A 3D print continuous fibre impregnation system and a multi-axis 3D printing system

Abstract

The application relates to a system for impregnation of continuous fibres for 3D printing wherein said system comprises a system (4) for continuous pressurized impregnation of continuous fibre and a system (5) for differentiating the continuous fibre movement speed between the continuous fibre impregnation system (4) and the collection of the impregnated continuous fibre by the printing system, wherein the fibre impregnation system (4) is operably connected to the speed differentiation system (5), wherein the speed differentiation system (5) comprises upper rollers (5a) and lower rollers (5b) slidably fixed within a rail (5c), an input roller (5e), an output roller (5f), and auxiliary rollers (5g), wherein said rollers are adapted to cooperate with the upper rollers (5a). The invention also relates to a multi-axis 3D printing system with continuous fibre impregnation.

Description

[0001] A 3D print continuous fibre impregnation system and a multi-axis 3D printing system

[0002] Thew invention relates to a 3D print continuous fibre impregnation system and a multi-axis 3D printing system

[0003] The scientific publication titled "The technology of continuous fibre-reinforced polymers: a review on extrusion additive manufacturing Methods" (Pandelidi Ch. et al., The International Journal of Advanced Manufacturing Technology (2021) 113: 3057-3077) provides an overview of techniques involving the use of modified continuous fibres.

[0004] Patent application no. US2023191651A1 presents a 6-axis 3D printing system. The presented system comprises a robotic arm with a 3D printhead and a rotary table. Similarly, a robotic tool with a rotary working table is presented in patent application no. US2022184880A1.

[0005] International PCT application no. W02024079018A1 discloses a multi-axis 3D printing system comprising a robotic arm and a rotary work table capable of changing the work plane inclination angle.

[0006] Patent application no. US2018356118A1 presents a solution wherein a continuous fibre is prepared by pulling it through a polymer solution.

[0007] Patent application no. US2018370129A1 describes a robotic device and a method for three- dimensional printing of continuous fibre composite materials, wherein the fibres are reinforced with resin overlays prior to introduction into the print head.

[0008] A system for continuous impregnation of the fibres is known in the art. However, said system is not free of certain shortcomings. In the current art, the fibre for the printing module is delivered in the impregnated form or impregnation occurs as the fibre is pushed from the nozzle of the printing system, simultaneously serving as an impregnation chamber. This can lead to a number of undesirable effects and applicability limitations. Problems with the use of low stiffness fibres are worth mentioning first in this context. Another disadvantage may consist in the formation of lumps during impregnation of the fibre within the nozzle of the printing system, resulting in the blockage of the device during printing, creating the risk of non-uniformity of fibre impregnation and the dripping of the molten thermoplastic material from the nozzle. In the case of fibres being prepared, i.e. impregnated before they are introduced to the printing system, other shortcomings of the solutions known from the prior art exist in addition to the above-mentioned disadvantages, such as the risk of variable fibre feeding speed. This may also lead to a decrease in the homogeneity of fibre impregnation. Another problem consists in providing a 3D printing system free from the above disadvantages. In addition, the printing system should also be characterized by good print quality, the possibility of creating spatially complex shapes, and the possibility of depositing the extruded thermoplastic material or fibre using a single tool.

[0009] The invention relates to a system for impregnation of continuous fibres for 3D printing characterized in that it comprises a system for continuous pressurized impregnation of continuous fibre and a system for differentiating the continuous fibre movement speed between the continuous fibre impregnation system and the collection of the impregnated continuous fibre by the printing system, wherein the fibre impregnation system is operably connected to the speed differentiation system, wherein the speed differentiation system comprises upper rollers and lower rollers slidably fixed within a rail, an input roller, an output roller, and auxiliary rollers, wherein said rollers are adapted to cooperate with the upper rollers.

[0010] In a preferred embodiment of the invention, the continuous fibre impregnation system comprises an impregnation chamber, consisting of a main heating block comprising a main channel, an inlet and an outlet adapted to the passing of the continuous fibre to be impregnated and a side channel with an inlet opening for the injection of the liquefied thermoplastic material from the extruder, wherein an output heating block is connected to the outlet of the main channel for the passing of the continuous fibre to be impregnated to the main heating block, and a collector adapted to receive the impregnated fibre from the output heating block and transfer it to the fibre speed differentiation system.

[0011] In a further preferred embodiment of the invention, the output heating block has a temperature lower than the main heating block.

[0012] Preferably, the input roller is adapted to receive the impregnated fibre from the fibre impregnation system collector, and the output roller is adapted to transmit the impregnated fibre to the printing system. Preferably, the auxiliary rollers are immovably fixed above the upper rollers. Likewise, the input roller and the output roller are preferably immovably fixed below the lower rollers.

[0013] The invention further relates to a multi-axis 3D printing system with continuous fibre impregnation comprising a robotic arm with a hybrid printhead comprising an FFF printhead, a biaxial positioner with a working platform, characterized in that said printing system comprises a system for 3D print continuous fibre impregnation as defined by the first object of the invention, wherein said hybrid printhead comprises a feeding head for the delivery of a continuous fibre filament, i.e. the fibre impregnated within the continuous fibre impregnation system as defined by the first object of the invention.

[0014] In a preferred embodiment of the invention, the multi-axis 3D printing system is a seven-axis system.

[0015] In a further preferred embodiment of the invention, the continuous fibre filament feeding head comprises a liquid-cooled extruder body comprising a stepper motor to power the drive roller, a section of the filament fed by pneumatic actuator being attached to the extruder body, and a plasticizing head attached at the continuous fibre filament output of the feeding head.

[0016] In a further preferred embodiment of the invention, the continuous fibre filament feeding head is oriented at an angle with respect to the printing head.

[0017] The invention facilitates the creation of robust and precise 3D objects from various materials, including basalt, aramid or carbon fibres.

[0018] The central element of the system comprises an advanced multifunctional device consisting of a robotic arm and a biaxial positioner, as well as components for fibre impregnation and deposition. The robotic arm is used to precisely manipulate the printhead while the biaxial positioner facilitates rotating and tilting the working platform on which the printing process takes place.

[0019] The process begins with fibre impregnation, the fibre passing through an impregnation chamber, where it is soaked in a chosen polymer material, for example material chosen from the group of polyamides or polyesters. Preferably, the fibre material and the soaking polymer come from the same group of materials, so that strong bond is established between the fibre and the polymer matrix. The impregnated fibre is then transferred to the printhead, which is manipulated by the robotic arm to precisely deposit the fibre in layers to create an object of a desired shape.

[0020] A key feature of this multi-axis system consists in its ability to synchronize the movements of the robotic arm and the biaxial positioner, ensuring precise and coordinated operation of the device throughout the printing process. As the result, excellent quality of printed objects can be achieved and errors resulting from inaccurate positioning can be avoided. The design allows for advanced 3D printing with the printhead moving in different planes, which opens up new possibilities for creating complex and robust structures. The robotic arm operating in five degrees of freedom facilitates precise control of the position of the printhead along with a greater range of movement and greater flexibility compared to traditional 3D printers. The biaxial positioner with the working platform tilts and rotates the working platform (two- degree-of-freedom movement), allowing the printing plane to be changed so as to facilitate application of layers at different angles.

[0021] The advantages of continuous impregnation include the possibility of using a constant speed of the fibre passing through the impregnation chamber, and thus achieving the stability of the extrusion process, resulting in a homogeneous impregnated fibre with a constant diameter.

[0022] The combination of continuous impregnation and multi-axis printing using a robotic arm and a biaxial positioner facilitates a fibre with constant predictable diameter being deposited in any orientation relative to the working platform.

[0023] The advantages of the solution according to the invention include precision, efficiency and flexibility, facilitating creation of complex and functional 3D objects from various materials. In addition, thanks to the use of a robotic arm and a biaxial positioner, the printing process becomes more efficient and economical. The method used allows printing in different planes and thus facilitates the material being applied at any angle to the previous layers to creating models with layers overlapping in different directions, thus increasing the mechanical robustness of the prints.

[0024] The embodiments of the invention are shown in the drawings, where:

[0025] Figure 1 shows a 3D printing system of the invention; Figure 2 shows an arrangement of the hybrid printhead;

[0026] Figure 3 shows a cross-section of the continuous fibre feeding mechanism;

[0027] Figure 4 shows a system consisting of a compensator and a continuous fibre impregnation mechanism;

[0028] Fig. 5 shows a cross-sectional view of the impregnation chamber.

[0029] Example 1. A multi-axis 3D printing system with impregnation

[0030] The multi-axis (seven-axis) printing system with continuous fibre impregnation and deposition comprises a robotic arm (1), the working tip of which is complete with a hybrid printhead (la), a biaxial positioner (2) with a mounted working platform (3), a thermoplastic material feeding system (for the sake of clarity, only the thermoplastic material container (7a) is shown in Figure 1) for FFF printing, a continuous fibre impregnation system (4), an impregnated fibre compensator (5), an impregnating material feeding system (for the sake of clarity, only the thermoplastic material containers (7b) and the continuous fibre subject to impregnation are shown in Figure 1). Preferably, the continuous fibre (6) is a basalt, aramid or carbon fibre. The system is digitally controlled.

[0031] The robotic arm (1):

[0032] The robotic arm is an important element of the system, ensuring precise manipulation of the printhead. It is equipped with a number of stepper motors or servo motors that control movements in different planes. As the result, the robotic arm can move in three dimensions, with a five-degree freedom of movement, facilitating the fibre being deposited in layers to create a desired shape of a 3D object. The design of the robotic arm is known in the art.

[0033] The hybrid printhead (la):

[0034] The hybrid printhead (la) of the 3D printer comprises two material feeding assemblies: an FFF printhead (8) for thermoplastic material (7a), preferably complete with a thermoplastic material presence sensor (9), and a continuous fibre feeding mechanism (10) with a pneumatic actuator (12) and a heatable plasticizing head (11). An example of such printhead is provided in the Polish patent no. 230139. The axes of the print head (8) and the continuous fibre delivery mechanism (10) are oriented at an angle, preferably at an angle of about 90°, to each other. Angular orientation of printheads is advantageous as it reduces the risk of collision of the unused printhead with the printed element or the working platform (3). Another advantage consists in that the change of the tool when switching from printing with the FFF printhead (8) to printing with the fibre feeding mechanism (10), or vice versa consists only in rotating the tip of the robotic arm (1). This is particularly evident in Figure 3.

[0035] The biaxial positioner (2):

[0036] The biaxial positioner is responsible for rotating and tilting the working platform (3) on which the printing process takes place. This is important for 3D printing as it facilitates the adjustments of the angle of inclination and orientation of the object layers. The positioner is controlled by stepper motors or servo motors, ensuring ensures precise positioning of the working platform (3).

[0037] The continuous fibre feeding mechanism (head) (10):

[0038] The design of the continuous fibre feeding mechanism (head) comprises includes a stepper motor (10b), an extruder body (10a), a drive roller (10c), a filament cutter (13), a heatable plasticizing head (11) and a pneumatic actuator (12). Preferably, channels (lOd) for distributing the liquid coolant (the cooling system is not shown in the figures) are provided inside the extruder body (10a). The cutter (13), driven by the pneumatic actuator (12) is responsible for the precise cutting of the filament after the printing of each layer is completed. The cutter (13) is activated when the corresponding command is read from the geode file determining the moment at which the filament should be cut. Actuation of the cutter (13) by means of compressed air ensures quick and precise cutting of the filament without damage.

[0039] Advanced control and monitoring systems:

[0040] The system for continuous fibre impregnation and deposition as part of the seven-axis 3D printing process makes use of uses advanced control and monitoring systems that ensure precise process control. These include a user interface for configuring print parameters, software for generating geode files, and sensors for the monitoring of print quality in real time.

[0041] The fibre preparation (impregnation) system:

[0042] The fibre preparation (impregnation) system consists of a system for feeding the fibre, preferably basalt, aramid or carbon fibre, from the fibre container (6), and a system for feeding a thermoplastic material (7b) from a thermoplastic material container; for the sake of clarity, the entire device has not been shown in the figures. The system further comprises an impregnation chamber (15) for the feeding of thermoplastic material (7b) from an extruder (14). Inside the impregnation chamber (15), the fibre (6a) is contacted with the liquid polymer (7b). Preferably, pressure facilitating the thermoplastic material (7b) penetrating between the individual threads of the fibre (6a) is present in the impregnation chamber (15). The impregnated fibre which exits the impregnation chamber preferably passes through the roller system (16), and then the collector (17), which is the only element that picks up the filament from the container (6) and pulls it through the impregnation chamber (15). The elements of the fibre preparation (impregnation) system are attached to the base (not marked in Figures 1 and 4), or in another way enabling stable and uninterrupted operation. In the current art, the fibre for the printing module is delivered in the impregnated form or impregnation occurs as the fibre is pushed from the nozzle of the printing system, simultaneously serving as an impregnation chamber. This distinguishes the prior art from the present invention, where the fibre is pulled through the impregnation chamber within the printing system. The resulting advantage consists in that it is much easier to pull than to push a non-rigid thread through a resistance system (impregnation chamber).

[0043] The method of fibre impregnation fibre consists in the fibre being pulled through the impregnation chamber (15) heated to the melting point of the thermoplastic material while feeding the thermoplastic material at the pressure produced by the extruder (14). The impregnation chamber (15) is preferably provided with a polymer feeding mechanism and temperature and pressure control systems to ensure optimal impregnation conditions. The impregnation process will be presented below.

[0044] A detailed cross-sectional view of the impregnation chamber (15) is shown in Figure 5. The fibre (6a) is introduced into the main heating block (15a) through the inlet opening (15c), and then pulled through the main channel (15f), into which the liquefied thermoplastic material is fed under pressure through the polymer inlet opening (15d) from the extruder (14) via the side channel (15e). Then, the impregnated fibre (6a) is passed to the output heating block (15b), preferably kept at a temperature lower than that of the main block (15a). By maintaining a temperature gradient between the main block (15a) and the output block (15b), a difference in the viscosity of the polymeric material in both zones can be obtained. Within the main block (15a), the more heated material is more fluid, so that it penetrates between the threads of the fibers. On the other hand, the polymer is pre-cooled within the output block (15b) and the fibre diameter is stabilised. Such a solution also facilitates greater pressure being generated within the main heating block (15a) by limiting the flow rate of the material towards the output block (15b).

[0045] The heating blocks may be made of heat-conducting and processable metal (e.g. by means of CNC machining). The main heating block (15a) may be made of steel, copper, or metal alloys. Most preferably, it is made of steel. The output block (15b) may be made of aluminum.

[0046] Pressurized impregnation of the fibre results in the continuous fibre achieving better saturation with the molten polymer. In addition, the impregnated fibre has no inclusions in the form of air bubbles. Air bubbles may appear after the impregnated fibre leaves the output heating block (15), resulting in local thickening of the filament. If a thickening forms on the filament, there is a risk that it will not be able to pass through the fibre feeding mechanism (10). For example, the fibre has a diameter of about 0.7 mm, and the through holes for guiding the fibre have a diameter of 0.8 mm. A 0.1-mm deviation from the impregnated fibre diameter may cause the impregnated fibre to jam within the fibre feeding mechanism (10) in front of the extruder heating block.

[0047] The impregnated fibre (6a) is passed on to the compensator (5) and wound onto the upper rollers (5a) and the lower rollers (5b), operating under loading and moving along the rail (5c) within the top-bottom plane. The rail (5c) may be mounted within a rack (5d) as in Figure 4 or be provided as a structural element of any other structure. In addition, the compensator (5) is provided with rollers (5g) within its upper part and with an input roller (5e) and an output roller (5f) within its lower part. Said rollers are attached to transverse arms fixed to the rack (5d), said arms being located at the ends of the rail (5c). The intermediating input roller (5e) receives the impregnated thread from the collector (17) and feeds it onto the upper roller (5a). The output roller (5f) receives the material from the upper roller (5a) and passes it towards the fibre feeding mechanism (10). The auxiliary rollers (5g) prevent the material from slipping from the upper roller (5a). The design of the compensator system (5) is not limited to the design shown in Figure 4. The compensator system (5) ensures the fibre being passed through the impregnation system (4) at a constant speed while the fibre impregnated within the continuous fibre feeding mechanism (10) is collected at variable speeds. When the speed within the impregnation system (4) is higher than within the feeding system (10), the compensator rollers (5a, 5b) move along the rail (5c) causing an increase in the amount of material in the compensator (5) and maintaining the appropriate speed at the compensator (5) outlet. The compensator is shown in Figure 4. For the quality of the impregnated material and the stability of its diameter, it is important that a constant impregnation speed be maintained, or at least any rapid changes in said impregnation speed are eliminated. On the other hand, the fibre feeding mechanism (10) delivers the fibre to the print as instructed within the geode file - once faster, once slower, or sometimes halting at all. In the absence of the compensator (5), fibre impregnation would have to stop immediately, usually accompanied by an uncontrolled outflow of the thermoplastic material and the formation of fibre "lumps" (resulting from the pressure being released from the impregnation chamber). The compensator (5) acts as a system's "shock absorber", preventing any sudden changes in the impregnation speed.

[0048] Thanks to the above solutions, the system described herein enables precise and effective execution of the seven-axis 3D printing process using continuous impregnation and deposition of the fibre, facilitating creation of high quality printed objects from various materials.

[0049] The method of printing with the use of impregnation and deposition of fibres consists in the fibres (6a) and thermoplastic material (7b) being placed into containers and then combined into a continuous fibre (6a) filament with within the impregnating system (4). The impregnated fibre is wound onto the compensator (5) and then deposited via the hybrid printhead (la) onto the working platform (3) or the surface of the print being created. The hybrid printhead (la) is also used to apply thermoplastic material (7a) in a process known from the FFF technology.

Claims

Claims1. System for impregnation of continuous fibres for 3D printing characterized in that said system comprises a system (4) for continuous pressurized impregnation of continuous fibre and a system (5) for differentiating the continuous fibre movement speed between the continuous fibre impregnation system (4) and the collection of the impregnated continuous fibre by the printing system, wherein the fibre impregnation system (4) is operably connected to the speed differentiation system (5), wherein the speed differentiation system (5) comprises upper rollers (5a) and lower rollers (5b) slidably fixed within a rail (5c), an input roller (5e), an output roller (5f), and auxiliary rollers (5g), wherein said rollers are adapted to cooperate with the upper rollers (5a).

2. The system according to claim 1 characterized in that the continuous fibre impregnation system (4) comprises an impregnation chamber (15), consisting of a main heating block (15a) comprising a main channel (15f), an inlet and an outlet adapted to the passing of the continuous fibre to be impregnated and a side channel (15e) with an inlet opening (15d) for the injection of the liquefied thermoplastic material from the extruder (14), wherein an output heating block (15b) is connected to the outlet of the main channel (15f) for the passing of the continuous fibre to be impregnated to the main heating block (15a), and a collector (17) adapted to receive the impregnated fibre from the output heating block (15b) and transfer it to the fibre speed differentiation system (5).

3. The system according to claim 2 characterized in that the output heating block (15b) has a temperature lower than that of the main heating block (15a).

4. The system according to claim 1 characterized in that the input roller (5e) is adapted to receive the impregnated fibre from the fibre impregnation system collector (17), and the output roller (5f) is adapted to transmit the impregnated fibre to the printing system.

5. The system according to claim 1 characterized in that the auxiliary rollers (5g) are immovably fixed above the upper rollers (5a).

6. The system according to claim 1 characterized in that the input roller (5e) and the output roller (5f) are immovably fixed below the lower rollers (5b).

7. A multi-axis 3D printing system with continuous fibre impregnation comprising a robotic arm with a hybrid printhead comprising a thermoplastic printhead, a biaxial positioner with a working platform, characterized in that said printing system comprises a system for 3D print continuous fibre impregnation according to claim 1, wherein said hybrid printhead comprises a feeding head for the delivery of a continuous fibre filament (10), i.e. the fibre impregnated within the continuous fibre impregnation system according to claim 1.

8. The multi-axis 3D printing system according to claim 7 characterized in that the multiaxis 3D printing system is a seven-axis system.

9. The multi-axis 3D printing system according to claim 7 characterized in that the continuous fibre filament feeding head (10) comprises a liquid-cooled extruder body (10a) comprising a stepper motor (10b) to power the drive roller (10c), a section of the filament (13) fed by pneumatic actuator (12) being attached to the extruder body (10a), and a plasticizing head (11) attached at the continuous fibre filament output of the feeding head (10).

10. The multi-axis 3D printing system according to claims 7 or 9 characterized in that the continuous fibre delivery mechanism head (10) is oriented at an angle with respect to the print head (8).

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