Multi-axis 3D printer and method for determining control commands

Abstract

The invention relates to a multi-axis 3D printer (1), comprising a printing plate (2), a print head (3) and at least two, preferably exactly three or exactly four, guide rails (9) running parallel to one another, wherein the printing plate (2) is mounted on the guide rails (9) via supports (10), wherein the supports (10, 51) can be displaced in the z-direction along the guide rails (9) and can be individually controlled, wherein the printing plate (2) has a support point (50) for each of the supports (10, 51), wherein the support points (50) of the printing plate (2) are mounted on the supports (10, 51) in such a way that they are each mounted displaceably in a displacement direction running at an angle to the z-direction. In a further aspect, the disclosure relates to a computer-implemented method for determining control commands for said multi-axis 3D printer (1).

Description

[0001] Multi-axis 3D printers and methods for determining control commands

[0002] The invention relates to a multi-axis 3D printer and a computer-implemented method for determining control commands for this multi-axis 3D printer. The invention further comprises a computing unit, a computer program, and a computer-readable data carrier.

[0003] Three-dimensional printing technologies have made significant progress in recent years, becoming an indispensable tool in manufacturing, prototyping, and even medicine. Conventional 3D printers are mostly based on a mechanism where the print bed moves vertically along the z-axis while the print head deposits material layer by layer. This architecture has proven reliable and cost-effective, but it is limited in terms of possible geometries and print quality. These systems reach their limits, particularly with complex structures, overhangs, or undercuts, as additional support structures are required, which must be removed afterward.

[0004] In recent years, so-called multi-axis 3D printers have been developed to overcome these limitations. Such systems integrate additional degrees of freedom into the movement of the print head or the print bed. One approach is the use of gimbal mechanisms or rotating platforms that allow the print bed to tilt around the x- and y-axes. Alternatively, print heads with multiple joints can be used, enabling them to deposit material not only vertically but also at an angle or horizontally. These devices, known as multi-axis 3D printers, are particularly capable of producing complex geometries with little or no support structure.

[0005] Despite their potential, multi-axis 3D printers have so far only achieved limited market penetration. A key reason for this lies in the technical complexity of the systems. The additional movement of the axes requires precise control mechanisms, which often lead to higher costs and longer printing times.

[0006] Another critical point is the mechanical stability and accuracy of these systems. Particularly at high printing speeds, inaccuracies in the axis control can occur, negatively impacting print quality. Furthermore, the use of more degrees of freedom increases maintenance requirements, as additional moving parts can wear out more quickly. At the same time, there is a lack of standardized interfaces and protocols for multi-axis printers, which complicates integration into existing production environments.

[0007] In summary, there remains a significant need for improved multi-axis 3D printers and control software that overcome the limitations of conventional systems without inheriting their drawbacks, such as high costs, complex operation, and limited reliability. The particular challenge lies in increasing the precision and efficiency of these devices while reducing complexity for the user.

[0008] The state of the art is formed by the documents US 2022 / 305655 Al, EP 3 736 108 Bl, US 2015 / 328840 Al, DE 102010004496 Al, DE 112020000705 T5, US 2018001625 Al and US 2019275783 Al.

[0009] Further state of the art is described in the following publication: PEREZ-CASTILLO JOSE LUIS ET AL: "Curved layered fused filament fabrication: An overview", ADDITIVE MANUFACTURING, ELSEVIER, NL, Vol. 47, September 25, 2021 (2021-09-25), XP086891641, ISSN: 2214-8604, DOI: 10.1016 / J.ADDMA.2021.102354

[0010] It is an object of the invention to provide multi-axis 3D printers and control software for these multi-axis 3D printers which overcome the aforementioned disadvantages.

[0011] In a first aspect of the invention, this problem is solved by a multi-axis 3D printer comprising a print plate, a print head and at least two, preferably exactly three or exactly four, parallel guide rails, wherein the print plate is mounted on the guide rails via supports, wherein the supports are displaceable in the z-direction along the guide rails and can be individually controlled, wherein the print plate has a support point for each of the supports, wherein the support points of the print plate are mounted on the supports in such a way that they are each displaceable along a displacement direction that runs at an angle to the z-direction.

[0012] This multi-axis 3D printer can be used to ensure that the print head is always perpendicular to the build plate surface by means of a corresponding tilting mechanism. This is essential to guarantee optimal adhesion of the fibers to the substrate. Furthermore, these measures prevent damage to the fiber, especially continuous fibers like carbon fiber, during the printing process. A steeper nozzle angle to the component could easily lead to fiber breakage, which is problematic, for example, in 3D printing with a robotic arm.

[0013] The multi-axis 3D printer according to the invention has the advantage that a particularly precise multi-axis 3D printing process can be achieved, in which a print bed that can be moved during pivoting can be used without the need for mechanical compensation of the pivoting. This allows for a particularly large degree of design flexibility in the construction of the multi-axis 3D printer.

[0014] Because the support points are each movable in a direction perpendicular to the z-axis, the print plate can be tilted by larger angles. It should be noted that tilting the print plate will also result in a displacement of the print plate (e.g., along the direction of displacement). In other words, when the print plate is tilted, the print plate and the print head will undergo a translational movement relative to each other. This relative movement is compensated for during a printing process according to the computer-implemented method described below.

[0015] Preferably, the displacement directions of all support points are orthogonal to the z-axis. This significantly simplifies the process for determining control commands. Alternatively, displacement directions could also be oblique upwards or obliquely downwards, with the terms "up" and "down" being understood in relation to the z-axis.

[0016] In a particularly preferred embodiment, the multi-axis 3D printer comprises exactly three guide rails and exactly three supports, wherein two support points of the print bed are slidably mounted on the supports in an x-direction and one support point of the print bed is slidably mounted on the supports in a y-direction. This results in a particularly easy-to-control multi-axis 3D printer.

[0017] Two variants in particular can be used to implement the displacement of the support points with respect to the supports along the displacement directions.

[0018] In the first variant, each support can comprise a support rail in which a support point of the pressure plate is slidably mounted. These support rails run parallel to the respective direction of movement and typically extend into the installation space.

[0019] In the multi-axis 3D printer of the first variant, it is preferred if the print plate is essentially rectangular and a first corner point and a second corner point of the print plate are each supported in parallel support rails and a side midpoint of the print plate is supported in the support rail that runs perpendicular to the other two support rails.

[0020] A disadvantage of the first type of multi-axis 3D printer is that the three support points of the print bed are typically extended downwards using spacers perpendicular to the print bed. Balls attached to the ends of these spacers are then mounted on support rails. Because the support rails always protrude into the build chamber, the print bed's tilt angle is limited in certain orientations; otherwise, the print bed would collide with the support rails. The maximum tilt angle can be increased by extending the spacers further, but this can lead to a loss of precision, partly due to increased instability resulting from the spacers' longer lever arms.

[0021] In the second variant, to solve this problem, it is provided that a connecting rail is slidably mounted in each support, wherein the connecting rails are slidably mounted with respect to their respective support along the respective direction of displacement, and wherein each connecting rail pivotally mounts a point of the pressure plate, preferably via a joint connection projecting parallel from the pressure plate, which is particularly preferably a ball joint.

[0022] While the support rails of the first variant are rigidly mounted to the support rails, the connecting rails of the second variant are slidably mounted in the supports along the direction of movement. This means that the connecting rails are not rigidly fixed within the build space, but can be moved almost completely through the support. As a result, the pressure plate has a significantly greater degree of pivoting capability, and the control mechanism is simpler.

[0023] In the second variant, there are generally no longer any spacers perpendicular to the pressure plate that connect the pressure plate to the ball joints. Instead, the ball joints can be attached directly to the pressure plate's support points in such a way that they no longer protrude perpendicularly, but parallel to the pressure plate. Instead of the balls being mounted on connecting rails that move horizontally on fixed tracks, the balls are instead attached to connecting rails that can be moved horizontally by the supports. This allows for a full 90° tilt in all directions without ever colliding. Furthermore, this eliminates the need for spacers between the ball joints and the pressure plate, thus minimizing any loss of precision.

[0024] In the second embodiment, it is particularly preferred if the printing plate is substantially rectangular and wherein a first corner point and a second corner point of the printing plate are each supported on connecting rails running parallel to each other, and a side midpoint of the printing plate is supported on a connecting rail running perpendicular to the other two connecting rails. The connecting rail engaging at the side midpoint of the printing plate preferably runs perpendicular to the side of the printing plate to which it engages.

[0025] In summary, in the first variant, the bearing points of the pressure plate are articulated and slidably mounted in the support rails, and the support rails are rigidly attached to the supports. In the second variant, the bearing points of the pressure plate are articulated but not slidably mounted on the connecting rails, and the connecting rails are slidably mounted on or within the supports.

[0026] In both of the above variants, it is preferred if the printing plate is essentially rectangular and wherein a first corner point and a second corner point of the printing plate are each supported in parallel support rails or on parallel connecting rails and a side center point of the printing plate is supported in a support rail or on a connecting rail normal to the other two support rails.

[0027] In a second aspect, the invention relates to a computer-implemented method for determining control commands for the aforementioned multi-axis 3D printer (or for a multi-axis 3D printer comprising a print head and a print plate, wherein the print plate and / or the print head undergo a translational movement relative to a pivoting of the print plate and / or the print head).

[0028] (performs in relation to each other), the procedure comprising the following steps:

[0029] - Receiving first path points, preferably in the coordinate system of the print head or the printing plate, wherein inclination information, in particular a normal vector, is received or determined for the path points,

[0030] - Determining a tilt of the print bed and / or print head to print the first path points according to the tilt information, and generating tilt control commands to bring the print bed and / or print head to the specified tilt,

[0031] - Performing a path correction, including the following steps:

[0032] o from the inclination information, determine the translational movement of the printing plate and / or print head at this inclination information, and perform a coordinate transformation of the first path points based on the determined translational movement to obtain second path points, and

[0033] o Generating print control commands to move the print head along the second path points,

[0034] Output of tilt control commands and pressure control commands.

[0035] The step of generating print control commands is performed based on the second path points. Preferably, the step of generating print control commands can further include determining the movement speed of the print head and / or the print bed based on the tilt information and coordinate transformation, ensuring that it remains constant during multi-axis 3D printing.

[0036] In summary, the aforementioned method, particularly with the multi-axis 3D printer described above, enables the advantageous production of elongated, curved objects, especially half-shells and shells for orthoses, exoskeletons, or prostheses. Without multi-axis 3D printing, such objects would have to be printed vertically. The higher the print head has to be positioned and the further it moves from the print bed, the greater the bending moment on the object would be, causing it to flex and vibrate, which would impair accuracy and adhesion. Only the method according to the invention, thanks to multi-axis 3D printing, allows for the horizontal production of these objects.Furthermore, the aforementioned objects can be manufactured to meet ideal structural requirements and dynamic mechanisms. This allows material layers to be precisely aligned along load vectors. This leads to significantly improved mechanical stability and load-bearing capacity of the structure. It is evident that this method is particularly suitable for numerically compensating for the displacement of the pressure plate's support points along the directions of displacement.

[0037] With the multi-axis 3D printer according to the invention, in particular an analytical coordinate transformation and a trigonometric support control method can be implemented for path correction.

[0038] In analytical coordinate transformation, the first path points and their corresponding normal vectors are used as input values, and explicit kinematic equations are applied to derive a transformation matrix. This transformation matrix can then be applied to the first path points to obtain the bed inclination and subsequently the second path points.

[0039] In the trigonometric support control method, the normal vectors of the corrected points can be converted into specific support displacements. These calculated displacements can be translated into precise stepper motor commands for real-time actuation of the supports. This ensures the synchronized repositioning of all three supports to maintain the correct bed tilt throughout the entire printing process.

[0040] The aforementioned method can be used particularly with a multi-axis 3D printer where the print head is movable along an x-axis and a y-axis, and the build plate is pivotable around the x-axis and the y-axis (and optionally also pivotable or movable around the z-axis to achieve steeper tilt angles through non-planar 3D printing by shifting along the z-axis). When the build plate is pivoted along the x-axis and / or the y-axis, the build plate shifts, representing the aforementioned translational movement. In this case, only the build plate is pivotable, not the print head (although this would be conceivable in other configurations). The build plate is controlled according to the tilt control commands, and the print head is controlled according to the print control commands.This can be used in particular with multi-axis 3D printers in which at least two, preferably exactly three or exactly four, guide rails extending in the z-direction are used. In this case, the invention relates to a computer-implemented method for determining control commands for a multi-axis 3D printer comprising a print head and a print bed, wherein the print head is movable along an x-axis and along a y-axis, wherein the print bed is pivotable about the x-axis and about the y-axis, and wherein the print bed moves when the print bed is pivoted along the x-axis and / or the y-axis, wherein the method comprises the following steps:

[0041] - Receiving first path points, preferably in the coordinate system of the x-axis and the y-axis, wherein inclination information, in particular a normal vector, is received or determined for the path points,

[0042] - Determining a print plate inclination to print the first path points according to the inclination information, and generating print plate control commands to bring the print plate into the print plate inclination,

[0043] - Performing a path correction, including the following steps:

[0044] o from the inclination information, determine the displacement of the pressure plate along the x-axis and / or the y-axis with respect to this inclination information, and perform a coordinate transformation of the first path points based on the determined displacement to obtain second path points, and

[0045] o Generating printhead control commands to move the printhead along the second path points,

[0046] Output of the print plate control commands and the print head control commands.

[0047] It is evident that only the plate is tilted or pivoted here, so that during the translational movement the plate shifts and the tilt control commands are print plate control commands. Furthermore, only the print head moves for the actual printing process, so the print control commands are print head control commands.

[0048] However, it should be noted that the method described at the beginning can also be used with other multi-axis 3D printers where a translational relative movement occurs between the print head and the print bed when one of the elements pivots.

[0049] In a particularly preferred embodiment, the method comprises the step of providing at least one data set in which at least one inclination information is specified and the translational movement with respect to that inclination information is specified, preferably also specifying the inclination control commands for the at least one inclination information. This is preferred because it is difficult or impossible to calculate the translational movement analytically for many inclination information sets. Therefore, it is preferable to calculate the translational movement in advance for predetermined inclination information, i.e., the translational movement for predetermined inclinations of the printhead or print plate when printing material is to be printed perpendicular to one of the path points according to the inclination information.

[0050] In the aforementioned embodiment, it is preferred if at least two, preferably at least ten or at least fifty, data records are provided, wherein each data record contains a plurality of inclination information and wherein the data records each specify different intervals of inclination information. This ensures that only the data record corresponding to the respective inclination information needs to be opened during readout.

[0051] As an alternative to extracting data from existing records, the process can include providing a model trained using a machine learning algorithm. This trained model takes tilt information as input and outputs tilt control commands based on this information and / or the translational movement based on this information. Such a model offers the advantage that the user is not limited to discrete tilt information, as might be the case with pre-defined datasets. Furthermore, it significantly increases processing speed, as it allows for the step of retrieving the tilt information directly from the datasets.

[0052] In the aforementioned embodiment, it is preferred if the machine learning algorithm is trained by supervised learning using at least one dataset in which at least one inclination information is specified and for which the inclination control commands and / or the translational movement with respect to this inclination information are specified. However, it is conceivable that the machine learning algorithm could also be trained differently.

[0053] In all the aforementioned embodiments, in which at least one data set is used, the method can include the step of creating the at least one data set by numerically calculating the tilt information and / or the translational movement based on discretely selected tilt control commands. In other words, the process first starts with an actual pivoted position of the pressure plate, e.g., the positions along the z-axis of the pressure plate's supports.

[0054] From this, the inclination of the printing plate and at least approximately its translational movement can be determined, e.g., the displacement of the printing plate's center point in a plane perpendicular to the z-axis. It goes without saying that the numerical calculation can also be performed differently.

[0055] Preferably, the method further comprises the step of issuing tilt control commands and pressure control commands to the multi-axis 3D printer, wherein the multi-axis 3D printer moves the print bed and / or print head according to the tilt control commands and moves the print head and / or print bed according to the pressure control commands, and during the movement of the print head and / or print bed, ejects printing material from the print head. In other words, the previously determined control commands are implemented by the multi-axis 3D printer to print a component such as an orthosis using multi-axis 3D printing.

[0056] In the aforementioned method, it is further preferred if the method includes the initial step of printing a support structure without tilting the print bed, wherein the inclination information for at least one of the first path points is a normal vector to the surface of the support structure. In other words, the support structure is initially printed using conventional printing, forming a curved surface onto which a layer can be printed using multi-axis 3D printing perpendicular to said surface.

[0057] Furthermore, the support structure can preferably be printed as follows using multi-axis 3D printing:

[0058] - Printing a first top layer onto the support structure,

[0059] - Printing a reinforcement onto the first top layer,

[0060] - Printing a second top layer onto the reinforcement.

[0061] If the print bed is tiltable, it is tilted during the printing of the first top layer, the reinforcement, and the second top layer.

[0062] In the aforementioned variant, the process can further include the step of printing a filler material after printing the reinforcement and before printing the second top layer, wherein the filler material is printed into free spaces of the reinforcement onto the first top layer.

[0063] The aforementioned variants are particularly suitable for printing orthoses and exoskeletons, whereby the reinforcement can be printed using continuous fibers. In a further aspect, the invention relates to a computing unit comprising a processor configured to execute the aforementioned method. The invention can further relate to a system comprising a multi-axis 3D printer and the aforementioned computing unit, wherein the multi-axis 3D printer and the computing unit are configured to perform the aforementioned method.

[0064] In general, the multi-axis 3D printer preferably comprises three guide rails extending in the z-direction, wherein the print plate is supported on the guide rails via supports, wherein the supports are movable in the z-direction along the guide rails and the print plate is slidably mounted on the supports in the x-direction and / or in the y-direction.

[0065] In another aspect, the invention relates to an orthosis manufactured using the aforementioned method, wherein the orthosis comprises the first cover layer, the reinforcement, optionally the filling material and the second cover layer.

[0066] In another aspect, the invention relates to a computer program comprising instructions which, when the program is executed by a computer, cause it to perform the said method.

[0067] In another aspect, the invention relates to a computer-readable data carrier on which the aforementioned computer program is stored.

[0068] Advantageous embodiments of the invention defined in the claims will be explained in more detail below with reference to the figures.

[0069] Figures aa to le show a multi-axis 3D printing process for an orthosis in schematic perspective views.

[0070] Figure 2 shows a multi-axis 3D printer with which the multi-axis 3D printing process of figures aa to le can be carried out.

[0071] Figure 3 shows the multi-axis 3D printer from Figure 2 in a top view.

[0072] Figure 4a shows a schematic view of the print bed of the multi-axis 3D printer of Figure 3 in a top view when the print bed is tilted about the y-axis.

[0073] Figure 4b shows a schematic view of the printing plate of Figure 4a in a top view.

[0074] Figure 5a shows a schematic view of the build plate of the multi-axis 3D printer of Figure 3 in a top view when the build plate is tilted about the x-axis. Figure 5b shows a side view of the build plate of Figure 5a.

[0075] Figure 5c shows a position of the printing plate with short spacers in a side view.

[0076] Figure 5d shows a position of the printing plate with long spacers in a side view.

[0077] Figure 6a shows the position of a point to be printed when the print bed is in a horizontal position.

[0078] Figure 6b shows the position of a point to be printed when the print bed is tilted.

[0079] Figure 7a shows point clouds of the positions of the corner points of the printing plate and the center point of the printing plate.

[0080] Figure 7a shows the point cloud of positions of the center of the printing plate.

[0081] Figure 8 shows a block diagram of the method according to the invention.

[0082] Figure 9a shows the first path points in the coordinate system of the multi-axis 3D printer.

[0083] Figure 9b shows second path points obtained from the first path points after a coordinate transformation.

[0084] Figure 10 shows a configuration of a multi-axis 3D printer with supports that have guide rails.

[0085] Figures 11 to 14 show a preferred embodiment of a multi-axis 3D printer in which the print plate is mounted on the supports via movable connecting rails, with the print plate being in a rest position.

[0086] Figures 15 to 18 show the multi-axis 3D printer of Figures 11 to 14 during a rotation of the print bed around the x-axis.

[0087] Figures 19 to 22 show the multi-axis 3D printer of Figures 11 to 14 during a rotation of the print bed around the y-axis.

[0088] Figures 1a to 1le show a method for multi-axis 3D printing using a multi-axis 3D printer 1. The illustrated method uses, for example, the multi-axis 3D printer 1 of Figure 2, which comprises a print bed 2 and a print head 3, wherein the print head 3 is movable along an x-axis and a y-axis. The print bed 3 is movable along the z-direction and can be pivoted about the x-axis as well as the y-axis, so that this multi-axis 3D printer 1 has five degrees of freedom. Optionally, the multi-axis 3D printer 1 could also have four or six degrees of freedom. The method according to the invention is therefore not limited to the multi-axis 3D printer 1 of Figure 2, but can also be carried out with another multi-axis 3D printer.Returning to Figures 1a to 1le, it is evident that with such a multi-axis 3D printer 1, a support structure 4 can first be printed in the step shown in Figure 1a. The support structure 4 is typically printed using conventional 3D printing, i.e., while the print bed 2 is in a horizontal position. The term "horizontal" here refers to the plane that encompasses the x-axis and the y-axis.

[0089] Once the support structure 4 has been printed, the component to be manufactured can be printed onto the support structure 4, whereby the print bed 3 is pivoted in such a way that the print head 3 is perpendicular to the surface of the component, i.e., perpendicular to the support structure 4 or to a layer already printed in multi-axis 3D printing. This printing process is referred to herein as "multi-axis 3D printing".

[0090] According to a specific example shown in Figures 1b to 1d, a first cover layer 5 is initially printed onto the support layer 4 using multi-axis 3D printing (Figure 1b). A reinforcement 6 can then be printed onto the cover layer 5 using multi-axis 3D printing (Figure 1c). Any gaps 7 between the reinforcement 6 can be filled with a filler material, which can also be printed using multi-axis 3D printing. Finally, a second cover layer 8 can be printed onto the reinforcement 6 or the filler material using multi-axis 3D printing (Figure 1d). This process encloses the reinforcement 6 between the first cover layer 5 and the second cover layer 8. The support 4 can then be removed to provide the component consisting of the first cover layer 5, the reinforcement 6, the second cover layer 8, and any filler material, as shown in Figure 1e.

[0091] The reinforcement 6 can, in particular, be a continuous fiber, such that the continuous fiber is printed in curved surfaces and / or in planar surfaces arranged at an angle to each other, especially in curved surfaces, wherein the continuous fiber is printed in curved lines within the curved surfaces. The continuous fiber can be a carbon fiber, a glass fiber, a basalt fiber, a Kevlar fiber, an aramid fiber, or a fiber with functional properties. The continuous fiber can be surrounded by a matrix material, e.g., already during multi-axis 3D printing.

[0092] The first cover layer 5 and / or the second cover layer 8 preferably consist of nylon, PETG, ABS, TPU, PET, PCTG, PCT, PP, PEEK, PEKK, or epoxy resin. Preferably, the first cover layer 5 and the second cover layer 8 consist of the same material. It is understood that a cover layer can also be provided laterally to the reinforcement 6, so that the reinforcement 6 can be completely surrounded by a cover layer made of the aforementioned materials.

[0093] The aforementioned method enables, in particular, the multi-axis 3D printing of an orthosis 20, since this is a curved hemisphere that can be printed lying down using the methods described herein, see Figure 1. This allows the print head 3 to remain as close as possible to the print bed 2, resulting in low moments acting on the object being manufactured.

[0094] As explained at the beginning, Figure 2 shows an exemplary multi-axis 3D printer 1, which can be used for multi-axis 3D printing. This multi-axis 3D printer 1 has three guide rails 9, each extending in the z-direction. The print bed 2 is supported at three points on the guide rails 9: at a first corner point, at a second corner point, and at the midpoint of one side (hereinafter: side point) of the print bed 2. However, this configuration can also be chosen differently, and the print bed 2 can generally be supported at three points on the guide rails 9 that are not in a straight line. For ease of understanding, however, reference is made to the aforementioned configuration of support at two corner points and at the midpoint of one side. In general, the procedure described below could also be carried out with a completely different multi-axis 3D printer 1, in which, for example,the printhead 3 pivots or in which the print plate 2 is mounted on a joint.

[0095] In the illustrated variant, the pressure plate 2 is mounted on the guide rails 9 via supports 10, i.e., each support 10 forms a connecting element between the guide rail 9 and the pressure plate 2. If all three supports 10 are moved upwards or downwards along the z-direction, the pressure plate 2 is moved upwards or downwards accordingly.

[0096] A special feature of the multi-axis 3D printer 1 shown in Figure 2 is that the print bed 2 is mounted on supports 10 in a pivoting and slidable manner (i.e., slidable along the x-axis and / or y-axis). This allows the print bed 2 to pivot about the x-axis and / or y-axis if only one or only two of the supports 10 are moved along the z-axis, and / or if at least two supports 10 are moved in opposite directions along the z-axis, and / or if at least two supports 10 are moved at different speeds along the z-axis. In other words, the supports 10 can be controlled independently of each other to cause the print bed 2 to pivot.

[0097] In a special variant, the supports 10 each comprise a rail, with the rails of the supports 10 at the corners of the print bed 2 being inclined to the x-axis and the y-axis and extending inwards from the guide rail 9. The rail of the support 10 at the side point of the print bed 2 runs parallel to the y-axis. A joint connected to the print bed 2 is slidably mounted in a rail. To understand the challenges of this multi-axis 3D printer 1, the pivoting of the print bed 2 will now be examined in more detail.

[0098] As shown in Figure 3, the printing plate 2 is in a horizontal position. The printing plate 2 is connected to the supports 10 at its two vertices and at the side vertex, forming an isosceles triangle 11 between these points. Figure 3 further shows the center M of triangle 11, which is defined here as the centroid of triangle 11, i.e., the intersection of the three medians, where one median connects a vertex to the midpoint of the opposite side. The center M of triangle 11 could also be defined as the incenter, circumcenter, or foot of the altitude. The center M of triangle 11 can likewise be defined as the center M of the printing plate 2.

[0099] Figures 4a and 4b now illustrate the pivoting of the printing plate 2 about the y-axis. For this, the lateral point of the printing plate 2 along the z-axis remains unchanged, while the corner points of the printing plate 2 move along the z-axis in opposite directions, resulting in a pivoting motion as shown in Figure 4a. Since the two corner points move away from each other vertically, they are pulled towards each other horizontally along the rails. Due to the inclined orientation of the two rails of the supports 10 at the corner points, the entire printing plate 2 is pushed outwards along the y-direction-oriented rail of the support 10 at the lateral point. This displacement of the printing plate 2, particularly of its center point, is represented in Figure 4b by the schematic and non-proportional arrow "M— >M".

[0100] Figures 5a, 5b, 5c, and 5d now illustrate a pivoting of the pressure plate 2 about the x-axis. In this movement, the two supports 10 at the corners move parallel to each other in the same direction along the z-axis relative to the support 10 at the side point, as shown in Figure 5a. Since the two supports 10 at the corners remain at the same height in this case, they cannot move horizontally. Therefore, the entire compensatory movement must be performed by the third support 10. This is shown in Figure 5b, where the centered support 10 at the side point of the pressure plate 2 is shown on the right. Reference numeral 12 indicates a permissible extension of the hinged connection between the pressure plate 2 and the support 10.

[0101] Figures 5c and 5d show that a larger tilt angle of the printing plate is made possible by using spacers of different lengths. Reference numeral 13 represents a limit on which the support 10 rests when the printing plate 2 is tilted. Reference numeral 14 indicates that a larger clearance is available without collision when the printing plate 2 is tilted accordingly. It is evident that the maximum possible tilt angle depends on the length of the spacers of the support 10. In summary, it is clear that even when the printing plate 2 is pivoted about the x-axis, a displacement of the printing plate 2, or rather of the center point M of the printing plate 2, occurs along the y-direction.

[0102] So far, only displacements of the printing plate 2 along the y-direction have been discussed. However, it is evident that a displacement along the x-direction can also occur, for example, during a multi-axis pivoting of the printing plate 2, when one corner point of the printing plate 2 is stationary and the other corner point and the side point of the printing plate 2 are displaced, as indicated, for example, in Figures 6a and 6b. Figure 6a shows the plane of the printing plate 2 in a horizontal position, and Figure 6b shows a corresponding displacement of a point after a multi-axis pivoting of the printing plate 2.

[0103] Figures 7a and 7b show point clouds of the vertices and the side point of printing plate 2, as well as the center point M (Figure 7a), for all possible rotations of printing plate 2. Specifically, PI represents the point cloud of the first vertex of printing plate 2, P2 the point cloud of the second vertex of printing plate 2, P3 the point cloud of the side point of printing plate 2, and P4 the point cloud of the center point M of printing plate 2. Figure 7b shows the point cloud P4 of the center point M of printing plate 2 in detail in the xy-plane. It is evident that printing plate 2, i.e., the center point M of printing plate 2, shifts during a rotation of printing plate 2; that is, a translational movement of printing plate 2, or rather of the center point M of printing plate 2, occurs.

[0104] In summary, the multi-axis 3D printer 1 described above is designed such that the print bed 2 shifts when the print bed 2 is pivoted along the x-axis and / or the y-axis, i.e., a translational movement occurs. It should be noted again that the multi-axis 3D printer 1 described above is only one example of a multi-axis 3D printer 1 in which the print bed 2 shifts when the print bed is pivoted along the x-axis and / or the y-axis. The solutions described below can also be used in other multi-axis 3D printers 1 in which the print bed 2 shifts when the print bed is pivoted along the x-axis and / or the y-axis.

[0105] With the aforementioned multi-axis 3D printers, multi-axis 3D printing is only possible with a loss of quality without further measures. It is therefore proposed to correct this displacement of the print bed 2 using the algorithm shown in Figure 8.

[0106] In the first step S1, initial path points are provided along which the multi-axis 3D printer 1 will print, for example, as shown in Figures 1b, 1c, and 1d. For clarity, the initial path points can be, for instance, the path of the reinforcement 6 shown in Figure 1c. The initial path points can be specified, for example, in the x-axis and y-axis coordinate system, and optionally also the z-axis. Figure 9a shows an example of initial path points. It is also evident that the initial path points are to be printed onto a curved surface, and the print head 3 should always be perpendicular to the surface during the printing process.

[0107] In step S2, slope information can be received or determined for each of the first path points. This slope information can, for example, be a normal vector N at the respective path point; that is, the normal vector N depends on the specific path point or the surface curvature beneath it. Figure 9a schematically shows two normal vectors N for different first path points, and it is evident that these point in different directions because the first path points are to be printed at locations on the substrate with different curvatures. It should be noted that the slope information does not necessarily have to be a normal vector N; however, it will generally be information from which the normal vector N can be derived.

[0108] The tilt information is used, among other things, to allow the print bed 2 to rotate into a specific tilt position during printing by the (non-rotating) print head 3, ensuring that the print head 3 prints perpendicular to the underlying material. In the example shown in Figure 9a, the print bed 2 will rotate clockwise around the y-axis via a first section A1 and counterclockwise around the y-axis via a second section A2. Therefore, in step S3, a print bed tilt can be determined to print the first path points according to the tilt information, and print bed control commands (generally: tilt control commands) can be derived from the tilt information to bring the print bed 2 into the specified tilt position.

[0109] However, as explained above, the print plate 2 shifts during pivoting along the x-axis and / or along the y-axis. To ensure that the first path points from the print head 3 are printed in the correct position, a path correction is calculated in step S4, which compensates for the translational movement of the print plate 2.

[0110] For path correction, the displacement of the pressure plate 2 along the x-axis and / or the y-axis can be determined from the inclination information. Subsequently, a coordinate transformation of the first path points can be performed based on the determined displacement to obtain second path points. Figure 9b shows the second path points, which are corrected to the first path points by the translational movement of the pressure plate 2 during inclination.

[0111] In step S5, printhead control commands (generally: print control commands) can be determined from the second path points to move the printhead 3 along the second path points. If material is then printed with the printhead 3 according to the printhead control commands and the print bed 2 is simultaneously controlled according to the print bed control commands, a body is printed that essentially takes on a shape as shown in the first path points, with the printhead 3 always remaining perpendicular to the surface of the build body during printing.

[0112] In step S6, the tilt control commands and the pressure control commands can be issued, so that the multi-axis 3D printing of figures 1b to Id can be carried out.

[0113] The following section discusses path correction in more detail. As mentioned earlier, the position of the print bed 2 itself changes when it shifts within its supports (or more generally, when it shifts during a print bed tilt). Therefore, the horizontal positions of the print bed 2 must be determined based on the vertical positions of the supports or bearing points, which are defined by the motors. This allows for the calculation of the print bed 2's shift and tilt. The shift and tilt are then required to correct the position of the object being printed. This correction is necessary for the multi-axis 3D printer to move the print head 3 to the correct position, which, due to the shift and tilt of the print bed 2, no longer corresponds to the digital model of the object being printed at that moment.

[0114] In theory, this can be achieved by representing the displacement and inclination of the printing plate 2 using a local coordinate system, where two axes lie in the plane of the printing plate 2 at any given time, while the third axis forms the normal vector of the printing plate 2. This local coordinate system is calculated from the position of the three supports 10, or the corner points and the side point of the printing plate 2, and allows the displacement and rotation of the object to be printed to the correct position at any given time by means of coordinate transformation.

[0115] Thus, only the determination of the horizontal position of the supports 10, or the corner points and the lateral point of the pressure plate 2 (in general: the bearing points of the pressure plate), is still missing, given the vertical positions of the three supports 10 or the bearing points. Mathematically, three equations can be formulated for this, containing a total of three variables for the given vertical positions and three unknowns for the horizontal positions. If only one support 10 or bearing point moves vertically, or if two of the supports 10 move in the same or opposite directions relative to the third, then the position can be quickly determined by simplifying the equations in this way. Such movements are referred to as uniaxial tilting.However, as soon as at least two of the three supports 10 move non-uniformly, which is called multi-axial inclination, the equations can no longer be sufficiently simplified and an analytical solution is not always possible or at least not easily possible.

[0116] To overcome this problem, the aforementioned equations can be solved numerically for all z-positions within a given range for the desired angular range with a certain step size or resolution using parallel computing and stored as data sets. For example, the data sets for each of the three supports can contain every z-position, the corresponding x-position and y-position, and the associated normal vectors. Due to the printer's symmetry, only half of all possible z-positions are needed for the computationally intensive calculations, which significantly reduces the computation time. To speed up data retrieval, not all data is stored in a single record, which would require opening the entire record each time the data is used. Instead, the data is grouped according to its normal vectors N and stored in multiple records.Thus, during the reading process, only those data records are opened whose groups contain the desired normal vectors.

[0117] However, the data for path correction could also be obtained through AI.

[0118] For example, a supervised learning (SL) model can be used, which is trained on pre-computed data. This pre-computed data can be obtained as described above. Such a trained SL model can replace the search mechanism for the datasets and significantly increase efficiency.

[0119] The data sets or the trained model can then be used in step S4 to easily enable path correction.

[0120] The preceding case considered where each support 10 comprises a rail (hereinafter also referred to as a support rail), wherein the support rails of the supports 10 are inclined to the x-axis and the y-axis at the corner points of the pressure plate 2 and extend inwards from the guide rail 9. The support rail of the support 10 at the side point of the pressure plate 2 runs parallel to the y-axis. With this arrangement, an analytical solution for path correction is not possible.

[0121] Surprisingly, it has been found that the calculation of the path correction is significantly simplified if the support rails of the supports 10, in which the corner points of the pressure plate 2 are mounted, run parallel to the x-axis, and the support rail of the support 10, in which the side point of the pressure plate 2 is mounted, runs parallel to the y-axis, as shown in Figure 10. In Figure 10, reference numeral 30 indicates that two bearing points of the pressure plate 2 run only along the x-direction, and reference numeral 40 indicates that one of the bearing points of the pressure plate 2 runs only along the y-axis. This significantly simplifies the equations for calculating the control of the supports 10, allowing them to be solved analytically. In particular, it is no longer necessary in this case to solve the equations for all z-positions beforehand and store the results as data sets.This results in a huge simplification both in terms of preparing for the printing process, since no equations need to be solved beforehand, and in terms of carrying out the printing process, since no searches need to be performed in countless data records.

[0122] This simplified path correction method can generally be implemented when two of the support rails are parallel to each other and one support rail is perpendicular to the other two. Path correction is particularly easy to implement for such a multi-axis 3D printer.

[0123] With reference to Figures 2 to 5d, it should be noted that the three points of the pressure plate 2 were extended downwards perpendicular to the pressure plate 2 by means of spacers. The balls attached to the ends of the spacers were mounted on the support rails, allowing them to rotate freely and moving only along the direction of the supports. The support rails themselves, on which the ball joints of the pressure plate moved, are only movable in the vertical direction. Since the rails protrude into the build space at all times, the tilt angle of the pressure plate is limited in certain orientations, as otherwise the pressure plate 2 would collide with the support rails. The maximum tilt angle can be increased by lengthening the spacers, but this can lead to a loss of precision, partly due to increased instability resulting from the long lever arms of the spacers.

[0124] To solve this problem, a dedicated multi-axis 3D printer 1 was developed, which is shown in Figures 11 to 22. This multi-axis 3D printer 1 also comprises a print bed 2, a print head 3, and three parallel guide rails 9. Three joint connections 50, each consisting of a ball, are provided on the print bed 2, projecting essentially parallel to the print bed 2. Furthermore, the multi-axis 3D printer 1 includes three supports 51, which are movable in the z-direction along the guide rails 9 and can be individually controlled. Connecting rails 52 are located between the joint connections 50 and the supports 51, and are movable in one direction perpendicular to the guide rails 9. At one end, each connecting rail 52 has a receptacle for the joint connection 50.

[0125] In this variant as well, the printing plate 2 is essentially rectangular and a first corner point and a second corner point of the printing plate 2 are each supported on a guide rail 9 via the supports 51 and the connecting rails 52 and a side center point of the printing plate 2 is supported on a guide rail 9 via a support 51 and a connecting rail 52.

[0126] Figures 11 to 14 show a rest position of the multi-axis 3D printer 1, in which the print bed 2 is in a horizontal position.

[0127] In contrast, Figures 15 to 18 show a rotation of the printing plate 2 about the x-axis. Here, the two supports 51 that hold the corner points of the printing plate 2 via the connecting rails 52 move downwards, and the support 51 that holds the side point of the printing plate 2 via a connecting rail 52 moves upwards. The connecting rails 52 that hold the corner points of the printing plate 2 remain static with respect to their respective supports 51, and the connecting rail 52 that holds the side point of the printing plate 2 moves with respect to its support 51 in the direction of the printing plate 2.

[0128] Figures 19 to 22 show a rotation of the printing plate 2 about the y-axis. The two supports 51 that hold the corners of the printing plate 2 via the connecting rails 52 move in opposite directions, upwards and downwards respectively, while the support 51 that holds the side point of the printing plate 2 via a connecting rail 52 remains stationary. The connecting rails 52 that hold the corners of the printing plate 2 move relative to their respective supports 51 in the direction of the printing plate 2. The connecting rail 52 that holds the side point of the printing plate 2 remains stationary relative to its support 51.

[0129] The multi-axis 3D printer 1 described above has three guide rails 9 extending in the z-direction. However, it should be noted that the multi-axis 3D printer 1 can also have at least two, e.g. exactly two or exactly four, guide rails 9, with exactly one support 10, 51 being provided for each guide rail 9.

Claims

Claims:

1. Multi-axis 3D printer (1) comprising a print plate (2), a print head (3) and at least two, preferably exactly three or exactly four, parallel guide rails (9), wherein the print plate (2) is supported on the guide rails (9) via supports (10), wherein the supports (10, 51) are displaceable in the z-direction along the guide rails (9) and can be individually controlled, wherein the printing plate (2) has a support point (50) for each of the supports (10, 51), characterized in that the support points (50) of the pressure plate (2) are mounted on the supports (10, 51) in such a way that they are each mounted slidably along a displacement direction which runs at an angle to the z-direction.

2. Multi-axis 3D printer (1) according to claim 1, wherein the displacement directions of all support points (50) are orthogonal to the z-axis.

3. Multi-axis 3D printer (1) according to claim 1, comprising exactly three guide rails (9) and exactly three supports (10, 51), wherein two support points (50) of the print plate (2) are slidably mounted on the supports (10, 51) in an x-direction and one support point (50) of the print plate (2) is slidably mounted on the supports (10, 51) in a y-direction.

4. Multi-axis 3D printer (1) according to one of claims 1 to 3, wherein the supports (10) each comprise a support rail in which a support point (50) of the print plate (2) is slidably mounted.

5. Multi-axis 3D printer (1) according to one of claims 1 to 3, wherein a connecting rail (52) is slidably mounted in each support (51), wherein the connecting rails (52) are slidably mounted with respect to their respective support (51) along the respective direction of displacement, and wherein each connecting rail (52) pivotally mounts a point of the print plate, preferably via a joint connection (50) projecting parallel from the print plate (2), which is particularly preferably a ball joint.

6. Multi-axis 3D printer (1) according to claim 4 or 5 in conjunction with claim 3, wherein the print plate (2) is substantially rectangular and wherein a first corner point and a second corner point of the print plate (2) are each supported in parallel support rails or on parallel connecting rails (52) and a side midpoint of the print plate (2) is supported in a support rail or on a connecting rail (52) normal to the other two support rails.

7. Computer-implemented method for determining control commands for a multi-axis 3D printer (1) according to any one of claims 1 to 6, wherein the method comprises the following steps: - Receiving first path points, preferably in the coordinate system of the print head (3) or the print plate (2), wherein inclination information, in particular a normal vector, is received or determined for the path points, - Determining an inclination of the print plate (2) and / or the print head (3) to print the first path points according to the inclination information, and generating inclination control commands to bring the print plate (2) and / or the print head (3) to the said inclination, - Performing a path correction, including the following steps: o from the inclination information, determine the translational movement of the printing plate (2) and / or the print head (3) for this inclination information, and perform a coordinate transformation of the first path points based on the determined translational movement to obtain second path points, and o Generating print control commands to move the print head (3) along the second path points, Output of tilt control commands and pressure control commands.

8. Method according to claim 7, wherein the print head (3) is movable along an x-axis and along a y-axis, wherein the print plate (2) is pivotable about the x-axis and about the y-axis, and wherein the print plate (2) moves when the print plate (2) is pivoted along the x-axis and / or the y-axis.

9. A method according to claim 7 or 8, comprising the step of providing at least one data set in which at least one inclination information is specified and for which at least one inclination information the translational movement with respect to this inclination information is specified, wherein preferably also the inclination control commands are specified for the at least one inclination information.

10. A method according to claim 9, wherein at least two, preferably at least ten or at least fifty, data sets are provided, wherein each data set contains a plurality of inclination information and wherein each data set specifies different intervals of inclination information.

11. Method according to any one of claims 7 to 10, comprising the step of providing a model trained by means of a machine learning algorithm, wherein the trained model is designed such that it accepts inclination information as input data and outputs inclination control commands with respect to this inclination information and / or the translational movement with respect to this inclination information as output data.

12. Method according to claim 11, wherein the machine learning algorithm was trained by supervised learning using at least one data set in which at least one inclination information is specified and for which the inclination control commands and / or the translational movement with respect to this inclination information are specified.

13. Method according to any one of claims 7 to 12, comprising the step of creating at least one data set by numerically calculating the inclination information and / or the translational movement from discretely selected inclination control commands.

14. Method according to any one of claims 7 to 13, comprising the step of issuing the tilt control commands and the pressure control commands to the multi-axis 3D printer (1) for a multi-axis 3D print, wherein the multi-axis 3D printer (1) moves the print plate (2) and / or the print head (3) according to the tilt control commands and moves the print head (3) and / or the print plate (2) according to the pressure control commands, and during the movement of the print head (3) and / or the print plate (2) ejects printing material from the print head (3).

15. The method of claim 14, further comprising the step of printing a support structure (4) without pivoting the print bed (2), wherein the inclination information for at least one of the first path points is a normal vector to the surface of the support structure (4).

16. The method of claim 15, further comprising the steps performed in multi-axis 3D printing: - Printing a first top layer (5) onto the support structure (4), - Printing a reinforcement (6) onto the first cover layer (5), - Printing a second top layer (8) onto the reinforcement (6), wherein the printing plate (2) is preferably pivoted during the printing of the first top layer (5), the reinforcement (6) and the second top layer (8).

17. Method according to claim 16, further comprising the step of printing a filler material after printing the reinforcement (6) and before printing the second cover layer (8), wherein the filler material is printed into spaces (7) of the reinforcement onto the first cover layer.

18. Computing unit comprising a processor configured to perform the method according to any one of claims 7 to 17.

19. System comprising a multi-axis 3D printer (1) according to any one of claims 1 to 6 and a computing unit according to claim 18, wherein the multi-axis 3D printer (1) and the computing unit are configured to perform the method according to any one of claims 7 to 16.

20. Orthosis manufactured by a method according to one of claims 14 to 17, wherein the orthosis (20) comprises the first cover layer (5), the reinforcement (6), optionally the filling material and the second cover layer (8).

21. Computer program comprising instructions which, when the program is executed by a computer, cause it to execute the method according to any one of claims 7 to 17.

22. Computer-readable data carrier on which the computer program according to claim 21 is stored.

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