectory can act only insufficiently accurate, as is assumed in each case of rigid components of the handling equipment.

The object of the invention is to avoid the disadvantages mentioned above and to provide handling equipment for injection molding machines that allow an accurate and fast positioning and thus a low cycle time, while minimizing vibrations of the handling device, in particular the tail with traversing object, wherein the tail may comprise a receiving head.

This is met with a control unit for a handling device of an injection molding machine with the features of claim 1.

After movements of one or more handling axes, clearly visible vibrations occur on the hand-held device, for example on the transfer head. The amplitude and frequency of these oscillations depend on the course of the trajectory and on the position of the respective axes of the preceding movements as well as the mass of the optionally attached load. By elastic deformations of the components of the handling equipment, such as the carrier profiles of the axes, as well as drive components, such as belts and bearings, the tracks of the motor-driven end piece of the handling device and optionally attached to be moved object from the actual nominal paths and Due to these deformations and the occurring forces and accelerations, the end piece becomes the one above due to these deformations and the occurring forces and accelerations excited vibrations. By taking into account the elastic properties of at least one, preferably movable, component of the handling device in which this elastic behavior is described at least approximately by means of a mathematical model and by modifying or generating the desired trajectory of the tail according to this model, the elastic or dynamic deviations of Reduces the position of the tail from the originally specified position and avoided the excited vibrations or at least reduced.

Further advantageous embodiments of the invention are defined in the dependent claims and are explained below.

The vibrations caused by the elastic properties of the components of the handling device also depend on the nature of the object to be moved with the end piece of the handling device. The characteristic sizes of the object to be moved, on which the oscillations can depend are u. a. the mass, the center of gravity, the geometric center and various moments of resistance, such as the moments of inertia or moments of deviation of this object. In a particularly preferred embodiment of the invention, the desired trajectory, which is calculated taking into account the elastic properties of at least one movable component of the handling device, additionally calculated taking into account at least one of these principle variable parameters of the object to be moved, in particular injection molded part. Preferably, all or at least several of the above-mentioned parameters are taken into consideration by the mathematical model which calculates the desired path.

These variable parameters may be e.g. be entered via an interface. In a preferred embodiment, sensors are mounted on the handling device, which can calculate one or more of these parameters of the part to be moved with the aid of the sensor signals and then supply a display or preferably forward automatically to the control unit.

In a preferred embodiment of the invention, the data of the desired trajectory calculated taking into account the elastic properties of at least one, preferably movable, component and optionally the variable parameters of the part to be moved comprise all relevant quantities of movement, i. not only the spatial location of the desired trajectory, but also the spatial location of the desired trajectory but additionally or alternatively, the desired speed along the desired path, the target acceleration along the desired path and the target pressure along the desired path. In particular, changes in the state of motion are relevant to vibrational excitations and are therefore preferable to consider when moving an object with a handling part. For injection molding machines in particular so-called Dreiachslinearroboter for translational movement of injection molded parts as a handling device in use. One of the axes of such a robot forms the Entformhub and serves to remove the parts from the movable or fixed platen of the injection molding machine. Another axis forms the vertical stroke and serves in its basic function for retracting and retracting from the tool area of the injection molding machine. The third of the axes of the Dreiachslinearroboters in turn forms the transverse transport and serves to extend and retraction in the storage area and the removal area. In one embodiment of the invention, the handling device is designed as such a three-axis linear robot, and the setpoint path is calculated in particular taking into account the elastic properties of at least one of the axes, for example of the respective carrier profile of the Dreiachslinearroboters. It is particularly preferred that the elastic properties of that axis, at the end piece, where the object to be moved is brought into abutment, the worst vibration behavior occurs, namely the vertical stroke forming the vertical stroke, is taken into account for the calculation of the desired trajectory.

The invention further relates to a method for moving injection-molded parts by a handling device of an injection molding machine, wherein a motor-driven end of the handling device with the injection molded part is brought into abutment and wherein the handling device, a control unit, in particular according to one of claims 1 to 8, with an electronic memory comprising, with the following steps:

Specifying or measuring the elastic properties of at least one component of the handling device,

Calculating the desired trajectory of the end piece taking into account the elastic properties of at least one component of the handling device,

Storing the data of the nominal path in the electronic memory,

Moving the end piece, preferably with brought-in injection molded part, by means of the control unit according to the calculated desired trajectory. • · · · · · · · · # "· · • · · · · · · · · · · · • · · · ····· 5

In order to take into account the elastic properties of at least one, preferably movable, component of the handling device, a desired path of the motor-driven end piece is calculated as mentioned above. For this calculation, a calculation rule based on a mathematical model is used, which can be stored in an electronic memory of the control unit. In this case, the calculation is carried out by a computing unit, which comprises customary electronic components and processors and can likewise be part of the control unit. The elastic properties of the components of the handling device flow as parameters in this mathematical model and can be specified or entered by means of an input unit in the control unit and stored in the electronic memory. However, it can also be provided that the elastic properties are determined by measuring elastic deflections, for example by means of strain gauges, acceleration sensors or measured variables of the drive. This measurement can be done during operation or in the context of specially performed test runs. It would also be possible for the mathematical model, which is stored in an electronic memory of the control unit, to have been specially set up for the handling device used and for the elastic properties of the handling device to be implemented and no longer required to be input. The data of the calculated desired trajectory are also stored in an electronic memory of the control unit and called to move the tail again from there.

In a particularly preferred embodiment, the calculation of the desired trajectory of the tail takes place taking into account at least one variable parameter of the part to be moved. This may be the mass and additionally or alternatively the center of gravity and / or the geometric center as well as one or more of the moments of resistance, such as moment of inertia and / or moment of inertia of the injection-molded part to be moved. It is particularly advantageous if one or more of the variable parameters is calculated by means of signals from attached to the handling device sensors or are and then preferably automatically the control unit is or will be.

In a preferred embodiment of the method according to the invention, the data of the desired path are stored in an electronic memory of the control unit in the case of an ideally rigid handling device, that is, without taking into account any elastic properties. In this case, these elastic properties are taken into account by deviations of these nominal paths with a mathematical model. Be calculated for rigid handling equipment and thereby the target position and / or the target speed and / or the target acceleration and / or the target pressure along the target path are changed. When specifying the target position as a function of time, the other listed variables can in principle also be calculated from the desired path.

To illustrate the operation of the control unit according to the invention or the method according to the invention on the vibrations at the end of a handling device acceleration can be measured at the end of the handling device and then compared with the vibrations that occur when taken into account in the control of the tail no elastic deformations of the handling device become.

It has been found that the modified target path based on the mathematical model produces significantly reduced vibrations of the tail.

As an example, such comparisons and measurements are performed on a three-axis linear robot serving as a handling device. With extended vertical axis and retracted axis for the Entformhub strokes in the transverse direction are thus carried out perpendicular to the direction predetermined by these two axes. At the end point of the vertical axis, ie at the end piece of the handling device, the accelerations occurring during the strokes are measured. Table 1 compares the results of the measurements. In column 2 and 3, the maximum acceleration amplitudes when swinging in the final position of the tail of the vertical track axis are given. Column 4 contains the factors by which the vibration amplitudes can be reduced.

Speed max. Accuracy amplitude for standard target runway max. Besdihamplitude with reduced nominal orbit Improvement factor% m / s * m / s * 50 1.40 0.94 1.5 70 1.36 0.50 2.7 100 1.47 0.73 2.0

Table 1: Experiments with modified nominal paths

Further details and advantages of the present invention will be explained in more detail below with reference to the description of the figures and a concrete example with reference to the drawings. It shows: • · · · · · · · ·····································································································································································

Fig. 1 Fig. 2 Fig. 3 Fig. 4 to 6 is a schematic representation of a handling device according to the invention for an injection molding machine, a schematic representation of the logic operations of a control unit according to the invention, a sketch to illustrate the arrangement for the example and numerical simulation results of the inventive control based on the example given.

In the schematic representation of FIG. 2, the logic operations of a control unit 1 according to the invention with a handling device 2 for moving an object 3 with the end piece of the handling device 2 are shown. In this case, the control unit has, in addition to a computing unit 4, which comprises an electronic processor unit, an electronic memory 5, which are both linked together as shown by the arrow 6 and can exchange data. The processor unit 4 uses a mathematical model stored in the electronic memory 5 and calculates the data of a desired trajectory, taking into account the elastic properties of at least one component of the handling device. In this case, from an input unit 7 different data, such as the output and end position of the tail of the handling device 2 and the object 3 or other parameters of the object 3, such as its mass entered, which then via the arrows 8 and 9 shown links to the arithmetic unit 4 and / or the electronic memory 5 are forwarded. The control unit 1 stands, as shown by the arrows 10 and 10 ', with the handling device 2 in connection, so that the handling device 2 can control the object 3 according to the calculated with the mathematical model setpoint trajectory. In this embodiment of the invention, a sensor 11 is further arranged on the handling device 2, which measures one or more of the parameters of the object 3 to be moved and then passes on the link shown by the arrow 10 to the control unit. These data are also forwarded to the processor unit 4 and / or the electronic memory 5.

Based on a concrete example is shown below how the elastic properties of a movable component of a handling device 2 in the form of the elastic properties of the vertical travel axis of a Dreiachslinearroboters be considered by means of a mathematical model and thereby the desired position, the target speed, and the target acceleration and the target pressure compared to the setpoint and setpoint speeds, as well as setpoint acceleration and setpoint pressure for a • ························································································

Handling device 2 are modified with a rigid travel axis and thereby excited vibrations are significantly reduced.

The elastic deflections of the vertical travel axis of the three-axis linear robot are modeled by means of a Ritz approach. To simplify the illustration, the vertical traverse axis should be in the fully extended state (there occurs in this example unfavorable vibration behavior) and additionally can only move along one direction. In addition, only deflections in this direction are considered. The invention is of course applicable to any position of the axle position.

The vertical travel axis is now assumed to be a horizontally movable elastic beam, at whose end point, ie at the end piece of the handling device 2, a mass is fastened. At the other end of the beam, a carriage is fixedly coupled to the beam. The driving force F acts on the carriage.

A linear scoring approach to describe the elastic deflection of the beam is: v (x, r) = v (x) r * (/). In this case, \ (x) contains the attachment functions and a (t) the elastic coordinates, depending on the coordinate xbzw. the time t. The superscript T denotes the transposition of the respective size. For the determination of the equation of motion, for example, the formalism according to Lagrange d_ dt idl] r (UäJ V 5J- «

L = E-V T

(D with the kinetic energy E, the potential energy V, the degrees of freedom of the system q and the vector of the impressed forces Q, are used.

The vector of degrees of freedom is q = 'yR &gt; and that of the impressed forces Q = v <&gt; y

YR denotes the rigid body degree of freedom. The kinetic energy is composed of ···· ··· * μ μ ··· ·· I ··· · »·. together from the partial energies of final mass, traversing carriage and beams. The potential energy, in turn, includes the weight and spring potential of the beam and the weight potential of the final mass.

After calculating the partial energies and inserting them into the Lagrange formalism £ 1), the equation of motion of the elastic beam can be determined. This has the form M.q + K.q = B.m. (2)

Here, M is the inertia matrix (mass matrix) and K is the stiffness matrix. The control force ultimately responsible for the vibration is given by the action matrix B, which in this example is B = (l θ) Γ, and the input quantity u = F determined by the driving force F.

The reference control for the ideal rigid system is obtained by blocking the elastic degrees of freedom, ie by setting a = 0.

By dividing the total movement into a reference movement, ie a movement qR of the rigid axis, and an elastic deformation one obtains q = qo + z =

yR qR 0 + z. If one carries out a Taylor expansion of the equation of motion by qo (up to the first order), one obtains with q = qo + z and u = uo + uc the equation of motion M.qo + K.qo - B.mo + Mz + Kz = B .wc, from which one can calculate uc and the vector z.

Calculation of the path correction:

The goal of almost all robot applications is that a gripper should follow a given path. The end position of the bar is given by the vector rE. For the deviation of the end point of the beam from its nominal path applies

ArE, is

x.

By a correction AqR the reference track this deviation is to be compensated. The end point deviation, which is to be compensated by the path correction, which is to compensate for the deviation ArE, is ## EQU1 ## · · 10

ArE, ref = .AqR S (1R ref

From the context ArE, + ArE, ref = 0, finally AqR can be calculated. Simulation results: A simulation was developed for the described elastic beam. The orbit correction is calculated by the above method and the new reference trajectory is qRn = qR + AqR.

FIG. 4 shows the comparison of the standard reference path and the modified reference path.

As already mentioned above, the control for the beam is calculated from the equation of motion by locking the elastic degrees of freedom. If the bar is then driven once with the standard reference path and in a further experiment with the modified path, the curves in FIG. 5 or FIG. 6 result for the positions of the bar end point. It can be seen that the oscillation behavior is significantly improved by changing the nominal path can be. The amplitude of vibration is about 75 mm with standard reference track, with modification about 18 mm, which is a reduction by a factor of 4.2.

This example will now be solved with numerical models and simulated for different scenarios. In particular, standard reference paths are compared without taking into account the elastic properties, ie by the elastic degree of freedom of the travel axis a = 0, compared with the above-modified desired paths.

4 shows a comparison of simulations of the control of the handling device 2 from the above example, where the (solid) curve A represents the control of a rigid system, ie the reference trajectory of the traversing carriage (ref.track) without taking into account the elasticity of the traversing axis. For this purpose, the elastic degree of freedom a in the above formulas is set to zero. In contrast, the (dashed) curve B represents the modified desired trajectory of the traversing carriage, that is to say the control of the handling device 2 taking into account the elastic deformations of the traversing axis.

In Fig. 5, the effects of such a modified nominal trajectory of the control of the tail of the traversing axis (EOA - End of Arm) can be seen. Curve A shows the position of the end piece of the handling device 2, so the Balkenendpunkt for the control according to curve A of Fig. 4. As can be seen, the beam end point after the trajectory has been moved to the desired end position by means of the carriage significantly around the end position to be reached Tail, if the elasticity of the track is not taken into account. In contrast, as can be seen in curve B, the vibrations of the tail significantly reduced when the desired trajectory of the carriage is changed to account for the elastic properties of the travel axis according to curve B of FIG.

Fig. 6 shows the marked in Fig. 5 section in an enlarged view. Although the control curve for the carriage, as shown in FIG. 4, only small precipitates, the effect thus produced is considerable. Taking into account the elastic properties, the vibrations of the tail as shown by curve B are drastically reduced. For example, for specific values of the length of the beam and the loads applied there, the oscillation amplitudes of the tail are reduced by a factor of more than four.

It goes without saying that the control unit according to the invention is not limited to the exemplary embodiments embodied in this example and illustrated in the figures, nor should they be limited by them. In particular, various mathematical models can be used to take into account the elastic properties of at least one, preferably movable, component of the handling device.

Innsbruck, on the 08th of September 2008

Claims (15)

1. Control unit for a handling device of an injection molding machine, wherein the handling device comprises a motor-driven end piece in the form of a receiving or Übemahmekopfes, which serves for moving an injection molded part, and wherein the control unit comprises an electronic memory in which the data of a desired path are stored for the tail, along which the end piece is movable by means of the control unit, characterized in that the desired trajectory is calculated taking into account the elastic properties of at least one component of the handling device (2). 2. Control unit according to claim 1, characterized in that the nominal trajectory is calculated taking into account at least one variable parameter of the molded part (3) to be moved and / or the at least one component of the handling device (2), wherein the at least one variable parameter is one for the Vibration behavior of the tail is characteristic size. 3. Control unit according to claim 2, characterized in that the variable parameter (s) one or more of the elements of the group consisting of the mass, the center of gravity, the geometric center, the mass moment of inertia and the resistance moments of the molded part to be moved (3) is or are. 4. Control unit according to claim 2 or 3, characterized in that the handling device at least one sensor (11) is arranged, with the aid of the signals of the sensor or the variable parameters of the injection-molded part to be moved (3) is calculable or are. 5. Control unit according to one of claims 1 to 4, characterized in that the data of the desired path, set position and / or the target speed and / or the target acceleration and / or the set pressure along the target path comprise. 6. Control unit according to one of claims 1 to 5, characterized in that the handling device (2) is designed as a Dreiachslinearroboter and the target path is calculated under 63855 35 / hn considering the elastic properties of at least one of the axes of the Dreiachslinearroboters. 7. Control unit according to claim 6, characterized in that the desired trajectory is calculated taking into account the elastic properties of the vertical travel axis of the Dreiachslinearroboters. 8. Handling device (2) for an injection molding machine with a control unit (1) according to one of claims 1 to 7. 9. A method for moving injection-molded parts by a handling device of an injection molding machine, wherein a motor-driven end of the handling device with the injection molded part is brought into abutment and wherein the handling device has a control unit, in particular according to one of claims 1 to 8, with an electronic memory, characterized by the following steps: - Specifying or measuring the elastic properties of at least one component of the handling device (2), - Calculating the desired trajectory of the tail, taking into account the elastic properties of at least one component of the handling device (2), - Store the data of the desired trajectory in the electronic memory (5), - moving the end piece, preferably with brought-in injection molded part (3), by means of the control unit (1) according to the calculated desired trajectory. 10. The method according to claim 9, characterized in that in addition at least one variable parameter of the molded part to be moved (3) is specified or measured and the desired trajectory of the tail is calculated taking into account the at least one variable parameter of the molded part to be moved (3). 11. The method according to claim 10, characterized in that the variable parameter (s) is one or more of the elements of the group consisting of the mass, 3 the center of gravity, the geometric center and the resistance moments of the molded part (3) to be moved or are. 12. The method according to claim 10 or 11, characterized in that the one or more variable parameters of the molded part to be moved (3) by means of the handling device (2) arranged sensors (11) is measured or be. 13. The method according to any one of claims 9 to 12, characterized in that the data of the desired path, the target position and / or the target speed and / or the target acceleration and / or the target pressure along the target path comprise. 14. The method according to any one of claims 9 to 13, characterized in that the handling device is designed as a Dreiachslinearroboter and the elastic properties of at least one component of the handling device (2) comprise the elastic deformations of the axes of the Dreiachslinearroboters. 15. The method according to any one of claims 9 to 14, characterized in that stored in the electronic memory, the data of the desired trajectory for a handling device (2) without consideration of elastic properties, and wherein taking into account the elastic properties of at least one component of the handling device (2 ) changes the desired position and / or the desired speed and / or the target acceleration and / or the set pressure along the desired path of the stored desired path. Innsbruck, on the 08th of September 2008