CABLE ROBOT 3D PRINTER AND METHOD FOR POSITION DETECTION AND POSITION CHANGE OF THE PRINT HEAD OF A CABLE ROBOT 3D PRINTER

Description

[0001] Cable robot 3D printers are particularly suitable for printing sensitive objects, such as prostheses and for producing bone replacements or for printing biomaterials or organs.

[0002] 3D printing has been successfully used in various industrial sectors for some time now. Geometrically complex objects that previously required high material consumption and required the production of forming or subtractive tools can now be designed and manufactured additively using computer-aided technology, meaning virtually no material loss.

[0003] To date, the initial attempt has usually been to replace defects resulting from trauma or surgery with a so-called autograft, i.e., bone taken from other parts of the patient's skeleton. The production of bone substitutes is highly complicated and risky. The disadvantages of this procedure are obvious: On the one hand, humans only have a limited amount of bone material available for this purpose, and on the other hand, the results are not always functionally precise or, as in the case of maxillofacial surgery, are often cosmetically unsatisfactory.

[0004] 3D printers and cable robots are already known which, on the one hand, divide the object to be produced into layers and, on the other hand, have complex cable reversals and thus longer cable lengths, which do not allow for individual and precise 3D printing.

[0005] For example, DE 10 2014 015 335 A1 discloses a generative manufacturing device for the layered construction of structures, which device has a dispensing head with at least one dispensing nozzle for curable starting material. The dispensing head is fluidly connected to a starting material source, and a drive device for the dispensing head is provided to move the dispensing nozzle of the dispensing head to predetermined target positions within a predetermined working space. The drive device is a cable robot.

[0006] Furthermore, Toru Makino and Takashi Harada in "Cable collision avoidance of a pulley embedded cable-driven parallel robot by kinematic redundancy" (http: / / dx.doi.org / 10.1145 / 3029610.3029620) disclose a novel parallel robot with eight redundant cable drives to avoid collisions between the cables.

[0007] The object of the invention is to create a 3D printer to produce, for example, bone replacements or organ replacements or other objects such as prostheses from biocompatible materials.

[0008] The problem is solved by a cable robot 3D printer having the features according to independent claim 1. Further developments are specified in the respective dependent claims.

[0009] The first end of the cables or straps is detachably attached to the print head, which is advantageous for maintenance or repair purposes, for example. This cable-based robot 3D printer is capable of producing millimeter-accurate or highly precise bone replications from organic biomaterial, for example. The eight cables on which the print head is suspended allow the print head to be freely moved and pivoted within the workspace in six axes with high precision. The eight cables are each controlled separately by a gear motor.

[0010] The printing process is genuinely three-dimensional, meaning it is original or true to the original, unlike previous systems available on the market, in which the object to be produced is divided into layers and then materialized layer by layer. For example, a customized CT scan taken directly from the patient serves as a template for the bone part to be replicated. The print head can also be positioned at an angle or twist.

[0011] With the cable robot 3D printer, complex geometries can be produced tailored to the patient without material loss and without the need for a mold. The material is synthesized as a porous structure during the printing process. This replicates or prints a spongy structure, similar to bone, or a net-like trabecular structure. After transplantation, the surrounding tissue bonds with the artificial bone. The spaces between the porous tissue are penetrated by blood vessels and filled with cells, allowing the body to form natural bone after the organic plastic or material, such as natural calcium, has been broken down or absorbed. Natural calcium can obviously contain a suitable binding agent, if necessary, to maintain the necessary stability and structure.

[0012] The printed biomaterial eliminates the need for the traditional removal of autologous bone material. Potential rejection reactions to the implanted foreign bodies are also largely avoided.

[0013] To reinforce the structure to be printed, titanium rods can be incorporated during printing so that the bone replacement or bone replications can bear full load immediately after insertion, or in areas subject to high stress. At least one mechanical gripping device can be provided on the print head for this purpose.

[0014] Other aids may also be provided.

[0015] If necessary, a milling tool removes the disruptive surface structure of the 3D print. This ensures that the printed object, i.e., the bone replacement or bone replication, achieves the smooth shape of the respective digital template. Furthermore, if necessary, the appropriate milling tool can be used to subsequently add additional machining, such as holes, grooves, etc., to the finished surface structure of the 3D-printed object, ensuring that the printed object already has the necessary connections for later screwing or assembling a joint.

[0016] To ensure a smooth surgical process, once a printing process has been completed, the system, unlike conventional 3D printers that have significantly more mechanical parts, can be easily disassembled and sterilized together with the rest of the surgical instruments in the disinfection systems already in place in the surgical departments, ensuring that a completely germ-free apparatus is available for the next printing process.

[0017] The printed object is created in a completely enclosed workspace. The workspace can be separated or sealed accordingly and is sterile. This prevents environmental influences such as dust, dirt, and bacteria. It can be placed under vacuum, overpressure, or a protective gas atmosphere to prevent the biomaterial from reacting with the ambient air. The workspace can also be heated. The printing process can be observed through viewing windows.

[0018] The 3D printer for biomaterials uses the cable robot principle to position the print head, with eight cables or straps used to position and load the manipulator in all six degrees of freedom. Up to two additional rotation axes can be attached to the print head if the mobility in the rotational degrees of freedom, i.e., the degrees of freedom of rotation, provided by the cable robot alone is insufficient.

[0019] The working space is, for example, cube-shaped or cuboid-shaped. The cable drums can be arranged in the area of ​​the corners of the cube-shaped or cuboid-shaped working space. Accordingly, due to the positions of the cable exits as the cable exit points of the cable drums, the cable drums and the working space form a cuboid or a cube, or the spatial dimensions of a cuboid or a cube.

[0020] Cable drums can be mounted in the floor or ceiling of the work area, near the corners. Likewise, the respective cable drums can be mounted in or on the side walls of the work area, near the corners. Mixed configurations are also possible.

[0021] The print head, or rather its frame, includes eight spherical cable or ribbon suspensions, a nozzle, and a valve. A pump conveys and dispenses the liquid or viscous polymer or the material to be printed for 3D printing to the print head. The printing material is fed to the print head via a flexible spiral hose, or a container on the print head is filled directly with the printing material. Power is also supplied via a spiral cable or along the material feed, or a battery is located on the print head. Signal transmission also takes place via spiral cable or wirelessly.

[0022] The print head may be arranged on or in an inherently flat or planar square or rectangular or round frame or an inherently spatial cubic frame or cross-vein-shaped frame or a tetrahedral frame.

[0023] The print head and frame can also be designed as one component or a combined component.

[0024] The first end of the respective ropes or straps can be attached to the frame in a floating or movable manner using a rope or strap attachment.

[0025] The fastening can also be detachable, for example, for maintenance purposes. The cable fastening or strap fastening corresponds to the cable end point on the frame or print head, or is considered equivalent to it.

[0026] The positions of the cable or strap attachments on the print head, either as a cable attachment or a strap attachment, can be arranged on the frame shown above, which surrounds the print head at least at its edges or supports it. Accordingly, one or two of the first ends of the cable or straps can be joined at a single point. In all frame variants, the points of the cable or strap attachment on the print head can be parallel to the work area in the neutral position or rotated by 45 degrees. Several or different cable arrangements are possible for the various variants.

[0027] Accordingly, a rope or strap is led from the respective rope drums above and below, individually or in pairs, to a corner of the frame.

[0028] Alternatively, the cables or straps are led from the cable drums of adjacent corners of a side surface or edge bordering the work area, from the corners diagonally opposite one of the side surfaces bordering the work area, from the corners diagonally opposite each other in the work area, individually or in pairs to a corner of the frame or print head and / or individually or in pairs to adjacent or diagonally opposite corners of the frame or print head. This allows the forces to be absorbed as a reaction in all three translational axes and the associated rotational axes. If the cables or straps cross in all three global axes, greater stability is achieved. The force balance is improved due to the larger lever. The length of the lever is greater by the height of the print head or its frame.

[0029] Within the workspace or pressure chamber, for example, the respective cable drums are located in the corners. The cable is wound planarly in the respective cable drum, i.e., perpendicular to the rotation axis of the cable drum, so that the cable does not cross over when wound in or on the cable drum. This way, the respective cable length is always clearly defined by the drum rotation, and the respective cable force is always clearly defined by the respective torque. The respective cable drum can be in two parts and can therefore be easily disassembled for sterilization.

[0030] Furthermore, the respective cable drums can be pivoted around the worm shaft, allowing them to follow the movements and directions of the cables or belts without tension, which arise from the different positions of the print head and thus from the different cable or belt lengths and directions. Furthermore, this allows the print head to reach all corners of the work area. The pivoting movement of the cable drum is not driven, but rather aligns itself with the print head through the cable tension.

[0031] Depending on the application, the eight worm shaft drives can be located outside the working area for hygiene reasons. The torque can be transmitted to the working area via a shaft or a contactless magnetic coupling.

[0032] Depending on the type of drive, the respective worm shaft can be guided from the working chamber to the drive via a seal, or it can be coupled or operatively connected to the drive via a coupling. In the former case, the working chamber is sealed at the entry point of the rotating shaft, for example, with a radial shaft seal. If no or less stringent hygiene requirements apply, the drives can also be arranged within the working chamber and coupled or operatively connected to the worm shaft.

[0033] The control loop's task is to track the constantly changing target position of the print head, interpolated from the programmed specifications (G-code), i.e., the x, y, and z coordinates, as accurately as possible. The control loop contains the digital function blocks geometry model, cable force control, position determination, position control, linearization, and an adaptive LQ controller, also known as a linear-quadratic controller.

[0034] To at least determine the position or control the position and to minimize errors, a defined standard cuboid with the highest surface quality and dimensional accuracy is first placed in the work space and then, as an adaptive scan, all possible coordinates or points, in particular the contour or surface of the cuboid as well as the extreme or boundary coordinates of the work space, are repeatedly scanned (scanned) or read in several times or in multiple passes. Any points can be measured as often as required with high precision. The measurement series and their deviations are recorded, taking into account all influencing factors such as the individual cable characteristics. Any deviations that occur are compensated or corrected. Through the repetitions, the system learns to compensate or correct any deviations that occur independently, since measurements and corrections are carried out alternately and continuously.

[0035] Furthermore, the working space is continuously measured in an independent measurement. The resulting results of the measurement series are averaged. This allows the influence of part or component characteristics to be recorded and taken into account at any time.

[0036] The respective measurement results can now be combined for highly precise positioning, so that precise control can be achieved in any position despite existing dependencies on parts or components.

[0037] There are areas that require less computing power or performance for position determination or position control than other areas in the workspace.

[0038] The measured variables for the control loop are the eight cable lengths, which are determined via encoders on the drives.

[0039] Additionally, an inertial system consisting of accelerometers and gyroscopes, a two-axis gravity pendulum, signal transmitters (preferably on the print head or frame for time-of-flight measurement), or statically mounted digital cameras can be used to increase measurement accuracy. The control loop's manipulated variables are the cable forces, or rather the torques, of the eight cable drums.

[0040] Advantageously, the blocks for linearization and the LQ controller can be clocked approximately 10 times slower, which reduces the necessary computing power and thus makes the hardware simpler and more cost-effective, at least for this area.

[0041] The geometric model calculates the cable vectors from the cable end at the print head to the cable exit point at the cable drum based on the target position and angle of the print head. From these, the cable lengths can be directly derived.

[0042] The respective products of normalized cable vectors and cable forces yield the vectorial forces acting on the print head generated by the respective cables. The cross product of the respective cable endpoints, i.e., the cable attachment or the ribbon attachment, and the respective cable forces yields the vectorial torques acting on the print head generated by the cables.

[0043] The input matrix of all cable forces in a print position has one column with six rows for each of the eight cables. The top three rows of each column contain the normalized cable vector, and the bottom three rows contain the cross product of the cable endpoints and the normalized cable vector of the respective cable. Multiplying the input matrix by all cable forces yields the total force generated by the cables and the total moment acting on the print head.

[0044] The cable force control calculates the ideal cable forces from the input matrix to keep the print head in equilibrium at this position. To do this, the eighth-order linear equation system of forces is reduced to a solvable sixth-order system by setting the two lowest cable forces to the fixed minimum preload force. To reduce the computational load, this calculation can be performed upstream, and the cable forces can either be specified in the G-code to match the motion sequence or stored in a multidimensional table depending on the print head position and interpolated at runtime.

[0045] The position determination determines the print head's position error from the aforementioned measured variables. Linearization of the geometric relationships shows that the transposed negative input matrix multiplied by the print head displacement in all six degrees of freedom yields the exact cable length difference. Reversing this equation reveals that the position error can be determined by the negative transposed pseudoinverse of the input matrix multiplied by the measurement errors. Applying the Moore-Penrose pseudoinverse ensures that the algorithm delivers the position that most accurately matches the measured cable lengths.

[0046] The algorithm can be advantageously extended to account for rope elongation. This is then calculated using Hooke's law and the entire rope length.

[0047] The position control calculates the necessary rope force corrections from the position error. The controller is a PID state controller with manipulated variable limitation and anti-windup. The actual rope forces that the drives are intended to generate are the sum of the ideal rope forces and the rope force corrections.

[0048] The linearization calculates the system matrix. This matrix indicates how the equilibrium changes for the current print head position when the cable vectors change due to a slight shift in the print head position. This matrix describes the system's inherent dynamics and is crucial for stability and control.

[0049] The adaptive LQ controller specifies the controller settings for position control. The LQ method uses the aforementioned linearization matrix to provide the controller settings with optimal settling time. The system matrix A and the input matrix B are known from the previous blocks.

[0050] In order to reduce the computing load, the calculation of the linearization and the LQ controller can either be carried out at a lower frequency and / or upstream and the controller setting can either be specified in the G-code to match the movement sequence or stored in a multidimensional table depending on the print head position and interpolated at runtime.

[0051] Several embodiments of the invention are illustrated in the drawings and described in more detail below. They show: Fig. 1 a cable robot 3D printer in a housing with cable drum drives located outside the printing chamber, Fig. 2 a cable robot 3D printer in a housing with drives for the cable drums arranged within the printing chamber, Fig. 3 to 15 schematic representations of a cable robot 3D printer with different cable guides and print heads or frames for print heads, Fig. 16a and16b Detailed view of a print head with frame and ropes of a rope robot 3D printer, Fig. 17 a detailed view of a screw shaft in the working area of ​​a cable robot 3D printer, Figs. 18 and 19 Detailed representations of a cable drum, worm shaft in the working area of ​​a cable robot 3D printer, Fig. 20 to 22 Detailed representations of a rope drum in different perspectives, Fig. 23 a schematic detailed representation of a feedthrough with seal of a screw shaft into the working space of a cable robot 3D printer. Fig. 24 a schematic detailed view of a magnetic coupling on a worm shaft in the working area of ​​a cable robot 3D printer, Fig. 25 a schematic detailed representation of a worm shaft with drive outside the working chamber and with a lead-through into the working chamber with seal, Fig. 27 a diagram for the rope force curve of the ropes of the rope robot 3D printer, Fig. 28a block diagram of the control circuit of the cable robot 3D printer and Fig. 29 a block diagram for the overall scheme of the control loop.

[0052] The cable robot 3D printer 1 according to the invention comprises, as shown in the Figures 1 to 15 eight ropes 2, which can also be designed as bands 2 or can be replaced by bands 2. The ropes 2 or bands 2 are, as described in detail in the Figures 16a and 16b is shown, is detachably and floatingly attached at a first end 3 to a frame 11 as a structural component of the print head 4. From the print head 4, the cables 2 or bands 2 are each guided to a cable drum 5. These other, second ends 6 of the cables 2 or bands 2, which are opposite from the print head 4, can be wound in a planar manner without crossing in the cable drum 5. The cable drums 5 are as shown in the Figures 1 and 2shown, arranged within a work space 7 on the floor and on the ceiling of the work space 7. The cable drums 5 are driven by drives 8. Depending on the intended use of the cable robot 3D printer 1, as shown in the Figure 1 shown, the drives 8 of the cable drums 5 are arranged outside the working space 7. In Figure 2 It is shown that the drives 8 are within the working space 7. Furthermore, as shown in the Figures 1 and 2 and 16a and 16b, at least one material supply 9 and at least one nozzle 10 are provided on the print head 4. In Figure 16b It is also shown that a gripping device 16 is also present on the print head 4.

[0053] The workspace 7 is, as in the Figures 1 and 2and 3 to 15, are cuboid-shaped. Cube-shaped work spaces are also possible. Other shapes or spatial dimensions of the work spaces 7 are not excluded, taking into account the corresponding cable routing of the cables 2 or baths 2 and the positions to be reached by the print head 4 or nozzle 10.

[0054] Depending on hygiene requirements, the work area 7 can be separated from the environment, locked, or sterile. As in Figure 1 and 2 As shown, the cable-driven 3D printer 1 is housed in a cabinet, preferably mobile for increased flexibility. The workspace 7 is cuboid-shaped, but can also be cube-shaped.

[0055] In the Figures 16a and 16b It is shown that a frame 11 is arranged around the print head 4.

[0056] In addition to the Figures 16a and 16b as well as in the Figures 7 to 12In addition to the shape shown, adapted to the print head 4, as a cube-shaped frame 11, the frame 11 can also have a cuboid shape (not shown) or, as shown in the Figures 13 to 15 , tetrahedral shape or, as in the Figures 3 to 6 , flat as a square or as a rectangle (not shown) or round (not shown) or oval (not shown).

[0057] The print head 4 can be arranged on or in the respective frame 11. The respective first end 3 of the respective ropes 2 or bands 2 is attached to the frame 11 in a floating or movable manner, as shown in the Figures 16a and 16b shown so that, depending on the position, the tensioned cables 2 or bands 2 can align themselves tension-free relative to the frame 11 or print head 4 or can follow the movement and change in position of the print head 4 or the frame 111.

[0058] As in the Figures 1 and 2As shown, the cable drums 5 are arranged in the area of ​​the corners 12 of the cube-shaped or cuboid-shaped working space 7. The cable drums 5 have, as shown in the Figures 18 to 21 shown, at least one of the pulleys 5 forms roller side discs 20 has an external toothing 14. The external toothing 14 of the cable drum 5 or the roller side disc 20 engages in a worm shaft 15. The cable drum 5 is pivotable about the worm shaft 15 in a holder 21 encompassing the worm shaft 15, as shown in the Figures 18, 19 and 21 shown.

[0059] The drive 8 drives the worm shaft 15 directly via a mechanical coupling, as shown in the Figures 23 and 25 shown, or indirectly via a magnetic coupling, as in the Figure 24shown, the worm shaft 15. The worm shaft 15 is guided from the working chamber 7 to the drive 8 through a seal and coupled to the drive 8 by means of a coupling 17, provided the drive 8 is outside the working chamber 7.

[0060] Alternatively, as in Figure 2 shown, the drive 8 is arranged within the working space 7 and is coupled or operatively connected to the worm shaft 15.

[0061] The worm shaft 15 has, in particular in the area of ​​the cable drum 5 or the engagement of the external toothing 14 of the roller side plate 20 of the cable drum 5, an area with a helical worm 22, as shown in the Figures 18, 19 , 25 and 26 is shown.

[0062] The print head 4 or components of the print head 4 are designed to rotate in two or more axes. (not shown) As shown in the Figures 3 to 15Different variants of the cable guide in the working space 7 are shown, in each of which a cable 2 or belt 2 is guided from the respective cable drums 5 above and below, individually or in pairs, to a corner 13 of the frame 11. For the sake of simplicity, only the cables 2 are referred to below, whereby the associated cable drums 5 are understood to be present and included, and the description also applies to belts 2, provided they are used or preferred instead of cables 2. For the following discussion, it is irrelevant where and how exactly the cable drums 5 are mounted; what is important is their arrangement in the area of ​​the corners 12 of the working space 7.

[0063] The respective workspace 7 has four side walls, each with four corners 12, and vertical and horizontal edges between each two corners 12. The horizontal edges are present at the top or bottom, as well as vertically between two side walls. Naturally, two adjacent side walls share a vertical edge, and two corners 12, namely an upper and a lower corner 12, share a common vertical edge with respect to the two adjacent side walls. Reference to this will be made only in a simplified manner below.

[0064] So in Figure 3 the ropes 2 from two adjacent corners 12 of one of the vertical edges are led together to the corner 13 of the flat square frame 11 closest to the edge.

[0065] So in Figure 4the ropes 2 are guided from two adjacent corners 12 of one of the horizontal edges together to a corner 13 of the flat square frame 11, wherein the affected edges of the working space 7 are parallel to each other at the bottom and at the top, but the affected edges of the working space 7 are offset by 90 degrees at the top and to the affected edges at the bottom of the working space 7.

[0066] In Figure 5 the ropes 2 are led from the diagonally opposite corners 12 in the working space 7 to a corner 13 of the flat square frame.

[0067] In Figure 6 the ropes 2 are led from the corners 12 diagonally opposite one side wall to the corner 13 of the flat square frame 11 facing this side wall.

[0068] Lateral inclinations of the flat frame 11 are only possible to a limited extent.

[0069] In the Figures 7 to 12the ropes 2 are guided to a cuboid or cube-shaped frame 11.

[0070] So in Figure 7 the cables 2 are each led from the corners 12 diagonally opposite one another on a side wall, on the one hand individually and crosswise to the corners 13 of the lower horizontal edge of the frame 11 pointing towards this side wall and on the other hand individually and not crosswise to the corners 13 of the upper horizontal edge of the frame 11 pointing away from this side wall.

[0071] In Figure 8 the cables 2 are each led individually from the adjacent corners 12 alternately from an upper and lower horizontal edge to the upper and lower corners 13 of a vertical edge of the frame 11 pointing towards this side wall or edge.

[0072] In Figure 9the cables 2 are, on the one hand, each led individually from the adjacent corners 12 of mutually parallel upper and lower edges of the working space 7 to the corners 13 of mutually and to the upper and lower edges of the working space 7 parallel lower and upper edges of the frame 11, so that a cable 2 of an upper corner 12 of a vertical edge of the working space 7 is led to a lower corner 13 of a vertical edge of the frame 11 and conversely a cable 2 of a lower corner 12 of the same vertical edge of the working space 7 is led to an upper corner 13 of the same vertical edge of the frame 11.

[0073] So in Figure 10the ropes 2 are led, on the one hand, individually from the adjacent corners 12 of mutually parallel upper edges of the working space 7 to the non-crossing opposite corners 13 of mutually parallel upper edges of the frame 11 and on the other hand, individually from the adjacent corners 12 of mutually parallel lower edges of the working space 7 crosswise to the corners 13 of mutually parallel lower edges of the frame 11.

[0074] In deviation from Figure 10 are in the Figure 11the ropes 2 are on the one hand each individually led from the adjacent corners 12 of mutually parallel upper edges of the working space 7 to the non-crossing opposite corners 13 of mutually parallel upper edges of the frame 11 and on the other hand each individually led from the adjacent corners 12 of mutually parallel lower edges of the working space 7 also to the non-crossing opposite corners 13 of mutually parallel lower edges of the frame 11 and to the lower edges of the working space 7.

[0075] In Figure 12the cables 2 are each led individually from the corners 12 diagonally opposite one side surface alternately to the upper and lower corners 13 of a vertical edge of the frame 11 pointing towards this side wall or edge, so that the cable 2 is led from a lower corner 12 of the respective side wall to the respective upper corner 13 of the vertical edge of the frame 11 and the cable 2 is led from an upper corner 12 of the respective side wall diagonally opposite the lower corner 12 on the respective side wall to the respective lower corner 13 of the same vertical edge of the frame 11.

[0076] In the Figures 13 to 15 the ropes 2 are guided to a tetrahedral frame 11.

[0077] So in Figure 13the cables 2 from two adjacent corners 12 of one of the horizontal edges of the work space 7 are led together to a corner 13 of the tetrahedral frame 11, wherein the affected edges of the work space 7 are parallel and opposite each other at the bottom and at the top, but the affected edges of the work space 7 at the top and at the bottom are offset by 90 degrees. The tetrahedral frame 11 is arranged such that one of its top edges and one of its bottom edges are each arranged horizontally. The cables 2 from the corners 12 of the lower horizontal edges of the work space 7 are led to the corners 13 of the upper horizontal edge of the tetrahedral frame 11, while the cables 2 from the corners 12 of the upper horizontal edges of the work space 7 are led to the corners 13 of the lower horizontal edge of the tetrahedral frame 11.

[0078] In Figure 14In contrast, the cables 2 are guided from two adjacent corners 12 of one of the horizontal edges of the working space 7 together to a corner 13 of the tetrahedral frame 11, wherein the affected edges of the working space 7 are parallel and opposite each other at the bottom and at the top, but the affected edges of the working space 7 at the top and at the bottom are offset by 90 degrees from the affected edges of the working space 7. The tetrahedral frame 11 is arranged such that one of its top edges and one of its bottom edges are arranged horizontally. The ropes 2 from the corners 12 of the lower horizontal edges of the working space 7 are led to the corners 13 of the lower horizontal edge of the tetrahedral frame 11, while the ropes 2 from the corners 12 of the upper horizontal edges of the working space 7 are led to the corners 13 of the upper horizontal edge of the tetrahedral frame 11.

[0079] In Figure 15 The cables 2 from two adjacent corners 12 of one of the vertical edges of the working space 7 are guided together to a corner 13 of the tetrahedral frame 11. The upper cables 2 and the lower cables 2 from two vertical edges of a side wall of the working space 7 can cross each other in the course of the tetrahedral frame 11.

[0080] The Figure 27 The cable force curve shows the calculated theoretical cable forces of a curved path at a minimum pre-tension force of 20 Newtons. A transition occurs at 9 and 24.5 seconds, where one cable with the minimum pre-tension force is replaced by another. This process occurs as soon as the third-lowest cable force threatens to drop below the minimum pre-tension force and is caused by the change in the cable vectors due to the movement along a curved path of the print head in the workspace or printing chamber.

[0081] In Figure 28The block diagram of the control circuit of the cable robot 3D printer is shown. Figure 29 A block diagram of the overall control loop is shown.

[0082] The geometric model calculates the cable vectors from the cable end at the print head 4 to the cable drum 5 from the target position and angle of the print head 4, from which the cable lengths can be directly derived. Multiplying the standardized cable vectors by the cable forces yields the vectorial forces generated by the cables 2 on the print head 4, while the cross product of the cable endpoints and the cable forces yields the vectorial torques generated by the cables 2 on the print head 4.

[0083] In the position determination, the position error of print head 4 is determined from the measured variables. By linearizing the geometric relationships by multiplying the transposed negative input matrix by the displacement of print head 4 in all six degrees of freedom, the exact cable length difference is obtained. Inverting this equation allows the position error to be determined from the product of the negative transposed pseudoinverse of the input matrix and the measurement deviations. By incorporating the Moore-Penrose pseudoinverse, the algorithm delivers the position that most accurately matches the measured cable lengths. Summary of reference symbols

[0084] 1- Cable robot 3D printer, cable robot 2- Rope, belt 3- First end of the rope or belt 4- Print head 5- Rope drum 6- Second end of the rope or belt 7- Working chamber 8- Drive 9- Material feed 10- Nozzle 11- Frame 12- Corner 13- Corner 14- External gear 15- Worm shaft 16- Gripping device 17- Coupling 18- Seal 19- Rope attachment or belt attachment on the print head 20- Roller side disc 21- Support 22- Helical screw

Claims

1. Cable robot 3D printer (1), comprising a cable robot (1) with eight cables (2) or bands (2), where the cables (2) or bands (2) are releasably attached at one end (3) to a print head (4) and led from the print head (4) to a respective cable drum (5), and the other end (6) opposite from the print head (4) of the cables (2) or bands (2) can be wound in the cable drum (5) in a planar, crossing-free manner, where the cable drums (5) are located within a workspace (7), and where the cable drums (5) are drivable and the drives (8) of the cable drums (5) are arranged outside or inside the workspace (7), and where at least one material feed (9) and at least one nozzle (10) are provided on the print head (4), characterised in that the cable drum (5) has an external gearing (14) and the external gearing (14) of the cable drum (5) engages a worm shaft (15), where the drive (8) directly or indirectly drives the worm shaft (15).

2. Cable robot 3D printer according to claim 1, characterised in that the workspace (7) is separable, closable, or sterile.

3. Cable robot 3D printer according to any of claims 1 and 2, characterised in that the workspace (7) is cubic or rectangular.

4. Cable robot 3D printer according to any of the preceding claims, characterised in that the cable drums (5) are arranged in the area of the corners (12) of the cubic or rectangular workspace (7).

5. Cable robot 3D printer according to any of the preceding claims, characterised in that the print head (4) is arranged on or in a square or rectangular or round frame (11), a cubic frame (11) or a cross-shaped frame (11) or a tetrahedral frame (11), and the first end (3) of the respective cables (2) or bands (2) are floatingly or movably attached to the frame (11).

6. Cable robot 3D printer according to any of the preceding claims, characterised in that the print head (4) or components of the print head (4) are executed to rotate about two or more axes.

7. Cable robot 3D printer according to claim 5, characterised in that a cable (2) or band (2) from the respective cable drums (5) is led individually or in pairs from above and below to a corner (13) of the frame (11) and / or that the cables (2) or bands (2) from the cable drums (5) of adjacent corners (12) of a side of the workspace (7) or an edge below or above, from one of the sides of the workspace (7) diagonally opposite corners (12), from the diagonally opposite corners (12) within the workspace (7) are led individually or in pairs to a corner (13) of the frame (11) and / or individually or in pairs to adjacent or diagonally opposite corners (13) of the frame (11).

8. Cable robot 3D printer according to any of the preceding claims 1 to 6, characterised in that the cables (2) or bands (2) from the cable drums (5) of adjacent corners (12) of a side of the workspace (7) or an edge below or above, from one of the sides of the workspace (7) diagonally opposite corners (12), from the diagonally opposite corners (12) within the workspace (7) are led individually or in pairs to a corner (13) of the print head (4) and / or individually or in pairs to adjacent or diagonally opposite corners (13) of the print head (4).

9. Cable robot 3D printer according to claim 1, characterised in that the cable drum (5) is pivotable about the worm shaft (15).

10. Cable robot 3D printer according to any of the preceding claims 1 and 9, characterised in that the worm shaft (15) is led through a seal from the workspace (7) to the drive (8) or is coupled or functionally connected to the drive (8) by a coupling (17), or that the drive (8) is arranged within the workspace (7) and is coupled or functionally connected to the worm shaft (15).

11. Cable robot 3D printer according to any of the preceding claims, characterised in that the print head (4) comprises at least one gripping device (16).