FIELD

[0001] The present application relates to additive manufacturing. In particular, the present application relates to a printhead end for a fiber printhead and a printing method.

BACKGROUND

[0002] In the field of additive manufacturing an additive manufacturing apparatus is also called a 3D-printer. In 3D-printing parts or workpieces are built/created/generated by subsequent depositing layers of build material (comprising at least one individual bead or strand of said build material) onto each other. This build material may be piastic material, and in particular, the depositing process may be the FDM or FFF or FLM process or any other polymer melt dispensing process. The build material supplied to the 3D-printer may be -but not limited to- filament or granulated thermoplastic material.

[0003] The 3D-printer usually comprises a printhead that moves in three directions along a printing trajectory or tool path. Also, there are 3D-printers that comprise print- head that move in two directions (commonly the X- and Y-direction or axis) and a printbed (the surface or structure on/to which the workpiece(s) are created) that moves in the third direction (commonly the Z-direction or axis). Also, there are printheads that are mounted to a conventional industrial robot such that the printhead can realize complex printing trajectories. The printhead generally comprises a liquefier to melt the build material and a printhead end that is located downstream of the liquefier. The printhead end may comprise further heating such that the melt produced by the liquefier is kept at a desired temperature until the point the build material leaves the printhead or the printhead end via a material opening or nozzle. Also, the liquefier and the printhead end may be a unitary piece such that the build material enters or is fed into the heated printhead end where the build material is molten. Conventionally the (overall) direction of the build material leaving the printhead end and a printing trajectory are not parallel to each other, most commonly they are perpendicular.

[0004] In order to produce workpieces with increased stability and rigidity, build materials comprising fibers are used. These build materials may be filaments (mostly round shaped cross section of the filament) or tapes (mostly rectangular cross section of the filament). There are two different sorts of fibers that are currently used in 3D- printing: short fibers and long or endless fibers. The short fibers are chopped endless fibers that usually are already incorporated in the build material (filament, tape, granulated material). Build materials comprising short fibers can be applied without major differences to build material comprising no fibers.

[0005] Build material comprising long fibers, however, needs to be processed significantly different from short fibers due to the need to cut the fibers e.g. at the end of a section of the print trajectory or couture or the print job. The long or endless fibers may be already incorporated in the build material (e.g. fiber reinforced tape or filament) or the fibers may be supplied to the printhead or printer separately from the plastic build material (filament, tape, granulates). The fibers will then be embedded in the printer or printhead into a matrix of said plastic build material resulting in a fiber-material matrix or fiber reinforced build material. Both procedures are commonly known. The fibers and the plastic material may be of any known kind and also biomaterials.

[0006] One problem that arises using endless fibers is the said cutting of the fibers since this poses numerous problems. So far fairly complicated mechanisms were developed that have the commonly known disadvantages of a decreased availability of a complex system as well as the position of cuting the fiber-material matrix or the build material containing the fibers. It is desirable to cut the fiber-material matrix as close as possible at the position the cut need to be. There are solutions where a cuting unit is fairly far upstream in the print head such that the fibers are cut long before they even exit the printhead e.g. WO 2019185194 A1 or EP 3613581 A1. However, this renders the printing process less reliable as the fibres are cut far from the point where they come to lie as a deposited strand. There is an inaccuracy as the length from the nozzle or material opening to the cutting unit needs to correspond to the distance of the printing trajectory the printhead has to travel such that the cut of the fibers comes to lie at the correct position. If these two distances do not correlate, there might be a fault in the workpiece. The longer the distance between the nozzle and the cutting unit is, the more likely it is that a fault will occur. As mentioned, there are technically considerably complicated solutions to cut the fibers "in situ" at the ideal position at the work piece (e.g. company Arevo: htps://youtu.be/PxRaOJylLQE?t=31). However, the aforementioned solutions all bear considerable disadvantages in view of process reliability and/or workpiece quality.

SUMMARY

[0007] It is the object of the present application to overcome the aforementioned disadvantages. This object is atained by the appended independent claims. Selected embodiments are comprised in the dependent claims. Each of which, alone or in any combination with the other dependent claims, can represent an embodiment of the present application.

[0008] According to one aspect of the present application a 3D-printhead end comprises a material channel and a cutting tool. Wherein the cuting tool is located at least partially in a cuting channel of the 3D-printhead end and the cuting tool intersects with the material channel in a cuting angle at a cuting point. The material channel changes its orientation within the 3D-printhead end. This may have the advantage that the cutting can be inside the 3D-printhead end and thus resulting in a less complicated design as well as the cuting can be close to the actual point where it needs to be. This may have the further advantage the material exiting the printhead end is already oriented in or even parallel to the print trajectory. The cuting tool may have a blade insert.

[0009] According to one aspect of the present application a 3D-printhead end comprises a material channel and a cuting tool. Wherein the cuting tool is located at least partially in a cutting channel of the 3D-printhead end and the cutting tool intersects with the material channel in a cuting angle at a cuting point. This may have the advantage that the cuting can be inside the 3D-printhead end and thus resulting in a less complicated design as well as the cuting can be close to the actual point where it needs to be.

[0010] According to one aspect of the present application a 3D-printhead end comprises a curved material channel. This may have the advantage that the change of orientation of the material channel is smooth and easy to follow by the fiber-material matrix.

[0011] According to one aspect of the present application the material channel of the 3D-printhead end comprises an inlet and a material opening. Further, the cross section of the material channel at the inlet is different from the cross section at the materia! opening. This may have the advantage that a flat and/or thin filament or tape can be supplied to the printhead end and can be heated thoroughly quickly. Further, this may have the advantage that feeding a flat and/or thin filament or tape is more reliable. By means of the cross-section change it is possible to have a cross-section of the build material that is well-suited for the related needs at the inlet (for example feeding and heating) and whose cross-section is further well-suited for the related needs at the materia! outlet (for example deposition form or cross-section of the build material).

[0012] According to one aspect of the present application regarding a 3D-printhead end, the cuting angle between the cuting tool and the material channel is different from 90 degrees. This may have the advantage that cuting the fiber-material matrix may be more easily.

[0013] According to one aspect of the present application regarding a 3D-printhead end, the material channel comprises a material opening through which build material or the fiber-material matrix in the material channel can leave the 3D-printhead end. The orientation of the material channel in the area of the material opening is essentially parallel to an orientation the 3D-printhead end is intended to move in while in use. In other words, the build material or fiber-material matrix leaves the 3D-printhead end via the material opening essentially in or parallel to the direction the 3D-printhead end is moving i.e. in or parallel to a printing trajectory. This may have the advantage, that the cuting of the build material is rendered more easily, and the quality of the printed workpieces may be enhanced. Further, if the build material leaves the 3D-printhead end essentially parallel to the printing trajectory, the fiber-material matrix is to some extend pulled out of the 3D-printhead end, reducing or even eliminating the need to feed the fiber-material matrix to the printhead (this effect is of course independent of the cuting feature(s)).

[0014] According to one aspect of the present application regarding a 3D-printhead end, the cuting point is downstream of a beginning of the change of orientation of the material channel. This may have the advantage that the cuting point is in the vicinity of the ideal "in situ" cuting position, yet still inside the 3D-printhead end.

[0015] According to one aspect of the present application regarding a 3D-printhead end, the cuting tool is actuated by at least one of an excentric, a cam plate or a drive wheel. This may have the advantage that the design of the 3D-printhead end may be kept compact.

[0016] According to one aspect of the present application regarding a 3D-printhead end, the cutting tool is a rotational blade or an excentric rotational blade. This may have the advantage that the service life of the cutting tool may be increased.

[0017] According to one aspect of the present application regarding a 3D-printhead end, the rotational blade or the excentric rotational blade can rotate in opposite directions. This may have the advantage that the service life of the rotational blade may be further increased by distributing the wear to both cuting directions.

[0018] According to one aspect of the present application regarding a 3D-printhead end, the cuting tool uses at least one of pressure air, radiation (e.g. laser, electron beam or plasma) or water as cuting medium. This may increase the service life of the cuting tool since no consumable materials such as blades have to be maintained which leads to down time of the cuting tool and thus the printer.

[0019] According to one aspect of the present application regarding a 3D-printhead end, the material opening is located adjacent to the cuting point. This may have the advantage that the cuting point is even closer to the ideal "in situ" position. [0020] According to one aspect of the present application regarding a 3D-printhead end, the cuting channel is curved. This may have the advantage that the cuting point may be positioned closer to the material opening and thus closer to the ideal "ins situ" position.

[0021] According to one aspect of the present application regarding a 3D-printhead end, the cuting tool can be moved in the cuting direction to at least partially extend to the outside of the 3D-printhead end. This may have the advantage that the cutting tool may be serviced without disassembly of the 3D-printhead end. This further may have the advantage that an already deposited' strand of fiber-material matrix may be pinned down and held in place.

[0022] According to another aspect of the present application at least one of the 3D- printhead end, a build platform or a 3D-printhead is rotatable. This may have the advantage that if the material opening is spaced from a rotational axis of the printhead or the build platform, the quality of the printed workpieces is increased because the deposited build material may follow the printing trajectory and e.g. the intended contour of the workpiece more accurately.

[0023] According to another aspect of the present application a computer program adapted to be used with an additive manufacturing device comprises instructions which cause, when the program is executed by the additive manufacturing system, a 3D- printhead ending or parts (above mentioned) thereof to be produced. This may have the advantage that the relatively complex design of the 3D-printhead ending may be manufactured more conveniently and cheaper.

[0024] According to another aspect of the present application, a 3D-printing method for printing fiber reinforced workpieces comprises the step of supplying a fiber-material matrix to a 3D-printhead end in one orientation, the step of changing the orientation along the way of the fiber-material matrix through the 3D-printhead end, the step of cuting the fiber-material matrix at least partially before the fiber-material matrix exits the 3D-printhead end. This may have the advantage that a fiber reinforced workpiece produced by such method has an increased quality. Further, cuting the material allows to for endless or long fibers to be used in the method and consequently increasing the stability of the produced workpiece. Further, a partial cuting of the fiber-material matrix may have the advantage that if the printing trajectory comprises e.g. a sharp bend, the at least partially cut and then deposited fiber-material matrix may follow the sharp bend more closely. This in turn results in a higher quality of the workpiece.

[0025] According to an aspect of the present application, a 3D-printing method further comprises the step to move a cuting tool to the outside of the 3D-printhead end to pin down a previously deposited strand of the fiber-material matrix. This may have the advantage that the previously deposited strand of the fiber-material matrix may be fixed and prevented from e.g. peeling. This may have the advantage that the quality of the workpiece will be increased.

[0026] According to an aspect of the present application, the 3D-printing method further comprises the step of keeping the cuting tool in a cuting position. This means that a material channel that is intersected by the cutting tool in order to cut the fibermaterial matrix, is at least partially closed by the cuting tool which in turn prevents e.g. oozing of the fiber-material matrix.

[0027] According to an aspect of the present application, the step of at least partially cuting the fiber-material matrix of the 3D-printing method comprises to rotate a rotational blade or an excentric rotational blade in one direction or an opposite direction. This may have the advantage that the service life of the blade may be increased by distributing the wear to both cuting directions.

[0028] 3D-printing method according to any of claims 15 to 17, wherein the step of at least partially cuting the fibre-plastic-material comprises to move a drive wheel of a feed unit into contact with the cuting too! (12) to move said cuting tool.

[0029] The cuting point is to be understood as a cuting area that at least covers the material channel at the cuting point. [0030] Each of the above aspects is to be considered an invention on its own. The aspects may be freely combined with each other and each feature not described as being dependent on another feature may also be freely combined with each other. The features of the disclosed method may be incorporated into an apparatus and vice versa.

BRIEF DESCRIPTION OF THE FIGURES

[0031] Further advantages and features of the present disclosure will be apparent from the appended figure. The figure is of merely informing purpose and not of limiting character. The figure schematically describes an embodiment of the present application. Hence, the appended figures cannot be considered limiting for e.g. the dimensions of the present disclosure.

[0032] Fig. 1 schematically shows an embodiment of a 3D-printhead end.

[0033] Fig. 2 schematically shows a cutting angle of the embodiment depicted in fig. 1.

[0034] Fig. 3 schematically shows another cuting angle of an alternative 3D-print- head end, similar to figs. 1 and 2.

[0035] Fig. 4 schematically shows the 3D-printhead end depicted in fig. 1 in a cutting position.

[0036] Fig. 5 schematically shows an alternative 3D-printhead end with a curved cutting tool.

[0037] Fig. 6 schematically shows an alternative 3D-printhead end with an excentric rotational blade.

[0038] Fig. 7 schematically shows a variation of the 3D-printhead end depicted in fig.

3. [0039] It is to be noted that in the different embodiments described herein same parts/elements are numbered with same reference signs, however, the disclosure in the detailed description may be applied to all parts/elements having the regarding reference signs. Also, the directional terms / position indicating terms chosen in this description like up, upper, down, lower downwards, lateral, sideward are referring to the directly described figure and may correspondingly be applied to the new position after a change in position or another depicted position in another figure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] Initially referring to fig. 1 a 3D-printhead end 10 is depicted. The 3D-printhead end 10 comprises a material channel 11 and a cuting tool 12. The cuting tool 12 is movably disposed in a cutting channel 14. The cutting tool 12 is movable along the course of the cutting channel 11 , that is in a cuting direction CD and vice versa. The material channel 11 comprises an inlet 15 and a material opening 16. The orientation and cross-section of the material channel 11 changes from the inlet 15 to the material opening 16 as can be seen from fig. 1. A fiber-material matrix 18 (build material, not shown in fig. 1) enters the 3D-printhead end 10 at the inlet and is deposited onto the workpiece at the material opening 16. Hence, the inlet 15 is upstream of the material opening 16. The cuting channel 14 intersects with the material channel 11 in the vicinity of the material opening 16 at a cuting point CP. It is desirable that the cuting point CP is as close as possible to the material opening 16 and thus the position or point at the workpiece where the fibers of the cut fiber-material matrix 18 need to come to lie.

[0041] Fig. 2 shows the 3D-printhead end 10 depicted in fig. 1 indicating a cutting angle CA between the cuting tool 12 and the material channel 11. In fig. 2 the cuting angle is an acute angle. As indicated in fig. 1 the cuting direction CD is parallel to the upstream direction of the material channel 11 in the vicinity of the inlet 15. Here, said directions are vertical.

[0042] Fig. 3 shows an alternative 3D-printhead end 10 where the orientation of the cuting tool 12 and thus the cutting channel 14 are slanted in comparison with figs. 1 and 2. As can be seen from figs. 2 and 3 this has the advantage that the cuting point CP moves further towards the material opening 16 and thus in the direction of the ideal "in situ” cutting position. Here, the cutting angle CA is about 90 degrees.

[0043] Fig. 4 shows the 3D-printhead end 10 depicted in fig. 1 and 2 with the cuting tool 12 in the cuting position CPO and further extending out of the 3D-printhead end 10 (see detail A). This has the advantage that an already deposited strand of fibermaterial matrix (not shown) can be pinned down onto the workpiece (not shown).

[0044] Fig. 5 shows an alternative 3D-printhead end 10, similar to fig. 3. However, here the cuting tool 12 is flexible and arranged in a curved cutting channel 14. This has the advantage that the cuting point CP -moves further towards the material opening 16 and the upper part of the cutting tool 12 is still parallel to the upstream part of the material channel 11 (vertical in case of fig. 4).

[0045] Fig. 6 shows an 3D-printhead end 10 comprising an excentric rotational blade 12. The cuting channel 14 is in this case a cavity in which the excentric rotational blade 12 is housed. When the excentric rotational blade 12 is rotated it intersects with the materia! channel 11 such that a fiber-material matrix 18 in the material channel 11 is cut. Due to the eccentricity the rotational blade 12 cuts in both directions of rotation. If a fixation bore of the rotational blade 12 is centric with regard to the rotational blade 12 and the eccentricity is achieved with a drive mechanism driving said blade, then the blade can be used more often since it only has to be loosened rotated by a bit and then fixed again to use one two other sections on the circumferential blade to cut. The material channel might be curved or straight with this embodiment. In other words, the rotational blade 12 can also be used if the material channel does not change its orientation in the 3D-printhead end.

[0046] Fig. 7 shows a variation of the 3D-printhead end 10 depicted in fig. 5. Here, the cuting channel 14 is also curved and the cuting tool 12 is flexible. The fiber-material matrix 18 enters the 3D-printhead end 10 in a feed direction FD that is here parallel to the cuting direction CD and both are vertical Further, the fiber-material matrix 18 may be fed into the 3D-printhead end 10 by a (e.g. friction) drive wheel 17. The drive wheel 17 is movable in an adjusting direction AD. This movement allows the drive wheel 17 to get into contact with either the fiber-material matrix 18 or the cuting tool 12. The drive wheel can turn in both senses of a drive wheel rotation. If the drive wheel 17 is in contact with the fiber-material matrix 18 and the drive wheel 17 is turned clockwise, then the fiber-material matrix 18 is fed into the 3D-printhead end 10. If the drive wheel 17 is moved parallel to the adjusting direction AD into contact with the cuting tool 12, the feed of the fiber-material matrix 18 stops and if the drive wheel 17 is turned anti-clockwise, the cuting tool 12 is moved into a cuting position (here downward and in cuting direction CD) and cuts the fiber-material matrix 18. If the drive wheel 17 the is rotated clockwise, the cuting tool 12 travels back along the cuting direction CD to its initial position and opening up the material channel 11 at the cuting point CP.

[0047] In all figures like reference sings are used for like or similar parts/elements as in the other figures. Thus, a detailed explanation of such part/element will only be given one for the sake of brevity.

[0048] The embodiments depict possible variations of carrying out the subject mater of the application, however, it is to be noted that the subject mater of the application is not limited to the depicted embodiments/variations but numerous combinations of the here described embodiments/variations are possible and these combinations lie in the field of the skills of the person skilled in the art being motivated by this description.

[0049] The scope of protection is determined by the appended claims. The description and drawings, however, are to be considered when interpreting the claims. Single features or feature combinations of the described and/or depicted features may represent independent inventive solutions. The object of the independent solutions may be found in the description.

[0050] It is further to be noted that for a beter understanding parts/elements are depicted to some extend not to scale and/or enlarged and/or down scaled. List of reference signs

10 3D-printhead end

11 material channel

12 cuting tool

14 cuting channel

15 inlet

16 material opening

17 drive wheel

18 fiber-material matrix

CA cuting angle

CD cuting direction

CP cuting point

CPO cuting position

FD feed direction

DWR drive wheel rotation

AD adjusting direction