DE102018203061B4 - Procedure for finding a suitable holding position - Google Patents

Abstract

Method for finding at least one suitable holding position (HP) for at least one holding device (26, 27, 28), which has a plurality of holding elements (34), relative to a workpiece rest (7 ) to be displaced or a workpiece part (16) to be carried by means of the holding device (26, 27, 28), comprising:a) determining a holding position (HP) of the holding device (26, 27, 28), in which at least one holding element (34 ) at least partially overlaps with the workpiece part (16) in order to act as an effective holding element (34a) on the workpiece part (16),b) determining one of the workpiece parts (16) when being displaced or when being carried onto a respective effective holding element (34a) exerted resulting force (Fres,i; Fres,i,z, Fres,i,xy),c) evaluating the holding position (HP) as suitable for moving or carrying the workpiece part (16) if for all effective holding elements (34a ) one from the effective date n holding element (34a) transversal force FQ,ior a holding force FH,iand/or transmissible to the workpiece part (16) to be carried in a transport direction (Z, X, Y) in a transport direction (Z, X, Y) on the workpiece part (16) to be shifted Shear force FQ,iein from the resulting force (Fres,i; Fres,i,z, Fres,i,xy)-dependent evaluation criterion fulfilled, with a partial overlap of effective holding elements (34a) with the workpiece part (16) which can be transferred to the workpiece part (16) to be displaced Lateral force (FQ,i) or holding force and/or lateral force (FH,i; FQ,i) that can be transferred to the workpiece part (16) to be transported is reduced by a predetermined factor.

Description

The present invention relates to a method for finding at least one suitable holding position for at least one holding device, which has a plurality of holding elements, relative to a generally plate-shaped workpiece that is to be (laterally) displaced on a workpiece support by means of the holding device or that is to be carried by means of the holding device workpiece part. The invention also relates to a computer program product for carrying out such a method.

If a workpiece part cut free from a plate-shaped workpiece is to be moved laterally on a workpiece support using a holding device alone or together with the surrounding residual skeleton, the workpiece part can slip relative to the holding device and/or relative to the residual skeleton. A displacement of the workpiece part relative to the residual skeleton can also occur if forces (e.g. the force of an acting cutting gas during laser cutting) act on the workpiece part at the moment of the free cut. A workpiece part that has been displaced relative to the holding device or the scrap skeleton can possibly only be removed from the processing machine automatically with difficulty or not at all. When carrying or transporting a workpiece part held by the holding device, for example sucked up, to a storage location, centrifugal forces also occur on the workpiece part, which must not exceed the holding force of the holding elements, for example in the form of suction grippers.

In order to avoid a relative movement of the workpiece part, it is off, for example DE102015223062B3 known to hold the workpiece part with the help of a holding unit (e.g. suction unit) relative to the residual skeleton in a defined position during lateral displacement. For this purpose, the suction cups are placed on the workpiece part in order to prevent a movement of the workpiece part in and/or against the direction of gravity. The workpiece part can be fixed more firmly by sucking on the workpiece part. Since the holding unit must not collide with a machining head for the separating machining of the workpiece, the holding unit covers in the method according to FIG DE102015223062B3 usually the workpiece part is not complete.

Out of DE19817213A1 it is known to use a vacuum gripping device to calculate whether a single suction gripper is sufficient or whether several suction grippers are necessary or at least advantageous for the safe transport of the workpiece, depending on the workpiece and process parameters (e.g. material, dimensions, surface quality, transport direction, transport acceleration).

In WO2007115633A1 it is proposed to use a process model stored in the controller of a vacuum handling device to adapt or optimize the acceleration and/or transport speed to the capabilities of a suction gripper. For example, it can be determined whether the suction gripper can generate a high holding force, so that a high speed can be driven.

the DE 198 17 426 A1 discloses a gripper system that can be attached to a robot hand and has at least two gripping elements that are independent of one another, each gripping element being provided with at least one force sensor for determining a force in a predetermined direction. If a gripping element is correctly positioned on the workpiece, the value determined by the force sensor is also within the specified tolerance range. If the workpiece is positioned incorrectly, the gripping element grips the workpiece in an offset manner and the force sensor determines a value that lies outside the tolerance range when the workpiece is lifted.

EP 2 522 471 A1 describes a handling device for lifting a plate-shaped workpiece, comprising: at least one suction cup that is designed to lift the workpiece, at least one vacuum source that generates a vacuum in the suction cup by providing a vacuum output, at least one pressure gauge for measuring the vacuum in the suction cup, as well as a control loop that regulates the vacuum output as a function of the vacuum in the suction cup in such a way that at least a minimum vacuum that is sufficient to lift the workpiece is generated in the suction cup.

object of the invention

In contrast, the present invention has the task of specifying a method by which a holding position can be found in which, with the aid of a predetermined number and position of holding elements, in particular suction grippers, which act on the workpiece part, the workpiece part can be moved reliably on a Workpiece support and/or safe carrying or transporting of the workpiece part that is held, in particular sucked on, is possible. In this way, a secure hold of the workpiece part on the holding elements of the holding device is to be achieved despite the acting friction, weight and/or centrifugal force.

subject of the invention

This object is achieved according to the invention by a method of the type mentioned at the outset, comprising the steps: a) determining a holding position of the holding device in which at least one holding element at least partially overlaps with the workpiece part in order to act on the workpiece part, b) determining one of the resultant force exerted on the workpiece part during displacement or carrying on a respective effective holding element, c) evaluating the holding position as suitable for the displacement or carrying of the workpiece part if for all effective holding elements a transverse force can be transmitted to the workpiece part to be displaced in a displacement direction or a holding and/or transverse force that can be transmitted to the workpiece part to be carried in a transport direction fulfills an evaluation criterion that depends on the resultant force, with a partial overlap of effective holding elements with the workpiece part the effective through this n Holding elements on the workpiece part to be displaced transferable lateral force or on the workpiece part to be carried transferable holding and / or lateral force is reduced by a predetermined factor.

With the help of the method according to the invention, depending on e.g at least partially overlap with the workpiece part, an evaluation criterion can be determined which allows a statement to be made about the strength of the fixation of the workpiece part on the holding device.

The basic idea of this method is that the resulting (horizontal and possibly vertical) forces acting on the holding device are distributed to the effective holding elements, taking into account the existing geometric relationships. In other words, the forces acting on the holding device do not necessarily act in an equally distributed manner on all effective holding elements. An evaluation criterion is therefore used which can make a statement for the selected holding position of the holding device and thus for each individual holding element that acts on the workpiece part, whether there is a relative movement between the workpiece part and the workpiece part when the workpiece part is displaced or carried Holding device comes. With the help of the evaluation criterion, a respective holding position of the holding device can therefore be evaluated as suitable or unsuitable.

If the evaluation criterion is met for each individual effective holding element, the workpiece part can be moved or carried in a process-reliable manner. If the evaluation criterion is not met, i.e. if the load is too great, the evaluation result is output or established that the workpiece part cannot be moved or carried safely with the present holding position of the holding device or the holding elements.

The partial area with the effective holding elements can contain both holding elements that rest completely (i.e. with the entire holding or suction surface) on the workpiece part, and holding elements with a partial overlap. A reduced transmissible transverse force (and load-bearing capacity or holding force) is assigned to these holding elements, which only partially cover the workpiece part. For example, the value of the transverse force that can be transmitted to the workpiece part can be multiplied by a factor of less than 1, for example 0.5, for the effective holding elements that only partially cover the workpiece part. The holding force that can be transferred to the workpiece part by a holding element can also be multiplied by a factor of e.g. 0.5.

In the simplest case, the evaluation criterion can consist of checking whether the transverse force that can be transmitted by the effective holding element or the transmittable holding force is at least as large or greater than the resulting force or the proportion of the resulting force in the relevant spatial direction. For this purpose, the evaluation criterion preferably includes the amount of the resultant force exerted on the effective holding element, multiplied by a safety factor. In the case of displacement of the workpiece, the evaluation criterion for the holding position of the holding device on the workpiece part requires that the load or the resulting force F _res,i on each individual holding element is smaller than the transmissible transverse force F _q,i against the direction of displacement, so that no Relative movement occurs between the holding element and the workpiece part, ie the following should apply: F _Q,i ≧SF _res,i , where S designates the safety factor, which is greater than 1, but can also be chosen to be 1 if necessary. If the workpiece is being carried or transported, the above formula applies accordingly to the resulting force in the horizontal direction, ie parallel to the plate-shaped workpiece part (opposite to the horizontal component of the transport direction). In addition, the evaluation criterion must also be met for the holding force _FH,i in the vertical direction, ie the following must apply in the vertical direction: _FH,i ≥ SF _res,i .

In principle, the evaluation criterion or the evaluation regulation can be used for all processes be used where it has to be decided whether the fixation of a (flat) workpiece part, which has to be moved in a spatial direction by means of a clamping or holding force and/or friction at discrete points (e.g. on suction cups or grippers), can be carried out reliably, or not, for example when holding or transporting the plate-shaped or flat workpiece part described above.

For the purpose of this application, carrying the workpiece is understood to mean lifting the workpiece part in the vertical direction, in which there is no movement of the workpiece part in the horizontal direction, so that only gravity and an acceleration force acting in the vertical direction act on the workpiece part. Carrying the workpiece also includes transporting the workpiece part, in which the workpiece part is not only lifted but also moved in at least one further spatial direction (horizontally). During transport of the workpiece part, acceleration forces act on the workpiece part both in the horizontal direction and in the vertical direction, as well as gravity. For the sake of simplicity, it is assumed in all of the following considerations that these forces act or act in the center of gravity of the workpiece part.

If, in step c) of the method according to the invention, the holding position is assessed as not suitable for the process-reliable displacement or carrying of the workpiece part, steps a) to c) can be repeated with a changed number of effective holding elements and/or with a changed holding position until the stopping position meets the evaluation criterion.

In the first case, for example, in a step d) those effective holding elements for which the evaluation criterion was not met can be ignored and the resulting force exerted can be calculated again for the remaining effective holding elements. If the evaluation criterion is met for all remaining effective holding elements, the (initial) holding position defined in step a) is evaluated as suitable. If this is not the case, step d) can be repeated. If, after possibly repeating step d) several times, no more effective holding elements remain, the holding position must be changed and then steps b), c) and, if necessary, d) must be repeated.

The value required for the comparison in step c) for the transverse force or holding force that can be transmitted by a holding element, for example a suction cup or gripper, depends on the suction, clamping or pressing force on the workpiece part and the coefficient of friction between the suction cup or gripper and the workpiece part, which depends on the material or the surface finish of the workpiece part (e.g. dry or oiled, etc.) and the material and surface finish of the suction cups or grippers. The value for the transmissible lateral force is either given in the data sheets of the manufacturer of the holding device, for example a suction cup manufacturer, or can be determined with the help of displacement or load tests. During the displacement of the workpiece part, the action of the holding device can take place by placing or pressing on a surface suction device or the effective suction device or by additionally generating a vacuum. The values that are valid in these cases for the transmissible lateral force of an individual suction cup typically have to be determined through a series of tests.

As a rule, the method is completed when a suitable holding position or positions for the holding device(s) has/have been found. If necessary, the method can be carried out further after a suitable or process-reliable holding position has been found, i.e. steps a) to c) can be repeated with changed holding positions until several process-reliable holding positions are found. From the process-reliable holding positions, that one can then be selected that best or optimally fulfills the evaluation criterion. In the event that two or more holding devices are used to move or carry one and the same workpiece part, the resulting force on a respective holding element of a holding device typically also depends on how many holding elements of the other holding devices act on the workpiece part and where they attack the workpiece part. For the sake of simplicity, it is assumed for the following considerations that only a single holding device is used for displacing or for holding the workpiece part.

When method step a) is carried out for the first time, an initial holding position of the holding device can be defined, in which a predetermined number of holding elements of the holding device completely or partially overlap with the workpiece part. A partial overlap is understood to mean that only a partial area of the effective surface of a holding element, for example a suction cup surface, overlaps with the workpiece part. In other words, the edge contour of the workpiece part intersects the effective surface of the holding element.

The initial holding position can be set by first a the to be removed Workpiece part enclosing, in particular rectangular enclosing contour is defined. The holding position is preferably initially defined uniformly, ie the holding device has the same distances to the edges of the enclosing contour. If this is not possible due to collisions between the holding device and other components, for example a processing head, the holding device is placed at equal distances from the edges of the enclosing contour, taking into account a minimum distance from the components, for example the processing head. If two or more holding devices are used to move or carry one and the same workpiece part, their initial holding positions are typically also defined in such a way that the holding devices are arranged evenly in relation to the enclosing contour, i.e. the holding devices are at the same distances from the edges of the enclosing contour .

In one variant, the resultant force is determined as a vectorial sum of a first force component and a second force component, with the first force component resulting from a total force acting on the center of gravity of the workpiece part to be moved or carried, and the second force component from a Lateral force on a respective holding element due to a moment acting on the center of gravity of a partial area of the holding device containing all effective holding elements. The resulting force on a holding element is generally made up of the two force components described above. In the event that the center of gravity of the partial area of the holding device with the effective holding elements coincides with the center of gravity of the workpiece part, the second force component does not apply, i.e. it has the value zero.

For the typically present case that the plate-shaped workpiece or the workpiece part cut free from it has a constant thickness and density, the center of gravity of the workpiece part coincides with the centroid of the area of the workpiece part. Correspondingly, the center of gravity of the partial area of the holding device corresponds to the centroid of the area of the partial area of the holding device, provided that the weight of the base or suction plate of the holding device is also distributed homogeneously.

In one variant, the first force component of the resultant force is determined by the total force acting on the center of gravity of the workpiece part to be displaced or carried being distributed evenly to the effective holding elements. In this case, the first force component results from the total force by dividing the total force by the number of effective holding elements.

In a further development, to find the holding position for moving the workpiece part, the total force is determined in the form of a frictional force acting against a direction of movement, which is generated by a weight of the workpiece part and a pressing force of the effective holding elements on the workpiece part. When the workpiece part with the holding device placed on it is displaced, friction arises between the workpiece part and the workpiece support. This static frictional force acts in the opposite direction to the direction of displacement and is referred to below as the equivalent force (combined force) F _R *. The frictional force F _R * acting against the direction of displacement is determined from the normal force F _N perpendicular to the workpiece support multiplied by the static friction coefficient µ _R between the workpiece part and the workpiece support, ie the following applies: F _R * = F _N µ _R . The workpiece support can be support brushes, for example, or the workpiece support can be formed from support brushes that are attached to strips, for example. In the event that the workpiece support is formed from sliding rollers, the static friction coefficient is replaced by the sliding friction coefficient of the workpiece support.

The normal force F _N has a first component F _N1 which is due to the weight of the workpiece part. The following applies: F _N1 = m _w g, where m _W denotes the mass of the workpiece part and g denotes the gravitational acceleration (9.81 m/s ² ). The normal force F _N also has a second component F _N2 which is due to the compressive force of the holding elements on the workpiece part. The compressive force F _N2 varies depending on whether a vacuum is applied to the holding elements, for example in the form of a suction cup or suction gripper, whether the holding device to which the holding elements are attached rests on the workpiece part with its own weight or is additionally pressed on the workpiece part becomes. If the holding device, e.g. in the form of a surface suction cup, rests with its own weight on the workpiece part, the following applies: F _N2 = gm _F nws / ns, where m _F is the weight of the holding device or the surface suction cup, nws the number of effective holding elements and ns designate the total number of holding elements of the holding device. As described above, the frictional force F _R * acting counter to the direction of displacement is distributed evenly over all effective holding elements or suckers, ie the following applies to an individual holding element i: F _R,i = F _R */nws.

In an alternative variant, when the holding position for carrying the workpiece part is found, the total force is the vectorial Sum of an acceleration force acting against a transport direction in the center of gravity of the workpiece part and a weight force acting on the workpiece part in the center of gravity of the workpiece part. The transport direction is basically arbitrary, but the workpiece part is often first lifted in the vertical direction and then transported or shifted in a horizontal plane parallel to the workpiece support. It goes without saying that the transport direction and also the acceleration force can vary over time while the workpiece part is being carried.

When comparing the resulting force with the evaluation criterion, this circumstance can be taken into account in that a maximum value of the total force occurring during transport or a respective maximum value of a force component of the total force in one of the three spatial directions is included in the resulting force , on which the evaluation criterion depends. In principle, the evaluation criterion dependent on the resultant force cannot consist of a single value that depends, for example, on the amount of the resultant force, but two or more force components of the resultant force that act in different spatial directions can form the evaluation criterion. For example, a force component of the total force that acts in a horizontal direction in space (or in a horizontal plane), so that the weight of the workpiece part does not affect it, a first force component of the resulting force in a horizontal direction in space form, which is compared with the transmissible lateral force. Correspondingly, a proportion of the first force component or the resulting force acting in the vertical direction can be compared with the holding force that can be transmitted in the vertical direction. However, it may also be possible to use the amount of the resulting force alone (without breaking it down into the components acting in different spatial directions) as an evaluation criterion.

In a further variant, the second force component is determined using a torque that is exerted by the workpiece part on the center of gravity of the subregion containing the effective holding elements when the workpiece part is displaced in a displacement direction or when the workpiece part is carried in a transport direction. When moving the workpiece part, the torque or torsional moment only acts horizontally, i.e. in a plane parallel to the workpiece support or to a plane in which the effective holding elements are arranged. In the event that the workpiece part is carried and only transported in the vertical direction, a torsional moment also acts on the center of gravity of the partial area, with the torsional moment being generated by the weight of the workpiece part. If the transport direction also has a component that acts in the horizontal direction, a torque or torsional moment also acts in the horizontal direction.

In a further development, when the holding position for moving the workpiece part is found, the torque exerted on the center of gravity of the partial area is determined from a frictional force of the workpiece part on the workpiece support and a distance between the center of gravity of the partial area and a center of gravity of the workpiece part perpendicular to the direction of displacement. The torque T _z is calculated from the frictional force F _R of the workpiece part multiplied by the distance L _R,x perpendicular to the direction of displacement between the (area) center of gravity of the workpiece part and the (area) center of gravity of the section with the effective holding elements. Only the dead weight of the workpiece part is taken into account for the calculation of the frictional force F _R , since the normal force, which is applied by the holding device or by the effective holding elements, lies in the pivot point or in the center of gravity of the sub-area. The following applies to the frictional force: F _R = m _W g µ _B , for the torque: Tz = F _R * L _R,x .

The moment T _z causes a transverse force F _Tz,i on an individual holding element perpendicular to the distance vector between the holding element and the center of gravity of the sub-area with the effective holding elements. The magnitude of the transverse force F _Tz,i is proportional to the length of the distance vector. For the case considered here of moving the workpiece part, the resultant force Fres on a holding element results from a vectorial addition of the first force component in the form of the friction force F _R,i (see above) and the second force component F _Tzi in the form of the transverse force resulting from the torque .

In an alternative variant, which relates to finding the holding position for carrying the workpiece part, the resultant force is compared individually with the lateral force in the horizontal direction and the holding force in the vertical direction. As described above, the non-positive connection between the effective holding elements and the workpiece part must exceed the load or the resulting force on the holding elements if the workpiece part is not to move relative to the holding device. In order to make a statement about the process-reliable carrying of the workpiece part, for each holding element, for example for each suction cup, the proportion of the resultant force in the horizontal direction is compared with the transverse force that can be transmitted by the suction cup and acts in the horizontal direction, as well as the proportion of the resultant force in the vertical direction with the one in ver compared to the holding force acting in the vertical direction of a respective holding element. Alternatively, the resultant force, which has not been broken down into its components in different spatial directions, can be compared with a vectorial sum of the transmissible transverse force and the transmissible holding force of a respective holding element.

A further aspect of the invention relates to a computer program product which is designed to carry out all the steps of the method as described above when the computer program runs on a data processing system. The data processing system can in particular be a programming system, i.e. a computer for programming the control programs for a numerical control device of a device for moving and/or supporting a workpiece part or a machine arrangement with such a device. If the computer program runs in the programming system, a machining program is generated which, among other things, contains a sequence of (control) commands for assuming a holding position suitable for moving or carrying the workpiece part using the device for moving and/or carrying the Workpiece part has. Based on the comparison described above with the evaluation criterion, placement or arrangement of the holding device at a specific holding position is evaluated and, if necessary, can be iteratively adjusted until the evaluation criterion is met for all effective holding elements. The machining program generated in this way can then be executed by a control device of the device or by a machine arrangement containing this device.

Further advantages of the invention result from the description and the drawing. Likewise, the features mentioned above and those listed below can each be used individually or together in any combination. The embodiments shown and described are not to be understood as an exhaustive list, but rather have an exemplary character for the description of the invention.

• 1a eine schematische Darstellung eines Beispiels einer maschinellen Anordnung mit einer Laserschneidmaschine und mit einer Vorrichtung zum Verschieben und zum Tragen eines von einem Restgitter freigetrennten Werkstückteils,
• 1b eine Darstellung einer Halteeinrichtung der Vorrichtung von 1a in Form eines (Vakuum-)Flächensaugers, dessen Halteelemente in Form von Saugern auf dem Werkstückteil und dem Restgitter aufliegen, um das Werkstückteil bei einer Verschiebung relativ zum Restgitter zu fixieren,
• 2a,b Darstellungen einer Saugerplatte des Flächensaugers, die einen Teilbereich aufweist, in dem sich wirksame Sauger mit dem Werkstückteil überschneiden, sowie von einer auf den Schwerpunkt des Teilbereichs wirkenden Gesamt-Kraft bzw. eines auf den Schwerpunkt des Teilbereichs wirkenden Moments,
• 3 eine Darstellung des Teilbereichs der Saugerplatte des Flächensaugers mit den wirksamen Saugern sowie der resultierenden Kraft auf einen der wirksamen Sauger, die eine vektorielle Summe einer ersten und zweiten Kraftkomponente bildet,
• 4 eine Darstellung der maschinellen Anordnung von 1a, bei welcher das entlang der Werkstückauflage verschobene Werkstückteil mit Hilfe von zwei Flächensaugern angehoben und transportiert wird, sowie
• 5a,b Darstellungen des Werkstückteils und eines Flächensaugers von 4 in einer Draufsicht und einer Seitenansicht mit den auf den Schwerpunkt des Werkstückteils wirkenden Kräften sowie mit den auf den Schwerpunkt eines Teilbereichs des Flächensaugers wirkenden (Torsions-)Momenten.

Show it:

• 1a a schematic representation of an example of a machine arrangement with a laser cutting machine and with a device for moving and carrying a workpiece part that has been separated from a residual skeleton,
• 1b a representation of a holding device of the device of FIG 1a in the form of a (vacuum) surface suction cup, the holding elements of which rest in the form of suction cups on the workpiece part and the residual skeleton in order to fix the workpiece part when it is displaced relative to the residual skeleton,
• 2a,b Representations of a suction plate of the surface suction cup, which has a partial area in which effective suction cups intersect with the workpiece part, as well as a total force acting on the center of gravity of the partial area or a moment acting on the center of gravity of the partial area,
• 3 a representation of the partial area of the suction plate of the surface suction cup with the effective suction cups and the resulting force on one of the effective suction cups, which forms a vector sum of a first and second force component,
• 4 a representation of the machine arrangement of 1a , in which the workpiece part shifted along the workpiece support is lifted and transported with the help of two surface suction cups, as well as
• 5a,b Representations of the workpiece part and a surface suction cup from 4 in a top view and a side view with the forces acting on the center of gravity of the workpiece part and with the (torsional) moments acting on the center of gravity of a partial area of the vacuum cleaner.

In the following description of the drawings, identical reference symbols are used for identical or functionally identical components.

1a shows a machine arrangement 1, which has a laser cutting machine 2 and a device for moving and supporting a workpiece part, which forms an unloading station 3 of the laser cutting machine 2. Alternatively, the mechanical arrangement 1 can also be in the form of a mechanical separating device, for example a punching machine, a punch/laser combination machine, a plasma cutting machine, a water jet cutting machine or the like. The laser cutting machine 2 shown here as an example has a guide structure (not shown) with a portal cross member 4, along which a moving unit 5 with a laser cutting head 6 extends perpendicularly to the plane of FIG 1a can be moved, ie in the X direction of an XYZ coordinate system. In addition, the laser cutting head 6 can perform movements in the vertical direction (Z-direction) relative to the portal cross member 4 .

The portal cross member 4 spans a workpiece support 7, which is occupied on its upper side in a conventional manner with support brushes. The workpiece support 7 includes a machining support table 8 on the side and a support table 9 on the unloading side aligned with it in the horizontal direction. The support table 8 on the processing side and the support table 9 on the unloading side are separated by a support space 10 (gap), in which there is a suction device and/or one or more workpiece support carriages 11 in X-direction can be arranged to be movable perpendicular to the plane of the drawing.

A cross rail 12 extending in the X direction, ie perpendicular to the plane of the drawing, is guided on the support table 8 on the machining side so that it can be moved by a motor in the positive and negative Y direction with the aid of a movement device 13 indicated by a double arrow. The cross rail 12 is provided with a plurality of clamping claws 14 which are offset relative to one another in the longitudinal direction of the cross rail 12 . The clamping claws 14 hold a plate-like workpiece 15 before and during cutting by means of the laser cutting head 6, the cutting of the workpiece 15 taking place in a working area of the laser cutting machine 2 between the two support tables 8,9. Like this in 1b is shown, after the machining of the workpiece 15 and the associated cutting out of a workpiece part 16 created as a workpiece cutout, the clamping claws 14 hold a remaining workpiece that is produced during the machining of the workpiece 15 in addition to the workpiece part 16 and is present as a residual skeleton 17.

The unloading station 3 comprises a frame 18 on which a horizontal support 19 is mounted such that it can be raised and lowered. Cantilever arms 20, which run perpendicular to the plane of the drawing, can be moved along the horizontal support 19. The cantilever arms 20 support a guide rail 21 when the guide rail 21 moves perpendicularly to the plane of the drawing, i.e. in the X-direction. Along the guide rail 21, three holding devices 22, 23, 24 can be moved in the positive and negative Y-direction over the workpiece support 7 with the aid of a movement device 25 indicated by a double arrow.

The first holding device 22 has a first holding device in the form of a first surface suction device 26 . Correspondingly, the second holding device 23 also has a second holding device in the form of a second surface suction device 27 and the third holding device 24 has a third holding device in the form of a third surface suction device 28 . The three holding devices or the surface suction devices 26, 27, 28 are identical in construction and can be displaced and advanced in the vertical direction (Z-direction) with the aid of pneumatic piston-cylinder units 29, 30, 31 acting as actuators.

the inside 1b The first surface suction device 26 shown has a housing 32 with a suction plate 33, which is provided with a plurality of holes, not shown in the figure. The bores are used to accommodate suction cups 34, each of which has a suction cup 35 folded like a bellows. The suction cups 35 are in the in 1b illustrated initial state of the surface suction device 26 in relation to the suction plate 33 of the housing 32 and are perpendicular to the suction plate 33 elastically deformable. The suckers 34 can be designed as active or passive suckers. A suction chamber inside each suction cup 35 can be connected to a vacuum generator, not shown, so that the vacuum generator sucks in air via the suction chambers of the suction cups 34 and can generate a vacuum or negative pressure either on all suction cups 34 simultaneously or in a controlled manner on selected suction cups , in order to suck in the workpiece part 16 or the scrap skeleton 17.

one inside 1a The programmable numerical control device 40 shown schematically controls all essential functions both on the laser cutting machine 2 and on the unloading station 3 of the machine arrangement 1. The numerical control device 40 controls in particular the motor drive 13 for the transverse rail 12, which acts as a workpiece drive and also as a residual workpiece drive of the laser cutting machine 2, the in 1a is indicated by a double arrow, as well as in 1a motorized movement device 25, also indicated by a double arrow, for the three holding devices 22, 23, 24. In addition to the workpiece drive 13 and the movement device 25 for the three holding devices 22, 23, 24, further motorized drives (not shown) are provided, among other things, for the sake of clarity , by means of which the lifting movements of the horizontal beam 19 and the horizontal movements of the cantilever arms 20 and the guide rail 21 are carried out and for the control of which the numerical control device 40 of the machine arrangement 1 is also used. In contrast to what was described above, the numerical control device 40 can form part of the unloading station 3 or two separate numerical control devices can be provided for the numerical control of the laser cutting machine 2 and the unloading station 3 . The control programs for the programmable numerical control device 40 are usually generated using a programming system that runs on a separate computer. The orientation of the workpiece parts 16 within the workpiece 15 (nesting), the machining parameters for the cutting machining and the positioning are programmed by means of the programming system other machine components such as the holding devices 22, 23, 24 set during and after processing.

In the representation of 1b If the laser cutting head 6 has made the final separating cut in the working area formed between the two support tables 8, 9 of the workpiece support 7 and thereby from the in 1a Workpiece 15 shown in 1b Workpiece part 16 shown is cut out and the residual grid 17 is additionally produced as a residual workpiece. The horizontal carrier 19 has moved so far down the frame 18 of the unloading station 3 that one or more of the holding devices attached to the extended piston rods of the pneumatic piston-cylinder units 29, 30, 31 in the form of the surface suction devices 26, 27, 28, more precisely the suction cups 35 of the suction cups 34, rest with their underside on the upper side of the workpiece part 16.

Based on the circumstances 1b the control device 40 activates the movement device 25 for moving the holding devices 22, 23, 24 in order to move the workpiece part 16 by means of one or more of the surface suction devices 26, 27, 28 out of the cutting area of the laser cutting machine 2 to the side in the direction of the support table 9 on the unloading side move it and, if necessary, then remove it upwards from the support table 9 on the unloading side. The number of surface suction devices 26, 27, 28 used for moving depends on the size and shape of the workpiece part 16. If the workpiece part 16 is different than in 1b shown is surrounded by the residual skeleton 17, the residual skeleton 17 can be displaced parallel to the movement of the surface suction devices 26, 27, 28 with the aid of the transverse rail 12 and the movement device 13 to the side. Relative movements between the residual skeleton 17 and the workpiece part 16 and relative movements between the workpiece part 16 and the surface suction cups 26, 27, 28 should be avoided as completely as possible.

In order to achieve this, in the example shown, the first surface suction cup 26 transmits a transverse force F _Q,i acting in the displacement direction Y to the suction cups 34 whose suction cup surfaces at least partially overlap with the workpiece part 16 (hereinafter referred to as effective suction cups 34a). Workpiece part 16, as follows with reference to 2a,b as well as based on 3 is described in more detail. In 2a,b For the sake of simplicity, the residual skeleton 17 and the second surface suction device 27 are not shown. In addition, to simplify the following calculations, the presence of the second suction pad 27 was not taken into account, ie it was assumed that only the first suction pad 26 transmits forces to the workpiece part 16 and absorbs forces from the workpiece part 16 .

The transverse force F _Q,i that can be transmitted by the effective suction cups 34a of the first surface suction cup 26 in the displacement direction Y to the workpiece part 16 (cf. 3 ) is the same for all effective suction cups 34 of the first surface suction cup 26. The transmissible lateral force F _Q,i of an effective suction cup 34a depends on the contact pressure of the effective suction cup 34a or the first surface suction cup 26 on the workpiece part 16 and on the coefficient of friction between the respective effective suction cup 34a and the workpiece part 16, which depends, among other things, on the surface condition of the workpiece part 16 is dependent. The action of the first surface suction cup 26 or the individual effective suction cups 34a can take place by placing or pressing on the surface suction cup 26 or by additionally generating a vacuum with the aid of the vacuum generator of the surface suction cup 26. The values that are valid in these cases for the transmissible transverse force F _Q,i of a respective effective suction cup 34a are typically empirically determined in advance by series of tests, ie the transmissible transverse force F _Q,i is known in advance.

In order to ensure that the workpiece part 16 does not shift relative to the residual skeleton 17 during the displacement along the workpiece support 7, it is necessary to find a holding position HP of the first surface suction device 26 relative to the workpiece part 16 in the programming system when generating the control program for the control device 40 , in which the transmissible transverse force F _Q,i satisfies an evaluation criterion for each individual effective suction cup 34a. A holding position HP of the first surface suction cup 26 is understood to mean a position relative to the workpiece part 16 in which at least one of the suction cups 34a, more precisely at least one suction cup surface, at least partially overlaps with the workpiece part 16 .

At the in 2a,b shown holding position HP overlaps a number nws of twelve effective suction cups 34a with their respective circular suction cup surfaces completely with the workpiece part 16. An in 2a,b The rectangular portion 36 of the first surface suction device 26, more precisely of the suction plate 33, delimited by a dashed border, contains all effective suction devices 34a, which are arranged uniformly distributed on the suction plate 33 in the example shown. The width B of the partial area 36 corresponds to the width of the suction plate 33 and the length L of the partial area 36 corresponds to one in 1b illustrated overlap length L, along which the first surface suction device 26 overlaps with the workpiece part 16.

wobei S einen Sicherheitsfaktor (>1) und i den i-ten Sauger 34a bezeichnet (i = 1, ... nws). Erfüllt die Halteposition HP das obige Bewertungskriterium, so kann das Werkstückteil 16 auf der Werkstückauflage 7 prozesssicher verschoben werden, ohne dass es zu einer unerwünschten Bewegung des Werkstückteils 16 relativ zum Restgitter 17 kommt.In the following considerations, an evaluation criterion is used in which the transverse force F _Q,i that can be transmitted from a respective suction cup 34a in the displacement direction Y to the workpiece part 16 is compared with a resultant force F _{res,i,y acting on a respective suction cup 34a counter to the displacement direction Y} is compared, ie it is checked whether the following applies to all twelve effective suckers 34a: $${\text{f}}_{\text{Q},\text{i}}\ge {\text{SF}}_{\text{res},\text{i},\text{y}},$$

where S denotes a safety factor (>1) and i denotes the ith sucker 34a (i=1,...nws). If the holding position HP satisfies the above evaluation criterion, the workpiece part 16 can be reliably displaced on the workpiece support 7 without the workpiece part 16 moving undesirably relative to the residual skeleton 17 .

To determine the component _{Fres,i,Y acting counter to the displacement direction Y,} of the resulting force Fres _,i exerted on a respective suction cup 34a during the displacement of the workpiece part 16, the resulting force _Fres,i on a respective effective suction cup is first calculated 34a determined. The resulting force F _res,i consists of the vector sum of a first force component F _R,i and a second force component F _Tz,i :

wobei F_N die in 1b dargestellte Normalkraft auf das Werkstückteil 16, vereinfacht auf den Schwerpunkt Sw des Werkstückteils 16, und µ_B den Reibungskoeffizienten zwischen dem Werkstückteil 16 und den Auflagebürsten der Werkstückauflage 7 bezeichnen. Die Normalkraft F_N variiert, je nachdem ob an den Saugern 34a ein Vakuum anliegt, ob der erste Flächensauger 26 mit seinem Eigengewicht aufliegt oder auf das Werkstückteil 16 gedrückt wird.The first force component F _R,i results from a total force F _R * (here: frictional force) acting on the center of gravity Sw of the workpiece part 16 (in simplified terms), which acts counter to the displacement direction Y in the example shown and which affects the static friction between the Workpiece part 16 and the support brushes of the workpiece support 7 is due. The following applies to the frictional force F _R * on the center of gravity Sw of the workpiece part 16: $${\text{f}}_{\text{R}}*={\text{f}}_{\text{N}}{\mathrm{\mu }}_{\text{B}},$$

where F _N is the in 1b illustrated normal force on the workpiece part 16, simplified to the center of gravity Sw of the workpiece part 16, and μ _B denote the coefficient of friction between the workpiece part 16 and the support brushes of the workpiece support 7. The normal force F _N varies depending on whether a vacuum is applied to the suction cups 34a, whether the first surface suction cup 26 is resting with its own weight or is being pressed onto the workpiece part 16.

wobei m_W die Masse des Werkstückteils 16, m_F das Eigengewicht des Flächensaugers 26, g die Schwerebeschleunigung (9,81 m/s²) und ns die Gesamtzahl der Sauger 34 des ersten Flächensaugers 26 (im gezeigten Beispiel ns = 44) bezeichnen.In the following it is assumed that the first surface suction device 26 rests with its own weight. In this case, the following applies to the friction force F _R *: $${\text{f}}_{\text{R}}*=\left({\text{m}}_{\text{W}}+{\text{m}}_{\text{f}}*\left({\text{n}}_{\text{WS}}{\text{/n}}_{\text{S}}\right)\right)*\text{G}*{\mathrm{\mu }}_{\text{B}},$$

where m _W denotes the mass of the workpiece part 16, m _F the weight of the surface suction cup 26, g the gravitational acceleration (9.81 m/s ² ) and ns the total number of suction cups 34 of the first surface suction cup 26 (ns = 44 in the example shown).

The frictional force F _R ^* acting counter to the direction of displacement Y is distributed evenly over all effective suction cups 34a, ie for the i-th effective suction cup 34a (cf. 3 ) is applicable: $${\text{f}}_{\text{R},\text{i}}={\text{f}}_{\text{R}}*{\text{/n}}_{\text{WS}}\left(\text{here}:{\text{n}}_{\text{WS}}=12\right).$$

The second force component F _Tz,i , which acts on an effective suction cup 34a, results from a moment Tz acting on the center of gravity Ss of the partial area 36 with the effective suction cups 34a (cf. 2 B) , which is generated by the workpiece part 16 during the displacement along the displacement direction Y. The moment T _Z is calculated from the frictional force F _R of the workpiece part 16 multiplied by the distance L _R,x between the (area) center of gravity Sw of the workpiece part 16 and the (area) center of gravity Ss of the partial area 36 with the effective suction cups 34a in X-direction, i.e. perpendicular to the displacement direction Y. In this case, only the dead weight of the workpiece part 16 is taken into account for the calculation of the normal force F _N , which is included in the frictional force F _R , since the proportion of the normal force that is caused by the first surface suction cup 26 is introduced, lies in the pivot point, ie the following applies: $${\text{f}}_{\text{R}}={\text{m}}_{\text{W}}\text{G}{\mathrm{\mu }}_{\text{B}}{\text{and t}}_{\text{Z}}={\text{f}}_{\text{R}}*{\text{L}}_{\text{R},\text{x}}.$$

wobei r_i den Betrag des Abstandsvektors $\overrightarrow{r_l}$

zwischen dem Schwerpunkt Ss des Teilbereichs 36 der Saugerplatte 33 und der Position des hier betrachteten, i-ten wirksamen Saugers 34a, sowie r_i,x die X-Komponente und r_i,y die Y-Komponente des Abstandsvektors $\overrightarrow{r_l}$

bezeichnen.For the force F _Tz,i on the i-th effective sucker 34a resulting from the moment Tz on the center of gravity Ss of the partial area 36: $$f_{T\mathrm{e.g},i}=\frac{T_Z*{\mathrm{right}}_i}{{\displaystyle {\sum }_{i=1}^{n_{WS}}{\mathrm{right}}_i^2}}=\frac{f_R*L_{R,x}*\sqrt{\left({\mathrm{right}}_{i,x}^2+{\mathrm{right}}_{i,y}^2\right)}}{{\displaystyle {\sum }_{i=1}^{n_{WS}}{\mathrm{right}}_i^2}},$$

where r _i is the absolute value of the distance vector $\overrightarrow{{\mathrm{right}}_l}$

between the center of gravity Ss of the partial area 36 of the suction plate 33 and the position of the i-th effective suction device 34a considered here, as well as r _i,x the X component and r _i,y the Y component of the distance vector $\overrightarrow{{\mathrm{right}}_l}$

describe.

$$F_{res,i,y}=F_{R,i}+F_{Tz,i}*\frac{r_{i,x}}{r_i}=\frac{F_R^{*}}{n_{WS}}+\frac{F_R*L_{R,x}*r_{i,x}}{{\displaystyle {\sum }_{i=1}^{n_{WS}}{r}_i^2}},$$

wobei F_res,i den Betrag der resultierenden Kraft $\overrightarrow{F_{res,l}}$

bezeichnet, d.h. $$F_{res,i}=\sqrt{F_{res,i,x}^2+F_{res,i,y}^2}.$$

For the force Fres,i resulting from the first force component F _R,i and from the second force component F _{Tz, i,} more precisely for its X component F _res,i,x or for its Y component F _{res,i, Y} applies: $$f_{\mathrm{right}es,i,x}=-f_{T\mathrm{e.g},i}*\frac{{\mathrm{right}}_{i,y}}{{\mathrm{right}}_i}=\frac{f_R*L_{R,x}*{\mathrm{right}}_{i,y}}{{\displaystyle {\sum }_{i=1}^{n_{WS}}{\mathrm{right}}_i^2}},$$

$$f_{\mathrm{right}es,i,y}=f_{R,i}+f_{T\mathrm{e.g},i}*\frac{{\mathrm{right}}_{i,x}}{{\mathrm{right}}_i}=\frac{f_R^{*}}{n_{WS}}+\frac{f_R*L_{R,x}*{\mathrm{right}}_{i,x}}{{\displaystyle {\sum }_{i=1}^{n_{WS}}{\mathrm{right}}_i^2}},$$

where F _{res,i is} the magnitude of the resultant force $\overrightarrow{f_{\mathrm{right}es,l}}$

called, ie $$f_{\mathrm{right}es,i}=\sqrt{f_{\mathrm{right}es,i,x}^2+f_{\mathrm{right}es,i,\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="DE102018203061B4\_0023.png,DE102018203061B4\_0025.png"\; state="\{\{state\}\}">y</figure-callout>}}^2}.$$

für den Vergleich herangezogen wird.As described above, for the comparison with the transmissible transverse force F _Q,i in the present case, in which the displacement takes place in the Y direction, the Y component F _res,i,y of the resulting force F _res,i with compared to the transmittable lateral force F _Q,i . It goes without saying that in the case of a displacement along a displacement direction that does not run in the Y direction, corresponding to the above procedure, the component of the resulting force acting against the displacement direction is force $\overrightarrow{f_{\mathrm{right}es,l}}$

is used for the comparison.

At the in 2a,b and 3 In the example described, the condition F _Q,i ≧SF _res,i,Y is met for all active suction cups 34a, ie the (initial) holding position HP is evaluated as being suitable for moving the workpiece part 16 . When an appropriate stop position HP is found by the judgment made in the manner described above, it is stored in the command set for the numerical control. During the machining of the workpiece part 16 or after it has been cut free, the numerical control unit 40 controls the movement device 13, the first surface suction device 26 to the in 2a,b to move the holding position HP shown relative to the workpiece part 16 and to place it on the workpiece part 16 with the effective suction cups 34a in order to move the workpiece part 16 along the workpiece support 7 .

In the event that not all effective suction cups 34a in the partial area 36 of the first surface suction cup 26 that overlaps the workpiece part 16 meet the evaluation criterion at the (initial) holding position HP, the evaluation of the holding position HP can be repeated by calculating the the forces transmitted to the effective suction cups 34a, those suction cups 34a for which the evaluation criterion was not met in the first step are not taken into account. If the evaluation criterion for all remaining effective suckers 34a is met under these changed (tightened) conditions, the holding position HP is evaluated as suitable.

If no suitable holding position can be found in this way, the holding position HP of the surface suction device 26 relative to the workpiece part 16 is changed in the programming system. For example, the number of effective suckers 34a or the overlapping partial area 36 can be increased here. It is also possible to try, while maintaining the number of effective suction cups 34a, by changing the positioning of the surface suction cup 26 relative to the workpiece part 16, so that the evaluation criterion is met.

In all of these cases, a holding position HP suitable for the shift is determined iteratively, i.e. the holding position HP used for the comparison with the evaluation criterion is changed until a suitable holding position HP is found or until a termination criterion is reached. In the simplest case, the termination criterion corresponds to a specified number of iterations. In the event that no suitable holding position HP is found, a warning message can be issued that the displacement may involve an increased risk of tilting. Alternatively, the orientation of the workpiece part 16 within the workpiece 15 can be changed in the programming system. If the holding devices 22, 23, 24 are designed with variably positionable suction cups instead of a surface suction cup, it is also possible to change the arrangement of the suction cups.

The method described above for finding a suitable holding position HP can also be applied analogously to the case where the workpiece part 16 is not pushed along the workpiece support 7, but is carried or transported with the aid of the first surface suction device 26 without the workpiece part 16 this is supported by the workpiece support 7. Such a transport of the workpiece part 3 can also take place with the aid of the unloading station 3 of the machine arrangement 1, as follows with reference to FIG 4 is shown. After the workpiece part 16 has been removed from the unloading-side support table upwards, it is held by one or more surface suction devices, in the example shown by the first and second surface suction devices 26, 27. To simplify the calculations, as in the case described above, an example is considered below in which the workpiece part is held only by the first surface suction device 26 .

For the first surface suction cup 26, the in 5b shown conditions. At the in 5b In the shown holding position HP of the surface suction cup 26, all suction cups 34 are active, i.e. they overlap with the workpiece part 16. The partial area 36 with the effective suction cups 34a thus corresponds to the entire surface of the suction cup plate 33. If the workpiece part 16 is held by several surface suction cups 26, 27, 28 held, the effective suction cups 34a of the surface suction cups 26, 27, 28 together form the partial area 36.

When holding or transporting the workpiece part 16 in the vertical direction Z, the weight force F _G = m _w g and possibly an acceleration force in the Z direction Fz = ± act on the center of gravity Sw of the workpiece part 16 and thus on the center of gravity Ss of the suction plate 33 a _z mw. The total force F _R * in the Z direction during the movement of the workpiece part 16 is therefore F _R * = F _G + Fz. As described above, the total force F _R * is evenly distributed over the effective Suction cup 34a divided, ie the following applies to the i-th suction cup: $${\text{f}}_{\text{R},\text{e.g},\text{i}}={\text{f}}_{\text{R}}*{\text{/n}}_{\text{WS}}\left(\text{here}:{\text{n}}_{\text{WS}}=\mathrm{8th}\right).$$

zwischen dem Schwerpunkt Ss der Saugerplatte 33 und der Position des i-ten wirksamen Saugers 34a abhängig.In addition to the total force F _R *, a moment T _g,z acts on the center of gravity Ss of the suction plate 33, which, analogously to the case described above, results in a (transverse) force F _g,z,i acting in the Z direction guides the i-th effective sucker 34a. The force F _g,z,i is analogous to the case of the distance vector described above $\overrightarrow{{\mathrm{right}}_l}$

between the center of gravity Ss of the sucker plate 33 and the position of the i-th effective sucker 34a.

The Z component of the resulting force F _res,i,z is made up of the two force components described above, ie the following applies: F _res,i,z = F _R,i,z + F _g,i,z . For the workpiece part 16 to be held securely on the surface suction cup 26, the holding force F _H,i of the i-th suction cup 34a must meet the following condition: $${\text{f}}_{\text{H},\text{i}}\ge {\text{SF}}_{\text{res},\text{i},\text{e.g}}.$$

In the event that the workpiece part 16 is also to be moved or transported along a transport direction in the horizontal direction, ie in a plane containing the X direction and the Y direction parallel to the workpiece support 7, the above for the Z direction apply specified equations continue. In addition, a resultant force F _res,i,xy acts in the plane parallel to the workpiece support, which consists of a component F _res,i,x acting in the X direction and a component F _res,i,y acting in the Y direction. The resulting force force F _res,i,xy in the horizontal direction is determined analogously to the resulting force F _res,i in the Z direction, i.e. the equations given above can be applied analogously, only the weight force F _G is not taken into account here, since this acts perpendicular to the XY plane.

$${\text{F}}_{\text{R},\text{y},\text{i}}=\pm {\text{a}}_{\text{y}}{\text{ m}}_{\text{W}}{\text{/n}}_{\text{WS}}.$$

for the inside 5a The ratios described above therefore apply to the proportion of the first force component in the X-direction and in the Y-direction: $${\text{f}}_{\text{R},\text{x},\text{i}}=\pm {\text{a}}_{\text{x}}{\text{m}}_{\text{W}}{\text{/n}}_{\text{WS}}\text{or}.$$

$${\text{f}}_{\text{R},\text{y},\text{i}}=\pm {\text{a}}_{\text{y}}{\text{m}}_{\text{W}}{\text{/n}}_{\text{WS}}.$$

$${\text{F}}_{\text{res},\text{i},\text{y}}={\text{F}}_{\text{R},\text{i},\text{y}}+{\text{F}}_{\text{T},\text{y},\text{i}}.$$

Correspondingly, a moment T _x or T _y on the center of gravity Ss of the suction plate 33 leads to a (transverse) force F _Tx,i or F _{Ty acting in the X direction or in the Y direction, analogous to the case described above. i} on the i-th sucker 34a. The two components F _res,i,x and F _res,i,y of the resulting force F _res,i,xy in the X and Y direction in the plane parallel to the workpiece support 7 are made up of the two force components, ie the following applies: $${\text{f}}_{\text{res},\text{i},\text{x}}={\text{f}}_{\text{R},\text{i},\text{x}}+{\text{f}}_{\text{tx},\text{i}}\text{or}.$$

$${\text{f}}_{\text{res},\text{i},\text{y}}={\text{f}}_{\text{R},\text{i},\text{y}}+{\text{f}}_{\text{T},\text{y},\text{i}}.$$

For the comparison with the transverse force F _Q,i that can be transmitted in the horizontal direction or in the (XY) plane on an individual suction cup 34a, the amount of the resulting force F _res,xy,i is typically determined, for which the following applies: $${\text{f}}_{\text{res},\text{i},\text{xy}}=\sqrt{{\text{f}}_{\text{res},\text{i},\text{x}}^2+{\text{f}}_{\text{res},\text{i},\text{<figure-callout id="2" label="y" filenames="DE102018203061B4\_0023.png,DE102018203061B4\_0025.png" state="{{state}}">y</figure-callout>}}^2}.$$

Analogously to the case of displacement described above, the evaluation criterion applies that the magnitude of the transverse force F _Q,i on a respective suction cup 34a must exceed the magnitude of the resultant force F _res,i,xy , with a safety factor S typically being taken into account, ie the following applies: $${\text{f}}_{\text{Q},\text{i}}\ge {\text{SF}}_{\text{res},\text{i},\text{xy}}.$$

As described above, the holding position HP is evaluated as suitable for carrying or transporting the workpiece part 16 if the evaluation criteria for the holding force F _H,i and for the transverse force F _Q,i are met for all effective suction cups 34a . Since the acceleration forces a _X , a _Y , a _z may change over time during the transport of the workpiece part 16 , the maximum values of the acceleration a _x,max , a _y,max , a _z,max occurring during transport can be used for the comparison will.

In the method described above, the number and arrangement of the suction cups 34 on the suction cup plate 33 is fundamentally arbitrary. As a rule, however, a larger number of suckers 34 is used than is shown in the figures. For example, a suction plate can have a number of 42×11 (passive) suction cups 34 . The diameter of the suction surface of a respective suction cup 34 can, for example, be of the order of approx. 10 mm. Depending on the geometry of the workpiece part 16, it may not be possible to guarantee that all effective suction cups 34 will engage with their (in usually round) suction cup surfaces completely overlap with the workpiece part 16.

As in 5a can be seen, the two right-hand outer suction cups 34a of the suction cup plate 36 only partially overlap with the workpiece part 16. Accordingly, the two suction cups 34a cannot transfer the entire lateral force F _Q,i or the entire holding force F _H,i to the workpiece part 16, as would be the case if the suction cups 34a completely overlapped the workpiece part 16 . To take this fact into account, the value of the transverse force F _Q,i or holding force F _H,i that can be transmitted from the two outer suction cups 34a to the workpiece part 16 is multiplied by a factor f (<1), for example, for the comparison with the evaluation criterion with a factor f = 0.5. Since the evaluation criterion must be met for all effective suction cups 34a, the use of effective suction cups 34a that only partially overlap increases the requirements for finding a suitable holding position HP.

The evaluation specification described above can basically be used for all processes in which a decision must be made as to whether the fixation of a (flat) part, for example a workpiece part, which has a holding force and/or friction at discrete points or positions (here: suction cup 34) has to be moved in one spatial direction, can be done reliably or not.

Claims (12)

Method for finding at least one suitable holding position (HP) for at least one holding device (26, 27, 28), which has a plurality of holding elements (34), relative to a workpiece rest (7 ) to be displaced or a workpiece part (16) to be carried by means of the holding device (26, 27, 28), comprising: a) determining a holding position (HP) of the holding device (26, 27, 28), in which at least one holding element (34 ) at least partially overlaps with the workpiece part (16) in order to act as an effective holding element (34a) on the workpiece part (16), b) determining one of the workpiece parts (16) when shifting or when carrying it on a respective effective holding element (34a) resulting force exerted (F _res,i ; F _res,i,z , F _res,i,xy ), c) evaluating the holding position (HP) as suitable for moving or supporting the workpiece part (16), if for all effective Holding elements (34a) each from effective holding element (34a) on the workpiece part (16) to be displaced in the displacement direction (Y) transferable transverse force F _Q,i or a holding force F _{H transferable to the workpiece part (16) to be carried in a transport direction (Z, X, Y), i} and/or transverse force F _Q,i in from the resulting force (F _res,i ; F _res,i,z , F _res,i,xy )-dependent evaluation criterion fulfilled, whereby in the case of a partial overlap of effective holding elements (34a) with the workpiece part (16), the holding elements (34a) acting through them on the workpiece part (16 ) transmissible transverse force (F _Q,i ) or holding and/or transverse force (F _H,i ; F _Q,i ) which can be transmitted to the workpiece part (16) to be transported is reduced by a predetermined factor. procedure after claim 1 , where the evaluation criterion is defined by the magnitude of the resulting force F _res,i,y ; _Fres,i,z ; F _res,i,xy is formed against the displacement direction (Y) or against the transport direction (Z, X, Y) multiplied by a safety factor S and is met if the following applies: F _Q,i ≥ SF _res,i,y and/ or F _H,i ≥ SF _res,i,z and/or F _Q,i ≥ SF _res,i,xy , with S > 1 . procedure after claim 1 or 2 , in which, in the event that in step c) the holding position (HP) is evaluated as not suitable for moving or carrying the workpiece part (16), steps a) to c) continue with a changed number of effective holding elements (34a) and/or repeated with a changed holding position (HP) until the specified holding position (HP) meets the evaluation criterion. Method according to one of the preceding claims, in which the resultant force (F _res,i ; F _res,i,z , F _res,i,xy ) is a vectorial sum of a first force component (F _R,i ; F _{R,i ,z} , F _R,i,x , F _R,i,Y ) and a second force component (F _Tz,i ; F _Tx,i , F _Ty,i ) is determined, with the first force component (F _R,i ; F _R,i,z , F _R,i,x , F _R,i,y ) resulting from a total force (F _R *) acting on the center of gravity (Sw) of the workpiece part (16) to be moved or carried, and wherein the second force component (F _Tz,i ; F _Tx,i , F _Ty,i ) is a transverse force (F _Tz,i ) on a respective effective holding element (34a), which is due to a center of gravity (Ss) of an all effective holding elements (34a) containing portion (36) of the holding device (26, 27, 28) acting torque (T _Z ; T _g,z T _X , T _y ) results. procedure after claim 4 , in which the first force component (F _R,i ) of the resulting force (F _res,i ) is determined by the total force (F _R *) acting on the center of gravity (Ss) of the workpiece part (16) to be displaced or carried ) is evenly distributed to the effective holding elements (34a). procedure after claim 4 or 5 , in which for finding the holding position (HP) to Ver pushing the workpiece part (16), the total force (F _R *) is determined in the form of a frictional force acting against a direction of displacement (Y), which is determined by a weight (gm _w ) of the workpiece part (16) on the workpiece support (7) and a Compressive force (gm _F n _WS / n _S )) of the effective holding elements (34a) on the workpiece part (16) is generated. procedure after claim 4 or 5 , in which, for finding the holding position (HP) for carrying the workpiece part (16), the total force (F _R ^* ) as the vectorial sum of an acceleration force (m _w a _Z ; m _w a _x ; m _w a _y ) in the center of gravity (S _W ) of the workpiece part (16) and a weight force (m _w g) acting on the workpiece part (16) counter to a transport direction (Z) in the center of gravity (S _W ) of the workpiece part (16) is determined. Procedure according to one of Claims 4 until 7 , in which the second force component (F _Tz,i ; F _Tx,i , F _Ty,i ) is determined using a torque (T _Z ; T _g,z , T _X , T _y ) that occurs when the workpiece part (16th ) in a displacement direction (Y) or when transporting the workpiece part (16) in a transport direction (Z, X, Y) from the workpiece part (16) to the center of gravity (Ss) of the part area (36) containing the effective holding elements (34a). becomes. procedure after claim 8 , in which, for finding the holding position (HP) for moving the workpiece part (16), the torque (Tz) exerted on the center of gravity (Ss) of the partial area (36) from a frictional force (F _R ) of the workpiece part (16) on the workpiece support (7) and a distance (L _R,x ; L _z , L _x , L _y ) between the center of gravity (Ss) of the partial area (36) and a center of gravity (Sw) of the workpiece part (16) along the displacement direction (Y; Z , X, Y) is determined. procedure after claim 8 , in which, for finding the holding position (HP) for carrying the workpiece part (16), the torque (T _g,z , T _x , T _y ) exerted on the center of gravity (Ss) of the partial area (36) from the on the center of gravity ( Sw) of the workpiece part (16) to be carried and a distance (L _z , L _x , L _Y ) between the center of gravity (Sw) of the workpiece part (16 ₎ to be carried and the center of gravity (Ss) of the Section (36) is determined. Method according to one of the preceding claims, in which, for finding the holding position (HP) for carrying the workpiece part (16), the resultant force (F _res,i ; _Fres,i,xy , _Fres,i,z ) is compared with the transverse force (F _Q,i ) in the horizontal direction (X, Y) and comparing the resulting force (F _res,i,xy , F _res,i,z ) with the holding force (F _H,i ) in the vertical direction ( Z) done individually. Computer program product which is designed to carry out all the steps of the method according to one of the preceding claims when the computer program runs on a data processing system.

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