Production device, especially a bending press, and method for operating said production device

A manufacturing system for folding sheet bars, particularly sheet metal bars, comprising a folding press with two press beams, which are adjustable in relation to each other and provided with folding dies, whereby the folding press is fed by means of an automated manipulating system. The manipulating system has three hinged arms connected via pivoting devices to form an arrangement of hinged arms. A first hinged arm is swivel-mounted on a swivel axle extending in a swivel device parallel to a guide track of a linearly displaceable chassis. A second and a third swivel axles supporting the hinged arms are arranged extending parallel to the swivel axle of the swivel device. A gripping system and a seizing device for picking up the sheet bars are arranged in another end area of the hinged-arm arrangement. A positioning device assures that the sheet bar is correctly positioned for the folding process.

BACKGROUND OF THE INVENTION

The invention relates to a manufacturing system in the form of a bending press or folding press, as well as to a method for operating such a manufacturing system.

A folding press with a manipulating device and a method for the automated folding of sheets of metal are known from document EP 0 914 879 A1. The manipulating device is adjustable in this connection on a chassis in the direction of the longitudinal expanse of the folding beams, and equipped with gripping devices for picking up and feeding the sheets of metal and for folding the latter between the folding dies. Provision is made for sensors for correctly positioning the sheets of metal and for controlling the correct position of the sheets of metal, and the folding process is controlled by means of the signals of said sensors.

A method and a device for inserting workpieces between the folding dies of a folding press with a manipulating device and with sensor-controlled adjustment of the position and control of the position of the workpiece are known from document U.S. Pat. No. 5,761,940 A. According to said method, and by means of the device inserting the workpiece for a folding operation, provision is made on the folding press for measuring systems equipped with pressure sensors, which are adjustable on a backside of the folding dies in at least two coordinate directions, and each provided with a scanning pin for resting against a stop edge of the workpiece. For positioning the workpiece, provision is made for at least two of such measuring systems, with scanning pins spaced from each other in the direction of the longitudinal expanse of the folding dies for scanning the stop edge of the workpiece, which is driven against the scanning pins for resting against the latter. Each measuring system is fitted with a sensor measuring the force, which is acted upon by the scanning pin via a lever arrangement, and the force with which the workpiece and any deviation from an intended position preset by the scanning pins are detected in this way, so that the position of the workpiece is corrected by means of the manipulating device if the measured values differ, until identical measured values are present on the measuring systems, and thus a position of the stop edge preset with respect to the folding plane is obtained, and reshaping of the workpiece by folding can thus be carried out on the workpiece with the latter in the correct position. The adjustment and control process requires high mechanical as well as controlling and regulating expenditure for the positioning process executed by the manipulating device.

A folding press that can be operated by a manipulator for a sheet folding process, and a method for positioning the sheet before it is inserted between the folding dies, are known from document U.S. Pat. No. 4,706,491 A. According to said document, a fixed stop is provided on the folding press on the front side, and the sheet is placed against said stop, whereby said stop is forming a reference position for the displacement of the manipulator for adjustments.

For feeding workpieces to a folding press by means of a manipulator, a detector device mounted on the manufacturing system is known from AT 402 372 B. The position of an edge of the workpiece with respect to parallelism in relation to a working plane is measured by means of said detector device, and if an angular position is detected to have occurred, readjustment is carried out by the manipulator. Based on the reference position so determined, the subsequent folding operations are carried out by computing the position and repositioning. The accelerative forces occurring as the workpiece is being driven into the folding position may cause the workpiece to be displaced in the gripping system when it is finally positioned between the folding dies, which may cause inaccuracies in the course of the folding process as well.

BRIEF SUMMARY OF THE INVENTION

The problem of the invention is to provide a manufacturing system with automated feed of the workpieces for carrying out exact folding processes, and for minimizing the cycle time.

In accordance with one embodiment of the invention, this problem is addressed by a folding press that includes a manipulating device for placing the sheet workpieces into the space between the folding dies of the press. The manipulating device comprises a rotating unit and a gripping device and is displaceable on a guiding arrangement in the direction of a longitudinal axis of the press beams. The manipulating device more particularly comprises three hinged arms connected via swiveling devices to form a hinged-arm arrangement, wherein an end of a first hinged arm is pivot-mounted by a swiveling device mounted on a linearly displaceable chassis of the guiding arrangement such that the first hinged arm is pivotable about a swivel axle extending parallel to a guiding track of the guiding arrangement. A second and a third swivel axle of the swiveling devices supporting the hinged arms are arranged extending parallel to the swivel axle of the swiveling device on the chassis. The rotating unit, having a rotation axle extending perpendicularly to the swiveling axles, is arranged in another end area of the hinged-arm arrangement. An image acquisition system is arranged in the end area of the hinged-arm arrangement, the acquisition system comprising at least one image-acquiring means and at least one illumination system and one laser for identifying and recognizing the workpieces. The positioning device is formed by a stop device with at least two stop fingers adjustably arranged on a backside of the folding dies facing away from the manipulating device in a plane disposed parallel to the folding plane and in the vertical direction in relation to said plane, the stop fingers having finger carriers and finger inserts adjustable in said finger carriers to a spacing in relation to sensors measuring said spacing.

The surprising benefit of this arrangement is that no highly demanding positioning requirements have to be satisfied in readying the sheets, so that a simple feeding and depositing system suffices, which in turn permits achieving a simplification of the system, and seizing of the sheet can be based on greater tolerances owing to exact final positioning of the sheet in the stop device. Furthermore, this brings about a simplified control sequence for the manipulating system, and thus a reduction in the cycle time combined with high positioning accuracy.

In other embodiments of the invention for achieving the lowest possible manufacturing tolerances, the sheet is aligned by preliminary positioning with subsequent final positioning against a fixed stop.

However, other embodiments are advantageous as well in that they permit maintaining narrow tolerance limits when the sheet bar is picked up by the gripping system, while the sheet bar to be seized is checked at the same time for conformity with the sheet bar data stored in the controlling and monitoring system, in order to detect any deviation already prior to the folding process, and to eliminate defective or incorrectly readied sheets, if any. Rough and fine recognition are carried out in subsequently following steps, whereby the spacing of the gripper arm of the manipulating system is fixed for positioning for the processing of the images by means of cross laser technology and the triangulation calculation technique. By using an illumination unit comprising one or more illuminating heads, which illuminate the sheet bar from a number of different angular directions per image for acquiring multiple images of the sheet bar, the effects of different reflections caused by the condition of the surface of the sheet bar are eliminated to the greatest possible extent upon generation of an overall image by superimposing the individual images in the computer, which provides the line of the contour of the sheet bar, or of a part area of the latter with the reproducibility required for detecting the position. Further very advantageous embodiments for eliminating interfering reflections and influences of foreign light comprise application of a band-pass filter in order to delimit the frequency range to narrow limits, or of polarized light with a polarizing filter on the lens of the camera. Such embodiments each assure high quality of the image, and detection errors are effectively avoided in this manner.

Advantageous further developments of the invention are also disclosed providing unrestricted rotational movement of the gripping system, combined with reliable signal, energy and/or media transmission.

Furthermore, the invention relates to a method for operating a folding press.

The problem of the invention includes providing a method for operating a manufacturing system by which a simplified process for feeding sheet bars readied for the folding process to a folding press is obtained for achieving a short cycle time combined with high positioning accuracy.

In accordance with one embodiment of the invention, by carrying out the positioning process in two steps, tolerances during pick-up of the sheet bar with the gripping system are compensated in a first step by measuring and computing an angular position, and regulating such angular position of the gripping system by means of the rotating unit, and in a second step by applying the sheet bar against the fixed stops positioned in accordance with the data preset in the program, which means that the sheet bars do not need to be intermediately deposited after they have already been exactly positioned before they are seized. Furthermore, the gripping system needs not to be released in the meantime, or the holding force of the gripping system does not have to be reduced, because the tolerances achieved with respect to the final position are within a range that is compensated by the elasticity of the gripping means holding the sheet bar, such as, for example the suction cups of a vacuum gripper, or the elastic inlays or intermediate layers of tong grippers, magnetic grippers or the like.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2show a manufacturing system1comprising a folding press2for reshaping particularly the sheet bars3, for example into components of housings or sections etc., and a manipulating device4. Such manufacturing systems1are entirely utilizable as well for producing long sections, U-profiles, Z-profiles etc., generally having a very high length-to-cross-section ratio.

A machine frame5of the manufacturing system1is substantially comprised of two C-shaped, upright side plates6and7, which are arranged parallel to one another with a spacing in between. Said side plates6and7are directly supported on a set-up surface9, or supported, for example via the damping elements8, or secured on a common floor or base panel10, particularly welded to the latter, as shown by way of example in another embodiment. Furthermore, the upright side plates6,7are connected with one another with a spacing11in between via the wall parts13extending perpendicular to a center plane12.

With respect to the folding plane14extending perpendicular to the set-up surface9, the manufacturing system1comprises the two press beams15and16opposing one another and extending over the length17, said length generally being fixed by the size intended for the machine, or the working length desired for folding the sheet bar3.

The press beam15facing the set-up surface9is secured on the machine frame5via a fastening arrangement19preferably directly on the front surfaces20of the legs21of the C-shaped side plates6,7associated with the floor panel10, particularly by means of a welded connection. The setting drives25and26of the driving arrangement27, which is formed by the double-action hydraulic cylinders28, are arranged on the side surfaces22and23of the legs24of the C-shaped, upright side plates6and7, said legs being spaced from the set-up surface9. The setting elements29, for example piston rods of the hydraulic cylinders28, are drive-connected with the press beam16via the ball-and-socket joints31and, e.g. the bolts32, said press beam being adjustably supported in the folding plane14in the guide arrangements16. The press beams15and16extend over the length17about symmetrically and in the vertical direction relative to the center plane12, whereby the length17is slightly greater than the spacing11.

On the front surfaces33and34, which face one another and extend parallel to the working plane14, the press beams15and16have the die-receiving means for supporting and detachably securing the folding dies36and37. It is known from the prior art that such folding dies generally form a drop-type die designed in the form of a matrix or lower die, and a bending punch designed in the form of an upper or counter die. Furthermore, it is known from the prior art to divide the folding dies36and37into sections, which results in easy variability for the die length in order to be able to adapt the dies to the given requirements, or also to allow easier refitting of the manufacturing system1, or to permit easier exchange of the folding dies36and37.

The die-receiving means35in the press beams15and16are designed for detachably securing the folding dies36and37, on the one hand, and they form the supporting surfaces43for transmitting the folding forces (as indicated by the arrow44), on the other hand.

It is particularly shown inFIG. 2that the manipulating device4is substantially comprised of the hinged devices46and47with the hinged arms49,50,51forming a pivot arm arrangement48, whereof a hinged arm49is pivot-mounted in an end area52on a chassis54that is linearly displaceable parallel to the working plane14on the laterally and vertically guiding tracks53, said hinged arm49swiveling about a pivot device55, whereby a swivel axle56is expending parallel to the folding plane14. A second and a third swivel axle57,58of the pivot devices46,47supporting the hinged arms49,50,51, extend parallel to the swivel axle56. A rotational system60with a gripper system61is arranged in another end area59of the hinged-arm arrangement48, whereby the rotational system60is forming a rotation axle62extending perpendicular to the swivel axles56,57,58. Furthermore, a detection system63for identifying and recognizing the position of the sheet bars readied on a depositing means or supplied by a feeding system, is secured on the hinged arm51.

Furthermore, the manufacturing system1comprises a support device64arranged on the stationary press beam15for receiving and supporting the sheet bars3, which are removed from said support device64by the gripping system61, or are deposited in said support device to be gripped there and removed from it.

Furthermore, in the direction of feed (as indicated by the arrow65) of the sheet bars3, a positioning system66for the sheet bar3or workpiece is arranged downstream of the working plane14. Said positioning system is line-connected with a controlling and monitoring system67or position-regulating element68of the controlling and monitoring system67, and adjustably supported on the machine frame5for adjustment in a plane parallel to the folding plane14, and in a direction perpendicular to said folding plane in an adjusting system69. A driving arrangement of the adjusting system69is designed in the form of a positioning drive, by means of which the positioning system66can be driven into the predetermined position via positioning data preset by the controlling and monitoring system67in accordance with the manufacturing or production program for detecting and positioning the sheet bar3or workpiece for the folding process.

Furthermore,FIG. 2shows the detection system63, which is arranged in a position defined in relation to the gripping system61in an end area59of the pivot-arm arrangement48or the hinged arm51. The detection system63is preferably secured on a front surface71of the hinged arm51, said front surface being arranged opposite the rotational system60for the gripping system61. The direction of action indicated by the arrow72for receiving information about the sheet bar such as about its contour, position etc., is thus exactly opposing the direction of action of the gripping system61.

The detection system63comprises an image detection means, preferably a camera73for rough recognition, and a camera74for fine recognition, as well as, furthermore, a diode laser75and an illumination system76for emitting light flashes in the infrared frequency range by means of the light-emitting diodes (LED's)77.

The rough-recognition camera73preferably operates within a range of distance between the sheet bar3and the rough-recognition camera73of about 500 mm and 2,000 mm. The fine-recognition camera74operates at a distance of about 300 mm. The data required for positioning the detection system at the spacing intended for both rough and fine recognition are determined by means of triangulation calculation based on a laser cross projected onto the sheet bar3with the diode laser. The camera73for rough recognition and the camera74for fine recognition are equipped with the different lenses78according to the effective spacing. Rough and fine recognition of the sheet bar3is accomplished based on CAD (computer-aided design) data from the planning or design stage, which are stored in a computer79of the controlling and monitoring system67. Patterns are generated from said data. The corresponding pattern is searched in the recorded image and, if corresponding, the position of the sheet bar3is determined in the subsequent fine recognition after the pivot arm arrangement48has been set to a position for fine recognition.

In order to grip the sheet bar in the exact position, processing of the image has to satisfy special requirements. The illuminating system76and the evaluation method are important in this connection. Several LED illumination units are basically arranged for the illuminating system76. In the exemplified embodiment, three such LED illumination units77are arranged on the detection system63, which subsequently illuminate the sheet bar with light flashes in fields of light radiation extending at angles relative to each other, and detect per activated LED illumination unit77an image of the sheet bar3, or of a cutout of the latter with the camera74for fine recognition. The three digital images generated in the concrete exemplified embodiment are then generated in the computer79into a summary image. Owing to the angular alignment of the field of light radiation for illuminating the sheet bar3and generating the digital image, as well as due to the formation of a summary image from the individual images, reflections and influences of scattered light are eliminated to the greatest possible extent, whereby it is naturally possible, furthermore, to realize other variations such as, for example application of light within a narrow infrared wavelength of about 820 to 880 nm; the arrangement of a band-pass filter on the camera74for fine recognition, but also to implement other measures for detecting the exact position and for generating the position data for seizing the sheet bar with the gripping system. One of such further possibilities for avoiding disturbing light reflections is linear polarization of the emitted light. The directly reflected light maintains its direction of polarization and is filtered out with the help of a analyzer turned by 90° on the lens78of the fine-recognition camera74, whereby diffuse light can pass unobstructed.

The determination of the position by means of fine recognition of the sheet bar3now permits exact acceptance or exact placement of the gripping system61on the sheet bar3, in the way it is required for positioning the sheet bar3in the folding press2for carrying out a folding operation. In addition, the spacing between the detection system63and the folding press2can be calibrated with the detection system63. Such calibration is accomplished by means of a calibrating plate83arranged on the folding press2, said plate being provided with, for example the marking dots84having a defined size and defined spacing between each other. By comparing the size and spacing ratio of the marking dots, which have different sizes per spacing, with the predefined values stored in the computer79, as well as with the help of the position of the individual marking dots84, a reference position is determined in the X- and Y-directions, and the required adjustment of the manipulating device4is controlled in order to bring the sheet bar3into the position in which it is worked.

Furthermore, provision is made according to another embodiment for using the detection system63, particularly the camera74for fine recognition for die recognition, or for checking the data of the set of dies employed in the folding press2at the given time. For this purpose, the folding dies36,37are provided with coding characters that are compared to codes stored in the controlling and monitoring system67.

It should be mentioned, furthermore, that also after the sheet bars2have been deposited following a preceding folding operation, the finished workpieces are transported away on readied pallets by means of the detection system63in order to ready the press for subsequent folding operations, and the sheet bar3is gripped again as required by the gripping system61by depositing it on the support device64, and re-positioning it with respect to the new gripping position of the gripping device, as described above overall for the positioning process.

In the exemplified embodiment shown inFIG. 2, the gripping system is formed by a vacuum gripping system85, which is comprised of the gripper plate76, which is fitted with the suction cups86with the required supply channels, and rotationally coupled via a rotational transmitter for endlessly revolving with the rotational system60of the hinged arm51. The rotation transmitter88is provided with the transmission elements89for transmitting energy and/or controlling and monitoring signals, and designed for a pressure medium such as, for example compressed air for applying a vacuum for the vacuum gripping system85. By interconnecting the rotation transmitter88, it is possible to supply the vacuum gripping system85with the required compressed air and also with vacuum, and provision can be made for sensors, if needed, in order to assure interruption-free transmission of controlling and/or monitoring signals to the controlling and monitoring system67of the manufacturing system1. The rotational transmitter89is preferably provided with bus capability; an AS-i-bus system is preferably employed. Provision is made for a multi-pole, but at least two-pole design for electrical energy transmission.

As shown in the exemplified embodiment, the gripping system61, the latter being formed by a vacuum gripping system85, can naturally be employed in other design variations as well. For the manufacturing system1as defined by the invention, the gripping system61naturally can be realized also in the form of a tong gripper, magnetic gripper etc.

FIG. 3shows a realizable design of the positioning system66for positioning the sheet bar3for carrying out a folding operation. Said positioning system is formed by a stop device90comprising at least two setting units93, which are displaceable independently of each other on a guide arrangement91in the direction of the longitudinal expanse of the folding dies as indicated by the double arrow92. Furthermore, each setting unit93is equipped with a carriage arrangement94and an advancing device95, by which a stop finger96projecting in the direction of the folding plane14can be adjusted perpendicularly to the folding plane14as indicated by the double arrow97, and in the direction extending perpendicularly to the set-up surface9as indicated by the double arrow98. This provides the stop finger96with the capability of moving along three axes.

Now,FIGS. 4 and 5show the stop finger96of the positioning system66in detail. A finger carrier99cantilevered in the direction of the folding plane14is secured in the carriage arrangement94. The finger carrier99is substantially formed by a U-shaped section with a base leg100and the side legs101. In an end area102facing the folding plane14, a stop element or finger insert104projecting beyond the finger carrier99is adjustably supported in a longitudinal guide formed by the guide grooves103. Said finger insert104is adjustable against the force exerted by a spring arrangement105, for example a coil pressure spring, in the direction perpendicular to the folding plane14. In its extended end position, said finger insert is limited by a stop arrangement106. At an end protruding beyond the finger carrier99, the finger insert104has a step-like recess108, which forms a stop surface109for the sheet bar3, said surface extending parallel to the folding plane14. Furthermore, a scanning pin111extending in about the area of a longitudinal center axis110in the direction opposite to the stop surface108, is arranged fixed in the finger insert104, said pin being enclosed by the coil pressure spring of the spring arrangement105. A contact switch, which may be an approximation sensor or distance-measuring sensor115, is associated with a spacing114in the finger carrier99with the scanning pin111or a front surface113formed in an end area112. Said contact switch is line-connected with the controlling and/or monitoring system67, for example via a line. Wireless signal transmission from the distance-measuring sensor115to the controlling and/or monitoring system67is naturally possible via suitable transmitting and receiving elements as well.

The figures show, furthermore, that the finger insert104and the stop surface109jointly form a variable stop means that can be adjusted to a fixed position set according to the manufacturing data for the workpiece.

A positioning operation is schematically shown inFIG. 6. In conjunction with a determination of any difference that may exist in the spacing between at least two stop fingers96of the stop arrangement106, said fingers being spaced from one another, the position of the sheet bar3is corrected with the rotational system60in a first positioning step, in which the sheet bar3is brought into a predetermined position in relation to the folding plane14, for example with a front surface116, whereby said position may be parallel, but also angular relative to said folding plane, by rotating the vacuum gripping system65by means of the rotating unit60as required. Following such a preliminary adjustment of the front surface116with respect to the folding plane14, the sheet bar3is adjusted with the gripping system61as indicated by an arrow, as the finger insert104is being elastically engaged by a stop plane118that is aligned parallel to the folding plane14, as shown by way of example. In this way, an exact folding distance119is obtained between the face edge116and the folding plane14, such distance being desired for the folding process. By pressing the face edge116against the stop plane118, which is formed by the finger carrier99, any other inaccuracies that may still exist following the rotation with the rotating unit, can be compensated by the elasticity of the suction cups86without requiring implementation of any other controlled adjustment measures. This results in a reduction of the cycle time in the manufacturing sequence. A comparator circuit120of the distance-measuring system121serves for determining the different adjustment distances found on the stop fingers96by means of the sensors115measuring the spacing or distance. Said measuring system121is connected to the sensors115measuring the spacing, and to the controlling and monitoring system67via lines, whereby said elements may be designed also for wireless signal transmission, as already stated above.

The position of the sheet bar3with its front surface116with respect to the folding plane14, is normally corrected in a simplified embodiment by a contact switch115, which is provided in the stop arrangement106. With angular approximation of the face edge116of the finger inserts104, one of the contact switches—which are spaced from one another—will respond first. According to a signal issued by said contact switch, the rotary unit60is caused to rotate in the direction of a further contact switch115, and the sheet bar3is rotated for compensating the angular position until said further contact switch will respond as well, which completes the preliminary positioning of the sheet bar3or face edge116. The expenditure in terms of control technology, which is more extensive when measuring sensors are employed with the required comparator circuit120, is simplified in such a design variation, and the same technical effect is realized at lower cost.

Furthermore,FIG. 7shows the rotary transmitter88for transmitting control signals and/or energy and supply for the vacuum gripping system85with unlimited rotational movement of the gripper system61. The rotary transmitter is formed by a tubular jacket housing122, which is secured on the hinged arm51via a flange-like element. In said jacket housing, a rotational insert123is rotationally supported via a bearing arrangement not shown in detail, and coupled for rotation with a rotation drive124. The gripper plate87fitted with the suction cups86is secured on a front surface125of the rotational insert123, said front surface being disposed opposite the rotation drive124.

Now, in order to transmit energy at least in a two-pole manner, but also signals, provision is made for at least two slip-ring arrangements126, which are arranged in the form of a ring in the jacket housing122, embracing the rotational insert123, and forming a permanent line connection between the stationary connection means127on the jacket housing122, and the connection means128, e.g. on the rotating gripper plate87.

For admitting the required vacuum to the suction cups86, the stationary supply lines129for feeding compressed air are connected to the jacket housing122. Said supply grooves131extending all around in a bore132of the jacket housing122receiving the rotational insert123. In the rotational insert123, provision is made for the further connection bores133, which are associated with the grooves131for producing a flow connection with the connecting means128of the gripper plate87, which is provided with the further supply bores134for admitting vacuum to the suction cups86. It is noted, furthermore, that sealing rings or gaskets are arranged in the jacket housing122for tight sealing between the grooves131, and also between the grooves131and the external environment, such gaskets surrounding the rotational insert123. Said gaskets consist of a material with a low friction factor. Furthermore, the slip-ring arrangements126are naturally accordingly insulated against the jacket housing122and versus the rotational insert123.

Now,FIG. 8shows in detail the detection system63without any protective cover, said system being arranged on the hinged arm51. The illuminating heads138fitted with the LED's137and forming the illumination system76, are secured via the mounting angles136on a carrier plate135, which is connected and fixed for moving with the hinged arm51. The longitudinal axes139defining the fields of light radiation are jointly forming a right angle between two of the total of three illumination heads138, and are each forming with the longitudinal axis139of the third illumination head138, an angle of about 45°. Each light exit surface140of the illumination heads138is inclined versus a plane extending perpendicularly at a right angle to the longitudinal axis of the hinged arm51within an angle range of from about 15° to 45°, in a manner such that the fields of light radiation are aligned conically against each other as the distance from the detection system63increases.

Furthermore, as already described above, the detection system63comprises the camera73for rough recognition, with the lens78, which preferably has a focal length of 6 mm, as well as the camera74for fine recognition, with the lens78, which preferably has a focal length of 16 mm.

Furthermore, the diode laser75for projecting a laser cross on the surface of the sheet bar3, is arranged on the carrier plate135. Said diode laser is employed for determining the distance between the detection system63and the sheet bar3to be photographed, as already described above as well.

Now,FIG. 9shows another embodiment of the positioning device66for positioning the sheet bar3without contact by means of the manipulating device4between the folding dies36,37. Said positioning device is provided in the realizable form of an optoelectronic measuring device141. Furthermore, a method for positioning the sheet bar3is described with the help ofFIG. 9. The optoelectronic measuring device141is substantially formed by at least one image acquisition means142, for example a CCD camera143, and a computer144, which is line-connected with the image detection means142and the controlling and monitoring system67of the folding press2. The image acquisition means142is combined, for example with a laser scanner145and the illumination system76. The unit so formed is designed for acquiring without contact an ACTUAL position of a contour area of the press space146—the latter being refined with respect to the folding plane14—with the manipulating device4for a folding operation on the sheet bar3inserted between the folding dies36and37, and several of such units may be selectively installed in a fixed manner. In the example shown, one unit is displaceably arranged on a two-coordinate, linear carriage arrangement. However, it is possible also to employ a multi-axis manipulator for using the unit.

A displaceable arrangement permits using simplified technical equipment for the optoelectronic measuring device141because the image acquisition means142can be positioned in accordance with the manufacturing program near the sheet bar3inserted in the press space146for determining the position data of the sheet bar.

With a fixed installation, several image acquisition means142are required depending on the size of the press space146.

The positioning of the sheet bar3between the folding dies36,37for obtaining a canting, is carried out by acquiring the contour area of the sheet bar3that is decisive for the folding process in accordance with the data preset in the manufacturing program for producing the workpiece. Said preset data are preferably obtained in an online operation from the CAD sector. By means of the positioning device66, the sheet bar3is inserted with the help of the manipulating device4until an actual position of the respective area of the contour corresponds with the reference data of a nominal or should-be position of the respective area of the contour. Said reference data are stored in a memory of the computer144or controlling and monitoring system67. The positioning process is executed by controlling the adjusting system69of the manipulating device4for executing the operational sequences.

Other possibilities for contactlessly positioning the sheet bar3between the folding dies36,37, such positioning taking place via the determination of the space coordinates by means of a coordinates acquisition device148of the sheet bar3, include the application of the triangulation sensors149known from the prior art, or comprise the utilization of the photosensors150instead of employing the image acquisition means described above.

Both methods permit contactless measuring or position acquisition, whereby a beam of the laser diode is focused on the workpiece through a lens. The scattered light emitted at a defined angle is absorbed via a shutter by a detector system, for example a CCD line array. The given actual data of the position, e.g. of a contour configuration of the sheet bar3, are determined by trigonometric computation of the course of the beams and scattered light, and conciliated with the stored nominal data by controlling the manipulating system4and/or the gripping system61.

The light interface method with the application of the photosensors150employs a laser beam for contactless data acquisition as well, such a laser beam being linearly widened and projected onto the sheet bar3by a laser diode via a focusing lens. The scattered light is projected via a reproducing lens onto a CCD matrix, whereby a surface array is used instead of the line array. In addition to determining the space coordinates of an area of the contour, said method is suited also for controlling the folding angles of preceding folding operations.

Components for calibrating the manipulating device4, and, furthermore, the calibration method are now explained in the following with the help of the system arrangement of the manufacturing system1formed by the folding press2and the manipulating device4as shown inFIGS. 10 and 11. So that offline programming can be carried out, it is additionally necessary for the basic calibration of the manipulating device4to compensate load-conditioned deviations of the position that may occur in actual folding operations.

The manipulation of workpieces in folding operations carried out on a folding press requires that exacting requirements have to be met with respect to the accuracy of the manipulating device4in order to manipulate the work-pieces, e.g. the sheet bar3, from the time it is received from its ready-for-processing position and positioned in the working space of the bending press2, and guided in the course of the folding process, and, furthermore, until the processed, folded workpiece is deposited in an oriented manner. Particularly absolute accuracy during positioning and guiding of the workpiece will directly affect the manufacturing accuracy. Now, in order to assure such absolute accuracy accordingly for all of such processes involved in a manufacturing sequence, and in the positioning of the workpiece in the working space of the press, provision has to be beneficially made for upstream calibration of the manipulating device4and the folding press2. For said purpose, the manipulating device4is fitted according to the invention with a measuring system156on a positioning means155normally positioning the gripper system61. In the folding press2, a reference body158, which is manufactured with high dimensional accuracy, is mounted in the stop device90in the preset position of the Z-axis as indicated by the double arrow157. Said reference body, which is facing the manipulating device4, is provided with a multitude of the reference means159, which have exactly preset and fixed positions and coordinates in terms of space with respect to the position assumed by the stop device90. The reference means159are preferably formed by the bores160in a multitude of the carrier metal sheets161. The latter are lined up at an angle in a row along a circumference, forming a type of drum, with the surfaces facing the measuring system and the reference means159provided in said surfaces in a measuring range162for the calibration process.

The measuring system156is comprised of a carrier plate163, which is mounted on and fixed for rotation with the rotational system60of the manipulating device4. On a plane surface164facing the reference body158, a camera, particularly a CCD camera166, is arranged on the carrier plate16eccentrically in relation to the rotational axle62of the rotational system60. The lens167of said camera is surrounded by a ring lamp168. Furthermore, for determining the exact spacing with respect to the reference body158, provision is made for a measuring instrument169measuring the spacing of the laser.

Furthermore,FIG. 11shows that for simulating an actual operation, in which the manipulating device4is loaded with a sheet bar3, provision is made on the carrier plate163for the arrangement of a reference weight170for determining the effects acting on the positioning process on account of the weight of the workpiece and caused by the elastic deformations of the manipulating device4. In at least two simulation processes, in which different reference weights170are used, the reference means159are targeted one after the other, and the compensation values conditioned by the load obtained from the nominal/actual comparison of the positioning, are stored in the control system or memory of a computer in a compensation matrix. In the actual operation, the actual compensation values are determined based on the results of said comparison by interpolation in accordance with the actual and known weight of the workpiece to be folded, and corrected postures of the robot are generated, which insures constantly exact positioning of the sheet bars3or work-pieces in the working space of the folding press2.

The calibration process is generally explained in greater detail in the following based on the following calibration steps, taking into account the load of the manipulating device4, particularly the robot:(1) Modeling of the robot.Generation of a displacement program.Measurement of the deviations in the positioning of the robot.Identification of the parameters of the robot model.Correction of the displacement program.

1. Modeling of the Robot

In the simplest case, the robot is modeled with the help of a calibration software that is basically capable of taking into account the influences that have to be compensated, or their effects on the components of the robot. In the present case, the influences include tolerances in the assembly and manufacture of the robot, as well as of the entire arrangement, which have effects on the following:Coordinate transformations between the components of the arrangement (comprising the robot, the machine and the reference bodies).The kinematic chain and the transmission behavior of the drives of the robot, as well asload effects caused by the individual mass of each of the elements of the kinematic chain of the robot, and of useful or additional loads flanged to the wrist of the robot, with effects on the positioning accuracy of the robot due to unknown or only insufficiently known elasticity factors of the drives and elements of the kinematic chain of the robot.

The mathematical model can be generated also independently of any preset software.

It must be possible with the mathematical model to represent the positioning behavior of the robot in the working space in dependency of the influences to be compensated, or their effects on the components of the robot.

2. Generation of a Displacement Program for Measuring the Positioning Errors Caused by Influences Exerted by Load as Well as Assembly and Manufacturing Tolerances

For such generation, the position and orientation data in the space, machine and basic robot systems of coordinates of known points (known from measurements or by securing an adequately high manufacturing accuracy), for example on a reference body161, are processed to a robot displacement program in a manner such that the positioning errors of the robot caused by the aforementioned influences can be measured at said points with the help of the displacement program with a measurement system159adapted to the robot. For this purpose, the points have to be represented in the form of suitable measurement features, e.g. in the form of the bores160serving as the reference means162.

Alternatively, it is possible also to use a measurement feature with an external measuring system (e.g. laser tracker, Theodolit etc.) that is mounted on the flange of the robot.

(Note: As far as the use of any desired points in the space in conjunction with an external measuring system is concerned, this step is a component of the normal procedure for calibrating a kinematic chain. The generation of a displacement program on a reference body is used in identical form within the framework of a temperature drift program).

3. Measurement of the Positioning Deviations of the robot With the Help of the Displacement Program

In the present step, the positioning errors of the kinematic chain at the measuring points are measured with the help of a measuring system and the displacement program generated in item2above. The measured data are output (if necessary also by conversion) in a system of coordinates fixed in the space, with known (if possible) reference to the basic system of coordinates of the robot.

As opposed to the conventional procedure for calibrating kinematic chains, this process is carried out two times, with different additional loads flanged to the wrist of the robot. Different measurement data are obtained in this way depending on the given additional load.

4. Identification of the Parameters of the Robot Model (Parameter Identification, Determination of the Actual Values of the Parameters of the Robot Model

As it is usually done in the conventional calibration of the robot, the coordinate transformation of the system of coordinates of the measuring points used, into the basic system of coordinates of the robot, is determined first. This is carried out with the help of the measurement data record (measurement data record No. 1) from step3above, with the help of, for example a “bestfit” method, or simply by determining the mean deviations in the individual coordinate directions.

The measurement data record No. 1 is transformed into the basic system of coordinates of the robot with the help of the determined coordinate transformation.

Subsequently, the elasticity parameters are identified first with the help of calibration software, and the other parameters of the kinematic chain to be identified are identified in a second step with the help of the transformed measurement data record No. 1.

With the help of the identified robot model as well as the previously determined transformation of the coordinates, the positioning errors that have to be expected under the following conditions are now calculated (with the calibration software) in the sense of a simulation:(a) The identified parameters are not taken into account by the robot control; however, they do have an effect on the positioning behavior of the kinematic chain considered. Said parameters are therefore used for calculating the positions actually assumed by the simulated kinematic chain.(b) The displacement program generated in item2above is applied as the basis in conjunction with the measuring points used for the measurements in item3above. The measuring points are approached (quasi in the form of a mathematical simulation) with exactly the same postures preset by the position-setting values of the kinematics as in the real measurement.(c) The additional weight used in item3for measuring the positioning errors in the second record of measured data (measured data record No. 2) is taken into account in the calculation. This conforms to a change in the load conditions vis-a-vis the identification conditions, the real effect of which is known from the measurement carried out in item3above (measured data record No. 2).

Said calculated positioning errors are now compared with the actual positioning errors from the measured data record No. 2 determined in item3above. It is sufficient in this connection to evaluate the proportions of the difference between the data records (simulated and measured data) in the direction of the effect of the force of gravity.

Now, either the averaged deviation between the two data records, or the sum of the squared errors of said deviations, can be used as the optimization criterion.

In the case of the average deviation, the latter has to be as close as possible to the zero value; in the case of the evaluation of the squared errors, the minimum of the sum of the squared errors has to be found.

Thereafter, the transformation of the coordinates (of the system of coordinates of the measuring points used, into the basic system of coordinates of the robot) determined at the outset with the help of the measured data record No. 1, is systematically changed step by step in the sense of an approximation method, by varying (at least) the proportion of the transformation in the direction in which the force of gravity is acting.

Following each variation, the transformation that has changed is again applied in each case to the non-transformed measured data record No. 1. As already explained above, the elasticities are first identified again with the measured data record so transformed, and subsequently then the remaining parameters of the robot model that have to be identified. Thereafter, the mathematical positioning errors are calculated again with the newly identified model for the displacement program generated in item2, under the conditions specified above, and compared with the deviations in the measured data record No. 2.

Said loop is run through until one of the optimization criteria specified above has been satisfied.

The background of this procedure is as follows:

Since the measured data are recorded only within a small area of the working space, the positioning errors caused by elasticities are often hardly distinguishable from the effects exerted of other influences. The robot is flexed within the entire measuring range to similarly high degrees, so that in the identification of the parameters, it is impossible only with the help of the values measured for a load condition to recognize which proportion of the deviation has to be attributed to a consequence of flexural bending, and which proportion thereof has to be ascribed to other parameters including the transformation of the coordinates. As a rule, therefore, the robot is identified as being stiffer than it actually is. In order to compensate this deficit, the result of an identification of the parameters is reviewed with the help of the data measured for another load condition. The residual deviation caused by the flexing of the robot in the measured data record is subsequently increased via the change in the transformation of the coordinates, and reliably allotted to the elasticity parameters via the exclusive identification of the elasticities in the first step. The remaining parameters can then be identified based on the identified elasticities.

5. Correction of the Displacement Program

The displacement program is corrected again as it is normally done in the conventional calibration of kinematic chains.

For the sake of good order, it is finally noted that in the interest of superior understanding of the structure of the manufacturing system, the latter and its components are partly represented untrue to scale and/or enlarged and/or reduced.

The problems on which the independent inventive solutions are based can be derived from the specification.

Most importantly of all, the individual embodiments shown inFIGS. 1 to 11may form the objects of independent inventive solutions. The problems and solutions as defined by the invention in relation to such objects are specified in the detailed descriptions of said figures.