Extruder system and additive manufacturing printer, comprising such an extruder, and a method of printing a product with such an additive manufacturing printer

Abstract

Extruder system (1), comprising: • a supply (2) comprising a heater (5) configured to melt raw material into an extrudable material; • an extruder (7) comprising a screw conveyor (8) configured to convey the extrudable material towards an extrusion nozzle (9) and cause an overpressure to allow extrusion via said extrusion nozzle; • a drive (10); • a pressure chamber (11); and • wherein the drive is configured to selectively move the extrusion nozzle between a printing state, wherein the extrusion nozzle is moved opposite to the conveying direction towards the tip of the screw conveyor, and an anti-oozing state, wherein the extrusion nozzle is moved away from the tip of the screw conveyor to increase an internal volume of the pressure chamber and thereby release at least a part of the overpressure to control a flow of extrudable material out of the outflow opening (13) and reduce oozing of extrudable material after stopping said flow. The invention further relates to an additive manufacturing printer, comprising such an extruder, and to a method of printing a product with such an additive manufacturing printer.

Description

[0001] Extruder system and additive manufacturing printer, comprising such an extruder, and a method of printing a product with such an additive manufacturing printer

[0002] The present invention relates to an extruder system, and to an additive manufacturing printer, comprising such an extruder. The invention further relates to a method of printing a product with such an additive manufacturing printer.

[0003] Extruder systems may be used for a large variety of applications, one of which is for extruding printing material in an additive manufacturing printer, “AM printer”. The skilled person will however understand that the invention is not limited to the field of additive manufacturing. Other applications for extruder systems are dosing applications such as for glue, paste, solder or hot melt, especially if these substances are to be applied in a specific pattern. Moreover, extruders may be used to fill holders, sometimes requiring a high accuracy, for example for vaccines. Extruder systems may also be applied in mixing devices, for example for mixing paint or chemicals.

[0004] Extruder systems often apply a screw conveyor that is configured to convey extrudable material, in particular a molten raw material, towards an extrusion nozzle. Especially if the extrudable material is highly viscous, conveying thereof by rotating the screw conveyor results in high friction, high drive torque and a large pressure build up inside the extruder system. In an AM printer, the pressure in the extruder may for example be in the range of 70 - 100 bar. In order to stop a flow of extrudable material out of the extrusion nozzle, simply stopping rotating, or rotating the screw conveyor in the opposite direction, may not result in an immediate stop of the flow, mainly due to the overpressure inside the extruder system. This results in oozing of the extrudable material. Although such oozing may not be an issue for some types of extruder system applications that require only a limited level of accuracy and control, it is considered a disadvantage for applications such as additive manufacturing. After all, the less oozing, the more accurate the to be printed product will be. Currently AM printing is limited to so called “vase mode”, meaning that the extruder starts extruding for only one to be printed product, i.e. without stopping / starting during the print job thereof. Moreover, less or no oozing at all means better control, and therefore increased consistency in the quality of the to be printed products. Furthermore, if oozing is prevented, the AM printer has the option to print multiple objects in one print job while jumping from one to be printed object to the another to be printed object without oozing I stringing, or polluting the extrusion nozzle.

[0005] In addition to preventing oozing as much as possible, the (surface) quality of an additive manufactured product also benefits from a controllable laminar flow at the extrusion nozzle, as well as from a homogeneous melt of extrudable material having a constant temperature and viscosity.

[0006] International patent application WO 2022 / 260512 A1 of the same Applicant discloses an extruder system, and an additive manufacturing printer comprising such an extruder, that effectively reduces oozing for medium-sized and large extruder systems. The extruder system disclosed in this international patent application, comprises:

[0007] - a supply configured to receive raw material and comprising a heater configured to melt the raw material into extrudable material;

[0008] - an extruder configured to receive the extrudable material from the supply and comprising a screw conveyor configured to convey the extrudable material towards an extrusion nozzle of the extruder and cause an overpressure inside the extruder to allow selective extrusion via said extrusion nozzle; and

[0009] - a plunger arranged in a tip of the screw conveyor and configured to selectively release at least a part of the overpressure and thereby control a flow of extrudable material out of said extrusion nozzle to reduce oozing of extrudable material after stopping said flow.

[0010] By moving the plunger, that is arranged in a tip of the screw conveyor, away from and upstream relative to the extrusion nozzle, the extruder system actively releases at least a part of the overpressure. In this way, the extruder system is able to reduce oozing, thereby providing an improved control of the flow of extrudable material. By reducing the oozing, the accuracy and consistency of the extruder system is improved.

[0011] The extruder system disclosed in WO 2022 / 260512 A1 is effective in preventing oozing in medium-sized and large extruder systems, that comprise a screw conveyor that is large enough to allow the plunger to be arranged in the tip of said screw conveyor. In practice, such a plunger may be applied in screw conveyors having a diameter of at least 12 mm. WO 2022 / 260512 A1 thus provides an effective antioozing system for medium-sized and large extruder systems, allowing these system to use granulate as the raw material, while still guaranteeing accurate and consistent printing, and consequently a high quality print.

[0012] With respect to this invention, the wording “granulate” is intended to cover any form of grains or particles, and explicitly also covers pellets and powders, which are considered granulates having a very fine texture. The versatility of an extruder system increases if it can use granulate as raw material. After all, granulate allows for a large freedom of choice regarding the raw material. The raw material is explicitly not limited to plastics that are suitable to be formed into a filament, which is a requirement of state of the art filament AM printers. For example the raw material may also comprise polymers or materials that are susceptible to breaking due to their brittleness, or highly flexible plastics.

[0013] As mentioned above, the extruder system that is the subject of WO 2022 / 260512 A1 is limited to medium-sized and large extruder systems, that comprise a screw conveyor that is large enough to allow the plunger to be arranged in the tip of said screw conveyor.

[0014] International patent application WO 2022 / 232888 A1 , is considered to define the closest prior art for the present invention, and discloses an extruder for an additive manufacturing printer. In this extruder system, a screw conveyor can be axially retracted in relation to a nozzle for selectively defining a positive displacement pump that controls a flow of feedstock output by the nozzle. By facilitating a pressure drop, oozing can be reduced.

[0015] An objective of the present invention is to provide an extruder system, that is improved relative to the prior art and wherein at least one of the above stated problems is obviated or alleviated. More in particular, it is an objective to provide an extruder system with improved versatility.

[0016] Said objective is achieved with the extruder system according to claim 1 of the present invention, comprising:

[0017] - a supply configured to receive raw material and comprising a heater configured to melt the raw material into an extrudable material;

[0018] - an extruder configured to receive the extrudable material from the supply and comprising a screw conveyor configured to convey the extrudable material in a conveying direction towards an extrusion nozzle of the extruder and cause an overpressure inside the extruder to allow selective extrusion via said extrusion nozzle; - a drive configured to selectively drive the screw conveyor to convey the extrudable material in the conveying direction towards the extrusion nozzle;

[0019] - a pressure chamber that is defined, in the conveying direction, between a tip of the screw conveyor and an outflow opening of the extrusion nozzle;

[0020] - wherein the extrusion nozzle is moveable relative to the tip of the screw conveyor; and

[0021] - wherein the drive is further configured to selectively move the extrusion nozzle between a printing state, wherein the extrusion nozzle is moved opposite to the conveying direction towards the tip of the screw conveyor, and an anti-oozing state, wherein the extrusion nozzle is moved in the conveying direction away from the tip of the screw conveyor to increase an internal volume of the pressure chamber and thereby release at least a part of the overpressure to control a flow of extrudable material out of the outflow opening of said extrusion nozzle and reduce oozing of extrudable material after stopping said flow.

[0022] The drive selectively moving the extrusion nozzle away from the tip of the screw conveyor will result in an increase of the internal volume of the pressure chamber. In this way, the internal pressure inside the pressure chamber may be reduced, thereby effectively controlling the outflow of extrudable material out of the outflow opening of the extrusion nozzle. As a result, the extruder system reduces the risk of oozing of extrudable material after stopping said flow.

[0023] Because the extruder system according to the invention is scalable in size, it provides increased versatility relative to the extruder system disclosed in WO 2022 / 260512 A1 , that was limited to medium-sized and large extruder systems only. Instead, the extruder system according to the present invention may also be applied in small extruder systems. By providing anti-oozing, extruder systems of all sizes may now benefit from increased accuracy and consistency of the flow of extrudable material out of the extrusion nozzle. When the extruder system is part of an AM printer, a reduction in oozing results in higher quality printed products. Moreover, the quality of the printed product will not only be better, but will also be more consistent. Furthermore, if oozing is prevented, the AM printer has the option to print multiple objects in one print job while jumping from one to be printed object to the another to be printed object without oozing I stringing, or polluting the extrusion nozzle, that could result in a poor or unacceptable print quality. Especially for small extruder systems, the present invention provides the option to use granulate as the raw material. Small extruder systems according to the prior art are mainly designed as filament AM printers, and are consequently limited to plastics that are suitable to be formed into a filament. However, since granulate may now be used as the raw material, the present invention provides an increased freedom of choice regarding the raw material for small extruders systems as well. More in particular, the raw material may also comprise polymers or materials that are susceptible to breaking due to their brittleness, or highly flexible plastics, that could therefore not be made available as a filament for a filament AM printer. In this respect it is mentioned that oozing may especially occur if granulate is used as the raw material in combination with an extruder system having a screw conveyor, because this type of raw material is often highly viscous, resulting in a large pressure build up inside the granulate extruder system. In a granulate based AM printer, the pressure in the extruder may for example be in the range of 70 - 100 bar, and due to the overpressure inside the extruder system the extrudable material has a tendency to ooze after stopping of the flow.

[0024] Further advantages relative to the extruder system disclosed in WO 2022 / 260512 A1 , is that the design is simpler, more easy to maintain, and moreover more reliable. It also provides easier access to the screw conveyor of the extruder for cleaning, inspection or exchanging the screw. With respect to maintenance, the extrusion nozzle is readily accessible and may be easily lubricated, whereas the plunger of WO 2022 / 260512 A1 is concealed inside the extruder. Also, the flow of extrudable material is more consistent than in WO 2022 / 260512 A1 , also contributing to a more consistent extrusion. After all, retraction of the plunger influenced the flow to some extent. Finally, contrary to the plunger of WO 2022 / 260512 A1 that is arranged in the tip of the screw conveyor, the anti-oozing features according to the present invention are less exposed to heat. After all, due to the high pressures and the molten extrudable material, the temperatures are very high at the tip of the screw conveyor, whereas the temperature in the nozzle is lower relative to the temperature at the tip.

[0025] Relative to the extruder system disclosed in the closest prior art document, WO 2022 / 232888 A1 , the present invention proposes to move the extrusion nozzle, that is small and lightweight compared to the screw conveyor. By moving the lightweight nozzle, contrary to the heavier screw conveyor that also experiences significant friction inside the housing of the extruder surrounding the screw conveyor, the present invention is capable of more swiftly and more accurately adjusting the internal volume of the pressure chamber. As a result, more accurate anti-oozing is obtained.

[0026] In order to obtain a constant and high print quality, it is key for extruder systems that are based on receiving raw material, such as pellets, wherein said raw material is successively heated to melt the raw material into an extrudable material, that the melt-flow is as constant as possible. The raw material is simultaneously melted and compressed to arrive at the desired pressure. Friction of the melt against the inner wall of a container of the extruder increases the temperature of the extrudable material even further, while said extrudable material is transported towards the nozzle. According to the invention, only the nozzle is moved. It is thereby guaranteed that the friction, pressure and temperature inside the extruder system remain unaffected. Thus, as soon as the extrusion of extrudable material is restarted after a short interruption, the complete extruder system is almost instantly in balance with respect to temperature and pressure of the extrudable material, thereby guaranteeing that the extruder system will continue with the same constant high quality print result as before the interruption. To the contrary, the extruder system disclosed in WO 2022 / 232888 A1 proposes to withdraw the screw as a whole. This movement of the screw will disturb the precious balance of friction, temperature and pressure inside the extruder system. Thus, as soon as the extrusion of extrudable material is restarted after a short interruption of the extruder system of WO 2022 / 232888 A1 , it will take some time to reach a balanced system with respect to temperature and pressure, and consequently the print quality will need some time to settle. As a result, the extruder system of WO 2022 / 232888 A1 will experience changes in print quality, especially when comparing the print quality before an interruption, and shortly thereafter when printing has restarted.

[0027] Moreover, with respect to maintenance, the extrusion nozzle is readily accessible and may be easily lubricated, contrary to the screw conveyor that is concealed inside the housing of the extruder.

[0028] According to a preferred embodiment, in the anti-oozing state, the extrusion nozzle is moved in the conveying direction away from the tip of the screw conveyor and thereby also away from a housing surrounding the screw conveyor. The screw conveyor is rotatably arranged inside the housing of the extruder, and there is no need, nor desire, that the screw conveyor is axially movable relative to the housing of the extruder surrounding said screw conveyor. A screw conveyor that is not moveable in the axial direction allows for a simpler and more reliable design.

[0029] According to a preferred embodiment, the extruder system is an extruder system of an additive manufacturing printer, “AM printer”. Using such an extruder for an AM printer allows the AM printer to have a large freedom of choice regarding the raw material. Moreover, the carbon dioxide footprint may be reduced if the intermediate step of producing a filament out of the raw material is rendered obsolete. The production step granulate to filament is skipped reducing the carbon oxide foot print and material price. The raw material is explicitly not limited to plastics that are suitable to be formed into a filament, which is a requirement of state of the art filament AM printers. For example the raw material may also comprise polymers or materials that are susceptible to breaking due to their brittleness, or highly flexible plastics.

[0030] The raw material is preferably a granulate, wherein the wording “granulate” covers any form of grains or particles, and explicitly also covers pellets and powders, which are considered granulates having a very fine texture. The extruder system is preferably a granulate extruder system. Such a granulate extruder system may also be referred to as a pellet extruder system.

[0031] The invention furthermore also relates to an additive manufacturing printer, “AM printer”, comprising an extruder system according to the invention, a controller configured to cause the extruder system to, when executing computerexecutable printing instructions for printing an object, print said object, and wherein the extruder system is configured to selectively move the extrusion nozzle in the conveying direction away from the tip of the screw conveyor to increase an internal volume of the pressure chamber and thereby release at least a part of the overpressure to control the flow of extrudable material out of the outflow opening of said extrusion nozzle and reduce oozing of extrudable material after stopping said flow.

[0032] According to a preferred embodiment of the AM printer, the controller is configured to simultaneously move the extrusion nozzle in the conveying direction away from the tip of the screw conveyor and move the extruder in a direction opposite to the conveying direction. In this way, it is guaranteed that the extrusion nozzle will not contact, and possibly damage, the to be printed object.

[0033] According to a preferred embodiment of the AM printer, the controller is configured to simultaneously move a platform carrying the to be printed object and the extrusion nozzle in the conveying direction away from the tip of the screw conveyor. This is an alternative way, that may also be used in combination with the measure in the previous paragraph, to guarantee that the extrusion nozzle will not contact, and possibly damage, the to be printed object.

[0034] The invention further relates to a method of printing a product with an additive manufacturing printer, “AM printer”, comprising the steps of:

[0035] - melting raw material into an extrudable material;

[0036] - conveying the extrudable material with a screw conveyor in a conveying direction towards an extrusion nozzle of an extruder of the AM printer, thereby causing an overpressure in a pressure chamber that is defined, in the conveying direction, between a tip of the screw conveyor and an outflow opening of the extrusion nozzle; and

[0037] - selectively moving the extrusion nozzle in the conveying direction away from a tip of the screw conveyor to increase an internal volume of the pressure chamber, thereby releasing at least a part of the overpressure to control a flow of extrudable material out of the outflow opening of said extrusion nozzle and reducing oozing of extrudable material after stopping said flow.

[0038] According to a preferred embodiment of the invention, the method comprises the step of, simultaneously with the step of moving the extrusion nozzle in the conveying direction away from the tip of the screw conveyor, moving the extruder in a direction opposite to the conveying direction. The extruder may be moved as such, or a print head assembly comprising the extruder system may be moved as an assembly, thereby also moving the extruder system. Combinations thereof are also possible.

[0039] According to a further preferred embodiment of the invention, the method comprises the step of, simultaneously with the step of moving the extrusion nozzle in the conveying direction away from the tip of the screw conveyor, also moving the platform carrying the to be printed object in the conveying direction. Again, it is noted that this measure may be combined with the alternative measures presented in the previous paragraph.

[0040] According to a preferred embodiment of the method, the raw material is a granulate and the extruder system is a granulate extruder system.

[0041] According to a preferred embodiment of the method, it comprises the step of using an extruder system according to the invention.

[0042] Preferred embodiments are the subject of the dependent claims.

[0043] The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, and in particular the aspects and features described in the attached dependent claims, may be an invention in its own right that is related to a different problem relative to the prior art. This applies, for example, to the valve described as the fourth embodiment.

[0044] In the following description preferred embodiments of the present invention are further elucidated with reference to the drawing, in which:

[0045] Figure 1 is a perspective view of an AM printer comprising an extruder system according to the invention;

[0046] Figure 2 is a detailed perspective view of a first preferred embodiment of the extruder system;

[0047] Figure 3A is a detailed cross-sectional side view during extruding of the extruder system of Figure 2;

[0048] Figure 3B is a detailed cross-sectional side view directly after stopping extruding of the extruder system of Figure 2;

[0049] Figure 3C is a detailed cross-sectional side view after moving the extrusion nozzle of the extruder system of Figure 2 into the anti-oozing state thereof;

[0050] Figure 4 is a cross-sectional side view of the extruder system according to the first preferred embodiment;

[0051] Figure 5 is a detailed perspective cross-sectional view of the extruder system according to the first preferred embodiment;

[0052] Figure 6A is a schematic side view of an AM printer showing that the extruder system is moved away from the object to be printed when the extrusion nozzle is brought into the anti-oozing state thereof;

[0053] Figure 6B is a schematic side view of an AM printer showing that a print head of said AM printer comprising the extruder system is moved away as a whole from the object to be printed when the extrusion nozzle is brought into the anti-oozing state thereof;

[0054] Figure 6C is a schematic side view of an AM printer showing that a platform carrying the product to be printed is simultaneously moved together with the extrusion nozzle when said extrusion nozzle is brought into the anti-oozing state thereof;

[0055] Figure 7A is a perspective view of the extruder system according to the first preferred embodiment in a printing state;

[0056] Figure 7B is a perspective view of the extruder system according to the first preferred embodiment in an anti-oozing state, wherein the extruder system is moved conform Figure 6A.

[0057] Figure 8 is a cross-sectional side view of the extruder system according to a second preferred embodiment;

[0058] Figure 9 is a cross-sectional side view of the extruder system according to a third preferred embodiment, with the extrusion nozzle in a printing state;

[0059] Figure 10 is a cross-sectional side view of the extruder system according to the third preferred embodiment, with the extrusion nozzle in an anti-oozing state;

[0060] Figure 11 is a perspective view of the extruder system according to the third preferred embodiment;

[0061] Figure 12A is a detailed cross-sectional side view during extruding of an extruder system according to a fourth preferred embodiment; and

[0062] Figure 12B after moving the extrusion nozzle of the extruder system of Figure 12A into the anti-oozing state thereof.

[0063] The invention relates to an extruder system 1 that comprises a supply 2 configured to receive raw material 3, for example granulate provided in a pellet hopper 4. The supply 2 may be integrated in an upstream part of the extruder 7. The extruder system 1 comprises a heater 5 configured to melt the raw material 3 into extrudable material 6. The extruder system 1 further comprises an extruder 7 configured to receive the extrudable material 6 from the supply 2 and that comprises a screw conveyor 8 configured to convey the extrudable material 6 in a conveying direction towards an extrusion nozzle 9 of the extruder 7 and cause an overpressure inside the extruder 7 to allow extrusion via said extrusion nozzle 9. A drive 10 is configured to drive the screw conveyor 8. A pressure chamber 11 is defined, in the conveying direction, between a tip 12 of the screw conveyor 8 and an outflow opening 13 of the extrusion nozzle 9.

[0064] As can be best seen in the successive steps shown in Figures 3A-C, the extrusion nozzle 9 is moveable relative to the tip 12 of the screw conveyor 8 to allow the extrusion nozzle 9 to be selectively moved in the conveying direction away from the tip 12 to increase an internal volume of the pressure chamber 11 and thereby release at least a part of the overpressure (Figure 3B) to control the flow F of extrudable material 6 out of the outflow opening 13 of said extrusion nozzle 9 and reduce oozing of extrudable material 6 after stopping said flow F (Figure 3C).

[0065] In the shown embodiment, the screw conveyor 8 is rotatable inside the housing of the extruder 7 surrounding the screw conveyor 8. During use, in particular when the extrusion nozzle 9 is moved by the drive 10, the axial position of the screw conveyor 8 remains substantially at the same position relative to the housing of the extruder 7 surrounding the screw conveyor 8. A screw conveyor 8 with a substantially fixed axial position relative to the housing of the extruder 7 allows for a relative simple design. When the extrusion nozzle 9 is moved in the conveying direction away from the tip 12, it is consequently also moved away from the housing surrounding the screw conveyor 8. Thus, in the anti-oozing state, the extrusion nozzle 9 is moved in the conveying direction away from the tip 12 of the screw conveyor 8 and thereby also away from a housing of the extruder 7 surrounding the screw conveyor 8. Contrary, in the printing state, the extrusion nozzle 9 is moved opposite to the conveying direction towards the tip 12 of the screw conveyor 8, and consequently also towards the housing surrounding the screw conveyor 8.

[0066] When raw material 3 is melted into extrudable material 6, often a relatively viscous composition is obtained. A typical viscosity may be in the range of 103 to 1013 mPa-s. In order to convey this viscous extrudable material 6 towards the extrusion nozzle 9, a relatively high pressure is required. For example, the pressure in the extruder 7 may be in the range of 70 - 100 bar. If the screw conveyor 8 is stopped from conveying the extrudable material 6 towards the extrusion nozzle 9, the pressure that has been build up inside the extruder 7 may continue to press extrudable material 6 out of the extrusion nozzle 9, which is known as oozing. By actively releasing at least a part of the overpressure, the extruder system 1 is able to reduce or prevent this oozing, thereby providing an improved control of the flow F of extrudable material 6. When the extruder system 1 is part of an additive manufacturing printer 14, “AM printer”, a reduction in oozing results in higher quality printed products 15. Moreover, the quality of the printed product will not only be better, but will also be more consistent. Furthermore, if oozing is prevented, the AM printer has the option to print multiple objects in one print job while jumping from one to be printed object to the another to be printed object without oozing I stringing, or polluting the extrusion nozzle, that could result in a poor or unacceptable print quality.

[0067] The raw material 3 may be a granulate and the extruder system 1 may be a granulate extruder system. It is mentioned that granulate covers any form of grains or particles, and explicitly also covers pellets and powders, which are considered granulates having a very fine texture. A granulate extruder system may also be referred to as a pellet extruder system. The supply 2 may be integrated in an upstream part of the extruder 7.

[0068] The extruder system 1 according to all embodiments comprises a drive 10 that is selectively switchable between a first drive direction and a second drive direction. This selective switching between drive directions may be controlled be the controller 14 and based on slicing software that is run by the controller 14. The first drive direction is associated with driving the screw conveyor 8 in a conveying direction for conveying the extrudable material 6 downstream towards the extrusion nozzle 9 (Figure 3A). The second drive direction, that is directed opposite relative to the first drive direction, is associated with stopping the flow F of extrudable material 6 out of said extrusion nozzle 9 by moving the extrusion nozzle 9 in the conveying direction away from the tip 12 of the screw conveyor 8 (Figure 3B). This configuration allows the extruder system 1 to be controlled by a conventional controller 16 with state of the art slicing software, which greatly improves the applicability. After all, there is no need for dedicated tailor-made slicing software. All functionality and features of common software, such as all adjustable parameters used to control a retracting, may be used in an identical manner.

[0069] The drive 10 may drive a drive system 17, such as a pulley system 18, comprising a first pulley 19 and a second pulley 20, that are connected via a belt 21. This belt 21 is preferably a toothed belt to prevent slip between the belt 21 and the first and second pulleys 19, 20. Using a toothed belt 21 , the rotation of the screw conveyor 8 may be accurately controlled. The skilled person will understand that the drive system 17 may also comprise gears as an alternative to the shown pulley system 18.

[0070] When the drive 10 is stopped or driven in the second drive direction, it is configured to stop driving the screw conveyor 8 in the conveying direction. A state wherein the screw conveyor 8 has just stopped is shown in Figure 3B. For illustrative reasons, an imaginary pressure sensor 22 is shown, that indicates the pressure of the extrudable material 6 in the pressure chamber 11. In Figure 3B, the pressure has already significantly dropped relative to the pressure indicated on the pressure sensor 22 in Figure 3A. Nevertheless, the remaining pressure may still cause oozing of the extrudable material 6, as shown by the droplet of extrudable material 6 hanging out of the extrusion nozzle 9. This may cause stringing and / or a polluted nozzle failing the print job.

[0071] In the shown preferred embodiments of the extruder system 1 , the drive 10 is configured selectively drive the screw conveyor 8 to convey the extrudable material 6 in the conveying direction F towards the extrusion nozzle 9. Drive 10 is further configured to selectively move the extrusion nozzle 9 between the printing state (Figure 3A, 4, 8, 9A and 10), wherein the extrusion nozzle 9 is moved opposite to the conveying direction F towards the tip 12 of the screw conveyor 8, and an anti-oozing state (Figure 3C, 9B and 11), wherein the extrusion nozzle 9 is moved in the conveying direction F away from the tip 12 of the screw conveyor 8. If only a single drive 10 is sufficient, the extruder system 1 may be relatively light weight. After all, a second high torque, high weight drive is redundant. A light weight extruder improves practical use, for example it allows for faster and more reliable displacement of the extruder system 1 , for example if the extruder system is an extruder system, in particular a print head, of an additive manufacturing printer, “AM printer” 14.

[0072] When the extrusion nozzle 9 is moved into the anti-oozing state, it is moved against a spring 23. In the first preferred embodiment, this spring 23 is a spiral spring that functions as a pretensioner 24 that is configured to force the extrusion nozzle 9 towards the printing state thereof.

[0073] Referring again to Figure 3B, when the drive 10 is driven in the second drive direction, said drive 10 may be configured to simultaneously stop driving the screw conveyor 8 in the conveying direction and move the extrusion nozzle 9 towards the anti-oozing state (Figure 3C) thereof by moving the extrusion nozzle 9 in the conveying direction F away from the tip 12 of the screw conveyor 8.

[0074] Please note that stopping driving of the screw conveyor 8 in the conveying direction does explicitly cover both the situation that the screw conveyor 8 is stopped from being driven at all, i.e. it stops rotating, but also covers the situation wherein the screw conveyor 8 is driven in a direction opposite to the conveying direction to thereby move the extrudable material 6 away from and upstream relative to the extrusion nozzle 9. This latter situation will be discussed in more detail for the second preferred embodiment shown in Figure 8.

[0075] In the first and second preferred embodiments, a screw spindle 25 is defined by a lead screw 26, that is selectively engageable with a drive shaft 59 of the drive 10, and a nut 27 moveable there along. The nut 27 is mechanically connected to the extrusion nozzle 9 to allow the drive 10, by driving the lead screw 26, to move said nut 27 and the extrusion nozzle 9. The nut 27 is mechanically connected to the extrusion nozzle 9 via a lever 28 that is pivotable relative to a pivot 29. In the shown first and second preferred embodiments, the nut 27 and the extrusion nozzle 9 are connected to the lever 28 at opposite sides relative to the pivot 29. The lever 28 has a first arm 30 extending between the nut 27 and the pivot 29, and a second arm 31 extending between the pivot 29 and the extrusion nozzle 9.

[0076] If the drive 10 is driven in the first drive direction, the screw conveyor 8 is rotated via the drive system 17, and extrudable material 6 is forced in the conveying direction towards the extrusion nozzle 9 where it flows out of the outflow opening 13. To allow the screw conveyor 8 to be rotated, it is rotatably suspended by a bearing 32.

[0077] The extruder system 1 comprises a one-way bearing 33 that is arranged between the drive 10 and the lead screw 26 to allow the lead screw 26 to be selectively engaged by the drive 10. More in particular, the one-way bearing 33 is arranged in line with the drive 10, and is configured to:

[0078] - when the drive 10 is driven in the first drive direction, decouple the drive 10 and the lead screw 26 to allow the lead screw 26 to stand still relative to the drive 10 and maintain the extrusion nozzle 9 in its printing state; and

[0079] - when the drive 10 is driven in the second drive direction, couple the drive 10 to the lead screw 26 to allow the drive 10 to move the extrusion nozzle 9 from the printing state towards the anti-oozing state. Due to this one-way bearing 33, the lead screw 26 will not be driven if the drive is driven in the first drive direction. However, if the drive 10 is reversed and driven in the second drive direction that is opposite to the first drive direction, the drive 10 will also drive the lead screw 26. If the lead screw 26 is rotated, it will act as a screw spindle 25, and the nut 27 will move along the outer screw thread of the lead screw 26. In this way, the drive 10 may actuate the extrusion nozzle 9 via the lever 28. Thus, due to this one-way bearing 33, a single drive 10 suffices to drive the screw conveyor 8 and to actuate the extrusion nozzle 9. If only a single drive 10 is sufficient, the extruder system 1 may be relatively light weight. After all, a second drive is redundant. A light weight extruder system 1 improves practical use, for example it allows for faster and more reliable displacement of the extruder system 1 , for example if the extruder system is an extruder system 1 , in particular a print head, of an additive manufacturing printer, “AM printer”. As will be elucidated in more detail with reference to Figures 6A and 6B, a light weight extruder 1 is particularly relevant for the present invention.

[0080] When the drive 10 is driven in the first drive direction, the drive 10 and the lead screw 26 are decoupled, i.e. disengaged. The pretensioner 24 in the form of pretensioned spring 23 forces the extrusion nozzle 9 in its printing state.

[0081] In the first preferred embodiment shown in Figure 4, the extruder system 1 comprises a further one-way bearing 34. This further one-way bearing 34 is configured to: when the drive 10 is driven in the first drive direction, couple the drive 10 to the screw conveyor 8 and thereby drive the screw conveyor 8 in the conveying direction; and when the drive 10 is driven in the second drive direction, decouple the drive 10 and the screw conveyor 8 to stop driving the screw conveyor 8 in both the conveying direction and a direction opposite to the conveying direction. Thus, full drive torque is available for fast anti-oozing I retraction.

[0082] If the extrusion nozzle 9 is moved from the printing state to the antioozing sate, said extrusion nozzle 9 moves away from the screw conveyor 8. The extrusion nozzle 9 thus extends relative to the extruder 7, i.e. it extends towards the to be printed object 15. In order to prevent that the extrusion nozzle 9 contacts, and possibly damages, the to be printed object 15, a variety of measures can be taken. In Figure 6A, the extruder system 1 is moved relative to a support 35 of a print head of an AM printer 14. However, in Figure 6B, the support frame 35 of the print head that supports the extruder system 1 is moved, thereby also displacing the extruder system 1. Finally, in Figure 6C, a platform 36 supporting the to be printed object 15 is moved away from the extruder system 1 when the extrusion nozzle 9 is moved into the antioozing state thereof. It is also conceivable that the measures of Figures 6A, 6B and 6C are combined. The extruder system 1 or the AM printer 14 may be configured to simultaneously move the extrusion nozzle 9 in the conveying direction away from the tip 12 of the screw conveyor 8 and move the extruder 7 in a direction opposite to the conveying direction. Alternatively, or in combination, the extruder system 1 or the AM printer 14 may be configured to simultaneously move the platform 36 carrying the to be printed object 15 and the extrusion nozzle 9 in the conveying direction away from the tip 12 of the screw conveyor 8.

[0083] The controller 16 of the AM printer 14 may control any of the measures of Figures 6A-C alone, or in combination. For example, the controller 16 may control these measures based on state of the art software of AM printer 14, which greatly improves the applicability. After all, there is no need for dedicated tailor-made software. All functionality of common software, such as all adjustable parameters used to control a retracting, may be used in an identical manner.

[0084] However, according to the preferred embodiments shown in the Figures, a mechanical alternative is proposed that is extremely fail-safe. Contrary to a software based control, this mechanical solution guarantees that the extrusion nozzle 9 cannot contact the to be printed object 15 as a result of the extrusion nozzle 9 being moved into the anti-oozing state thereof. To achieve this effect, the extruder 7 is slidably connectable to a frame, i.e. the support frame 35, of the AM printer 14, and the extrusion nozzle 9 is connectable in a fixed position to said frame of the AM printer 14. If the extrusion nozzle 9 is in a fixed position relative to the support frame 35, it simply cannot move. Instead, if the lever 28 causes the extrusion nozzle 9 to move towards the anti-oozing state, the extruder system 1 itself will automatically pivot relative to a pivot point 36 associated with the extrusion nozzle 9. Consequently, the extruder system 1 will slide relative to the support frame 35 (Figures 7A, 7B). In order to see this sliding effect, notice how far the sliding guides 39 are away from an upper end 40 of legs 41 of support frame 35.

[0085] Please note that pivot point 36 is arranged on a further lever 38 that is fixed relative to lever 28. Consequently, pivot point 36 is associated with the extrusion nozzle 9. However, by using a further lever 38, pivot point 36 may be arranged at an offset away relative to the extrusion nozzle 9, providing space around the extrusion nozzle 9.

[0086] An extruder system 1 according to a second preferred embodiment is shown in Figure 8. This second preferred embodiment is very closely related to the first preferred embodiment discussed above. Like parts are numbered alike in the figures, and only the difference of the second preferred embodiment relative to the first preferred embodiment is discussed.

[0087] When Figure 8 and Figure 4 are compared, it becomes clear that the only difference relative to the first preferred embodiment is the absence of the further one-way bearing 34. Consequently, when the drive 10 of an extruder system 1 according to the second preferred embodiment is driven in the second drive direction, the drive 10 is configured to drive the screw conveyor 8 opposite to the conveying direction, and the screw conveyor 8 will move the extrudable material 6 away from and upstream relative to the extrusion nozzle 9.

[0088] In a more preferred embodiment, when the drive 10 is driven in the second drive direction, said drive 10 is configured to simultaneously drive the screw conveyor 8 opposite to the conveying direction and thereby move the extrudable material 6 away from and upstream relative to the extrusion nozzle 9, and move the extrusion nozzle 9 away from the tip 12 of the screw conveyor 8 to increase the internal volume of the pressure chamber 11 and thereby release at least a part of the overpressure to control the flow F of extrudable material 6 out of the outflow opening 13 of said extrusion nozzle 9 and reduce oozing of extrudable material 6 after stopping said flow. Thus, the drive 10 will not only move the extrusion nozzle 9 towards the antioozing state thereof by moving the extrusion nozzle 9 in the conveying direction away from the tip 12 of the screw conveyor 8, but it will also simultaneously drive the screw conveyor 8 opposite to the conveying direction. This corresponds to Figure 3C of the first preferred embodiment.

[0089] Relative to the first preferred embodiment, the drive 10 of the second preferred embodiment will need to be somewhat stronger and consequently heavier. This embodiment therefore sacrifices some speed but significantly improves the level of retraction of the flow F of the extrudable material 6, which renders this second preferred embodiment especially suitable for extruding material 5 that expands, like foams or low viscosity materials. Furthermore, the second preferred embodiment is beneficial for applications that require relatively long stops, i.e. more than 2 seconds. An advantage of the second preferred embodiment is that the screw conveyor 8 contributes to a pressure release and withdrawal of extrudable material 6, and consequently allows for an increased retraction volume relative to embodiments wherein only the volume of the pressure chamber 11 is increased by moving the extrusion nozzle 9 into the anti-oozing state.

[0090] A third preferred embodiment is shown in Figures 9-11. In Figure 9 the extrusion nozzle 9 is in a printing state, whereas in Figure 10, said extrusion nozzle 9 is moved into the anti-oozing state. Again, the position of the extrusion nozzle 9 may be fixed relative to the (not shown) support frame 35. As a result, the extruder system 1 is moved upwards when Figure 10 is compared with Figure 9. The third embodiment proposes an alternative solution to the lead screw 26 of the first and the second preferred embodiment. Instead, the third preferred embodiment comprises a coupling 42 that is arranged in line with the drive, wherein said coupling 42 comprises two coupling parts 43, 44 that are rotatable relative to each other and that each comprise a contact surface that exhibits a sloping part and an axial abutment, configured to:

[0091] - when the drive 10 is driven in the first drive direction, and one way bearing 48 is disengaged, allow both coupling parts 43, 44 to stand still with abutting contact between the axial abutments of their contact surfaces; and

[0092] - when the drive 10 is driven in the second drive direction, one way bearing 48 is engaged rotating coupling 43 relative to coupling 44 by sliding contact along the sloping parts 49 of their contact surfaces, to thereby axially extend the coupling 42 and pull the lever 28 upward to thereby move the extrusion nozzle 9 to the anti-oozing state thereof.

[0093] The upper coupling part 44 is connected to the lever 28 via a connection 45 embodied as a rod 46. Rod 46 extends from the coupling 42 through a drive shaft 59 of the drive 10 towards the lever 28. Coupling 42 and lever 28 are arranged on opposite sides relative to the drive 10, and by extending the rod through the drive shaft 59, a simple, elegant and compact design of the extruder system 1 is obtained. After all, there is no need for mechanical systems bypassing the drive 10 from the outside. The rod 59 is preferably concentrically arranged inside the drive shaft 59. The pretensioner 23 is now embodied as a compression spring 47 arranged around said rod 46.

[0094] During normal extrusion, as shown in Figure 10, the compression spring 47 maintains the extrusion nozzle 9 in its printing state. One-way bearing 32 is engaged, and drives the screw conveyor 8. Further one-way bearing 48 is disengaged.

[0095] The sloping parts 49 of the contact surface of the two coupling parts 43, 44 define a helical shape 50.

[0096] In order to stop extrusion, the drive 10 is drive in the second drive direction. One-way bearing 32 disengages, and the screw conveyor 8 is no longer driven by drive 10. In the second drive direction, the further one-way bearing 48 engages the drive 10 and the lower coupling part 43 will be driven in the second drive direction. The upper coupling part 44 cannot rotate due to bracket 51 that is prevented against rotation by protrusion 52. Upper coupling part 44 can only move vertically, and will do so as a result of the sliding contact along the helical shapes 50 of the contact surfaces. As a result, rod 46 will be pulled upwards against the compression of compression spring 47. Via lever 28, the extrusion nozzle 9 will move towards the antioozing state thereof.

[0097] The fourth embodiment shown in Figures 12A and 12B shows a more preferred alternative embodiment of the extrusion nozzle 9, and the skilled person will acknowledge that such an alternative extrusion nozzle 9 may be applied in all previously described embodiments of the extruder system 1. It is however especially suitable to be used for extruding material 6 that expands, like foams or low viscosity materials. The extruder system 1 shown in Figures 12A, 12B, further comprises a valve 53 that is arranged upstream relative to the outflow opening 13 of the extrusion nozzle 9 and downstream relative to the screw conveyor 8, wherein said valve 53 is configured to restrict or shut off the flow F towards the outflow opening 13 of the extrusion nozzle 9 when the extrusion nozzle 9 is moved in the conveying direction away from the tip 12 to increase an internal volume of the pressure chamber 11.

[0098] The valve 53 comprises a valve body 54 and a valve plug 55. The valve body 54 is defined by a narrowed passage 56 in the extrusion nozzle 9 having a circumferential edge defining a valve seat 57 that is directed towards the outflow opening 13 of the extrusion nozzle 9. More in particular, the valve plug 55 is substantially arranged in the center line of the extrusion nozzle 9. The valve plug 55 is connected to the screw conveyor 8 via a spacer 58, wherein said spacer 58 extends from the screw conveyor 8 through the narrowed passage 56 towards the outflow opening 13 of the extrusion nozzle 9. When the extrusion nozzle 9 moves in the conveying direction away from the screw conveyor 8, the valve body 54 moves downstream towards the valve plug 55 to restrict or close off the flow of extrudable material 6 towards the outflow opening 13 of the extrusion nozzle 9.

[0099] A maximum cross-sectional area of the valve plug 55 is smaller than a maximum cross-sectional area of the extrusion nozzle 9. As a result, the extrusion nozzle 9 and valve body 54 moving towards the valve plug 55 will cause a suction effect, that reduces the risk of oozing while closing the valve 53. The cross-sectional area is defined in a cross-section that is directed transverse to the conveying direction.

[0100] Although they show preferred embodiments of the invention, the above described embodiments are intended only to illustrate the invention and not to limit in any way the scope of the invention. Accordingly, it should be understood that where features mentioned in the appended claims are followed by reference signs, such signs are included solely for the purpose of enhancing the intelligibility of the claims and are in no way limiting on the scope of the claims. Furthermore, it is particularly noted that the skilled person can combine technical measures of the different embodiments. The scope of protection is defined solely by the following claims.

Claims

CLAIMS1. Extruder system, comprising:- a supply configured to receive raw material and comprising a heater configured to melt the raw material into an extrudable material;- an extruder configured to receive the extrudable material from the supply and comprising a screw conveyor configured to convey the extrudable material in a conveying direction towards an extrusion nozzle of the extruder and cause an overpressure inside the extruder to allow extrusion via said extrusion nozzle;- a drive configured to selectively drive the screw conveyor to convey the extrudable material in the conveying direction towards the extrusion nozzle;- a pressure chamber that is defined, in the conveying direction, between a tip of the screw conveyor and an outflow opening of the extrusion nozzle; and- wherein the extrusion nozzle is moveable relative to the tip of the screw conveyor, characterized in that- the drive is further configured to selectively move the extrusion nozzle between a printing state, wherein the extrusion nozzle is moved opposite to the conveying direction towards the tip of the screw conveyor, and an anti-oozing state, wherein the extrusion nozzle is moved in the conveying direction away from the tip of the screw conveyor to increase an internal volume of the pressure chamber and thereby release at least a part of the overpressure to control a flow of extrudable material out of the outflow opening of said extrusion nozzle and reduce oozing of extrudable material after stopping said flow.

2. Extruder system according to claim 1 , wherein, in the anti-oozing state, the extrusion nozzle is moved in the conveying direction away from the tip of the screw conveyor and thereby also away from a housing surrounding the screw conveyor3. Extruder system according to claim 1 or 2, wherein the drive is selectively switchable between a first drive direction associated with driving the screw conveyor in the convey direction for conveying the extrudable material downstream towards the extrusion nozzle, and a second drive direction, opposite relative to the first drivedirection, and associated with stopping the flow of extrudable material out of said extrusion nozzle by moving the extrusion nozzle in the conveying direction away from the tip of the screw conveyor.

4. Extruder system according to claim 3, wherein the drive, when it is driven in the second drive direction, is configured to stop driving the screw conveyor in the conveying direction.

5. Extruder system according to claim 3 or 4, wherein the drive, when it is driven in the second drive direction, is configured to drive the screw conveyor opposite to the conveying direction to thereby move the extrudable material away from and upstream relative to the extrusion nozzle.

6. Extruder system according to one or more than one of claims 3-5, wherein, when the drive is driven in the second drive direction, said drive is configured to simultaneously stop driving the screw conveyor in the conveying direction and move the extrusion nozzle towards the anti-oozing state thereof by moving the extrusion nozzle in the conveying direction away from the tip of the screw conveyor.

7. Extruder system according to one or more than one of claims 3-6, in dependency of at least claim 5, wherein, when the drive is driven in the second drive direction, said drive is configured to simultaneously drive the screw conveyor opposite to the conveying direction and thereby move the extrudable material away from and upstream relative to the extrusion nozzle, and move the extrusion nozzle towards the anti-oozing state thereof by moving the extrusion nozzle in the conveying direction away from the tip of the screw conveyor.

8. Extruder system according to one or more than one of the foregoing claims, wherein:- a screw spindle is defined by a lead screw that is selectively engageable by the drive, and a nut moveable along said lead screw; and- the nut is mechanically connected to the extrusion nozzle to allow the drive, by driving the lead screw, to move said nut and the extrusion nozzle.

9. Extruder system according to claim 8, wherein the nut is mechanically connected to the extrusion nozzle via a lever that is pivotable relative to a pivot.

10. Extruder system according to claim 9, wherein the nut and the extrusion nozzle are connected to the lever at opposite sides relative to the pivot.

11. Extruder system according to one or more than one of claims 2-10, comprising a one-way bearing that is arranged in line with the drive, that is configured to:- when the drive is driven in the first drive direction, decouple the drive and the lead screw to allow the lead screw to stand still relative to the drive and maintain the extrusion nozzle in its printing state; and- when the drive is driven in the second drive direction, couple the drive to the lead screw to allow the drive to move the extrusion nozzle from the printing state towards the anti-oozing state.

12. Extruder system according to claim 11 , comprising a further one-way bearing that is configured to:- when the drive is driven in the first drive direction, couple the drive to the screw conveyor and thereby drive the screw conveyor in the conveying direction; and- when the drive is driven in the second drive direction, decouple the drive and the screw conveyor to stop driving the screw conveyor in both the conveying direction and a direction opposite to the conveying direction.

13. Extruder system according to one or more than one of the foregoing claims, comprising a coupling that is arranged in line with the drive, wherein said coupling comprises two coupling parts that are rotatable relative to each other and that each comprise a contact surface that exhibits a sloping part and an axial abutment, configured to:- when the drive is driven in the first drive direction, and one way bearing is disengaged, allow both coupling parts to stand still with abutting contact between the axial abutments of their contact surfaces; and- when the drive is driven in the second drive direction, and one way bearing is engaged, rotating the coupling parts relative to each other by sliding contact along the sloping parts of their contact surfaces, to thereby axially extend the coupling and pull the lever upward to thereby move the extrusion nozzle to the anti-oozing state thereof.

14. Extruder system according to claim 13, wherein the sloping parts of the contact surface of the two coupling parts define a helical shape.

15. Extruder system according to claim 13 or 14, further comprising a rod extending from the coupling through a drive shaft of the drive towards the lever.

16. Extruder system according to one or more than one of the foregoing claims, wherein:- the extruder is slidably connectable to a frame of an additive manufacturing printer, “AM printer”; and- the extrusion nozzle is connectable in a fixed position to said frame of the AM printer.

17. Extruder system according to one or more than one of the foregoing claims, further comprising a valve that is arranged upstream relative to the outflow opening of the extrusion nozzle and downstream relative to the screw conveyor, wherein said valve is configured to restrict or shut off the flow towards the outflow opening of the extrusion nozzle when the extrusion nozzle is moved in the conveying direction away from the tip to increase an internal volume of the pressure chamber.

18. Extruder system according to claim 17, wherein the valve comprises:- a valve body defined by a narrowed passage in the extrusion nozzle having a circumferential edge defining a valve seat that is directed towards the outflow opening of the extrusion nozzle; and- a valve plug connected to the screw conveyor via a spacer, wherein said spacer extends from the screw conveyor through the narrowed passage towards the outflow opening of the extrusion nozzle; and- wherein, when the extrusion nozzle moves in the conveying direction away from the screw conveyor, the valve body moves downstream towards the valve plug to restrict or close off the flow of extrudable material towards the outflow opening of the extrusion nozzle.

19. Extruder system according to claim 18, wherein a maximum cross-sectional area of the valve plug is smaller than a maximum cross-sectional area of the extrusion nozzle.

20. Extruder system according to one or more than one of the foregoing claims, further comprising a pretensioner configured to force the extrusion nozzle towards the screw conveyor in the printing state.

21. Extruder system according to one or more than one of the foregoing claims, wherein the raw material is a granulate and the extruder system is a granulate extruder system.

22. Extruder system according to one or more than one of the foregoing claims, wherein the supply is integrated in an upstream part of the extruder.

23. Extruder system according to one or more than one of the foregoing claims, wherein the extruder system is an extruder system of an additive manufacturing printer, “AM printer”.

24. Additive manufacturing printer, “AM printer”, comprising:- an extruder system according to one or more than one of the foregoing claims 1-23;- a controller configured to cause the extruder system to, when executing computer-executable printing instructions for printing an object, print said object; and- wherein the extruder system is configured to selectively move the extrusion nozzle in the conveying direction away from the tip of the screw conveyor to increase an internal volume of the pressure chamber and thereby release at least a part of the overpressure to control the flow of extrudable material out of the outflowopening of said extrusion nozzle and reduce oozing of extrudable material after stopping said flow.

25. AM printer according to claim 24, configured to simultaneously move the extrusion nozzle in the conveying direction away from the tip of the screw conveyor and move the extruder in a direction opposite to the conveying direction.

26. AM printer according to claim 24 or 25, configured to simultaneously move a platform carrying the to be printed object and the extrusion nozzle in the conveying direction away from the tip of the screw conveyor.

27. Method of printing a product with an additive manufacturing printer, “AM printer”, comprising the steps of:- melting raw material into an extrudable material;- conveying the extrudable material with a screw conveyor in a conveying direction towards an extrusion nozzle of an extruder of the AM printer, thereby causing an overpressure in a pressure chamber that is defined, in the conveying direction, between a tip of the screw conveyor and an outflow opening of the extrusion nozzle; and- selectively moving the extrusion nozzle in the conveying direction away from a tip of the screw conveyor to increase an internal volume of the pressure chamber, thereby releasing at least a part of the overpressure to control a flow of extrudable material out of the outflow opening of said extrusion nozzle and reducing oozing of extrudable material after stopping said flow.

28. Method according to claim 27, comprising the step of, simultaneously with the step of moving the extrusion nozzle in the conveying direction away from the tip of the screw conveyor, moving the extruder in a direction opposite to the conveying direction.

29. Method according to claim 27 or 28, comprising the step of, simultaneously with the step of moving the extrusion nozzle in the conveying direction away from the tip of the screw conveyor, also moving the platform carrying the to be printed object in the conveying direction.

30. Method according to one or more than one of the clams 27-29, wherein the raw material is a granulate and the extruder system is a granulate extruder system.

31. Method according to one or more than one of the clams 27-30, comprising the step of using an extruder system according to one or more than one of the claims 1-23.

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