DEVICE FOR ADDITIVE MANUFACTURING USING AN FFF PROCESS

Description

[0001] The invention relates to a device for additive manufacturing using an FFF process, in which a polymer filament, together with a wire or fiber, is printed or deposited in a feed direction onto the surface of a substrate or a previously deposited polymer filament. The substrate can be a so-called build platform on which a component or part of a component can be manufactured using the FFF process.

[0002] The wire can be metallic wire, and the fiber can be various materials such as glass, carbon, ceramic, or textile fibers.

[0003] Exemplary application areas include the automated integration of cable harnesses and their connection to structural components, mechanical protection through polymer sheathing (automotive / power tools), printing of heating wires onto foil substrates for subsequent injection molding, and the production of complex consumer electronics within a single machine. Additive manufacturing processes are particularly well-suited for the production of complex components that can typically only be manufactured conventionally through numerous process steps and individual parts. A very high degree of functional density can be achieved. For this reason, a wide variety of materials are combined in the process. Fused Filament Fabrication (FFF) is particularly suitable for the integration of foreign materials. This process is currently experiencing strong growth due to the use of continuous reinforcing fibers.Beyond these passive functions, there is a desire to also give such components active or sensory functions. So far, this can only be achieved to a limited extent using electrically conductive polymers.

[0004] Functional fibers, such as carbon fiber, glass fiber, or metallic strands, are to be embedded in a component during the manufacturing process. They are usually fed orthogonally to the layer-by-layer build-up, parallel to the polymer feed. In the methods described, the respective functional fiber can be present in three different forms. For example, otherwise untreated fibers can be impregnated in the melt zone of the respective polymer within an extrusion die. Pretreated fibers can also be heated and pressed onto the substrate material. Furthermore, hybrid filaments can be used, involving the co-extrusion of the substrate polymer and the fiber material.

[0005] These methods require a 90° deflection of the polymer material after exiting the nozzle, thus placing a high mechanical load on it. This is particularly problematic for fibers with an outer diameter greater than 0.3 mm, severely impacting the printing process. This reduces placement accuracy, achievable printing speed, and design freedom.

[0006] In the Fibre Encapsulation Additive Manufacturing (FIMA) process, this problem is addressed by feeding the wire or fiber laterally beneath the extrusion die of the printhead. This has led to a significant improvement in process behavior. However, this one-sided feed is insufficient for producing complex structures. Therefore, in the described approach, the workpiece is rotated along a rotational axis. With regard to large workpieces, this is not always feasible and results in a loss of dynamics and accuracy. The developed toolhead requires considerable space and necessitates a special motion system for manipulating the workpiece and its carrier. In particular, it is problematic to perform large changes in direction during the feed movement and to synchronize the orientation of the polymer filament with the orientation of the respective fiber or wire.

[0007] It is therefore an object of the invention to provide possibilities by which a wire or a fiber with a polymer filament can be flexibly used and processed in additive manufacturing in order to produce fiber-reinforced components and / or components having functional elements, by taking into account larger and faster changes in feed direction in an improved form and by maintaining a predetermined orientation of polymer filament and wire or fiber without causing damage to the material to be printed during the printing process.

[0008] US patent 10 254 499 B1 discloses a device for the additive manufacturing of components using dielectric, electrically conductive and magnetic materials.

[0009] CN 2 09 955 318 U relates to a printing device with which an FFF process can be carried out.

[0010] According to the invention, this problem is solved with a device having the features of claim 1. Advantageous embodiments and further developments of the invention can be realized with features specified in dependent claims.

[0011] In the device according to the invention, a polymer filament is fed via a first feeder to a nozzle opening, and a wire or fiber is fed from a feeder device via a second feeder into the exit region of the polymer filament from the nozzle opening of the first feeder. The first and the second feeders are guided by a printhead rotatable through at least 360°, which is rotatable about the axis of rotation defined by the central longitudinal axis of the first feeder by means of a rotary drive.

[0012] The second feeder terminates at an angle between 45° and 90° to the central longitudinal axis of the first feeder, where the polymer filament exits the nozzle opening.

[0013] The conveying of polymer to form the polymer filament into and through the first feed, as well as the conveying of wire or fiber into and through the second feed, can be achieved in a conventional manner. For example, a pre-formed polymer filament or an extruder capable of conveying polymer into and through the first feed can be used. A wire or fiber can be unwound from a spool and fed into the second feed.

[0014] Polymer filament and wire or fiber can be synchronized by rotating the printhead in a specific desired feed direction. The printhead can also be rotated multiple times in the same direction around its axis of rotation, which coincides with the central longitudinal axis of the first guide. Changes in the direction of rotation are also easily possible.

[0015] Advantageously, a cutting device can be arranged on the printhead downstream of the nozzle opening in the feed direction of the polymer filament and wire or fiber, allowing for the separation of the polymer filament and / or wire or fiber as needed. The cutting device can, for example, include at least one cutting blade. Separation can be achieved by a suitable movement of the cutting device or by a corresponding movement of the printhead parallel to or at an angle to the central longitudinal axis of the first guide or the axis of rotation of the printhead.

[0016] In the feed direction of the polymer filament, an electric heating device can be arranged in front of the nozzle opening to heat the polymer filament, which is located within the first feed in the rotatable print head during its feed movement.

[0017] The rotary drive can consist of a permanently installed electric motor and a gearbox, with the gearbox engaging the printhead. Belt drives are preferred. Alternatively, a toothed belt driven by the electric motor can engage the printhead, allowing it to rotate accordingly.

[0018] The printhead should be movable in at least three degrees of freedom via a rotary drive using a manipulator. These degrees of freedom can be the three axes of a Cartesian coordinate system. A suitably designed robot, to which the printhead can be attached, can be used as the manipulator.

[0019] The end section of the second feeder can also be curved to maintain the desired angle at which the wire or fiber is directed towards the molten polymer filament and to avoid damage from excessive bending.

[0020] A third supply for a gaseous cooling medium, in particular compressed air, may also be routed through the print head, directing the gaseous cooling medium towards the polymer filament exiting the nozzle opening to accelerate its curing.

[0021] At least one feed device or extruder for a polymer filament and at least one feed device for a wire or fiber should be arranged outside the printhead so as not to rotate with the printhead.

[0022] The printhead can be rotatably mounted in a housing, whereby the housing with the printhead can be moved at least three-dimensionally by means of a manipulator.

[0023] The invention essentially relates to the printhead. The motion system (manipulator) and the associated printhead exchange system can be a commercial system.

[0024] A melting chamber can be arranged in the area of ​​the first feed and the heating element. The first and second feeds are integrated into the printhead. All necessary material, power, and signal feeds should be rotatably mounted on the printhead or the housing. In particular, the nozzle opening of the first feed should be located at the center of the axis of rotation. The polymer filament is guided along the axis of rotation, enabling continuous rotation. The rotational capability influences the achievable functionalities and geometries with which components or parts of components can be manufactured using the device according to the invention. For example, the production of coil elements for actuators or sensors may require repeated rotation in a constant direction, which can be achieved with the invention.Unrestricted performance is only truly achieved through unrestricted rotation.

[0025] To design a small and lightweight printhead, the feed of the polymer filament and the wire or fiber can be decoupled from the printhead. This enables high feed speeds without vibration or increased wear, and allows for a wide variety of feed directions in which the polymer filament and wire or fiber can move together.

[0026] The wire or fiber can be fed at a shallow angle in the direction of the printhead's movement to create an overprint and encapsulation effect. The extruded and molten polymer filament can flow around the deposited wire or fiber, thus fixing it in place. The feed rate of the wire or fiber can correspond to the feed movement (travel path) of the printhead. By defining a difference in the feed rates of the polymer filament and the wire or fiber, certain properties of a component, particularly its mechanical properties, can be influenced. For example, a higher feed rate of the polymer filament with the wire or fiber can generate tensile stresses in the component after the polymer has solidified.

[0027] The print head can be moved in such a way that the conveying length of the wire or fiber is smaller than the distance traveled by the print head during its feed movement with the polymer filament on the support or component, so that a mechanical stress acts on the wire or fiber material after the polymer of the polymer filament has solidified.

[0028] The separate media routing of polymer and wire or fiber, and the connection of these outside the printhead, enables a clear separation of enclosed and exposed wire or fiber sections.

[0029] Polymer extrusion can be based on standard parts. Common polymer filament diameters of 1.75 mm can be used. Engineering thermoplastics with processing temperatures up to 500°C can be used. The guide elements for wires or fibers can be interchangeable and allow the use of outer diameters in the range of 0.1 mm to 1.0 mm.

[0030] The printhead can be connected to supply lines, in particular a filament tube through which the polymer can be fed, a wire or fiber tube, a compressed air hose for cooling medium, an electrical power supply for a heating element, a 24V fan and a signal cable for a thermistor to control the temperature of the polymer filament during its melting.

[0031] These feed lines would become twisted and damaged by repeated rotation, or they would impede the printhead's movement. For this reason, a feed unit can be used that, through its own rotation, relieves the tension on the feed lines to the printhead. The feed unit should be positioned on the side of the printhead opposite the nozzle opening.

[0032] The feeding unit can consist of an outer frame and a rotating body. Various functional elements can be attached to the rotating body. These include, for example, a polymer extruder, a spool on which the polymer filament is wound, electrical contacts for the electrical or electronic connection of the rotating body and printhead elements to a control system, and two vacuum pumps. The vacuum pumps can supply compressed air as a cooling medium. Signal transmission to a control system can be achieved via a slip ring. This should be centrally located and have a through-hole through which polymer for a polymer filament, or a prepared polymer filament, can be fed in the first feeder along the axis of rotation of the rotating body and the printhead. The slip ring thus connects the static frame to the moving rotating body.The bearing can be mounted using 45° inclined rolling bearings.

[0033] Due to the size and weight of a polymer filament spool, the polymer filament feeder should not be positioned on the rotating body itself, but rather guided through the through-hole of the slip ring before the polymer filament enters the first feeder. This allows for the mounting of the polymer extruder, the motor for rotation, and a daughterboard for the electrical or electronic control of the print head and the feeder unit to the frame.

[0034] The feed unit is arranged in the conveying direction of the polymer filament and / or a wire or fiber in front of the printhead. According to the invention, the feed unit is formed with a frame and a rotating body, which is rotatably mounted on the non-rotating frame. Furthermore, functional elements are fixed to the rotating body, and feed lines are led to it.

[0035] The feed unit can be suspended above the work area. Due to the length of the cables and feed hoses, the printhead can rotate freely 180° in any direction, independent of the feed unit. This allows the agile rotation of the printhead to adapt to the respective feed direction at maximum speed, and enables the feed unit to relieve the stresses on the feed lines during subsequent movements.

[0036] The invention enables the integration of wire or fiber materials into an additively manufactured component during the FFF process without placing high mechanical stress on the wire or fibers (large bending radii). The wire or fiber and polymer filament can be fed independently (combination only on the component). The device can be used in any motion system (especially in a system with multiple printheads).

[0037] Continuous rotation for winding electrical coils is possible without the need for specific movement sequences. Furthermore, wire or fiber feeding is possible without simultaneous polymer extrusion (open sections for contacting; winding of high-density electrical coils in a single pass). High feed rates and a low printhead mass can be achieved.

[0038] Due to the independence of the rotation axes of the printhead and feed unit, not every movement of these elements needs to be synchronized, but only when stress drops occur that require relief of the feed lines. The invention also allows the nozzle opening geometry to be adapted for shaping the deposited polymer webs (the round shape of the extruded form can cause some quality problems), so that polygonal polymer cross-sectional profiles can also be deposited.

[0039] The invention will be explained in more detail below by way of example.

[0040] This shows: Figure 1 a sectional view of an example of a printhead that can be used with the device; Figure 2 a sectional view of the in Figure 1 example shown in a top view; Figure 3 a representation of a feed unit that can be used together with a printhead and Figure 4another perspective representation of the in Figure 3 shown feed unit.

[0041] Figure 1 Figure 5 shows an example of a printhead 5 that can be rotated about an axis of rotation. The axis of rotation coincides with the central longitudinal axis of a first feeder 2 through which a polymer filament 1 can be conveyed through a nozzle opening 2.1 towards the respective component 10. A second guide 4 is also guided through the printhead 5, through which a wire 3 can be conveyed towards the component 10. The second guide 4 has a curved end section 4.1 through which the wire 3 can be conveyed almost parallel to the surface of the component 10, so that the wire 3 is subjected to only very minimal mechanical stress from the second guide 4 and its end section 4.1 during its conveying.

[0042] The wire 3 can be fed into the second guide 4 from a feeding device located outside the printing head 5 and a feeding unit 12 not shown here.

[0043] A cutting device 11, in this case a cutting blade, is also attached to the printhead 5. The polymer filament 1 and / or the wire are moved past this cutting device during its feed movement. The cutting device 6, either via a mechanism on the printhead 5 or by a suitable movement of the printhead 5, can cut the polymer filament 1 and / or wire 3.

[0044] A third feed, containing a gas guide 8.1 for a gaseous cooling medium, in particular compressed air, is routed through the printhead 5. The gaseous cooling medium can thus be directed from a cooling nozzle 8.2 towards the polymer filament 1 exiting the nozzle opening 2.1 in order to accelerate the curing or solidification of the polymer material.

[0045] In the direction of conveyance of the polymer filament 1, an electric heating device 7 is integrated into the print head 5 in front of the nozzle opening 2.1.

[0046] The printhead 5 is rotatably mounted in a housing 9 and can be set in rotation by a rotary drive 6, which consists of a fixed electric motor 6.1 and a gearbox 6.2. In this example, the gearbox 6.2 is formed by a toothed belt that can be driven by the electric motor 6.1. This can be seen in the illustration of Figure 2 recognize.

[0047] In Figure 3A feeding unit 12 is shown in which a rotating body 14 is rotatably mounted in a frame 13. The mounting can be achieved with two 45° rolling bearings 17.

[0048] On the rotating body 14, in addition to other functional elements, at least one vacuum pump 16 (shown here as an example) is attached. This pump can supply compressed air for cooling the polymer exiting the nozzle opening 2.1 through the third feed through the gas guide 8.1 and the cooling nozzle 8.2. Electrical contact elements 15, which can be used for transmitting electrical energy and measurement signals, are also attached. At least polymer for a polymer filament, wire 3 or fibers, and electrical energy can be supplied to the feed unit 12 via feed lines (not shown here).

[0049] In Figure 4Additionally, the arrangement of a polymer extruder 18 within the frame 13, a conveying device 19 for wire 3 and a wire spool 20, on which a wire 3 can be held in coiled form and unwound by means of the conveying device towards the second guide 4, can be seen. Reference sign

[0050] 1 Polymer filament 2 First feed 2.1 Nozzle opening 3 Wire or fiber 4 Second feed 4.1 End section 5 Print head 6 Rotary drive 6.1 Electric motor 6.2 Gearbox 7 Heating unit 8 Third feed 8.1 Gas guide 8.2 Cooling nozzle 9 Housing 10 Component 11 Cutting device 12 Feeding unit 13 Frame 14 Rotating body 15 Electrical contact elements 16 Vacuum pump 17 Roller bearings 18 Polymer extruder 19 Wire feeder 20 Wire spool

Claims

1. A device for additive manufacturing using an FFF method, with which a polymer filament (1) is printed together with a wire or a fibre (3) in a feed direction onto the surface of a carrier or a polymer filament (1) already laid down in advance, with which a polymer filament (1) can be conveyed via a first feed (2) to a nozzle opening (2.1) and a wire or fibre (3) can be conveyed from a feed device through a second feed (4) into the exit region of the polymer filament (1) from the nozzle opening (2.1), wherein the first and second feeds (2, 4) are guided by a print head (5) that is rotatable by at least 360° and which can be rotated by a rotary drive (6) around the axis of rotation defined by the central longitudinal axis of the first feed (2), and wherein the second feed (4) opens with its end region (4.1) into the region of the nozzle opening (2.1) at an angle between 45° and 90° relative to the central longitudinal axis of the first feed (2), in which the polymer filament (1) exits from the nozzle opening (2.1), wherein at least one feed device or extruder for a polymer filament (1) and at least one feed device for a wire or fibre (3) outside of the print head (5) are not positioned to rotate with the print head (5), and that a feed unit (12) is positioned in the conveying direction of the polymer filament (1) and / or the wire (3) or the fibre in front of the print head (5) with a non-rotating frame (13) and a rotational body (14) that is rotatably mounted on the frame (13) and has functional elements affixed to it and to which feed lines are connected.

2. The device according to claim 1, characterised in that a separation device (11) is positioned on the print head (5) in the feed direction of the polymer filament (1) and wire or fibre (3) after the nozzle opening (2.1).

3. The device according to any one of the preceding claims, characterised in that an electric heating device (7) for heating the polymer filament (1), which is arranged within the first feed (2) in the rotatable print head (5), is arranged in the feed direction of the polymer filament (1) in front of the nozzle opening (2.1).

4. The device according to any one of the preceding claims, characterised in that the rotary drive (6) is configured with a permanently installed electric motor (6.1) and a gear unit (6.2), wherein the gear unit (6.2) engages with the print head (5).

5. The device according to any one of the preceding claims, characterised in that, by means of a manipulator with the rotary drive (6), the print head (5) can be moved in at least three degrees of freedom.

6. The device according to any one of the preceding claims, characterised in that the end region (4.1) of the second feed (4) is bent.

7. The device according to any one of the preceding claims, characterised in that a third feed (8) for a gaseous cooling medium is guided through the print head (5), which directs the gaseous cooling medium towards the polymer filament (1) exiting from the nozzle opening (2.1).

8. The device according to any one of the preceding claims, characterised in that the print head (5) is rotatably mounted in a housing (9).

9. The device according to any one of the preceding claims, characterised in that the print head (5) is movable such that the conveying length of the wire (3) or fibre is smaller than the distance travelled by the print head (5) during its feed movement with the polymer filament (1) on the carrier or component (10), so that mechanical tension acts on the wire or fibre material after the polymer of the polymer filament (1) has solidified.