DESIGN OF GRIPPING TOOLS FOR A LASER CUTTING MACHINE FOR SORTING PARTS

Abstract

A design unit and a computer-implemented method for calculating a design data set for designing a part-specific gripping tool for gripping parts that have to be transported from or to a processing machine is disclosed. The method includes the steps of providing part parameters for at least one part which is to be gripped with the part-specific gripping tool and executing a design algorithm which designs the part-specific gripping tool from the part parameters provided and thereby outputs a gripping tool data set as a result.

Claims

1. A computer-implemented method for calculating a design data set (kds) for designing a part-specific gripping tool (W) for gripping parts (P) that have to be transported from or to a processing machine (L), having the following method steps: providing (S1) part parameters (pp) for at least one part (P) which is to be gripped with the part-specific gripping tool (W); executing (S3) a design algorithm (KA) which designs the part-specific gripping tool (W) from the part parameters (pp) provided and thereby provides a gripping tool data set (gds) as a result, wherein in response to the provided gripping tool data set (gds), a database (DB) is accessed in which availability data (vds) is stored which represents which gripping tools (W) and/or which gripping tool components (K) are locally are currently available on the processing machine (L) in order to check (S4) whether the gripping tool (W) designed for the part to be gripped is locally available with the components (K) and, if so, assembly instructions are calculated in order to be able to assemble the part-specific gripping tool (W).

2. The computer-implemented method according to claim 1, in which the part parameters (pp) comprise: a weight and/or a centre of gravity of the part (P), cut-outs or projections in the part and/or bending-relevant parameters and/or other design parameters and/or material-based parameters of the part (P).

3. The computer-implemented method according to claim 1, in which the design algorithm (KA) is in two parts and comprises a gripper determination function (GBF) for determining the type, size and/or number of minimal required grippers and a position calculation function (PBF) for determining the position of each gripper.

4. The computer-implemented method according to claim 3, in which a position specification for a component (K) of the gripping tool (W) can be configured in the position calculation function (PBF).

5. The computer-implemented method according to claim 3, in which at least one acceleration value is processed as an input variable in the position calculation function (PBF) and/or in which the position calculation function (PBF) executes a brute force algorithm, a randomised algorithm and/or a mixed form.

6. (canceled)

7. The computer-implemented method according to claim 1, in which a design data set (kds) is calculated (S6) from the gripping tool data set (gds) if the designed gripping tool (W) is not locally available with its components.

8. The computer-implemented method according to claim 1, in which the design data set (kds) contains a parts list for the designed gripping tool (W) with components (K) and connecting parts and in particular designs a gripper holder (10, 30).

9. The computer-implemented method according to claim 1, in which the gripping tool (W) has a modular structure from a quantity of gripping tool components (K) and/or is operated by a robot as part of a pick-and-place application.

10. The computer-implemented method according to claim 1, in which, in addition to the part parameters (pp), an electronic cutting plan (sp) of the processing machine (L), which is designed as a cutting machine, is provided for executing the design algorithm (KA).

11. The computer-implemented method according to claim 1, in which an error message is generated and output if it is not possible to design the gripping tool (W) for the part (P) to be gripped.

12. The computer-implemented method according to claim 1, in which an interface to an ordering application is formed, so that, in response to an instruction signal, an automatic ordering process can be triggered for the gripping tool (W) designed according to the design data set (kds).

13. The computer-implemented method according to claim 1, further comprising a computer program product which can be loaded into an internal memory of a digital computer, the computer program comprising computer program sections, with which the method according to the preceding method claim 1 is executed when the computer program sections are executed on the digital computer.

14. A design unit (KO) for calculating a design data set (kds) for designing a part-specific gripping tool (W) for gripping parts (P) that have to be transported from or to a processing machine (L) having: an import interface (ES) for providing part parameters (pp) for at least one part (P) to be gripped which is processed by the processing machine (L); a processing unit (CPU) which, in response to the provided part parameters (pp), is intended to execute a design algorithm (KA) that designs the part-specific gripping tool (W) using the imported part parameters (pp) and provides a gripping tool data set (gds) as a result, wherein in response to the provided gripping tool data set (gds), a database (DB) is accessed in which availability data (vds) is stored which represents which gripping tools (W) and/or which gripping tool components (K) are locally are currently available on the processing machine (L) in order to check whether the gripping tool (W) designed for the part to be gripped is locally available with the components (K) and, if so, assembly instructions are calculated in order to be able to assemble the part-specific gripping tool (W).

15. A processing machine (L) having a design unit (KO) according to claim 14.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0042] Further advantages features and details of the various embodiments of this disclosure will become apparent from the ensuing description of a preferred exemplary embodiment or embodiments and further with the aid of the drawings. The features and combinations of features recited below in the description, as well as the features and feature combination shown after that in the drawing description or in the drawings alone, may be used not only in the particular combination recited but also in other combinations on their own without departing from the scope of the disclosure.

[0043] The following is an advantageous embodiment of the invention with reference to the accompanying figures, wherein:

[0044] FIG. 1 depicts a view of a laser cutting machine with a shuttle table on which cut parts are positioned and must be sorted by a robot-based gripping device;

[0045] FIG. 2 depicts a schematic view of a computer unit which is designed as a design unit KO and is determined on the basis of the parts parameters for calculating a design data set;

[0046] FIG. 3 depicts a flowchart of a method according to a preferred embodiment of the invention;

[0047] FIGS. 4a and 4b each depict a side view of a gripping device with a one- and two-element gripping tool according to a preferred embodiment of the invention;

[0048] FIG. 5 depicts an example of a sheet metal part with cut-outs for calculating the positioning of the gripper(s);

[0049] FIG. 6 depicts a further example of a sheet metal part with cut-outs for calculating the positioning of the gripper(s);

[0050] FIG. 7 depicts a further example of a sheet metal part with cut-outs for calculating the positioning of the gripper(s); and

[0051] FIG. 8 depicts an alternative form of the gripper holder in the form of a U-rail according to a preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0052] As used throughout the present disclosure, unless specifically stated otherwise, the term “or” encompasses all possible combinations, except where infeasible. For example, the expression “A or B” shall mean A alone, B alone, or A and B together. If it is stated that a component includes “A, B, or C”, then, unless specifically stated otherwise or infeasible, the component may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. Expressions such as “at least one of” do not necessarily modify an entirety of the following list and do not necessarily modify each member of the list, such that “at least one of “A, B, and C” should be understood as including not only one of A, only one of B, only one of C, or any combination of A, B, and C.

[0053] FIG. 1 depicts an exemplary view of a shuttle table WT for a laser processing machine, in particular a laser cutting system L, on which cut parts P are positioned, which must be gripped and transported from there by means of a robot-based gripping device, in particular the parts P must be removed from the scrap skeleton and, for example, stacked on pallets. Depending on the cutting plan, different types (shapes, sizes) of parts P can be transported and thus also gripped.

[0054] Depending on the size, shape and other parameters of the part P, different gripping tools W are necessary in order to be able to fulfil the gripping task. For example, large and heavy parts P require more or more powerful gripping tools W, in particular with correspondingly more or more powerful gripper components (for example mechanical, magnetic or pneumatic suckers) than small, light parts. According to the invention, the design of the gripping tool W is advantageously part-specific. A first quantity of parts P.sub.1 is thus gripped by a first gripping tool W.sub.1, while a second quantity of parts P.sub.2 is gripped by a second gripping tool W.sub.2, etc. The quantity is characterised by the respective part parameter P. The part parameters P can be partially or completely calculated from the cutting plan of the laser processing machine.

[0055] The gripping tool W can be attached to a robot arm via a connection element, such as a so-called gripper holder or a gripper plate. The robot arm with the gripping tool W, which is movable in the three spatial axes, forms a gripping device.

[0056] In a preferred embodiment of the invention, the gripper plate 30 (FIG. 4a) or the gripper holder (rail) 40 (FIG. 4b), 10 (FIG. 8) is automatically designed if no standard parts (e.g. sucker 80) are available or can be used for the pending gripping task. The gripper plate 30, 40 is designed so that the necessary components K can be attached to the position calculated (by the position calculation function PBF).

[0057] Basically, the end customers of laser cutting systems manufacture sheet metal parts in a broad and unpredictable array of variations. The cut parts P are then removed from a sorting device by means of (for example vacuum and/or magnetic) gripping tools and placed on a pallet. For this purpose, a limited number of prepared gripping devices can be offered in the known systems. The problem with the systems known in the prior art is that these gripping devices cannot fit all possible parts (for example because a suction cup could be positioned over a hole or the gripper does not cover the part geometry). Another problem is that the necessary design knowledge is often not available for the design of new, suitable gripping devices. This is where the invention comes in and provides a method (as a use or application) and a design unit KO which automatically designs a suitable gripper and outputs it as a 3D file with a parts list at the end. An electronic description (e.g. STEP file) of a sheet metal part is loaded into the application. The application checks whether existing grippers are available or can be provided on site. If no existing gripper fits, a suitable gripping tool G is automatically designed. The method makes use of a database of components, in particular based on the modular principle, in order to automatically design the gripper. For example, various (suckers, magnets, hoses, base plates, etc.) are stored. In the design algorithm, factors such as the dimensions of the piece, weight, centre of gravity, cut-outs and/or bending problems are calculated and taken into account. After the gripper has been designed, a finished assembly is output as an electronic description (e.g. STEP file) including a parts list.

[0058] Advantageously, several parts P of a cutting plan sp or even several cutting plans are taken into account in the design of the gripping tool. The method can thus be carried out very efficiently in that—if possible—sometimes only one gripping tool has to be calculated and provided for a quantity of different cutting plans. It is therefore not necessary to change the gripping robot and the gripping task can also be carried out for different parts P and/or for different cutting plans by the same gripping tool.

[0059] For this purpose, the invention executes a design algorithm KA on a computer unit CPU (e.g. a computer, a computer network, processor, microprocessor or an embedded device).

[0060] FIG. 2 shows, in the manner of a block diagram, a design unit KO which is intended as an electronic unit for carrying out the method. The design unit KO comprises an import interface ES for importing part parameters pp for at least one part P to be gripped which is processed by the processing machine L and a processing unit CPU which, in response to the imported part parameters pp, is intended to execute the design algorithm KA that can design the part-specific gripping tool W from the imported part parameters pp and provide a gripping tool data set gds as a result—in particular on a user interface UI—or execute further calculation steps. If no gripping tool can be designed for the required gripping task, an error message can be output on the user interface UI. As shown schematically in FIG. 2, the calculated gripping tool data set gds can be further processed in the design unit KO. For this purpose, availability data or an availability data set vds can also be imported from a database DB, which represents the local availability of gripping tools W and their components K on or at or for the laser L. The two data sets: the gripping tool data set gds and the availability data set vds are calculated using a further algorithm to produce a result in the form of a design data set kds. The design data set kds specifies the specifications according to which the gripping tool W must be designed. For this purpose, the design data set kds contains design instructions and a selection of required gripping components K as well as positioning information for the required gripping components K. This has the advantage that the design data set kds only needs to be calculated if the required specification of the gripping tool W is not available. Computing resources can thus be saved.

[0061] As shown schematically in FIG. 2, a cutting plan sp can also be imported. The part parameters pp can be calculated from the cutting plan sp by means of a further algorithm. It is possible to import both the part parameters pp and the cutting plan sp in order, for example, to verify the correctness of the imported part parameters pp using the data from the cutting plan sp. Alternatively, only the cutting plan sp or only the part parameters pp can be imported. The imported data (part parameters pp and/or cutting plan sp) can also be imported as a STEP file.

[0062] The database DB can, as in the example shown in FIG. 2, be connected to the design unit KO as an external, separate entity via appropriate data connections (LAN; WLAN) and, for example, be provided centrally. The database DB can, however, also be designed internally and locally on the design unit KO. The same applies to the user interface UI. It can be formed locally on the design unit KO or on another electronic entity, for example on a mobile unit with corresponding data connections (smartphone, etc.).

[0063] As shown in FIG. 2, the design unit KO can interact with a model M. The model M contains electronic data sets which characterise the mechanical properties of the respective part P, such as the centre of gravity, weight, length, width and/or other part-specific parameters that specify a certain gripping tool for a certain gripping task. The model M can be designed to be self-learning and can be fed with the calculated gripping tool data set gds and/or design data set kds as feedback variables. Furthermore, other feedback variables can be taken into account, such as an evaluation by the user about the quality of the automatic design.

[0064] FIG. 3 shows the sequence of the method according to a preferred embodiment of the invention. After the start of the method, the part parameters are imported via the import interface ES in step S1. Additionally or alternatively, the cutting plan sp can be imported in step S2. It is also possible that the cutting plan or at least parts thereof are contained in the part parameters and thus only the cutting plan sp, possibly with selected part parameters pp, is imported in step S1. In step S3, the design algorithm KA is executed with the imported data and the gripping tool data set gds is provided. In the simplest case, the gripping tool data set gds can consist of a quantity of standard parts that are in stock for the robot arm. The robot then only has to select the standard parts from a store and position them in the correct position, which is done on the basis of the calculated position. In step S4, the local availability of the designed gripping tool W with its components K is checked. If this is available for the respective gripping task for the part P gripping tool W to be gripped, no design data set kds has to be created. It is only necessary that a command be generated in step S5 with which, for example, the robot or another actuator selects and removes the gripping tool W or its parts or components K from the store. Otherwise, if the necessary components K are not in stock and the gripping tool W has to be specially designed, the design data set kds is calculated in step S6 and can be output on the user interface UI and/or passed on to other electronic entities as a file, in particular a STEP file. It is also possible that no gripping tool for the respective part P can be designed for the gripping task (e.g. too heavy, too big, etc.). In this case, the error message is output in step S7 (for example on the UI) and/or made available to other entities.

[0065] FIGS. 4a and b show the structure of a gripping device. This includes a robot-based actuator (e.g. robot arm, not shown), which is connected to the gripping device via a coupling 50. The gripping device contains the gripping tool W, which is designed here as a sucker 80. The gripping device also contains a flange 20, a pneumatic distributor 100, a pneumatic connection 90 and a spring plunger 70. The gripping device comprises a gripper plate or a differently shaped gripper holder (for example a U-shaped rail) on which—in this example two—suckers 80 are positioned and fastened. FIG. 4b shows a gripping device with a U-shaped mounting bracket 40, which in this case is designed as a gripper holder and serves to receive and attach a sucker. The mounting bracket 40 can be connected to the coupling 50 via a washer 110 and a ring 120. In this example, the gripping device comprises a stopper 10, screws 160 and, on the lower part of the mounting bracket 40, further washers 130 and nuts 140 for fastening the part-specific sucker. Further connection modules can be used to hold the modular gripping components K, for example the sucker 80. The gripping components K can basically comprise different types of suckers 80 (pneumatic, magnetic, adhesive, etc.) and/or other (for example mechanical) gripping components K. The components K are selected specifically for the respective gripping task in relation to the part P to be gripped.

[0066] In summary, a method (and a corresponding device) is provided that uses an input design (e.g. STEP of a part or sheet metal part) to determine whether and which of the existing gripping components (e.g. gripping heads) would fit on the part. If no existing components fit, the software automatically designs a suitable gripper head using the supplied database of pieces. This means that the method outputs a finished assembly (e.g. as a STEP file including parts list) as the result. When calculating using the design algorithm, factors such as the dimension of the piece, weight and/or bending-specific parameters and problems are taken into account. The procedure also communicates the reasons why an automatic design is not possible in certain cases.

[0067] The design algorithm KA comprises at least two functions:

1. a gripper determination function GBF and
2. a position calculation function PBF.

[0068] The position calculation function PBF can be implemented using a brute force algorithm. The brute force algorithm is based on the following aspects, which are explained in connection with the schematic drawing of FIG. 5:

1. In order to calculate the optimal position of the gripper head on the sheet metal part, the possible positions that the vacuum gripper could have are successively checked. FIG. 5 shows the simulation of the search for the positions of a vacuum gripper.
2. The distance between the circles when searching for possible positions can be parametrised. For example, in FIG. 5, the two circles at the top left are more spaced apart than the circles that follow on the right. The greater the distance between the circles, the faster the search will be, but the lower the chance of finding a good solution.
3. If no or no good solution is found (for example, the top row of the circles is represented by a dashed line in FIG. 5), the process can be repeated with a smaller distance in order to find more possible positions.
4. After the possible positions have been obtained (see the dotted circles in FIG. 5, in this example 3/three positions), a head base is sought that matches the positions of the vacuum grippers that have been found.
5. If there is no existing gripper head, the optimal solution is chosen by the system to generate a new gripper head.

[0069] A further, second possibility to implement the position calculation function consists of the randomised algorithm, which is explained below with reference to FIG. 6:

In this second proposal (see FIG. 6), the suction cup positions are generated according to the random principle (all circles). As in the Monte Carlo simulation, a large number of random values are generated which are then compared to see whether or not they are possible candidates.
1. A large number of random values are generated for the possible sucker positions. In FIG. 6, the dashed thin circles represent positions which do not meet the requirements; and the dash-dotted circles in bold are positions that meet the requirements (in this example 3/three positions).
2. After the possible positions have been obtained (see the bold, dash-dotted circles in FIG. 6), a gripper head is sought that matches one of the vacuum positions found.
3. If there is no possible solution, the optimal solution is chosen, which is a new gripper head.

[0070] A further, third possibility to implement the position calculation function consists of the mixing algorithm, which is explained below with reference to FIG. 7:

One of the major disadvantages of the algorithms mentioned above is that the system has to determine a very large number of possible positions in order to obtain an (almost) optimal solution. The system therefore has a certain percentage inaccuracy. The third version is a mixture of the two previous versions that tries to take advantage of both versions.

[0071] The process starts with the second proposed version (calculate positions—random principle). First, the possible positions of the vacuum grippers are searched for at random (as explained above). From the possible positions found, the brute force algorithm calculates the possible positions in the vicinity of the point found in order to find the best possible positions for lifting the sheet metal part. Not only does this increase the likelihood of finding a better position, but it also makes the process a lot faster.

[0072] In addition, there are other implementation options for the position calculation function in the application of methods of artificial intelligence, deep learning, etc. Furthermore, physical models can be used to calculate the deflection of the parts or standard formulas to position the suckers so that no or little deflection arises when removing.

[0073] FIG. 8 shows a further example of a gripper holder in the form of an interchangeable frame, which is identified here with the reference numeral 10. Bores 50 can be formed in the interchangeable frame in order to receive further connection elements, as explained above in connection with FIGS. 4a and b.

[0074] Finally, it should be noted that the description of the invention and the exemplary embodiments are not to be understood as limiting in terms of a particular physical realisation of the invention. All of the features explained and shown in connection with individual embodiments of the invention can be provided in different combinations in the subject matter according to the invention to simultaneously realise their advantageous effects.

[0075] The scope of protection of the present invention is given by the claims and is not limited by the features illustrated in the description or shown in the figures.

[0076] It is particularly obvious to a person skilled in the art that the invention can be used not only for laser cutting systems, but also for other machines and systems in production that require parts or components to be gripped. Furthermore, the components of the device or design unit can be produced so as to be distributed over several physical products.