A filament feeding device for use in 3d-printing and method for feeding a filament or changing a filament

Abstract

The present disclosure relates a filament feeding device and method for changing the filament in a filament feeding device. The device has a housing with an elongated opening configured to allow replacement of an elongated filament portion received between a first feeding wheel and a second feeding wheel through the elongated opening in a direction being at least partly transverse to said feeding direction. The feeding wheels are movable to increase the separation distance. The filament feeding device may be configured to allow a transverse replacement of a filament together with a hot end. Further, a filament feeding device and method where the filament feeding device has a feeding wheel (20) that can pivot around a distanced axis (A1), the engagement force exerted from the first feeding wheel onto the filament (F) thereby depends on the filament feeding resistance is disclosed.

Description

[0001] A FILAMENT FEEDING DEVICE FOR USE IN 3D-PRINTING AND METHOD FOR FEEDING A FILAMENT OR CHANGING A FILAMENT

[0002] Technical Field

[0003] The present disclosure relates to 3D printing and more specifically 3D printing with filaments and the feeding of such filaments and changing of such filaments in the 3D printer.

[0004] Background

[0005] In 3D-printing a filament used for being melted and forming a 3D object is fed by a filament feeding device towards a hot end in which the filament melts. Filaments may be of different materials, different diameter and feature different hardness and surface properties which ultimately affects the printing and feeding process. In 3D printing several different filament materials can be used such as PVA, Nylon, ABS, ABSi, HDPE, PPSF, PLA, PC, PTFE, PEEK, ASA, HIPS and PETG. Different materials and diameters of the filament may be used for different purposes. To allow several different materials and diameters to be used while maintaining efficient 3D-printing it is important for the filament feeding device of a 3D-printer to allow a smooth change of filament. Current solutions on the market often entail cumbersome or expensive solutions for changing filaments. Thus, there is a need for a filament feeding device and method for facilitating filament change in a 3D printer.

[0006] Further, In 3D-printing the filament is fed by a filament feeding device into a hot end where it melts and prints into a 3D-object. One challenge when the filament is fed is that the feeding resistance varies with how fast the filament is melting downstream. The viscosity of the filament usually varies with the temperature. Filament may have a glass transition temperature under which the material is stiff. When printing fast, a high flow of material is needed and the filament will be fed fast and there is not always enough time to heat to the filament to the same extent as when printing slower. Thus, the viscosity of the filament is higher when printing fast than when printing slower resulting in that the feeding resistance of the filament flow increases in fast printing and thereby the force required to feed the filament downstream. This sometimes generate problems relating to feeding and printing quality during fast prints.

[0007] Summary

[0008] Accordingly, it would be desirable to provide a feeding device for enabling fast prints that has an improved feeding function and at least alleviates some of the mentioned drawbacks in present solutions. The invention is based on the inventors’ realization that by constructing a filament feeding device that allows for changing the filament in a direction being transverse to the feeding direction a much simpler change of filament is achieved.

[0009] The present disclosure therefore relates to a filament feeding device and method for changing the filament in a filament feeding device. The device has a housing with an elongated opening configured to allow replacement of an elongated filament portion received between a first feeding wheel and a second feeding wheel through the elongated opening in a direction being at least partly transverse to said feeding direction. The feeding wheels are movable to increase the separation distance.

[0010] In a first aspect of the invention, the inventors have realized that fast / slower prints would benefit from having different filament engaging forces from the feeding wheel. This applies both in faster / slower prints, and also when printing a hard filament, e.g. PLA, with a high material flow which would benefit from a higher engaging force as compared to when printing a softer filament, e.g. TPU, with a lower material flow which can be done with a lower engagement force onto the filament. The inventors’ have created a solution to this problem by arranging a feeding wheel that can pivot around a distanced axis, the engagement force exerted from the first feeding wheel onto the filament thereby depends on the filament feeding resistance. The above-mentioned advantages are achieved by the filament feeding device and method for feeding a filament with the filament feeding device during 3D-printing as claimed in the independent claims.

[0011] According to a first aspect of the inventive concept there is provided a filament feeding device for use in a 3D-printer. The filament feeding device comprises: a first drive wheel configured to be driven about a first axis by a motor, a first feeding wheel mechanically coupled to be driven by the first drive wheel, wherein said first feeding wheel is rotationally arranged about a second axis at a distance from the first axis and comprises filament engaging means for feeding a filament, a second feeding wheel arranged about a fourth axis at a distance from the second axis for feeding a filament received between said first and second feeding wheel, wherein the first feeding wheel is pivotably coupled about the first axis so that an engagement force exerted from the first feeding wheel onto the filament depends on a filament feeding resistance.

[0012] The filament feeding device may comprise a second drive wheel rotatable about a third axis and the second feeding wheel may be pivotably coupled about the third axis. Further, the first axis and third axis may be distanced such that the first and second feeding wheels will pivot upwards along the filament to increase the engagement force when the filament feeding resistance increase.

[0013] By said filament feeding device, the filament may be fed downstream towards a hot end where the filament is melted in order to be applied to a print to form the 3D printed element. The filament is moved by engagement of the filament with the filament engaging means of the first filament feeding wheel.

[0014] The filament engaging means may be a rifled surface along the circumference of the wheel, said rifled surface may be configured to be in contact with said filament to grip it and push it in the direction of the feeding wheel rotation. By the first feeding wheel being pivotably coupled about the first axis, the separation distance between the first feeding wheel and the second feeding wheel is variable based on the pivoting position of the first feeding wheel relative the first drive wheel.

[0015] The filament is fed by means of a downward force exerted onto the filament by the first feeding wheel, by rotation of said first feeding wheel.

[0016] The filament may be of different types such as PVA, Nylon, ABS, ABSi, HDPE, PPSF, PLA, PC, PTFE, PEEK, ASA, HIPS or PETG. Different materials and diameters of the filament may be used for different purposes. Different types of filaments have different hardness and therefore require higher or lower engagement to be fed towards the hot end where the filament is melted. Additionally, the filaments may be melted at different temperatures which will result in differently high filament feeding resistance when being fed towards the hot end. The feeding resistance may also vary with diameter and density of the filament. Higher density of the filament may imply higher filament feeding resistance and a larger diameter of the filament will result in a higher filament feeding resistance.

[0017] Arranging the first feeding wheel pivotable about the first axis enables that when the filament feeding resistance is increased, the engagement force exerted from the first filament wheel onto the filament is increased. Thereby, an increment of the filament flow resistance, e.g. due to a change of filament type increase in feeding flow / speed or lowered temperature at the hot end, is automatically resulting in an increment of said exerted engagement force onto the filament. This results in an improved filament feeding function with a dynamic filament engaging force from the filament feeding wheel onto the filament. The dynamic filament engagement force is achieved by two major contributing factors; The first contributing factor is that as the feeding resistance from the filament increases, more of the torque from the drive wheel will be converted to engagement force towards the filament. As the driving wheel pushes the feeding wheel to rotate, the higher feeding resistance will also push the wheel towards the filament which will result in a higher engagement force.

[0018] The second contributing factor is that when the feeding resistance from the filament increases, some of the feeding wheel torque will be converted to an upwards directed force, and since the feeding wheel is pivotable around the first axis this upwards directed force will be converted to an added engagement force. The feeding wheel wants to “climb” up the filament if the resistance to push the filament downwards is too high. Such a climb will occur along a pivoting trajectory, which will result in a squeeze of the filament so that the filament engagement force even further increase.

[0019] In one embodiment the first drive wheel and the first feeding wheel are driveably connected with gear wheels. Gear wheels may be suitable for the first drive wheel to drive the first feeding wheel. In one embodiment the first drive wheel has a diameter that is different from the first feeding wheel.

[0020] Hereby, the rotational speed may be geared to a desired speed in the feeding wheel relative e.g. a drive motor that drives the drive wheel.

[0021] In one embodiment the filament feeding device further comprises a spring arrangement arranged to exert a pretension force from said first feeding wheel towards said filament.

[0022] Hereby, the spring arrangement may further contribute to the engagement force exerted from the first filament wheel onto the filament. The spring arrangement may further facilitate that the first feeding wheel is in contact with the filament also before the drive wheel is initiated. Further, it allows the drive wheel to be reversed driven without loosing contact between the feeding wheel and the filament.

[0023] In one embodiment the first feeding wheel is driven by the first driving wheel by means of a cog coupling.

[0024] A cog coupling may be suitable for rotational energy of the first drive wheel to be efficiently transferred to the first feeding wheel. The cog coupling is also one way of enabling that an increment of the filament feeding resistance is counteracted by an increment of the engagement force applied to the filament by the filament feeding wheel as explained above.

[0025] In one embodiment the cogs of the first driving wheel that are coupled with the cogs of the first feeding wheel are moved towards the filament when the filament feeding device feeds the filament towards the hot end. This creates an increased engagement force, which increase friction against filament during feeding. The hot end may comprise a nozzle in which the filament is to be melted.

[0026] In one embodiment the first axis is placed further from a hot end than the second axis. Hereby, the drive wheel is located further from the hot end than the filament feeding wheel and the engagement force exerted from the first filament feeding wheel onto the filament is increased when the filament feeding resistance is increased. If the hot end is located below the first feeding wheel, this feature means that the first drive wheel is located above the first feeding wheel.

[0027] In one embodiment the filament feeding device further comprises a second drive wheel rotatable about a third axis and wherein the second feeding wheel is rotatable about a fourth axis and is driven by the second drive wheel.

[0028] Hereby, the second feeding wheel may be arranged on the other side of a filament to squeeze the filament between the first and second feeding wheel which ensures a good feeding function. The second drive wheel may be driven directly or indirectly by the first drive wheel. Hereby, only a single motor may be used to drive both drive wheels. There may be a cog coupling between the first drive wheel and the second drive wheel. As an alternative, the second drive wheel may be separately driven by a separate source such as a second motor.

[0029] The first drive wheel and the second drive wheel may each comprise a first gear wheel and a second gear wheel. The first gear wheel of the first and the second drive wheel may be configured to drive the first and the second feeding wheel, respectively. The second gear wheel of the first and the second drive wheel may be configured to be in cog coupling with each other. Hereby, the rotational speed of the drive wheels may be geared to a desired speed relative a driving motor.

[0030] The first gear wheel of the first and the second drive wheel may have a smaller diameter than the second gear wheel of the first and the second drive wheel.

[0031] In one embodiment the second feeding wheel comprises filament engaging means for feeding the filament. Hereby, an increased feeding force may be exerted onto the filament with a contribution also from the second filament wheel.

[0032] In one embodiment the second feeding wheel is pivotably coupled about the third axis so that an engagement force exerted from the second feeding wheel onto the filament depends on the filament feeding resistance.

[0033] By the second filament feeding wheel being pivotable about a third axis the engagement force exerted from the second feeding wheel onto the filament may also be dynamically variable. An increment of the filament feeding resistance will thereby also be counteracted by that the engagement force from the second filament feeding wheel also increases.

[0034] In one embodiment, the filament feeding device further comprise a first linking arm, wherein said first linking arm is coupled at said first axis to the first drive wheel and at said second axis to the first feeding wheel so that the first feeding wheel is pivotable relative said first drive wheel by rotation of said first linking arm. Hereby, the pivoting motion is enabled through the linkage arm.

[0035] The first linking arm may be coupled with two shafts onto which the first drive wheel and the first feeding wheel are arranged, respectively.

[0036] In one alternative, the fourth axis is static relative the second drive wheel, so that the second feeding wheel is in a fixed position with its rotational center.

[0037] The first axis and third axis may be distanced longer from each other than the distance between the second axis and the fourth axis. Hereby, the first and second feeding wheels will pivot upwards along the filament to increase the engagement force when the filament feeding resistance increases.

[0038] In one embodiment, the exerted force from the first filament wheel towards the filament increases by means of the first linking arm when the resistance of filament feeding increases.

[0039] The first linking arm and the second linking arm may be connected by the spring arrangement mentioned above. Hereby, one or both feeding wheels may be resiliently loaded towards each other.

[0040] In one embodiment the first feeding wheel may be configured to rotate in two opposite directions such that the filament feeding device may feed the filament backwards. In one embodiment the second feeding wheel may be configured to rotate in two opposite directions such that the filament feeding device may feed the filament backwards.

[0041] In one embodiment the first drive wheel and the second drive wheel are in mechanical connection to be driven together.

[0042] By said mechanical connection the first driving wheel and the second driving wheel may be rotating with the same rate. This may imply that the filament is feed with equal engagement forces from the first and the second feeding wheels.

[0043] In one embodiment the exerted force from the first filament wheel towards the filament increases by means of the first linking arm when the resistance of filament feeding increases.

[0044] In one embodiment the filament feeding device further comprises a second linking arm, wherein said second linking arm is coupled at said third axis to the second drive wheel and at said fourth axis to the second feeding wheel so that the second feeding wheel is pivotable relative said second drive wheel by rotation of said second linking arm.

[0045] By having the second linking arm the second feeding wheel movable in a pivoting movement relative the filament comprising a movement component both in the filament feeding direction and in a direction perpendicular to said filament feeding direction.

[0046] The first linking arm and the second linking arm may facilitate movement of the first feeding wheel and the second feeding wheel by means of the mechanical connection between the first drive wheel and the second drive wheel. Hereby, the dynamic engagement force of the feeding wheels towards the filament may be enabled in a simple mechanical construction with the two linking arms.

[0047] In one embodiment the first linking arm and the second linking arm are mechanically coupled to move in tandem. Hereby, the first feeding wheel and second feeding wheel also move in tandem towards and from the filament when the first and second linking arms are moved.

[0048] In one embodiment the coupling between the first linking arm and the second linking arm retains the first and second feeding wheels at equal distance from the filament thread regardless of their pivoting positions. Hereby, the first and second linking arm moving in tandem equal engagement forces may be applied onto the filament by the first and the second feeding wheel.

[0049] The solution with the two linking arms and the coupling between them enables the first and second linking arm to move in tandem which is of great advantage in the presented system having a dynamic engagement force achieved by the pivoting feeding wheel(s).

[0050] However, the solution with the two linking arms and the coupling between the which enables the the first and second linking arm to move in tandem is of value also in a system that has fixed feeding wheel(s), i.e. not dynamic force. Thus, one further aspect of the invention is a filament feeding device for use in a 3D-printer, wherein said filament feeding device comprises a first drive wheel configured to be driven about a first axis by a motor, a first feeding wheel mechanically coupled to be driven by the first drive wheel, wherein said first feeding wheel is rotationally arranged about a second axis at a distance from the first axis and comprises filament engaging means for feeding a filament, a second feeding wheel arranged about a fourth axis at a distance from the second axis for feeding a filament received between said first and second feeding wheels. Further such a filament feeding device would comprise a first linking arm and a second linking arm being mechanically coupled to move in tandem. Hereby, the first feeding wheel and second feeding wheel would also move in tandem towards and from the filament when the first and second linking arms are moved. Such a filament feeding device could entail that the feeding wheels are locked (to avoid pivoting) in the rotational driven position to have a fixed (non-dynamic) engagement force towards the filament when in use. According to another aspect of the invention there is provided a method for feeding a filament with a filament feeding device during 3D printing, wherein the filament feeding device comprises a first drive wheel, a first feeding wheel and a second feeding wheel. The first feeding wheel comprises a filament engaging means configured for feeding a filament, and the method comprises the steps of:

[0051] - rotating the first drive wheel about a first axis with a motor,

[0052] - driving the first feeding wheel by a mechanical coupling to the first drive wheel, wherein said first feeding wheel is rotationally arranged about a second axis at a distance from the first axis and pivotably coupled about the first axis, and

[0053] - increasing a force exerted from said filament engaging means towards said filament by pushing the first feeding wheel towards the filament with said mechanical coupling between the first drive wheel and the first feeding wheel when rotating the first drive wheel to feed filament towards a hot end.

[0054] Hereby, the method for feeding the filament enables efficiently feeding filament towards the hot end. The method contributes to a steadier flow of filament. The increment of engagement force exerted from said filament engaging means towards said filament is dependent on the filament flow resistance and an increment of the filament flow resistance will be counteracted by an increment of the engagement force exerted from the first feeding wheel towards the filament, since the first feeding wheel is pivotable coupled about the first axis, as explained above in relation to the filament feeding device.

[0055] In one embodiment the method further comprises the step of pivoting the first feeding wheel upstream relative the filament flow when the flow resistance of the filament increase. Hereby, the a “climbing effect” may contribute to the dynamic force. The climbing effect occurs with the current setup when there is a force component of the first feeding wheel that allows a movement of the feeding wheel upstream relative the feeding of the filament. Thus, the engagement point between the filament engaging means and the filament is preferably horizontally offset relative the pivoting point, in this case being the axis of the corresponding drive wheel.

[0056] Slightly pivoting the first feeding wheel upstream (climbing the filament as explained above) of the filament flow when the flow resistance of the filament increases further contributes to a steady flow of filament since the force from the filament feeding wheel in the downstream direction increases when the filament feeding wheel squeeze the filament in the pivoting motion.

[0057] In one embodiment the method for feeding the with the filament feeding device further comprises a second drive wheel, wherein the second feeding wheel comprises a filament engaging means configured for feeding a filament, and wherein the method further comprises the steps

[0058] - rotating the second drive wheel about a third axis,

[0059] - driving the second feeding wheel by a mechanical coupling to the second drive wheel, wherein said second feeding wheel is rotationally arranged about a fourth axis at a distance from the third axis and pivotably coupled about the third axis, and

[0060] - increasing a force exerted from said filament engaging means of said second drive wheel towards said filament by pushing the second feeding wheel towards the filament with said mechanical coupling between the second drive wheel and the second feeding wheel when rotating the second drive wheel to feed filament towards the hot end.

[0061] Increasing a force exerted from said filament engaging means of said second feeding wheel towards said filament by pushing the second feeding wheel towards the filament may further contribute to a steady flow of filament since, in this case, both of the feeding wheels exerts an increased force onto the filament when the filament flow resistance increases. According to a third aspect of the inventive concept, the inventors have realized that it would be desirable to provide a feeding device for enabling fast prints that has an improved feeding function and at least alleviates some of the mentioned drawbacks in present solutions. The invention is based on the inventors’ realization that by constructing a filament feeding device that allows for changing the filament in a direction being transverse to the feeding direction a much simpler change of filament is achieved.

[0062] The present disclosure therefore relates to a filament feeding device and method for changing the filament in a filament feeding device. The device has a housing with an elongated opening configured to allow replacement of an elongated filament portion received between a first feeding wheel and a second feeding wheel through the elongated opening in a direction being at least partly transverse, or traverse, to said feeding direction. The feeding wheels are movable to increase the separation distance. The filament feeding device may be configured to allow a transverse replacement of a filament together with a hot end.

[0063] For this purpose, there is provided a filament feeding device for use in 3D-printing, wherein the filament feeding device comprises: a housing, a first feeding wheel configured to rotate about a second axis, a second feeding wheel configured to rotate about a fourth axis. The first and second feeding wheels are separated by a separation distance to allow a filament material to be received between the first and second feeding wheels and be fed in a feeding direction towards a hot end when in use.

[0064] The housing comprises an elongated opening configured to allow replacement of an elongated filament portion received between the first feeding wheel and the second feeding wheel through the opening in a direction being transverse to the feeding direction, and at least one of the first feeding wheel and second feeding wheel is movable to increase the separation distance during the replacement of the elongated filament portion.

[0065] The elongated opening may be configured so that a filament segment can be inserted or removed through the opening in a direction transverse to its extension.

[0066] In the context of this application "through the opening in a direction being transverse to the feeding direction" is meant to be understood as that the filament is removed "transverse" to the feeding direction of the portion of the filament that is removed through the opening. This is clear since a filament is often stored and fed from a filament wheel, which of course has different feeding directions. However, in the hot end the filament is typically fed in a straight direction, often downwards towards a printing plate.

[0067] Hereby, the filament may be replaced efficiently during a print or between prints. By temporarily increasing the distance between the feeding wheels, the filament does not have to be feed the entire way through the feeding hose and replaced with a new in the feeding direction. Instead, the filament may be removed straight out of the housing, perpendicularly to the feeding direction.

[0068] In addition, the separation distance may be varied to load different types of filaments which may have differently large diameters. The filament feeding device may therefore accommodate different types of filaments such as PVA, Nylon, ABS, ABSi, HDPE, PPSF, PLA, PC, PTFE, PEEK, ASA, HIPS or PETG.

[0069] In one embodiment the elongated opening is further configured to allow replacement of a hot end of the filament through the elongated opening. By replacing the filament together with the hot end, the filament may be replaced without pulling the filament out of the melting nozzle. In one embodiment the filament feeding device further comprises a first drive wheel configured to rotate about a first axis and to drive the first filament wheel and a second drive wheel configured to rotate about a third axis and configured to drive the second filament wheel.

[0070] The first and the second drive wheels may be coupled to each other in order for the first and second feeding wheels to rotate with the same rate.

[0071] In one embodiment the filament feeding device further comprises a first linking arm wherein the first feeding wheel is pivotable about the first axis by means of the first linking arm. The first linking arm may be pivoted such that the first feeding wheel is moved with one movement component being perpendicular to the filament feeding direction. Thereby, the separation distance between the first filament feeding wheel and the second filament feeding wheel increases to allow a filament material to be received between said the first and second feeding wheels and to replace a loaded filament towards another filament.

[0072] The pivoting position of the first linking arm may be set dependent on the diameter of the filament that is to be loaded.

[0073] In one embodiment the filament feeding device further comprises a second linking arm and the second feeding wheel is pivotable about the third axis by means of the second linking arm.

[0074] By the second feeding wheel being pivotable about the third axis by means of the second linking arm, the separation distance between the first feeding wheel and the second feeding wheel may be further varied. Both the first feeding wheel and the second feeding wheel may thereby be pivoted with one movement component being perpendicular to and away from the filament in order to efficiently replace the loaded filament and to allow for filaments of different diameters to be used. This solution is also volume efficient, since only half the distance from the center is needed to create an opening of specific size as compared to if only one of the feeding wheels would be moved.

[0075] In one embodiment the first and second drive wheels of the filament feeding device are connected with a coupling configured to synchronize the feeding wheels such that they move symmetrically with respect to the filament.

[0076] In one embodiment the filament feeding device further comprises a spring arrangement for exerting a pretension force from the first feeding wheel towards the filament. The spring arrangement may bias the separation distance between the first filament wheel and the second filament feeding wheel to a specific value.

[0077] In one embodiment the filament feeding device further comprises actuating means configured to actuate the first linking arm and / or the second linking arm. The actuating means may be used to efficiently pivot the first linking arm and the second linking arm, to change the separation distance between the first filament feeding wheel and the second filament feeding wheel so that it is possible to replace the filament.

[0078] In one embodiment the actuating means is further configured to manually or with e.g. a motor or other automation, increase the separation distance between the first filament wheel and the second filament wheel. This may be done by compressing the spring arrangement and pivoting the linking arms.

[0079] By adjusting the distance between the first filament wheel and the second filament wheel, the increased distance between the first filament wheel and the second filament wheel allows removal of a filament and / or insertion of a new filament.

[0080] According to a fourth aspect of the inventive concept there is provided a method for changing a filament in a filament feeding device for a 3D-printer, The filament feeding device comprises a housing, a first feeding wheel and a second feeding wheel, wherein the method comprises the steps of:

[0081] receiving a first filament between the first feeding wheel and the second feeding wheel, for feeding the first filament in a feeding direction, increasing a separation distance between the first feeding wheel and the second feeding wheel,

[0082] removing the first filament in a transverse direction relative the feeding direction,

[0083] inserting a second filament in a transverse direction relative the feeding direction,

[0084] decreasing the separation distance between the first feeding wheel and the second feeding wheel, and

[0085] feeding the second filament in the feeding direction.

[0086] By the method for replacing the filament, the filament loaded to the filament feeding device may be efficiently replaced. The advantages are largely analogous to those described in relation to the device above.

[0087] In yet one embodiment, the filament feeding device further comprises a first linking arm and a second linking arm and the first feeding wheel is pivotable by means of the first linking arm and the second feeding wheel is pivotable by means of the second linking arm. The advantages of this are similar to what has been described above in relation to other aspects of the invention.

[0088] In yet one embodiment, the step of increasing a separation distance between the first feeding wheel and the second feeding wheel comprises pivoting the first feeding wheel and the second feeding wheel away from the filament and wherein the step of decreasing the separation distance between the first feeding wheel and the second feeding wheel comprises pivoting the first feeding wheel and the second feeding wheel towards the filament. Hereby, an efficient way of increasing and decreasing the distance is achieved with allows for a simple replacement of the filament. In yet one embodiment, the method includes a step of removing a hot end of the filament in a transverse direction relative the feeding direction and inserting a hot end in a transverse direction relative the feeding direction. Hereby, the filament may be removed together with the nozzle which vastly facilitates the handling. In some embodiments, both the removed filament is moved with the nozzle, and the new filament is inserted with another nozzle. This also facilitates printing with different materials, sizes and colors.

[0089] The invention is defined by the appended independent claims, with some embodiments being set forth in the appended dependent claims, in the following description and in the drawings.

[0090] Brief description of the drawings

[0091] The invention will in the following be described in more detail in the non-limiting detailed description of preferred embodiments, with reference to the enclosed drawings, wherein:

[0092] Fig. 1 illustrates a filament feeding device with a filament extruder according to one embodiment of the inventive concept.

[0093] Fig. 2 illustrates a first view of a filament feeding device without the extruder according to one embodiment of the inventive concept.

[0094] Fig. 3 illustrates a front view of a filament feeding device according to one embodiment of the inventive concept.

[0095] Fig. 4 illustrates a back view of a filament feeding device according to one embodiment of the inventive concept.

[0096] Fig. 5 illustrates a perspective view of a filament feeding device according to one embodiment of the inventive concept. Fig. 6 illustrates another perspective view of a filament feeding device according to one embodiment of the inventive concept.

[0097] Fig. 7a illustrates a front view of a filament feeding device according to one embodiment of the inventive concept.

[0098] Fig. 7b illustrates a close-up perspective view of a filament feeding device according to one embodiment of the inventive concept.

[0099] Fig. 7c illustrates a close-up front view of a filament feeding device according to one embodiment of the inventive concept.

[0100] Fig. 8a illustrates another perspective view of a filament feeding device housing according to one embodiment of the inventive concept.

[0101] Fig. 8b illustrates another perspective view of a filament feeding device without the housing according to one embodiment of the inventive concept.

[0102] Fig. 9 illustrates a 3D printer with a filament feeding device.

[0103] Fig. 10 illustrates a method flow chart of the steps for feeding a filament according to one embodiment.

[0104] Fig. 11 illustrates a method flow chart of the steps for changing a filament according to one embodiment.

[0105] Fig. 12a illustrates a front view where a filament feeding device housing according to one embodiment in a first position.

[0106] Fig. 12b illustrates a front view where a filament feeding device housing according to one embodiment in a second position. Detailed description

[0107] In the following detailed description, some embodiments of the present invention will be described. However, it is to be understood that features of the different embodiments are exchangeable between the embodiments and may be combined in different ways, unless anything else is specifically indicated.

[0108] Even though in the following description, numerous details are set forth to provide a more thorough understanding of the present invention, it will be apparent to one skilled in the art that the present invention may be practiced without these details. The scope of the invention is defined by the claims.

[0109] Fig. 1 illustrates a filament feeding device with a fan 3 and a housing 4. Fig. 2 illustrates the filament feeding device where the housing 4 has been removed to illustrate the mechanical drive inside the filament feeding device. Here a motor drive wheel M and a motor housing M4 is shown which drives the filament feeding device.

[0110] The driving mechanism of the filament feeding device 100 is illustrated in closer views in Fig. 3 and Fig. 4 and in which views the surrounding details are removed for clarity.

[0111] The filament feeding device 100 comprises a first linking arm 1 and a second linking arm 2 which each is pivotably arranged onto the filament feeding device 100. Each linking arm 1 , 2 comprises a front portion a back portion and two connecting portions which connects the front and the back portion. In other, not illustrated embodiments, the linking arms may comprise only a single (front or back) portion.

[0112] Each linking arm 1,2 comprises an upper portion, a lower portion and a central portion which connects the upper and the lower portion. In the context herein, the “upper portion” is meant as the upper part as illustrated in these embodiments. Obviously, the device may be held in any orientation without departing from this definition. A first drive wheel 10 is rotatably arranged about a first axis A1 , going through the central portion of the first linking arm 1.

[0113] A first feeding wheel 20 is rotatably arranged about a second axis A2going through the lower portion of the first linking arm 1.

[0114] In the upper portion of the first linking arm 1 , a spring arrangement 50 is arranged, which is resi liently loaded to push the upper portion away from the spring arrangement. The linkage arm is pivotably arranged around the first axis A1 , why the spring arrangement also pushes the lower portion towards a center line C.

[0115] The motor wheel M is illustrated as a cog wheel but may in in any drivable form. In this illustration the motor wheel M is in cog contact with and is configured to drive the first drive wheel 10.

[0116] A first shaft S1 connects the first drive wheel 20 to the center portion of the first linking arm 1. In the illustrated example, the first shaft S1 extends through both the front portion and the back portion.

[0117] A second shaft S2 connects the first feeding wheel to the lower portion of the first linking arm. In the illustrated example, the second shaft S2 extends through both the front portion and the back portion of the first linking arm.

[0118] The first feeding wheel 11 has filament engaging means which is a rifled surface onto the periphery of the first feeding wheel’s 20. The first drive wheel 10 and the first feeding wheel 20 have cogs and they are connected to each other by means of a cog coupling.

[0119] The second linking arm 2 may have the same features as described in relation the first linking arm but coupling the second drive wheel 30 to a third shaft S3 arranged through the third axis A4, and the second feeding wheel 40 to a fourth shaft S4 arranged through the fourth axis A4. The first axis A1 and third axis A3 may be distanced longer from each other than the distance between the second axis and the fourth axis. This is best seen in fig. 3. In fig. 3, The first and second linking arms 1, 2 couples the first drive wheel 10 to the first feeding wheel 20 and the second drive wheel 30 to the second feeding wheel 40. Given that the distance is further between the first and third axes A1 , A3 than between the second and fourth axes A2, A4, the linking arms are pointing towards each other at the end of the feeing wheels 40. This means the first and second feeding wheels 20, 40 will pivot upwards along the filament and increase the engagement force if the filament feeding resistance increases.

[0120] The first linking arm 1 and the second linking 2 are in the illustrated example, which is best seen in fig. 3, coupled by means of a coupling 70. The coupling 70 keeps the first feeding wheel and the second feeding wheel at equal distances from the centre line C. Hereby, when one of the linking arms is pivoted, the coupling forces the other linking arm will be moved in tandem away from or towards the center line C.

[0121] As mentioned, in the illustrated example, also the second linking arm comprises a front portion, a back portion and two connecting portions which connect the front portion with the back portion.

[0122] A second drive wheel 30 and a second feeding wheel 40 are rotatably arranged about a third axis A3 and a fourth axis A4, respectively onto the second linking arm 2 of the filament feeding device 100. A third shaft S3 connects the second drive wheel to the front portion and the back portion of the second linking arm, at the center portion. Further, a fourth shaft S4 connects the second feeding wheel 40 to the front portion and the back portion of the second linking arm 2 at a lower portion.

[0123] In the illustrated example, the second feeding wheel 40 has filament engaging means which is a rifled surface onto the periphery of the second feeding wheel 20.

[0124] In the illustrated example, the first and second drive wheel each comprises two cog wheels 10a, 10b of which one of said cog wheels 10B is in cog contact with the other of the two drive wheels and the other 10A of said wheels of the first and the second drive wheels is in cog contact with the first and the second filament feeding wheel, respectively.

[0125] The cog wheels 10a, 10b 30a, 30b of the drive wheels have different diameters. The second cog wheel 10B is in cog coupling with the second cog wheel 30B of the drive wheel 30 and has a larger diameter than the first cog wheel 10A, which is in cog coupling with the feeding wheel 20.

[0126] Both cog wheels of the first drive wheel are arranged onto the first shaft S1. Similarly, both cog wheels of the second drive wheel are arranged onto the third shaft S3. Thus, they are also connected to the same point onto the linking arm, respectively.

[0127] By the cog coupling between the first drive wheel 10 and the first feeding wheel 20 the first drive wheel and the first feeding wheel rotates with opposite rotational directions but the same rotational rate.

[0128] In the embodiment illustrated in the figures in shown in a front view (all except figs 4 and 6) when the filament feeding direction is downward the first filament feeding wheel 20 rotates clockwise and the first drive wheel, thereby, rotates counterclockwise. Followingly, the second filament feeding wheel rotates counterclockwise and the second drive wheel rotates clockwise.

[0129] During feeding the filament is in contact with both the first filament feeding wheel and the second filament feeding wheel.

[0130] In some embodiments, the filament feeding device may be driven in reverse direction so that the filament is fed upwards, and the wheels do in such operation rotate with opposite directions than described above for when the filament is fed downwards.

[0131] By the first linking arm 1 and the second linking arm 2 being pivotable about the first axis A1 and the third axis A3, respectively, the separation distance between the first feeding wheel and the second feeding wheel is variable. In relation to figures 7a-7c some details about the configuration will be discussed. The first feeding wheel 20 is pivotably arranged around the first axis A1. The second feeding wheel 40 is pivotably arranged around the fourth axis A4.

[0132] - The main filament feeding direction D1 is shown. The filament feeding may also be reversed such that filament is fed in a direction opposite the filament feeding direction D1 , in order to reverse the filament from the print.

[0133] The filament feeding wheels 20, 40 will pivot about the axes A1 , A3 as a consequence of a changed filament feeding resistance. The pivoting trajectories are shown by arrows P1 and P2.

[0134] When the feeding filament feeding resistance is increasing the filament feeding wheels will pivot in the direction P1 and P2 since they will “climb” upwards along the filament. The movement is not large, but it results in an increased engagement force from the feeding wheel onto the filament.

[0135] When the filament feeding resistance decreases again the filament feeding wheels will pivot back, or at least the force will decrease, in the opposite directions relative the pivoting directions P1, P2.

[0136] This enables printing with hard filament such that PLA with high flow which requires high extrusion force and high engagement force as well as printing with soft filament such that TPU with normal low flow which requires low extrusion force and low engagement force.

[0137] Sometimes it is desirable to change filament type in a print, or between different prints. In order to facilitate filament changes, a filament may be replaced with a new filament by manually pivoting the linking arms to compress the spring arrangement 50. Hereby, the distance between the feeding wheels may be increased as the feeding wheels move in the opposite directions relative the pivoting directions P1 and P2. This will be further discussed in relation the method flow chart in figures 10 and 11.

[0138] The dynamic filament engaging force is explained above to be achieved by two major contributing factors. These are described furth in relation to figures 7b and 7c.

[0139] The first contributing factor is best seen in Fig 7b. When the feeding resistance from the filament F increases, more of the torque from the drive wheel 10 will be converted to engagement force towards the filament. As the driving wheel 10 pushes the feeding wheel 20 to rotate (see bent arrow), the higher feeding resistance will also push the wheel towards the filament (see straight arrow over the first feeding wheel) which will result in a higher engagement force onto the filament.

[0140] The second contributing factor is best understood in relation to figure 7c. When the feeding resistance from the filament increases, some of the feeding wheel torque will be converted to an upwards directed force, and since the feeding wheel is pivotable around the first axis this upwards directed force will be converted to an added engagement force. The feeding wheel wants to “climb” up the filament if the resistance to push the filament downwards is too high. Such a climb will occur along a pivoting trajectory, as shown in P1 and P2 in figure 7a, which will result in a squeeze of the filament so that the filament engagement force even further increase.

[0141] Since the first and third axes are wider apart than the position of the second and fourth axes are apart, any movement inwards of the feeding wheels will also be a slight movement upwards of the feeding wheels. Thus, as the feeding wheels “climb” on the filament they will incur an increased engagement force onto the filament, which is originating from the increased resistance in the filament feeding. The movement is illustrated in pivoting trajectory arrows P1 and P2.

[0142] The climb will occur as long as the distance d1 between an engagement point between the filament and the feeding wheel is displaced in a direction perpendicular to the filament moving (or resistance) direction. Due to the displacement distance d1 , there is a lever that converts the force from the resistance in the filament to the pivoting / climbing of the feeding wheel.

[0143] In figure 8a, the housing 4 is illustrated together with a filament F, and in which housing 4 there is an elongated opening EO along the house. The elongated opening EO is configured to allow replacement of an elongated filament portion F received between the first feeding wheel 20 and the second feeding 40 wheel through an separation distance (Do) in a direction being at least partly transverse to said feeding direction. Moreover, the feeding device as illustrated herein is configured so that at least one of the first feeding wheel and second feeding wheel is movable to increase the separation distance Do during the replacement of an elongated filament portion, as indicated by the arrows point outwards on each of the filament feeding wheels.

[0144] Figure 9 illustrates a 3D-printer (1000) with a filament feeding device 100, which can be any one of the filament feeding devices as described above. Further, the 3D printer may be configured to feed filament according to any one of the embodiments as described in this application.

[0145] Figure 10 illustrates a flow chart of the different steps of the method for feeding filament in a 3D printer.

[0146] The method comprises a first method step S1 of rotating the first drive wheel 10 about a first axis A1 with a motor. This is performed by driving the first drive wheel by the motor wheel M as explained above.

[0147] The method comprises a second method step S2 of driving the first feeding wheel 20 by the first driving wheel. Rotational energy is transferred to the first feeding wheel by means of cog coupling.

[0148] The method comprises a third method step S3 of increasing a force exerted from said filament engaging means towards said filament by pushing the first feeding wheel towards the filament with said mechanical coupling between the first drive wheel and the first feeding wheel when rotating the first drive wheel to feed filament towards a hot end.

[0149] The method further comprises an optional step S4 of pivoting the first feeding wheel upstream relative the filament flow when the flow resistance of the filament increases.

[0150] The first filament feeding wheel is pivoted with one movement component being perpendicular to the filament feeding direction and one movement component being along the filament feeding direction upstream, i.e. away from the hot end. This has been explained above in relation to figure 7c.

[0151] The method further comprises an optional step S5 of rotating the second drive wheel 30 about a third axis A3. The second drive wheel is rotated by a cog coupling to the first drive wheel.

[0152] The method further comprises an optional step S6 of driving the second feeding wheel 40 by a mechanical coupling to the second drive wheel, wherein said second feeding wheel is rotationally arranged about a fourth axis A4 at a distance from the third axis and pivotably coupled about the third axis A3.

[0153] The method further comprises an optional step S7 of increasing a force exerted from said filament engaging means of said second drive wheel towards said filament by pushing the second feeding wheel towards the filament with said mechanical coupling between the second drive wheel and the second feeding wheel when rotating the second drive wheel to feed filament towards the hot end.

[0154] The first filament feeding wheel 20 is pivoted with one movement component being perpendicular to the filament feeding direction and one movement component being along the filament feeding direction upstream, i.e. away from the hot end.

[0155] In Fig. 11 there is illustrated a flow chart of a method of changing a filament in a filament feeding device 100 for a 3D printer. The filament feeding device 100 comprises the steps of receiving S1 a first filament between the first filament feeding 20 wheel and the second feeding wheel 40. The filament is fed in the main filament feeding direction D1.

[0156] The method comprises a second method step S2 of increasing a separation distance between the first feeding wheel 20 and the second feeding wheel 40. This step may optionally be performed by pivoting the first filament feeding wheel 20 and the second filament feeding wheel 40 away from the filament. This is how it is illustrated in the figures, namely that the first feeding wheel 20 is pivoted away from the filament by means of the first linking arm 1 and the second feeding wheel 40 is pivoted away from the filament by means of the second linking arm 2.

[0157] The method comprises a third method step S3 of removing the first filament in a transverse direction relative the feeding direction D1.

[0158] The method comprises a fourth method step S4 of inserting a second filament in a transverse direction relative the feeding direction D1. The method further comprises a fifth method step S5 of decreasing the separation distance between the first feeding wheel and the second feeding wheel. The first feeding wheel 20 is pivoted towards the filament by means of the first linking arm 1 and the second feeding wheel 40 is pivoted towards the filament by means of the second linking arm 2.

[0159] The method comprises a sixth method step S6 of feeding the second filament in said feeding direction. This step may be performed by driving the filament feeding device by the motor wheel M which is in contact with the first drive wheel 10. The first drive wheel in its turn may be in cog contact with the second drive wheel 30 and the first filament feeding wheel 20. In the illustrated examples the second drive wheel 30 drives the second filament feeding wheel 40.

[0160] The method comprises an optional seventh step S7 of removing a first hot end H1 of the filament in a transverse direction relative the feeding direction and inserting a second hot end H2 in a transverse direction relative the feeding direction. This step may be performed when the separation distance d2 between the first feeding wheel 20 and the second feeding wheel 40 has been increased. In this context, the hot end may be the nozzle in which the filament is melted.

[0161] Fig. 12a illustrates a front view where a filament feeding device housing according to one embodiment in a first closed position. In this position the filament may be fed by the feeding wheel. In Fig. 12b the same view is shown, but in which the feeding wheels are in a second, open position.

[0162] In the closed position the separation distance Do is adapted to house a filament that is fed by the feeding wheels. The spring arrangement pushes the top portions of the linking arms away from each other so that the feeding wheels are kept together in contact with a filament. In the open position the separation distance Do is increased and adapted to allow a filament to be removed from the feeding wheels in a direction straight out of the figure, i.e. transversal to the feeding direction. The spring arrangement is compressed in relation to the closed position, and the top portions of the linking arms are compressed towards each other so that the feeding wheels are pushed apart to allow the larger separation distance D1 as shown.

[0163] The change of position from the closed position to the open position or vice versa may be done by an actuating means 15. This may be in the form of a lever, a bolt, a wheel, a pin, a spring or any other means for actuating the movement. In the illustrated example the actuating means is in the form av a lever. The actuating means may be manually pushed, pulled or otherwise removed.

[0164] In the illustrated example, the actuating means further comprises a control pin 16. The control pin may be any type of controlling means that mechanically pushed / pulls / rotates or otherwise moves the actuating means. The control pin 16 in this case is an eccentric rotational pin that is in a first position when the actuating means is in the first position. The first position is illustrated as pointing downwards with the protruding portion of the eccentric rotational pin, as illustrated in fig. 12a. When the control pin 16 is rotated, it pushes the actuating means to change the position of the actuating means so that the feeding device moves from the closed position into the open position.

[0165] The control pin may be a motorized rotation. Additionally or alternatively, the control pin may also be manually moved to actuate the actuating means.

Claims

1. Claims1. A filament feeding device (100) for use in 3D-printing , wherein said filament feeding device comprises:3.a housing (4),4.a first feeding wheel (20) configured to rotate about a second axis;5.a second feeding wheel (40) configured to rotate about a fourth axis; wherein said first and second feeding wheels are separated by a separation distance to allow a filament material to be received between said first and second feeding wheels and be fed in a feeding direction towards a hot end when in use,6.wherein7.said housing comprises an elongated opening (EO) configured to allow replacement of an elongated filament portion received between said first feeding wheel and said second feeding wheel through said opening in a direction being at least partly transverse to said feeding direction, and wherein at least one of said first feeding wheel and second feeding wheel is movable to increase the separation distance during the replacement of the elongated filament portion.

2. The filament feeding device according to claim 1 , wherein said elongated opening further is configured to allow replacement of a first hot end H1 of said filament through said elongated opening.

3. The filament feeding device according to claim 1 or 2 wherein said filament feeding device further comprises a first drive wheel configured to rotate about a first axis and to drive the first feeding wheel and a second drive wheel configured to rotate about a third axis and configured to drive the second feeding wheel.

4. The filament feeding device according to claim 3 further comprising a first linking arm wherein the first feeding wheel is pivotable about said first axis by means of said first linking arm.

5. The filament feeding device according to claim 4 further comprising a second linking arm and wherein the second feeding wheel is pivotable about said third axis by means of said second linking arm.

6. The filament feeding device according to any one of claims 3-5 wherein the first and second drive wheels are connected with a coupling configured to synchronize the feeding wheels such that they move symmetrically with respect to the filament.

7. The filament feeding device according to any one of claims 3-6 further comprising a spring arrangement for exerting a pretension force from said first feeding wheel towards said filament is arranged to said first feeding wheel.

8. The filament feeding device according to any one of claims 5-7, further comprising actuating means configured to actuate the first linking arm and / or the second linking arm.

9. The filament feeding device according to claim 8 wherein the actuating means is further configured to increase the separation distance between the first feeding wheel and the second feeding wheel.

10. A method for changing a filament in a filament feeding device (100) for a 3D-printer, wherein said filament feeding device comprises a housing, a first feeding wheel (20) and a second feeding wheel (40), wherein said method comprises the steps:- Receiving (S1 ) a first filament between the first feeding wheel and the second feeding wheel, for feeding the first filament in a feeding direction,16.- Increasing (S2) a separation distance between the first feeding wheel and the second feeding wheel,17.- removing (S3) the first filament in a transverse direction relative the feeding direction,18.- inserting (S4) a second filament in a transverse direction relative the feeding direction,19.- decreasing (S5) the separation distance between the first feeding wheel and the second feeding wheel, and20.- feeding (S6) the second filament in said feeding direction.

11. The method according to claim 10 wherein the filament feeding device further comprises a first linking arm and a second linking arm and the first feeding wheel is pivotable by means of the first linking arm and the second feeding wheel is pivotable by means of the second linking arm.

12. The method according to claim 11 wherein the step of increasing a separation distance between the first feeding wheel and the second feeding wheel comprises pivoting the first feeding wheel and the second feeding wheel away from the filament and wherein the step of decreasing the separation distance between the first feeding wheel and the second feeding wheel comprises pivoting the first feeding wheel and the second feeding wheel towards the filament.

13. The method of according to any one of claims 10-12 further comprising the step of removing a first hot end of the filament in a transverse direction relative the feeding direction and inserting a second hot end in a transverse direction relative the feeding direction.

14. A filament feeding device (100) for use in a 3D-printer, wherein said filament feeding device comprises:24.a first drive wheel (10) configured to be driven about a first axis (A1 ) by a motor,25.a first feeding wheel (20) mechanically coupled to be driven by the first drive wheel, wherein said first feeding wheel is rotationally arranged about a second axis (A2) at a distance from the first axis and comprises filament engaging means (22) for feeding a filament,26.a second drive wheel (30) rotatable about a third axis (A3),27.a second feeding wheel (40) arranged about a fourth axis (A4) at a distance from the second axis (A2) for feeding a filament received between said first and second feeding wheel,28.wherein the first feeding wheel (20) is pivotably coupled about the first axis (A1) and wherein the second feeding wheel (40) is pivotably coupled about the third axis (A3),29.so that an engagement force exerted from the first feeding wheel and the second feeding wheel onto the filament depends on a filament feeding resistance, and wherein the first axis (A1) and third axis (A3) are distanced such that the first and second feeding wheels will pivot upwards along the filament to increase the engagement force when the filament feeding resistance increase.

15. The filament feeding device according to claim 14, further comprising a spring arrangement (50) arranged to exert a pretension force from said first feeding wheel towards said filament.

16. The filament feeding device according to claim 14 or 15, wherein the first feeding wheel (20) is driven by the first driving wheel (10) by means of a cog coupling.

17. The filament feeding device according to claim 16, wherein the cogs of the first driving wheel (10) that are coupled with the cogs of the firstfeeding wheel (20) are moved towards the filament when the filament feeding device feeds the filament towards a hot end H1.

18. The filament feeding device according to any one of claims 14-17, wherein the first axis is placed further from a hot end than the second axis.

19. The filament feeding device according to any one of claims 14-18, wherein the second feeding wheel (40) is driven by the second drive wheel.

20. The filament feeding device according to any one of claims 14-19, wherein the second feeding wheel comprises filament engaging means (42) for feeding the filament.21.The filament feeding device according to any one of claims 14-20, further comprising a first linking arm, wherein said first linking arm is coupled at said first axis to the first drive wheel and at said second axis to the first feeding wheel so that the first feeding wheel is pivotable relative said first drive wheel by rotation of said first linking arm.

22. The filament feeding device according to claim 21, further comprising a second linking arm, wherein said second linking arm is coupled at said third axis to the second drive wheel and at said fourth axis to the second feeding wheel so that the second feeding wheel is pivotable relative said second drive wheel by rotation of said second linking arm.

23. The filament feeding device according to claim 22, wherein the first linking arm and the second linking arm are mechanically coupled to move in tandem so that the first feeding wheel and second feeding wheel move in tandem towards and from the filament when the first and second linking arms are moved.

24. The filament feeding device according to claim 23, wherein the coupling between the first linking arm and the second linking arm retains the first and second feeding wheels at equal distance from the filament thread center regardless of their pivoting positions.

25. A method for feeding a filament with a filament feeding device (100) during 3D printing, wherein the filament feeding device comprises a first drive wheel (10), a first feeding wheel (20) and a second feeding wheel (40), wherein the first feeding wheel comprises a filament engaging means (22) configured for feeding a filament, a second drive wheel (30), wherein the second feeding wheel (40) comprises a filament engaging means (42) configured for feeding a filament, and wherein the method comprises the steps of:40.- rotating (S1 ) the first drive wheel (10) about a first axis (A1 ) with a motor,41.- driving (S2) the first feeding wheel (20) by a mechanical coupling to the first drive wheel, wherein said first feeding wheel is rotationally arranged about a second axis (A2) at a distance from the first axis and pivotably coupled about the first axis (A1), and42.- increasing a force (S3) exerted from said filament engaging means towards said filament by pushing the first feeding wheel towards the filament with said mechanical coupling between the first drive wheel and the first feeding wheel when rotating the first drive wheel to feed filament towards a hot end43.- rotating (S4) the second drive wheel (30) about a third axis (A3), - driving (S6) the second feeding wheel (40) by a mechanical coupling to the second drive wheel, wherein said second feeding wheel is rotationally arranged about a fourth axis (A4) at a distance from the third axis and pivotably coupled about the third axis (A3), and44.- increasing a force (S7) exerted from said filament engaging means of said second drive wheel towards said filament by pushing the second feeding wheel towards the filament with said mechanical coupling between the second drive wheel and the second feeding wheel when rotating the second drive wheel to feed filament towards the hot end, and45.- pivoting the first and second feeding wheels upwards along the filament to increase the engagement force when the filament feeding resistance increase.

26. A 3D printer comprising a filament feeding device according to anyone of claims 13-24, and / or configured to perform the method according to claim 25.

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