WO2019166481A1

WO2019166481A1 - Method for locating a suitable holding position

Info

Publication number: WO2019166481A1
Application number: PCT/EP2019/054843
Authority: WO
Inventors: Christoph BLOEMKER; Jens Ottnad; Fabian MATTER
Original assignee: Trumpf Werkzeugmaschinen Gmbh + Co. Kg
Priority date: 2018-03-01
Filing date: 2019-02-27
Publication date: 2019-09-06
Also published as: DE102018203061B4; DE102018203061A1

Abstract

The invention relates to a method for locating at least one suitable holding position (HP) for at least one holding device (26), which has a plurality of holding elements (34), relative to a workpiece part (16) to be supported by means of the holding device (26) or to be displaced on a workpiece support by means of the holding device (26), comprising: a) defining a holding position (HP) of the holding device (26), in which at least one holding element (34) overlaps at least partially with the workpiece part (16), so as to act as an effective holding element (34a) on the workpiece part (16), b) determining a resulting force exerted on a particular active holding element (34a) by the workpiece part (16) when displaced or when supported, c) evaluating the holding position (HP) as suitable for displacing or supporting the workpiece part (16) if, for all effective holding elements (34a), a transverse force which can be transferred in the displacement direction (Y) onto the workpiece part (16) to be displaced or a holding and/or transverse force which can be transferred in a transport direction onto the workpiece part (16) to be supported complies with an evaluation criterion dependent on the resulting force.

Description

Method for finding a suitable holding position

The present invention relates to a method for finding at least one suitable holding position for at least one holding device having a plurality of holding elements, relative to a by means of the holding device on a workpiece support (side) to be moved or one by means of

Holding device to be supported, usually plate-shaped workpiece part. The invention also relates to a computer program product for carrying out such a method.

If a workpiece part separated from a plate-shaped workpiece is to be displaced laterally by means of a holding device alone or together with the surrounding residual grid on a workpiece support, the workpiece part can slip relative to the holding device and / or relative to the residual grid. Likewise, a displacement of the workpiece part relative to the residual grid may occur if, at the moment of free-cutting, forces (for example the force of an acting cutting gas during laser cutting) act on the workpiece part. One opposite the

Holding device or the residual grid shifted workpiece part may possibly only difficult or not automated to be removed from the machine. When carrying or transporting a held by means of the holding device, for example sucked workpiece part to a storage location also occur centrifugal forces on the workpiece part, which may not exceed the holding force of the holding elements, for example in the form of suction pads.

In order to avoid a relative movement of the workpiece part, it is known, for example from DE102015223062B3, to hold the workpiece part in a defined position relative to the residual grid during lateral displacement by means of a holding unit (for example suction unit). For this purpose, the suckers are placed on the workpiece part to prevent movement of the workpiece part in and / or against the direction of gravity. A stronger fixation of the workpiece part can be done by suction of the workpiece part. Since the holding unit is not allowed to collide with a machining head for separating machining of the workpiece, in the method according to DE102015223062B3 the holding unit usually does not completely cover the workpiece part.

From DE19817213A1 it is known in a vacuum gripper in

Dependence on workpiece and process parameters (including material, dimensions, surface condition, transport direction, transport acceleration) to calculate whether a single suction pad is sufficient or whether several

Suction gripper for safe transport of the workpiece required or at least advantageous.

In W02007115633A1 it is proposed to use one in the control of a

Vacuum handling device filed process model the acceleration and / or transport speed on the capabilities of a vacuum gripper

adapt or optimize. For example, it can be determined whether the suction gripper can generate a high holding force, so that a high speed can be driven.

Object of the invention In contrast, the present invention has the object to provide a method by which a holding position can be found in which by means of a predetermined number and location of holding elements, in particular of suction pads, which act on the workpiece part, a reliable movement of the workpiece part on a Workpiece support and / or a safe carrying or transporting the held, in particular sucked workpiece part is possible. In this way, despite acting friction, weight and / or

Centrifugal force a secure hold of the workpiece part on the holding elements of the

Holding device can be achieved.

Subject of the invention

This object is achieved by a method of the type mentioned, comprising the steps: a) setting a holding position of

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 a resulting force exerted by the workpiece part when moving or carrying on a respective effective holding element, c) evaluating the

Holding position as suitable for moving or carrying the workpiece part, if for all effective holding elements each transferable to the workpiece part to be displaced in a direction transverse force or a transferable to the workpiece to be supported workpiece in a transport direction holding and / or transverse force of the resulting force-dependent evaluation criterion met.

With the aid of the method according to the invention, depending on e.g. from the geometry of the workpiece part, from the material properties (type of material, thickness, size), the friction coefficient of the material of the workpiece part on the

Workpiece support, as well as the location and number of effective holding elements, ie those holding elements that overlap at least partially with the workpiece part, an evaluation criterion are determined, which allows a statement about the strength of the fixation of the workpiece part to the holding device. The basic idea of this method is that acting on the holding device resulting (horizontal and possibly vertical) forces on the effective

Holding elements are distributed, taking into account the existing geometric relationships. In other words, the forces that act on the holding device, not necessarily equally distributed to all effective

Retaining elements. Thus, an evaluation criterion is used which corresponds to the selected holding position of the holding device and thus to each of the

Holding elements that act on the workpiece part, can make a statement as to whether there is a relative movement between the workpiece part and the holding device when moving or when carrying the workpiece part. With the help of

Evaluation criterion, a respective holding position of the holding device can therefore be assessed as suitable or unsuitable.

If the evaluation criterion for each individual effective holding element is met, the displacement or the carrying of the workpiece part can be carried out reliably. If the evaluation criterion is not met, i. if the burden is too high, the result of the evaluation will be issued or determined

present holding position of the holding device or the holding elements no safe displacement or no safe carrying the workpiece part can be done.

In the simplest case, the evaluation criterion may be to check whether the transferable by the effective holding element transverse force or the transferable holding force is at least as large or larger than the resulting force or the proportion of the resultant force in the relevant spatial direction.

Preferably, the evaluation criterion for this includes the amount of resultant force applied to the effective holding member multiplied by a safety factor. The evaluation criterion for the holding position of the holding device on the workpiece part, in the case of displacement of the workpiece, requires that the load or the resulting force Fres.i on each individual holding element is smaller than the transmittable transverse force F _q , i against the displacement direction, thus no relative movement arises between the holding element and the workpiece part, ie it should apply: FQ.I> S Fresj, where S denotes the safety factor, which is greater than 1, but if necessary also = 1 can be selected. In the case of carrying or transporting the workpiece, the above formula applies accordingly to the resulting Force in the horizontal direction, ie parallel to the plate-shaped workpiece part (against the horizontal component of the transport direction). In addition, the evaluation criterion must also be fulfilled for the holding force FH.I in the vertical direction, ie in the vertical direction must apply: FH, I> S Fresj.

The evaluation criterion or the evaluation rule can basically be used for all processes in which a decision must be made as to whether the fixation of a (flat) workpiece part, which via a clamping or holding force and / or friction at discrete points (for example, suckers or grippers) must be moved in a spatial direction, can be carried out reliably or not, for example, in the above-described holding or transport of the plate-shaped or flat workpiece part.

For the purposes of this application, the term "carrying the workpiece" is understood to mean a lifting of the workpiece part in the vertical direction, in which no movement of the workpiece part takes place in the horizontal direction, so that only the force of gravity and a vertical direction acting on the workpiece part

Acceleration force acts. The carrying of the workpiece also includes one

Transport of the workpiece part, in which the workpiece part is not only raised but in addition in at least one other spatial direction (horizontal) is moved. In a transport of the workpiece part act on the workpiece part both in the horizontal direction and in the vertical direction

Acceleration forces, plus gravity. For simplicity, it is assumed in all subsequent considerations that these forces in

Center of gravity of the workpiece part act or attack.

If, in step c) of the method according to the invention, the holding position is assessed as unsuitable for the reliable shifting 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 stop position meets the evaluation criterion.

In the former case, for example, in a step d) those effective holding elements for which the evaluation criterion was not met, neglected and the calculation of the applied resultant force can be performed again for the remaining effective holding elements. If the evaluation criterion for all remaining effective holding elements is fulfilled, then the (initial) holding position defined in step a) is evaluated as suitable. If this is not the case, then step d) can be repeated. If, after repeated repetition of step d) if necessary, no 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 transferable by a holding element, for example by a nipple or gripper, or

Holding force is dependent on the suction, clamping or contact force against the workpiece part and the coefficient of friction between the nipple or gripper and the workpiece part, the material or the surface finish of the workpiece part (for example, dry or oiled, etc.) and the material and the

Surface texture of the teat or gripper depends. The value for the transmittable shear force is either in the data sheets of the manufacturer

Holding device, for example, a vacuum cleaner manufacturer, specified or can be determined by means of displacement or by means of carrying out tests. During the displacement of the workpiece part, the action of the holding device can be done by applying or pressing a surface suction or the effective suction or by additional generation of a vacuum. The applicable values for the transmittable shear force of a single nipple in these cases must typically be determined by test series.

In general, the method is completed when a suitable holding position or holding positions for the holding device (s) has been found (s). Optionally, the method may be further performed after finding a suitable holding position, i. E. The steps a) to c) can be repeated with changed holding positions until several process-safe holding positions are found. From the process-safe holding positions can then be selected that which the

Evaluation criterion best or optimally fulfilled. In the event that two or more holding devices are used to one and the same workpiece part too move or carry, the resulting force depends on a respective one

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 engage the workpiece part. For the following considerations, it is assumed for the sake of simplicity that only a single holding device is used for displacing or holding the workpiece part.

During the first execution of the method step a), an initial holding position of the holding device can be defined, in which a predetermined number of

Retaining elements of the holding device completely or partially overlap with the workpiece part. A partial overlap is understood to mean that only a partial region of the effective surface of a holding element, for example a suction surface, overlaps 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 determined by first a, the particular workpiece to be taken part enclosing, in particular rectangular

Contour contour is set. The initial definition of the holding position preferably takes place uniformly, i. the holding device has equal distances to the edges of the Umschließungskontur. If this is due to collisions between the holding device and other components, such as a

Processing head is not possible, the holding device is in consideration of a minimum distance to the components, e.g. to the machining head, placed at equal distances to the edges of the enclosing contour. If two or more holding devices for moving or carrying on and

the same workpiece part, their initial holding positions are typically also set so that the holding means are arranged uniformly in relation to the Umschließungskontur, i. the holding devices have equal distances to 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, the first force component being one of the center of gravity of the one to be displaced resulting in a force acting on the workpiece part resulting total force, and wherein the second force component results from a transverse force on a respective holding element due to acting on the center of gravity of all effective holding elements containing portion of the holding means torque. The resulting force on a retaining element is generally made up of the two described above

Force components together. In the event that the center of gravity of the portion of the holding device coincides with the effective holding elements with the center of gravity of the workpiece part, eliminates the second force component, i. this has the value zero.

For the typically present case that the plate-shaped workpiece or the workpiece part cut free from this has a constant thickness and density, the center of gravity of the workpiece part coincides with the centroid of the workpiece part. Correspondingly, the center of gravity of the subregion of the holding device coincides with the area center of gravity of the subregion of FIG

Holding device match, if 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 resulting force is determined by the on the center of gravity of the to be moved or to be supported

Workpiece part acting total force is divided evenly on 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, the total force is in the form of a counter to a finding of the holding position for moving the workpiece part

Displacement direction acting frictional force determined, which is generated by a weight force of the workpiece part and a contact force of the effective holding elements on the workpiece part. During the displacement of the workpiece part with the holding device placed thereon arises between the workpiece part and the

Workpiece support friction. This adhesive frictional force acts opposite to the displacement direction and is hereinafter referred to as a replacement force (combined force) FR ^* . The frictional force FR acting against the direction of displacement FR ^* is calculated from the normal force FN perpendicular to the workpiece support multiplied by the adhesion friction coefficient PR between the workpiece part and the

Workpiece support determined, i. the following applies: FR * = FN PR. The workpiece support may, for example, be support brushes or the workpiece support may be formed by support brushes, which may be e.g. mounted on strips. In the case where the workpiece rest is formed of casters, the adhesion friction coefficient is replaced by the sliding friction coefficient of the workpiece rest.

The normal force FN has a first fraction FNI, which is due to the weight of the workpiece part. The following applies: FNI = m _w g, where mw denotes the mass of the workpiece part and g the gravitational acceleration (9.81 m / s ² ). The normal force FN also has a second fraction FN2, which is due to the compressive force of the holding elements on the workpiece part. The pressure force FN2 varies, depending on whether a vacuum is applied to the holding elements, for example in the form of a nipple or suction gripper, whether the holding device on which the

Holding elements are mounted, rests with its own weight on the workpiece part or is additionally pressed onto the workpiece part. Is that lying

Holding device, for example in the form of a surface suction, with her

Dead weight on the workpiece part, then: FN2 = g ITIF nws / ns, where ITIF the weight of the holding device or the surface suction, nws the number of effective holding elements and ns the total number of holding elements of

Designate holding device. As has been described above, the frictional force FR ^* acting counter to the direction of displacement distributes uniformly over all effective holding elements or suckers, ie, for a single holding element i: FRJ = FR ^* / nws.

In an alternative variant, when finding the holding position for carrying the workpiece part, the total force as the vectorial sum of an acting opposite to a direction of transport acceleration force in the center of gravity

Workpiece part and a weight force acting on the workpiece part in

Center of gravity of the workpiece part determined. The transport direction is basically arbitrary, but often the workpiece part is first raised in the vertical direction and subsequently in a direction parallel to the workpiece support horizontal Level transported or moved. It is understood that the transport direction and also the acceleration force can vary over time during the carrying of the workpiece part.

When comparing the resulting force with the evaluation criterion, this circumstance can be taken into account by the fact 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 can not consist of a single value, for example dependent on the magnitude of the resultant force, but two or more force components of the resultant force acting in different spatial directions can form the evaluation criterion.

For example, a force component of the total force that is in an in

Direction of space in the horizontal direction (or in a horizontal plane) acts, so that in this the weight of the workpiece part is not received, a first

Form force component of the resultant force in a horizontal spatial direction, which is compared with the transmittable shear force. Accordingly, a component acting in the vertical direction of the first component Kraftkom or the

resulting force to be compared with the transferable in the vertical direction holding force. However, it may also be possible to use only the amount of the resulting force (without decomposition into the portions acting in different spatial directions) as the evaluation criterion.

In a further variant, the second force component is based on a

Torque determines when moving the workpiece part in a

Displacement direction or when carrying the workpiece part in a transport direction of the workpiece part on the center of gravity of the effective holding elements containing portion is exercised. When moving the workpiece part, the torsion or torque acts only horizontally, i. 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 transported only in the vertical direction, in addition acts a torsional moment on the

Center of gravity of the subregion, where the torsional moment by the weight of the workpiece part is generated. In the event that the transport direction also has a proportion which acts in a horizontal direction, in addition acts a torsional or torsional moment in the horizontal direction.

In a further development, when finding the holding position for the displacement of the workpiece part, the force exerted on the center of gravity of the partial area

Torque from a frictional force of the workpiece part on the workpiece support and a distance between the center of gravity of the portion and a

Center of gravity of the workpiece part determined perpendicular to the displacement direction. The torque T _{z is} calculated from the frictional force FR of the workpiece part multiplied by the distance LR, _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 portion with the effective Flalteelementen. For the calculation of

Frictional force FR is considered only the weight of the workpiece part, since the normal force, which by the Flalteeinrichtung or by the effective

Flalteelemente is applied, in the fulcrum or in the center of gravity of the

Subarea is located. For the frictional force is: FR = mw g me, for the torque results: T _z = FR * LR, _x .

The moment T _z causes a transverse force FT _Z perpendicular to the distance vector between the flapping element and the center of gravity of a single flapping element

Subarea with the effective Flalteelementen out. The amount of lateral force F _Tz , i is proportional to the length of the distance vector. For the case of shifting the workpiece part considered here, the resulting force Fres results at a flattening element by a vectorial addition of the first

Force component in the form of frictional force FRJ (S.O.) and the second

Force component FT _ZI in the form of the transverse force resulting from the torque.

In an alternative variant, which relates to finding the position of the fold for supporting the workpiece part, the resulting force is compared with the lateral force in the horizontal direction and the force of the fold in the vertical direction individually. As described above, the frictional connection between the effective pad members and the workpiece member must exceed the load on the pad members when the workpiece member should not move relative to the holding device. To make a statement about that

to meet process-safe carrying the workpiece part, for each holding element, for example, for each sucker, the proportion of the resultant force in the horizontal direction with the transmittable by the sucker, acting in the horizontal direction transverse force and the proportion of the resultant force in the vertical direction with the vertical direction acting holding force of a respective holding element compared. Alternatively, a comparison of the resulting force, which has not been broken down into its proportions in different spatial directions, can be made with a vectorial sum of the transmittable shear force and the transmittable holding force of a respective holding element.

In a further variant, in a partial overlap of effective holding elements with the workpiece part, the transferable by these effective holding elements on the workpiece part to be displaced transverse force or on the workpiece to be transferred workpiece holding and / or lateral force to one

reduced predetermined factor. The partial area with the effective holding elements may contain both holding elements which rest completely (i.e., with the entire holding or suction surface) on the workpiece part, as well as holding elements with a partial covering. This part of the workpiece only partially

Covering holding elements is a reduced transmittable shear force (and carrying capacity or holding force) assigned. For example, the value of the transferable to the workpiece part transverse force for the workpiece part only partially

covering effective holding elements with a factor smaller than 1,

0.5, for example. Also, the holding force transferable to the workpiece part by a holding element can be reduced by a factor of e.g. 0.5 multiplied.

Another 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 may in particular be a

Programming system, i. a computer for programming the

Control programs for a numerical control device of a device for moving and / or carrying a workpiece part or a machine Arrangement act with such a device. If the computer program is running in the programming system, a processing program is generated, which includes a sequence of (control) commands for taking one for the

Move or suitable for carrying the workpiece part holding position by the device for moving and / or carrying the workpiece part. On the basis of the comparison with the evaluation criterion described above, a placement or arrangement of the holding device is evaluated at a certain holding position and, if necessary, iteratively adjusted until the evaluation criterion for all effective holding elements is met.

The processing program generated in this way can then be replaced by a

Control device of the device or a machine assembly containing this device are executed.

Further advantages of the invention will become apparent from the description and the drawings. Likewise, the features mentioned above and the features listed further can be used individually or in combination in any combination. The embodiments shown and described are not to be understood as exhaustive enumeration, but rather have exemplary character for the description of the invention.

Show it:

Fig. 1a is a schematic representation of an example of a machine

Arrangement with a laser cutting machine and with a device for moving and supporting a workpiece part which is separated from a skeleton grid,

Fig. 1 b is a representation of a holding device of the device of Fig. 1 a in

Shape of a (vacuum) surface vacuum, the holding elements in the form of suckers rest on the workpiece part and the skeleton grid in order to fix the workpiece part in a displacement relative to the skeleton grid,

Fig. 2a, b representations of a suction plate of the surface sucker, the one

Part area, in which effective sucker with the workpiece part overlap, as well as of an acting on the center of gravity of the sub-area total force or acting on the center of gravity of the sub-area torque,

3 is an illustration of the portion of the suction plate of the surface suction with the effective suckers and the resulting force on one of the effective sucker, which forms a vectorial sum of a first and second force component,

Fig. 4 is a representation of the mechanical arrangement of Fig. 1 a, in which the workpiece along the displaced workpiece part is lifted and transported by means of two surface suckers, and

Fig. 5a, b representations of the workpiece part and a surface suction of Fig. 4 in a plan view and a side view with the forces acting on the center of gravity of the workpiece part forces and acting on the center of gravity of a portion of the surface suction (Torsions-) moments.

In the following description of the drawings are for the same or

functionally identical components identical reference numerals used.

1 a 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 machine assembly 1 may also be used as a mechanical separator, e.g.

Punching machine, as a punching laser combination machine, as

Plasma cutting machine, water jet cutting machine or similar be executed. The laser cutting machine 2 shown here by way of example has a non-pictorial

represented guide structure with a portal cross member 4, along which a movement unit 5 with a laser cutting head 6 perpendicular to the plane of Fig. 1 a can be moved, i. in the X direction of an XYZ coordinate system.

In addition, the laser cutting head 6 relative to the portal cross member. 4

Perform movements in the vertical direction (Z direction). 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 comprises a machining-side support table 8 as well as a discharge-side support table 9 aligned therewith in the horizontal direction

The support table 8 and the discharge-side support table 9 are separated by a support space 10 (gap) in which a suction device is located and / or one or more workpiece support slides 11 can be arranged to be movable in the X-direction perpendicular to the plane of the drawing.

On the machining side support table 8, an X direction, i.

perpendicular to the plane, extending crossbar 12 by means of a direction indicated by a double arrow movement device 13 in a positive and in the negative Y-direction guided by a motor. The cross rail 12 is offset with a plurality of longitudinally of the cross rail 12 against each other

Spannpratzen 14 provided. The clamps 14 hold a plate-like

Workpiece 15 before and during the cutting machining by means of the

Laser cutting head 6, wherein the cutting machining of the workpiece 15 in a working range of the laser cutting machine 2 between the two

Support tables 8, 9 takes place. As shown in Fig. 1b, hold the

Spannpratzen 14 after machining the workpiece 15 and the associated removal of a created as a workpiece cutout workpiece part 16 a in the processing of the workpiece 15 in addition to the workpiece part 16 generated and present as a residual grid 17 remaining workpiece.

The unloading station 3 comprises a frame 18, on which a horizontal support 19 is mounted and lowered. Cantilevers 20 which are perpendicular to the plane of the drawing, along the horizontal support 19 are movable. The cantilevers 20 support a guide rail 21 upon movements of the guide rail 21 perpendicular to the drawing plane, i. in X direction. Along the guide rail 21, three holding devices 22, 23, 24 by means of a direction indicated by a double arrow movement means 25 in the positive and negative Y-direction over the

Workpiece support 7 are moved. The first holding device 22 has a first holding device in the form of a first surface vacuum 26. Correspondingly, the second holding device 23 also has a second holding device in the form of a second planar vacuum 27, and the third holding device 24 has a third holding device in the form of a third holding device

Surface suction 28 on. The three holding devices or the surface suction cups 26, 27, 28 are identical and can by means of acting as actuators

pneumatic piston-cylinder units 29, 30, 31 in the vertical direction (Z direction) are shifted and delivered.

The illustrated in Fig. 1 b first surface vacuum cleaner 26 has a housing 32 with a suction plate 33, which with a plurality of non-illustrated

Holes is provided. The bores are used to receive suckers 34, each of which has a bellows-like folded Saugermanschette 35. The

Sucker cuffs 35 are in the illustrated in Fig. 1 b initial state of the surface suction 26 against 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 in the interior of each Saugermanschette 35 can be switched to a vacuum generator not shown, so that the vacuum generator via the suction chambers of the suckers 34 suck air and either at all suckers 34 simultaneously or controlled on selected suckers can generate a vacuum or a suppression to suck the workpiece part 16 and the rest grid 17.

A programmable numeric shown schematically in Fig. 1a

Control device 40 controls all essential functions both on the laser cutting machine 2 and on the unloading station 3 of the machine

Arrangement 1. Controlled by the numerical control device 40, in particular, acting as a workpiece drive and as a residual workpiece drive motor drive 13 for the cross rail 12 at the

Laser cutting machine 2, which is indicated in Fig. 1a by a double arrow, as well as in Fig. 1a also indicated by a double arrow motorized movement device 25 for the three holding devices 22, 23, 24. In addition to the workpiece drive 13 and the movement device 25th for the three

Holding devices 22, 23, 24 are not among other things for the sake of clarity shown further motorized drives provided by means of which the lifting movements of the horizontal support 19 and the horizontal movements of the cantilever arms 20 and the guide rail 21 are executed and their control also the numerical control device 40 of the machine assembly 1 is used. Contrary to what has been described above, the numerical control device 40 may form part of the unloading station 3 or may be used for the numerical control of the laser cutting machine 2 and the

Entladestation 3 be provided two separate numerical control devices. The control programs for the programmable numeric

Controller 40 is typically generated using a programming system that runs on a separate computer. By means of the

Programming system, the orientation of the workpiece parts 16 within the workpiece 15 (nesting), the machining parameters for the cutting machining and the positioning of other machine components such as the fixtures 22, 23, 24 defined during and after processing.

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

Based on the conditions shown in FIG. 1 b is of the

Control device 40, the movement means 25 for moving the

Holding devices 22, 23, 24 activated to the workpiece part 16 by means of one or more of the surface suction cups 26, 27, 28 from the cutting area of

To move laser cutting machine 2 to the side in the direction of the discharge-side support table 9 and possibly then upward from the discharge side To remove support table 9. The number of used for moving

Surface suction cups 26, 27, 28 depends on the size and shape of the workpiece part 16. If the workpiece part 16 is surrounded differently than in Fig. 1 b shown by the skeleton 17, the skeleton grid 17 can parallel to the movement of the surface sucker 26, 27, 28 be moved by means of the cross rail 12 and the movement device 13 to the side. Relative movements between the residual grid 17 and the workpiece part 16 and relative movements between the workpiece part 16 and the surface suckers 26, 27, 28 should be avoided as completely as possible.

In order to achieve this, in the example shown, the first surface vacuum 26 transmits those suction devices 34 whose suction surfaces at least partially overlap with the workpiece part 16 (hereinafter referred to as effective suction devices 34a

referred to) acting in the direction of displacement Y lateral force FQ.I on the

Workpiece part 16, as described below with reference to FIG. 2a, b and with reference to FIG. 3 in more detail. In Fig. 2a, b was omitted for simplicity on the representation of the residual grating 17 and on the representation of the second surface suction 27. In addition, in order to simplify the following calculations, the presence of the second surface vacuum 27 has not been taken into account, i. it was assumed that only the first surface vacuum 26 transfers forces to the workpiece part 16 and absorbs forces from the workpiece part 16.

The of the effective suckers 34 a of the first surface suction 26 in the

Displacement direction Y transmittable to the workpiece part 16 transverse force FQ.I (see Fig. 3) is the same for all effective sucker 34 of the first surface vacuum 26. The transmittable lateral force FQ.I of an effective sucker 34a is dependent on the contact pressure of the effective sucker 34a and the first surface suction 26 on the workpiece part 16 and the coefficient of friction between the respective effective sucker 34a and the workpiece part 16, which u.a. of the

Surface texture of the workpiece part 16 is dependent. The action of the first surface vacuum 26 or of the individual effective suction elements 34a can be effected by applying or pressing the surface vacuum 26 or by additionally generating a vacuum with the aid of the vacuum generator of the surface vacuum 26. The values applicable in these cases for the transmittable shear force FQ.I one respective effective sucker 34a are typically determined in advance empirically by series of tests, ie the transmittable shear force FQJ is known in advance.

In order to ensure that the workpiece part 16 does not shift relative to the residual grid 17 during the displacement along the workpiece support 7, it is necessary in the programming system in the generation of the control program for the

Control device 40 to find a holding position HP of the first surface suction 26 relative to the workpiece part 16, in which for each individual effective sucker 34a, the transmittable transverse force FQ meets an evaluation criterion. A holding position HP of the first surface vacuum 26 is understood to be a position relative to the workpiece part 16, in which at least one of the suction elements 34a, more precisely at least one suction surface, at least partially overlaps the workpiece part 16.

In the holding position HP shown in Fig. 2a, b, a number nws of twelve effective suckers 34a with their respective circular suction surfaces completely overlaps with the workpiece part 16. A in Fig. 2a, b by a dashed line

Border limited, rectangular portion 36 of the first surface suction 26, more precisely, the suction plate 33, contains all the effective suction 34a, which are arranged uniformly distributed on the suction plate 33 in the example shown. The width B of the portion 36 corresponds to the width of the suction plate 33 and the length L of the portion 36 corresponds to an overlap length L shown in Fig. 1 b, along which the first surface suction cup 26 overlaps with the workpiece part 16.

In the following considerations, an evaluation criterion is used in which the from a respective sucker 34a in the direction of displacement Y on the

Workpiece part 16 transmittable transverse force FQJ is compared with a force acting on a respective sucker 34a against the direction Y resulting force Fresj.y, i. it is checked whether the following applies to all twelve effective suckers 34a:

F _Q , i> SF res, i, y _: where S denotes a safety factor (> 1) and i denotes the ith sucker 34a (i = 1, ... nws). If the stop position HP meets the above evaluation criterion, then this can Workpiece part 16 are moved reliably on the workpiece support 7, without causing undesirable movement of the workpiece part 16 relative to the residual grid 17.

In order to determine the proportion Fres, i, Y acting in opposition to the displacement direction Y, the resulting force Fres exerted on the displacement of the workpiece part 16 on a respective sucker 34a first determines the resulting force Fres on a respective effective sucker 34a. The resulting force Fresj is composed of the vectorial sum of a first force component FR, I and a second force component FTZ:

The first force component FR, I results from a (in simplified terms) acting on the center of gravity Sw of the workpiece part 16 total force FR ^* (here friction force), which counteracts the displacement direction Y in the example shown and the force acting on the flange between the workpiece part 16th and the brushes of the

Workpiece support 7 is due. For the frictional force FR ^* on the center of gravity Sw of the workpiece part 16, the following applies:

FR ^* = FN PB, where FN denotes the normal force shown in FIG. 1 b on the workpiece part 16, simplified to the center of gravity Sw of the workpiece part 16, and PB the coefficient of friction between the workpiece part 16 and the support brushes of the workpiece support 7. The normal force FN varies, depending on whether a vacuum is applied to the suckers 34a, whether the first surface vacuum 26 rests with its own weight or is pressed onto the workpiece part 16.

Subsequently, it is assumed that the first surface vacuum 26 rests with its own weight. In this case, the frictional force FR ^* applies:

FR ^* = (mw + ITIF * (nws / ns)) ^* g ^* PB, where mw is the mass of the workpiece part 16, ITIF the dead weight of the workpiece

Surface vacuum 26, g the gravitational acceleration (9.81 m / s ² ) and ns the Total number of suckers 34 of the first surface suction 26 (ns = 44 in the example shown).

The frictional force FR ^* acting counter to the displacement direction Y is distributed

uniformly on all effective suckers 34a, i. for the ith effective sucker 34a (see Fig. 3):

FR = FR ^* / nws (here: nws = 12).

The second force component FTZJ acting on an effective sucker 34a results from a moment Tz acting on the center of gravity Ss of the portion 36 with the effective suckers 34a (see Fig. 2b), which is displaced from the workpiece part 16 during displacement Shifting direction Y is generated. The moment T _{z is} calculated from the friction force FR of the workpiece part 16 multiplied by the distance LR, _X between the (area) center of gravity Sw of the workpiece part 16 and the (area) center of gravity Ss of the portion 36 with the effective suckers 34a in X- Direction, ie perpendicular to the displacement direction Y. For the calculation of the normal force FN, which is included in the friction force FR, only the weight of the workpiece part 16 is considered in this case, since the proportion of the normal force, which is introduced by the first surface suction 26, in Fulcrum lies, ie it applies:

FR = mw g PB and T _z = FR * LR, _X.

For from the moment Tz on the center of gravity Ss of the portion 36th

resulting force FT _Z on the ith effective sucker 34a is:

where n is the amount of the distance vector r \ between the centroid Ss of the portion 36 of the sucker plate 33 and the position of the i-th effective sucker 34a considered here, and n, _{x is} the X component and n, _{y is} the Y component of the distance vector designate r _t . For the force Fres resulting from the first force component FR and from the second force component FTZ.I, more precisely for its X component Fres, x or for its Y component Fres.i, Y, the following applies:

where Fres.i denotes the amount of the resultant force F _{res i} , ie, res, i

As described above, for the comparison with the transmittable lateral force FQ in the present case where the displacement is in the Y direction, the Y component Fres.i, _{y of} the resultant force Fres.i with the transmittable one

Transverse force FQJ compared. It is understood that, in the case of a displacement along a displacement direction which does not run in the Y direction, according to the above procedure, the portion of the resultant force F _{res [} 'acting counter to the direction of displacement is used for the comparison.

In the example described in Fig. 2a, b and Fig. 3, the condition FQJ> S Fres, Y is satisfied for all the effective suckers 34a, i. the (initial) holding position HP is judged suitable for the displacement of the workpiece part 16. If the evaluation carried out in the manner described above is an appropriate one

Holding position HP found, this is stored in the numerical control command set. During the processing of the workpiece part 16 or after its free cut, the numerical control unit 40 controls the

Moving device 13 to move the first surface suction cup 26 to the holding position HP shown in Fig. 2a, b relative to the workpiece part 16 and put this with the effective suckers 34a on the workpiece part 16 to move the workpiece part 16 along the workpiece support 7. In the event that not all effective suckers 34a in the partial area 36 of the first planar vacuum 26 overlapping with the workpiece part 16 at the (initial) holding position HP meet the evaluation criterion, the evaluation of the holding position HP can be repeated by counting in the calculation of FIG the effective suckers 34a transmitted forces remain those suckers 34a disregarded, for the first step, the evaluation criterion has not been met. If, under these changed (tightened) conditions, the evaluation criterion for all remaining effective suckers 34a is fulfilled, the holding position HP is evaluated as suitable.

Can no suitable holding position can be found in this way, the holding position HP of the surface suction 26 is changed relative to the workpiece part 16 in the programming system. For example, in this case the number of effective suckers 34a or the overlapping partial area 36 can be increased. Also, while maintaining the number of effective suckers 34a, it may be attempted by changing the positioning of the planar suction pad 26 relative to that

To achieve workpiece part 16 that the evaluation criterion is met.

In all these cases, a hold position HP suitable for shifting is determined iteratively, i. the holding position HP used for the comparison with the evaluation criterion is changed until a suitable stop position HP is found or until an abort criterion is reached. In the simplest case, the termination criterion corresponds to a predetermined number of iterations. In the event that no suitable stop position HP is found, a

Warning message may be issued, that during the shift may be 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 flattening devices 22, 23, 24 are implemented with variably positionable suckers instead of a surface suction, a change of the suction arrangement is also possible.

The method described above for finding a suitable

Holding position HP can be applied analogously to the case that the workpiece part 16 is not moved along the workpiece support 7, but with Help the first surface vacuum cleaner 26 is carried or transported without the workpiece part 16 is supported by the workpiece support 7 here. Such a transport of the workpiece part 3 can also take place with the aid of the unloading station 3 of the mechanical arrangement 1, as shown below with reference to FIG. 4. After removal of the workpiece part 16 from the discharge side support table up this is held by one or more surface suckers, in the example shown by the first and second surface suction 26, 27. To simplify the calculations, as in the case described above, consider an example in which the workpiece part is held only by the first surface suction cup 26.

For the first surface vacuum cleaner 26, the conditions shown in Fig. 5b arise. In the hold position HP of the surface vacuum 26 shown in Fig. 5b, all of the suckers 34 are effective, i. these overlap with the workpiece part 16. The portion 36 with the effective suckers 34a thus corresponds to the entire surface of the suction plate 33. If the workpiece part 16 of several

Surface suckers 26, 27, 28 held, so the effective suckers 34a of the surface suckers 26, 27, 28 together form the portion 36th

When holding or during transport of the workpiece part 16 in the vertical direction Z 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, the weight FG = m _w g and possibly an acceleration force in the Z direction Fz = ± a _z mw. The total force FR * in the Z direction in the movement of the workpiece part 16 is thus FR * = FG + Fz. As described above, the total force FR * is divided evenly among the effective suckers 34a, ie it applies to the i-th sucker:

FR.ZI = FR ^* / nws (here: nws = 8).

In addition to the total force FR * acts on the center of gravity Ss of the suction plate 33 and a moment T _g , _z , which analogous to the case described above to a force acting in the Z direction (transverse) force F _g , _z , i on the i-th effective sucker 34a leads. The force Fg, _z , i is analogous to the case described above of the distance vector r _t between the center of gravity Ss of the sucker plate 33 and the position of the ith effective sucker 34a.

The Z component of the resulting force Fres. is composed of the two force components described above, ie it applies: Fres, i, z = FRJ.Z + F _g , i, _z For the secure holding of the workpiece part 16 on the surface suction 26, the holding force FH of the ith must Sucker 34a meet the following condition:

FH, i S Fres, i, z.

In the event that the workpiece part 16 is additionally to be moved or transported parallel to the workpiece support 7 along a transport direction in the horizontal direction, ie in a plane containing the X direction and the Y direction, those apply further above for the Z direction given equations continue. In addition, a resultant force Fres, i, x _y acts in the plane parallel to the workpiece support composed of an X-directional component Fresj.x and a Y-directional component Fres.y. The resulting force force Fres, i, xy IP

The horizontal direction is determined analogously to the resulting force Fres.i in the Z direction, i. the equations given above can be applied analogously, only the weight force FG is not taken into account, since it acts perpendicular to the XY plane.

For the ratios described in FIG. 5a, the proportion of the first force component in the X direction or in the Y direction thus applies:

FR, X, I = ± a _x mw / nws or

F _R , y, i = ± a _y mw / nws.

Correspondingly, a moment T _x or T _{y leads} to the center of gravity Ss of the suction plate 33, analogous to the case described above, to a (transverse) force FT _X J or Fj _y acting in the X direction and in the Y direction, respectively the i-th sucker 34a. The two parts Fresj.x and Fresj.y the resulting force Fres.xy in the X or Y direction in the plane parallel to the workpiece support 7 are made up of the two

Force components together, ie it applies: Fres, i, x - FR, I, X + FTX.I bZW.

Fres, i, y ⁼ FR, i, y + Fl, y, i.

For comparison with the transverse force FQ.I transmittable in the horizontal direction or in the (XY) plane at a single sucker 34a, the magnitude of the resulting force Fres.xyj is typically determined, for which the following applies:

For the evaluation criterion, similarly to the case of shifting described above, the amount of lateral force FQJ at a respective sucker 34a must exceed the magnitude of the resultant force Fresj.xy, typically taking into account a safety factor S, i. it applies:

FQ, I> S Fres, i, xy.

As described above, the holding position HP is judged to be suitable for carrying or transporting the workpiece part 16 when the

Evaluation criteria for the holding force FHJ and for the lateral force FQJ for all effective suckers 34a is met. Since the acceleration forces ax, ay, a _z possibly change with time during the transport of the workpiece part 16, the values of the acceleration 3x, max, 3y, max, 3z, max which occur during transport at the maximum can be used for the comparison.

In the method described above, the number and the arrangement of the suction cups 34 on the suction plate 33 is basically arbitrary. In general, however, a larger number of suckers 34 is used as shown in the figures. For example, a sucker plate may have a number of 42 x 11 (passive) suckers 34. The diameter of the suction surface of a respective vacuum cleaner 34 may be, for example, on the order of about 10 mm. Depending on the geometry of the workpiece part 16, it may not be possible to ensure that all effective suckers 34 completely overlap with the workpiece part 16 with their (usually round) suction surfaces. As can be seen in FIG. 5 a, the two right outer suckers 34 a of the suction plate 36 only partially overlap with the workpiece part 16. Accordingly, the two suckers 34 a can not transfer the entire transverse force FQ 1 or the entire holding force F HJ to the workpiece part 16 as would be the case with a complete overlap of the suckers 34a with the workpiece part 16. In order to take this circumstance into account, the value of the transverse force FQJ or holding force FH transmittable by the two outer suckers 34a on the workpiece part 16 is multiplied by a factor f (<1), for example by a factor f = 0, for comparison with the evaluation criterion ; 5. Since the evaluation criterion for all effective suckers 34a must be satisfied, the use of only partially intersecting effective suckers 34a aggravates the requirements for finding a suitable holding position HP. The evaluation rule described above can in principle for all

Processes are used in which it must be decided whether the fixation of a (planar) part, for example, a workpiece part, which must be moved via a holding force and / or friction at discrete points or positions (here: suction 34) in a spatial direction, can be done reliably or not.

Claims

claims

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 means of the holding means (26, 27, 28) on a workpiece support (7) to be moved or by means of the holding means (26, 27, 28) to be supported workpiece part (16), 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 the workpiece part (16) in order to act as an effective holding element (34a) on the workpiece part (16) to act,

b) determining one of the workpiece part (16) when moved or carried on a respective effective holding element (34 a)

resulting force (Fresj, Fresj, z, Fresj, _xy ),

c) evaluating the holding position (HP) as suitable for the displacement or carrying the workpiece part (16), if for each effective holding elements (34a) each from the effective holding element (34a) on the workpiece part to be displaced (16) in the direction of displacement (Y ) transmittable transverse force FQJ or a holding force FHJ and / or transverse force FQJ transmittable respectively to the workpiece part (16) to be supported in a transport direction (Z, X, Y) from the resulting force (Fresj; Fresj, z, Fres, i, xy ) dependent evaluation criterion.

2. The method of claim 1, wherein the evaluation criterion is determined by the amount of the resultant force Fresj, _y ; Fresj, _z ; Fresj, _xy against the direction of displacement (Y) or against the transport direction (Z, X, Y) multiplied by a

Safety factor S is formed and is satisfied, if:

FQ J> S Fres, i, y and / or FH J> S Fres, i, z and / or FQ, i> S Fres.i.xy,

with S> 1.

3. The method of claim 1 or 2, wherein in the event that in step c), the holding position (HP) as not suitable for moving or carrying the Workpiece part (16) is evaluated, the steps a) to c) are repeated with an altered number of effective holding elements (34 a) and / or with a changed holding position (HP) until the specified

Hold position (HP) meets the evaluation criterion.

A method according to any one of the preceding claims, wherein the resultant force (Fres, i! Fres.i.z, Fres, i, xy) is expressed as a vectorial sum of a first

Force component (FR ,,; FR, FR, FRJ.Y) and a second force component (FTZJ; FTX.I, F _Ty , i) is determined, wherein the first force component (FR ,, FR., FRJ.X , FR, i, _y ) results from a total force (FR ^* ) acting on the center of gravity (Sw) of the workpiece part (16) to be displaced or supported, and wherein the second force component (FTZ.I; FTX, FTy _, ) is a transverse force (FTZ.I) on a respective effective holding element (34a), the torque acting on the center of gravity (Ss) of all effective holding elements (34a) containing portion (36) of the holding device (26, 27, 28) acting torque (Tz, _{Tg, z} , Tx, _Ty ) results.

5. The method of claim 4, wherein the first force component (FRJ) of the

resulting force (Fres) is determined by the total force (FR ^* ) acting on the center of gravity (Ss) of the workpiece part (16) to be displaced or supported is divided equally between the effective holding elements (34a).

6. The method according to claim 4 or 5, wherein for finding the holding position (HP) for moving the workpiece part (16), the total force (FR *) in the form of a counter to a direction of displacement (Y) acting frictional force is determined by a weight force (gm _w ) of the workpiece part (16) on the

Workpiece support (7) and a compressive force (g ITIF nws / ns)) of the effective

Holding elements (34 a) on the workpiece part (16) is generated.

7. The method of claim 4 or 5, wherein for finding the holding position (HP) for supporting the workpiece part (16), the total force (FR ^* ) as the

vectorial sum of an acceleration force (m _w az; m _w a _x ; m _w a _y ) acting counter to a transport direction (Z, X, Y) in the center of gravity (Sw) of the

Workpiece part (16) and one opposite to a transport direction (Z) on the Workpiece part (16) acting weight (mw g) in the center of gravity (Sw) of the workpiece part (16) is determined.

8. The method according to any one of claims 4 to 7, wherein the second

Force component (FT _Z J, FT _X J, FT _{y, i} ) by means of a torque (Tz, T _{g, z} , Tx, T _y ) is determined, when moving the workpiece part (16) in a

Displacement direction (Y) or when transporting the workpiece part (16) in a transport direction (Z, X, Y) of the workpiece part (16) on the center of gravity (Ss) of the effective area elements (34a) containing portion (36) is applied.

9. The method according to claim 8, wherein for locating the holding position (HP) for displacing the workpiece part (16), the torque (Tz) exerted on the center of gravity (Ss) of the subregion (36) is determined from a frictional force (FR) of the workpiece part (16). 16) (on the workpiece support 7) and a distance (LR, _x; _z l_, L _x, L _y) (Ss between the gravity center) of the portion (36) and a

Center of gravity (Sw) of the workpiece part (16) along the displacement direction (Y; Z, X, Y) is determined.

10. The method according to claim 8, wherein for finding the holding position (HP) for supporting the workpiece part (16) on the center of gravity (Ss) of the

Teilbereich (36) applied torque (T _{g, z} , Tx, T _y ) from the on the

Center of gravity (Sw) of the workpiece part (16) to be supported acting total force (FR) and a distance (L _z , L _x , LY) between the center of gravity (Sw) of the workpiece part to be supported (16) and the center of gravity (Ss) of the Subarea (36) is determined.

A method according to any one of the preceding claims, wherein for finding the holding position (HP) for supporting the workpiece part (16), comparing the resultant force (Fresj; Fres, i, _xy , Fresj, _z ) with the lateral force (FQJ ) in the horizontal direction (X, Y) and comparing the resultant force (Fresj, _xy , Fresj, _z ) with the holding force (FHJ) in the vertical direction (Z) individually.

12. The method according to any one of the preceding claims, wherein in a partial overlap of effective holding elements (34 a) with the

Workpiece part (16) by this effective holding elements (34a) on the workpiece to be displaced part (16) transferable transverse force (FQ) or on the workpiece to be transported workpiece (16) transferable holding and / or transverse force (FH; FQJ) by a predetermined factor is reduced.

13. Computer program product, which is used to carry out all steps of the

Method according to one of the preceding claims is formed when the computer program runs on a data processing system.