Device for a 3D printer with a print bed, system and method

Abstract

Device (30) for retrofitting a 3D printer (20) with a flat printing bed (22) for receiving a melt layer of a meltable material comprising a shaft (32) extending along a rotation axis (34) and designed as a hollow shaft (44) with a lateral surface (33), a drive motor (40) for driving the shaft (32), and - a bearing (38) for receiving and supporting the shaft (32), - where - the bearing (38) is designed to be attached to the 3D printer (20); and - the lateral surface (33) is designed to receive the melt layer; and - the hollow shaft (44) has a wall (48) which is cut in the longitudinal direction so that end regions (50) of the wall (48) partially overlap in an overlap region (52) in the direction of rotation.

Description

[0001] The present invention relates to a retrofittable device for a 3D printer with a print bed for receiving a melt layer of a meltable material, a system comprising the device and a 3D printer, and a method for controlling the device.

[0002] 3D printers are used to produce three-dimensional products quickly and easily. There are different models of 3D printers that can be used depending on the application and materials used. Fused Deposition Modeling (FDM) printers, in particular, have a print head or nozzle through which a meltable material, particularly a molten plastic, is applied layer by layer in the form of a filament or thread to a print bed or base plate. The print head, which includes a type of nozzle, must be suitable for the product to be printed. The cross-section of the nozzle or nozzle opening must be small enough to allow even fine structures to be produced.On the other hand, the diameter of the nozzle opening or the print head opening must be large enough to achieve sufficient print throughput to produce larger areas or products.

[0003] The print head is usually movable in one plane in two directions. Furthermore, the print head's height can be varied and adjusted so that it can always be moved at a small distance, first above the print plate or print bed and then above the layers of the object being manufactured that have already been printed. This allows almost any object to be printed. These printers are particularly used for rapid prototyping, for the production of simple samples or test specimens, or for one-off production. They are not only suitable for industrial use. More and more 3D printers are also being used in the home, allowing private users to produce individual pieces.

[0004] In industrial applications, 3D printers are also frequently used to produce cylindrical geometries, such as hoses, nozzles, or even cable sheaths. However, this poses the problem that the hoses must be printed along their length, which is usually aligned vertically during printing. The length of the hoses is severely restricted due to the limited height of the printer. In addition, this type of printing can cause the component to bulge or warp, causing it to lean sideways or collapse. A heated print bed is used to compensate for or prevent this disadvantage, known as the warping effect.

[0005] However, conventional 3D printers, including those using the fused-layer 3D printing process, are only partially suitable for producing complex, rotationally symmetrical shapes and structures. These can often only be realized using support structures. It has also proven difficult to achieve high dimensional accuracy, as stability is often lacking during the manufacturing process, especially for thin-walled components.

[0006] With regard to known systems and methods, reference is made, for example, to the disclosure in the documents DE 10 2018 215 546 A1, US 2016 / 0 318 247 A1, CN 2 05 871 201 U, DE 10 2020 000 148 A1 and EP 3 750 687 A1.

[0007] The object of the present invention is therefore to propose a device which eliminates the problems identified in the prior art in 3D printing and which is particularly suitable for rotationally symmetrical components.

[0008] The present object is achieved by a device having the features according to claim 1 and by a system having the features according to claim 9 and a method according to claim 10.

[0009] In a first aspect, the present invention thus relates to a device for receiving a melt layer of a meltable material. The device for retrofitting a printer with a flat print bed comprises a shaft which extends along a rotation axis and is a hollow shaft, a casing surface which extends around the rotation axis, a motor for driving the shaft, and a bearing for receiving and supporting the shaft. The bearing is designed to be attached to the 3D printer. The casing surface is suitable for receiving the melt layer which is applied and deposited by the 3D printer. This results in a device with a casing surface which can be rotated about a coaxially extending shaft, wherein the shaft is driven by a motor. The casing surface and shaft are preferably connected to one another in such a way that a bearing or movement of the shaft requires a bearing orThis results in movement of the outer surface. The preferably cylindrical outer surface of the device is positioned and moved in such a way that meltable material from a 3D printer's print head can be applied to the shaft and absorbed there.

[0010] The device thus forms a substantially rotationally symmetrical print bed on which hollow bodies with a round cross-section, preferably a circular cross-section, can be printed. The preferred circular cross-section may have unevenness or minor offsets, as long as their size is not relevant for practical application.

[0011] To enable the production of hollow bodies with different diameters, it is advantageous if the diameter of the outer surface is variable. The shaft is a hollow shaft with a wall that is cut longitudinally, so that the hollow shaft is not formed by a continuous cylinder. With the cut wall, the end regions of the wall overlap at least partially in the direction of rotation.

[0012] Preferably, the overlap of the end regions of the wall is adjustable, allowing the overlap area to be changed, i.e., enlarged or reduced. Changing the overlap simultaneously varies the outer diameter of the shaft. This allows the outer diameter and thus the outer surface to be varied. This allows the device to be used for 3D printing hollow bodies with different diameters.

[0013] The outer surface is preferably designed such that it has a suitable roughness so that the material remains on the outer surface during application and does not run off the outer surface even when the shaft is rotated about its longitudinal axis. The outer surface of the shaft can preferably be matched to the molten material to be printed, which is applied by the print head. The material of the outer surface preferably has high flexibility while still maintaining good dimensional stability. The shaft is preferably made of metal; however, it can also be made of a preferably heat-resistant plastic.

[0014] The device preferably comprises a connection unit for communication between the device and the 3D printer for coordinating the movement of the shaft with a print head of the 3D printer. This coordinates the rotation or rotary movement of the shaft with the print head and / or with the dispensing of the meltable material. The movement of the shaft can be coordinated, for example, with the movement or speed of the print head or the dispensing quantity of the material or the dispensing speed of the material.

[0015] The connection unit can be a data connection, which can be wired or wireless. The connection unit can comprise a controller and control the printer to which the device is connected, as well as regulate the dispensing position and quantity of material. Alternatively, the connection unit can receive control commands from the 3D printer and control the movement of the shaft according to the commands. Alternatively, the connection unit can comprise a camera and determine the position of the print head and adjust the movement of the shaft accordingly.

[0016] Preferably, the shaft of the device is arranged horizontally or substantially horizontally. The uppermost line of the shaft's lateral surface is preferably aligned horizontally. An embodiment in which the shaft of the device is arranged parallel to the printer's print bed is also preferred. The shaft can be supported at only one end. The second end of the shaft can be designed as a free end, so that printed workpieces can be easily removed.

[0017] The bearing can preferably be attached to the print bed of the 3D printer. The bearing can be arranged in a housing that is attached to the printer, for example, mounted on the print bed of the 3D printer. Alternatively, the bearing can be arranged on a holding element or guide element. The holding element can be attached to the printer or to the print bed. It is conceivable that the 3D printer has a support frame or a cross member on which the print head of the 3D printer is guided and moved. The bearing or the holding element can be attached to the cross member or the support frame. It can advantageously be attached to the preferably vertically movable cross member. Alternatively, the bearing can be arranged on the support frame by means of a guide element and can preferably be movable in height. It is conceivable that the bearing or a holding element or an adapter is coupled or connected directly or indirectly to the 3D printer in another way.The connection is generally detachable, so that the device according to the invention can be retrofitted to a printer, but can also be removed from it again.

[0018] In a further embodiment, the bearing may comprise a holding element for attachment to the 3D printer, wherein the holding element may preferably be a housing of the bearing.

[0019] In a preferred embodiment, in which the upper line of the lateral surface and the shaft are aligned horizontally, the typical printing principle of a 3D printer, in which a print head applies a molten material to a horizontally extended print plate (print bed) located below the print head, can be retained.

[0020] In a preferred embodiment, the device is designed such that the bearing that supports and holds the shaft is attached to the print bed of the 3D printer. When using the device according to the invention, only the distance between the print head of the 3D printer and the outer surface needs to be adjusted. This is usually done by adjusting and establishing a new zero point for the 3D printer. No further measures are necessary to retrofit a standard 3D printer, in particular an FDM printer, with the device according to the invention. Consequently, the device according to the invention is easy to retrofit and can be designed, for example, as an additional product. It can therefore be easily implemented in standard 3D printers according to the plug-and-play principle. Only the holder or a housing, which, for example, comprises the shaft bearing, must preferably be designed for mounting or fastening to the printer, for example on the print bed.

[0021] Alternatively, the bearing can be mounted directly or indirectly on a guide element, such as a traverse for the print head or on a support frame for the print head. Thus, only a one-time adjustment of the distance to the print head is necessary.

[0022] In a preferred embodiment, the outer surface of the device is rotationally symmetrical. This makes it possible to produce rotationally symmetrical hollow bodies with high dimensional accuracy. In particular, pipes, nozzles, diffusers, or hoses can be manufactured much more easily and efficiently. Threads or threaded parts on hollow pipes with very specific requirements can also be produced with considerably less effort and significantly higher quality.

[0023] In a preferred embodiment, the diameter of the outer surface is variable. The diameter can thus be adapted to the diameter of the hollow body to be produced. It is determined before the printing process. This enables the production of rotationally symmetric hollow bodies with any diameter and very high dimensional accuracy. Particularly in a device with a horizontally aligned shaft and outer surface, various options are available for producing rotationally symmetric hollow bodies.

[0024] The shaft can only be supported at one end. Preferably, the shaft of the device is supported at both ends by a bearing each. In this way, a horizontal alignment of the shaft can be realized simply and stably. Due to simple removal possibilities and a detachable decoupling of the shaft from the bearings, it is possible to remove the shaft and the outer surface after production of the hollow body. The hollow body, which extends around the outer surface, can then be easily stripped off from the outer surface in the axial direction.

[0025] The shaft is driven by a drive motor. The drive motor is located at one or more of the bearing ends of the shaft. In another special embodiment, a motor is located at both ends of the shaft to drive the shaft. The shaft can be moved very smoothly, allowing the rotational movement of the shaft to occur continuously. This ensures a seamless application of the molten material to the outer surface of the device.

[0026] With conventional 3D printers, even elongated, rotationally symmetrical hollow bodies are printed vertically, meaning the print head is only moved vertically. Printing begins on the print bed and then continues vertically upwards, with the print head moving slightly upwards after each subsequent layer is applied. However, stability, particularly with elongated hollow bodies, decreases with increasing length. In contrast, the horizontally arranged shaft and the surface surrounding the shaft enable an even application of molten plastic to the device without the risk of the hollow body being produced bending or toppling over.

[0027] In conventional 3D printers, heating the print bed has proven beneficial when the printing material used is a thermoplastic. However, this effect diminishes after just a few millimeters of component height, which can lead to uneven cooling of the printed material. This results in instability of the produced objects.

[0028] In a preferred embodiment, the outer surface of the device can be heated from the inside. This allows the manufacturing process to be improved. The cooling process of the object to be manufactured can be actively controlled. The outer surface of the device preferably has good thermal conductivity, so that the heat is evenly distributed across the surface and immediate solidification of the meltable material is counteracted. On the other hand, the outer surface must be designed so that the filament cools sufficiently quickly so that it does not drip from the underside of the shaft after half a rotation of the shaft or deform due to gravity.

[0029] In a preferred embodiment, a plurality of heating elements are used to heat the outer surface. These heating elements are arranged inside the hollow shaft when using a hollow shaft. Very preferably, the heating elements can be individually controlled and activated, allowing different locations to be heated differently. Alternatively, the shaft can be heated inductively.

[0030] In a likewise preferred embodiment, several of the heating elements are distributed in the longitudinal direction of the rotation axis so that the outer surface can be heated over its entire length and not just over its circumference. In this way, it is possible to heat the outer surface of the device evenly in order to achieve optimal printing results. The required temperature of the outer surface depends on the filament used, which is applied to the outer surface. In particular, heating is also carried out here to prevent excessive temperature differences between the applied filament and the outer surface, which could lead to warping of the component. Heating the outer surface also improves the adhesion of the filament to the surface itself.

[0031] In one embodiment of the present invention, the outer surface is formed by the outer surface of the shaft itself. It is also possible for the outer surface and shaft to be separate components. In this case, it is conceivable for the outer surface to project beyond the shaft in the longitudinal direction. The shaft can also be arranged at only one end of the outer surface in order to enable a drive of the outer surface and a bearing. In a preferred double-sided bearing, two shaft sections can be directly connected to the outer surface at both ends. The shaft sections can also be designed as shaft journals. It is also possible for the shaft or shaft sections to be connected to the outer surface via intermediate elements or fastening elements.

[0032] In a preferred embodiment, the inner end region of the wall is connected to the shaft journals of the shaft by means of a fastening element. The fastening elements ensure, on the one hand, that the wall of the hollow shaft is coupled to the shaft journals, so that rotating the shaft journals by motors results in rotation of the hollow shaft. On the other hand, the fastening elements serve as adjustment elements to change and adjust the overlap area of ​​the end regions of the wall.

[0033] In a preferred embodiment, the fastening elements can be designed as springs, very preferably as spiral springs. Other designs of the fastening element are also conceivable, for example as an adjustable clamp or slider. Furthermore, a motor can preferably be arranged between the shaft journal and the fastening element, in particular the spiral spring, so that a change in the overlap area of ​​the end regions can be achieved by means of a motor (e.g., servo motor). The motor, referred to as the adjustment motor, can be controlled accordingly by a controller. Moving the adjustment motor in one direction leads to an enlargement of the overlap area, thereby reducing the outer diameter of the shaft. Moving it in the opposite direction reduces the overlap area, so that the outer diameter of the shaft is increased and larger hollow bodies can be produced using the 3D printing process.

[0034] In a preferred embodiment, in which the fastening element is preferably designed as a spring or spiral spring, the hollow shaft has a shaft journal at each end, which is held by bearings. An adjustment motor is arranged between the fastening element and the shaft journal at each end of the shaft. These can preferably be controlled and moved independently of one another. By appropriately controlling the two adjustment motors, different shaft shapes can be generated. If the two adjustment motors are moved in opposite directions, the outer diameter of the shaft is reduced at one end and simultaneously increased at the other end. In this way, a conical or tapered shaft can be formed, which is preferably used for the production of nozzles or diffusers.

[0035] According to a further aspect, the present invention relates to a system for 3D printing with the features of claim 9. The system comprises a 3D printer with a flat print bed and a retrofittable device as described above. The retrofittable device is mounted on the flat print bed of the printer, and the printer's print head is positioned so that meltable material is applied to the outer surface of the device. The device is mounted on the horizontal print bed of the printer. It is detachably attached to the printer so that it can be removed if necessary. This creates a high degree of flexibility because the 3D printer can also be used for "normal" 3D printing, i.e. whenever rotationally symmetrical or elongated round hollow bodies are not to be printed.When using the device and mounting it on the print bed of the 3D printer, it is preferable to turn off the optional heating of the print bed of the 3D printer.

[0036] In a preferred embodiment, the system comprises a control unit that is designed to control the device and that preferably performs control in cooperation with the 3D printer. Optionally, the control unit controls the device and 3D printer. Thus, for example, the print head of the 3D printer can be controlled depending on the rotation of the device's shaft. In this way, it is possible to apply meltable material to the outer surface of the device in a desired manner and along a predetermined trajectory. Elongated hollow bodies can be easily printed in various ways. The control unit can comprise the device's connection unit or communicate with it and exchange data.The control unit can - preferably together with the connecting unit - regulate the device and the print head in such a way that meltable material is applied to the outer surface of the device in a desired and predetermined manner and / or along a predetermined trajectory.

[0037] Preferably, one type of printing involves printing in the circumferential direction. The shaft of the device rotates at a constant speed around its longitudinal axis. The print head moves at a desired (low) speed along the longitudinal axis, so that the meltable material is applied to the outer surface of the shaft, strip by strip in the circumferential direction. This type of printing creates hollow bodies that are ideally suited to tensile and compressive forces in the circumferential direction.

[0038] According to a second variant of controlling the device's print head and shaft, the print head first moves longitudinally along the shaft and applies filament to the outer surface. After a web of filament has been applied over the desired length of the shaft, the shaft rotates around its axis of rotation according to the web width of the applied material or filament, allowing the next (adjacent) web to be applied. The print head then moves in the opposite direction along the longitudinal axis. This type of printing process makes it possible to produce hollow bodies that are ideally suited for applications where tensile and compressive forces occur in the longitudinal direction.

[0039] In another printing method, the molten filament is applied to the shaft at a predetermined angle, for example, a 45° angle. The rotation of the shaft and the movement of the print head along the longitudinal direction of the rotation axis are coordinated accordingly. When applied at a 45° angle, the movements are identical. At other angles, the movements and speeds must be adjusted accordingly. Once the print head reaches the end of its travel along the rotation axis, the direction is reversed, creating a multi-layer hollow product, which is preferably used when torsional forces act on the product.

[0040] Depending on the expected load of the products to be printed, the appropriate print head and shaft control variant can be used. Of course, it is also possible to combine different variants to achieve greater mechanical strength. In this case, multiple layers of filament are printed on top of each other.

[0041] According to the invention, the present object is also achieved by a method having the features of claim 10. In the method according to the invention, a device as described above is first provided and mounted on the 3D printer. In one step, an overlap of the wall of the hollow shaft of the device is adjusted in order to set a predetermined conical shape of the shaft. In a further step, the shaft is moved in the direction of rotation until it assumes a predetermined rotational position. A further step comprises moving the print head of the printer to a predetermined print head position. An additional step concerns the application of meltable material, for example filament, to the outer surface of the shaft of the device. A further optional step comprises moving the shaft and / or the print head to the next desired position.

[0042] The steps can be performed in the specified order or in a different order. Individual steps can also be performed multiple times before another step is performed. It is also possible for several steps to be performed simultaneously. The moving steps can involve continuous movement. Stepwise movement is also possible. The application of filament or meltable

[0043] Material can also be applied to the shaft surface continuously or step by step.

[0044] The invention is described and explained in more detail below using selected exemplary embodiments in conjunction with the accompanying drawings. The features shown in the figures may also occur individually or in other combinations. The embodiments shown in the figures do not represent a limitation of the individual features or their combinations. They show: Fig. 1a shows a system for 3D printing according to the invention with a 3D printer and a device according to the invention; Fig. 1b shows an alternative embodiment of the system according to the invention; Fig. 2a-c different printing forms; Fig. 3 a schematic diagram of the device according to the invention; Fig. 4 a particular embodiment of the device according to the invention with a conical outer surface; Fig. 5a, b a schematic diagram of a cross-section through a shaft according to the invention; Fig. 6a, b show a further particular embodiment of the device according to the invention; and Fig. 7 another embodiment of the device with heating.

[0045] Fig. 1a shows a system 10 according to the invention for 3D printing rotationally symmetrical elongated hollow bodies with a 3D printer 20 and a device 30 for 3D printing.

[0046] The 3D printer 20 comprises a print bed 22 and a print head 24 configured to apply a filament 21 made of meltable material, in particular meltable plastic, to a substrate, for example the print bed 22. A control unit 26 preferably controls both the movement of the print head 24 and the dispensing of meltable material by the print head.

[0047] The device 30 according to the invention has a shaft 32 extending along a rotational axis 34. The shaft 32 has a lateral surface 33 as a surface, which is suitable and designed to receive the material, e.g., in the form of a filament, so that an elongated hollow body with a round cross-section can be printed on the shaft 32. At each of its two ends 36, the shaft 32 is mounted in a bearing 38 and is driven by a drive motor 40, which enables rotation of the shaft about the rotational axis 34.

[0048] In the embodiment shown here, the shaft 32 has a shaft journal 42 at each of its ends 36, which is supported in the bearing 38. The bearing 38 comprises a receptacle for the shaft. Preferably, the bearing 38 comprises a retaining element 37 for holding and securing the shaft to the printer. The retaining element 37 can preferably be, as shown here, a housing 39 that is releasably attached to the print bed 22.

[0049] The device 30 according to the invention preferably comprises an optional connection unit 12, by means of which a connection to the 3D printer 20 can be established. Preferably, communication between the device 30 and the printer is established in order to coordinate the movement of the shaft 32 with the movement of the print head 24 and / or the dispensing of the meltable material from the print head. The connection unit can serve to establish communication, i.e., to exchange information between the device and the printer, wherein the exchange can be unidirectional or bidirectional. For example, a connection or communication between the connection unit 12 and the control unit 26 is possible, which preferably takes place wirelessly.Preferably, control parameters or control commands are exchanged between the printer and the device, for example to adapt the rotational movement of the shaft 32 to the material dispensing of the print head and to preferably enable the material dispensing along a predetermined trajectory.

[0050] Fig. Figure 1b is a schematic representation of an alternative preferred embodiment. According to this embodiment, the print head 24 of the 3D printer 20 is guided along a cross member 72, which is part of a holding device 70. The cross member 72 can preferably be adjusted vertically in height.

[0051] The device 30 is now not attached to the print bed 22 of the printer with its bearings 38 and their holding elements 37, but rather to the holding device 70. The shaft 32, which extends along the rotation axis 34, is mounted at both ends in a bearing 38 by means of bearing pins 42. The bearing 38 with its holding element 37 is preferably integrated into the holding device 70 and supports the shaft 32. The bearings 38 and holding elements 37, which are arranged in vertical holding struts 74 of the holding device 70, can be changed in their vertical position. Thus, the shaft as a whole can be varied in its height and / or inclination. Drive motors 40 are also integrated into the holding struts 74 to drive the shaft 32 and execute a rotational movement. In addition, motors (not shown) are provided for changing the vertical position of the shaft 32.

[0052] According to this embodiment, the communication connection between 3D printer 20 and device 30 is also established via connection unit 12, which, for example, establishes a wireless or wired connection to the control unit 26 of system 10 if this is part of 3D printer 20. Information is exchanged between 3D printer 20 and device 30 via connection unit 12, which in the simplest case can be a cable. Connection unit 12 can preferably be integrated into a control unit of device 30, which can convert control commands into a rotary movement of the shaft.

[0053] In the embodiment of the system 10 shown here, the print head is arranged and aligned to deliver the filament 21 of meltable material directly onto the shaft 32 and its outer surface 33. The bearings 38 of the device 30, which include the drive motors 40, are arranged and positioned on the print bed 22 of the 3D printer 20. In the embodiment shown here, printing occurs in the circumferential direction while the shaft 32 rotates.

[0054] The Fig. 2a to 2c show three different ways of applying filament 21 from the print head to the outer surface 33 of the shaft 32. In Fig. Figure 2a shows a circumferential print. The shaft 32 rotates around its rotational axis 34, while the print head initially remains unchanged in its position until the filament has been printed once circumferentially around the shaft 32. After a complete revolution of the shaft 32, the print head 24 is moved in the direction of the arrow before another rotation of the shaft 32 occurs, and the next track of filament is printed, which is in contact with the previous one, so that the material flows into each other. The movements of the print head 24 and the shaft 32 are coordinated.

[0055] This printing process is used to print elongated hollow bodies that can absorb high tensile or compressive forces in the circumferential direction.

[0056] Fig. Figure 2b shows a longitudinal print. With the shaft 32 stationary, the print head 24 moves in the direction of the rotation axis from one end of the shaft 32 to the other. Once the print head has reached the opposite end 36 of the shaft 32, the shaft can be moved by the width of a filament 21, allowing another molten layer to be applied next to the molten layer already applied. Of course, it is also possible to first print several layers on top of each other before the shaft is rotated in the direction of rotation. This longitudinal printing produces hollow bodies that are ideally suited to tensile or compressive forces in the longitudinal direction.

[0057] Fig. Figure 2c shows printing at a 45° angle. Both shaft 32 and print head 24 are moved. The print head moves in the direction of arrow 28, i.e., in the direction of rotation axis 34. By appropriately selecting the movement speed of print head 24 and shaft 32, the angle at which filament 21 is applied to the outer surface 33 of shaft 32 can be adjusted. This printing process produces hollow bodies with high torsional strength. Of course, this printing process can also be used to print multiple layers on top of each other.

[0058] Of course, it is possible to use the individual printing processes according to the Fig. 2a to 2c to combine and print multiple layers with different structures.

[0059] Print head 24 and shaft 32 are each controlled by the control unit 26, and their speed is determined. Alternatively, a separate control unit can be used, which has an interface to both the device 30 and the 3D printer 20.

[0060] Fig. Figure 3 shows the device 30 according to the invention, in which the shaft 32 is designed as a hollow shaft 44. The shaft journals 42 at the two ends 36 of the hollow shaft 44 are mounted in bearings 38 and are driven by the drive motors 40.

[0061] The hollow shaft has a cut 47 in its wall 48. The wall 48, which is preferably made of sheet metal, overlaps at the respective end regions 50 resulting from the cut 47, so that an overlap region 52 is formed. In this way, the diameter of the hollow shaft 44 can be varied and adjusted to a desired value. The smaller the diameter of the hollow shaft 44, the larger the overlap region 52. Depending on the desired and adjusted diameter of the hollow shaft 44, the position of the shaft 32 and thus its distance from the floor (print bed 22) can be varied. Therefore, the bearings 38 are preferably adjustable in height.

[0062] Optionally, the position of the shaft 32, particularly its height, can be adjusted. To do this, the height of the bearings 38 and the shaft mounts are varied. This can be done automatically and with the help of position motors 43. The position motors 43 and mounts are moved within the housing 39 mounted on the print bed 22.

[0063] In a preferred embodiment, a plurality of heating elements 64 are provided inside the hollow shaft 44, which heat and warm the outer surface 33 of the shaft 32 (cf. Fig. 7). A heated print surface is particularly advantageous when using FDM printers. The print surface is the surface to which the meltable material is applied. In this case, the print surface is the outer surface 33 of the hollow shaft 44.

[0064] Fig. 4 shows a particular embodiment of the device 30 according to the invention. The shaft 32, designed as a hollow shaft 44, can be varied in its diameter. The hollow shaft 44 has a cut 47 (not shown here) in the longitudinal direction of the rotation axis 34, so that the wall 48 of the hollow shaft 44 overlaps in its end regions 50. The wall 48 of the hollow shaft is connected to the shaft journals 42 by means of a fastening element (not shown here). By displacing the wall ends in the end regions 50 relative to one another, the diameter of the hollow shaft 44 can be changed. This is preferably accomplished by two motors 46 arranged inside the hollow shaft 44, so that it is possible to give the hollow shaft a conical shape.

[0065] In the Fig. 5a and Fig. 5b shows a section through the hollow shaft 44. The motor 46, which is used to adjust the outer diameter of the hollow shaft 44, is arranged inside the hollow shaft 44. Alternatively, in an optional embodiment, the motor 46 can be arranged outside the hollow shaft 44. The wall 48 of the hollow shaft is cut in the longitudinal direction of the axis of rotation, so that the end regions 50 of the wall 48 overlap in an overlap region 52. A fastening element 54 is connected to the motor 46 at a fastening point 58. The other end 60 of the fastening element 54 is connected to the inner end region 50 of the wall 48. In the preferred embodiment shown here, the fastening element 54 is designed as a spiral spring 56.

[0066] By rotating the motor 46, the attachment point 58 on the motor 46 moves clockwise, as shown in Fig. 5b. This causes the inner end region 50 of the wall 48 to also move clockwise, so that the overlap area 52 of the wall 48 is enlarged. This reduces the outer diameter of the hollow shaft 44.

[0067] Since the motors 46 are each arranged at the ends of the hollow shaft 44, the outer diameter of the entire hollow shaft 44 can be changed by moving the motors 46 arranged inside the hollow shaft 44. With a uniform movement of the motors 46, different diameters can be set that remain constant for the entire hollow shaft 44. Since the two motors 46 can be moved and controlled independently of one another, conical shapes of the hollow shaft 44 can also be set (see Fig. 4, Fig. 6a, Fig. 6b), so that nozzles and diffusers in particular can be printed using such a conical hollow shaft.

[0068] In a preferred embodiment of the device 30, in which the wall 48 is cut in the longitudinal direction of the rotation axis, the overlap of the end regions 50 of the wall 48 in the overlap region results in the outer contour of the hollow shaft 44 not being completely rotationally symmetrical. However, the offset 62 resulting from the overlap of the wall 48 is generally not relevant in practice. For example, it can be compensated for by the applied meltable material in the hollow body to be produced.

[0069] The Fig. 6a and Fig. 6b show an embodiment in which the hollow shaft 44 is designed as a conical shaft 32. In order to be able to produce the most uniform and simple 3D printing possible, it is advantageous if the printing surface over which the print head 24 moves is aligned horizontally. In this case, the print head only needs to move in one spatial direction. A change in its position in the vertical direction is not necessary. In a conical hollow shaft 44, in which the rotation axis 34 extends horizontally, the outer surface 33 of the shaft 32 is not horizontal, as Fig. 6a.

[0070] In a preferred embodiment, the position of the bearings 38 and thus the position of the shaft journals 42 can be shifted vertically within the housings 39 of the bearings 38. It is generally sufficient if one of the shaft journals 42 is shifted in its horizontal position. In the embodiment shown here according to Fig. 6b, the horizontal position of the right shaft journal is shifted upward. The shaft journal 42 is shifted upward until the vertically uppermost position of the lateral surface 33 is aligned horizontally. The rotation axis 34, which runs coaxially with the hollow shaft 44, then encloses an angle to the horizontal that differs from 0 degrees.

[0071] In Fig.Figure 7 shows a particular embodiment of the device according to the invention, in which heating elements 64 are arranged inside the hollow shaft 44. In the embodiment shown, four heating elements are distributed in the longitudinal direction of the rotation axis. The four heating elements can be controlled and activated individually. The heating power generated by the heating element can vary. In this way, it is possible to generate a constant temperature on the surface of the casing surface 33 with conically shaped hollow shafts 44. Depending on the outer diameter of the hollow shaft 44, the individual heating elements can be controlled separately. Control is preferably carried out by means of the control unit 26 or by means of the 3D printer 20. Of course, a separate control unit can be used to control the heating elements.Each heating element can therefore be heated to different temperatures, resulting in a uniform temperature distribution on the surface of the jacket surface 33.

[0072] The device according to the invention for a 3D printer, described here with reference to the individual figures, can be used as an add-on module, so that conventional 3D printers can be retrofitted with this device. The retrofittable device 30 thus forms a rotationally symmetrical print bed, in which, in particular, rotationally symmetrical hollow bodies with an elongated extension can be printed. The size of the shaft 32, in particular its length and diameter, can be adapted to the hollow bodies to be produced, such as hoses, pipe sections, nozzles, or diffusers. The length of the shaft 32 determines the maximum possible length of the hollow body to be produced. The diameter of the hollow bodies to be produced can, as described above, be varied by the particular embodiment of the device and the hollow shaft.

[0073] The invention has been comprehensively described and explained with reference to the drawings and the description. The description and explanation are to be understood as exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other embodiments or variations will become apparent to those skilled in the art upon use of the present invention and upon careful analysis of the drawings, the disclosure, and the following claims.

[0074] The print bed of a conventional 3D printer is a substantially horizontally oriented plate onto which the filament from the print head can be applied and which holds and supports, or receives and carries, the object to be printed. The device's bearing is an element that supports and supports the device's shaft and enables and establishes a connection to the 3D printer. The bearing may include other elements or components, such as the described housing or a holding element.

[0075] In the claims, the words "comprising" and "having" do not exclude the presence of further elements or steps. The undefined article "a" or "an" does not exclude the presence of a plurality. A single element or unit can perform the functions of several of the units recited in the claims. An element, unit, device, and system can be partially or completely implemented in hardware and / or software. The mere reciting of some measures in several different dependent claims should not be understood to mean that a combination of these measures cannot also be used advantageously.

Claims

[1] Device (30) for retrofitting a 3D printer (20) with a flat printing bed (22) for receiving a melt layer of a meltable material comprising a shaft (32) extending along a rotation axis (34) and designed as a hollow shaft (44) with a lateral surface (33), a drive motor (40) for driving the shaft (32), and - a bearing (38) for receiving and supporting the shaft (32), - where - the bearing (38) is designed to be attached to the 3D printer (20); and - the lateral surface (33) is designed to receive the melt layer; and - the hollow shaft (44) has a wall (48) which is cut in the longitudinal direction so that end regions (50) of the wall (48) partially overlap in an overlap region (52) in the direction of rotation. [2] Device (30) according to claim 1, characterized bythat the device (30) comprises a connection unit (12) for communication between the device (30) and the 3D printer (20) for coordinating the movement of the shaft (32) with a print head (24) of the 3D printer (20). [3] Device (30) according to one of the preceding claims, characterized by that the outer surface (33) of the shaft (32) is conical. [4] Device (30) according to one of the preceding claims, characterized by that the bearing (28) comprises a holding element (37) for fastening to the 3D printer, wherein the holding element (37) is a housing (39) of the bearing, and wherein the bearing (28) is mountable on the flat printing bed of the 3D printer. [5] Device (30) according to one of the preceding claims, characterized bythat the outer surface (33) can be heated from the inside, wherein preferably a plurality of heating elements (64) are arranged in the interior of the shaft (32), very preferably the heating elements (64) can be controlled and activated individually and particularly preferably a plurality of heating elements (64) are distributed in the longitudinal direction of the axis of rotation (34). [6] Device (30) according to one of the preceding claims, characterized by that the shaft (32) is mounted at both ends and preferably a drive motor (40) is arranged at both ends of the shaft (32) in order to drive the shaft (32). [7] Device (30) according to the preceding claim, characterized by that the overlap of the end regions (50) of the wall (48) can be changed such that the outer diameter of the shaft (32) can be varied. [8] Device (30) according to claim 7, characterized bythat the inner end region (50) of the wall (48) is connected to the shaft journal (42) of the shaft (32) by means of a fastening element (54), wherein the fastening element (54) is preferably a spring, very preferably a spiral spring (56). [9] System (10) for 3D printing comprising a 3D printer (20) with a flat print bed (22) and a device (30) according to one of the preceding claims, wherein the device (30) is suitable for retrofitting and is detachably mounted on the flat print bed of the 3D printer (20) and a print head (24) of the 3D printer (20) can apply a meltable material to the outer surface (33) of the device (30). [10] A method for controlling a device (30) according to any one of claims 1 to 8 or a system (10) according to claim 9 or 10, wherein the device (30) is arranged on a 3D printer (20) and receives meltable material from a print head (24) of the 3D printer (20) on its outer surface (33), comprising the following steps: - Providing and mounting a device according to claim 1 on a 3D printer; - Adjusting an overlap of the wall of the hollow shaft (44) in order to set a predetermined conical shape of the shaft; - moving the shaft (32) in a rotational movement to a predetermined rotational position; - moving the print head (24) of the 3D printer (20) to a predetermined print head position; - applying meltable material to the outer surface (33) of the shaft (32) of the device (30); - optionally moving the shaft (32) and / or the print head (24) to the next desired position.

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