Manufacturing plant and process for three-dimensional printing

Abstract

Manufacturing system (200) for three-dimensional printing of components (202) from a wire-shaped printing material (240) with - an application head (220) which is configured to dispense a wire-shaped printing material (240) continuously supplied to the application head (220) for the production of a component (202), - a material feeder (250) to continuously feed the wire-shaped printing material (240) from a material storage unit (242) to the application head (220), and - a thermal energy source (222) which is configured to introduce a predetermined amount of thermal energy into the wire-shaped printing material (240) during dispensing through the application head (220), characterized in that a cross-sectional change device (252) is arranged in the material feed (250) between the material storage (242) and the application head (220), which is configured to change the wire-shaped printing material (240) during continuous feeding from a first cross-section with a first cross-sectional area to at least a second cross-section with a second cross-sectional area smaller than the first by means of a wire drawing process, wherein the cross-sectional change device (252) has a plurality of drawing dies arranged one behind the other in the feeding direction.

Description

[0001] The invention relates to a manufacturing system for the three-dimensional printing of components from a wire-shaped printing material.

[0002] The invention also relates to a method for three-dimensional printing of components from a wire-shaped printing material using such a manufacturing system.

[0003] Using additive manufacturing processes and a suitable material, components of almost any shape can be produced. 3D printing with a 3D printer is a well-known example of additive manufacturing. In this process, a material, such as a thermoplastic or a metallic material, is printed layer by layer using a 3D printer, resulting in a three-dimensional component or structure at the end of the process.

[0004] Several processes exist for 3D printing metallic materials. Common methods include powder bed fusion (LPBF - Laser Powder Bed Fusion, SLM - Selective Laser Melting, LMF - Laser Metal Fusion, etc.) in which the material is applied layer by layer and locally melted in the required areas by a heat source, usually a laser. The powder bed lowers incrementally, and new material is applied. This process builds the new component layer by layer. Some of the unmelted powder can be reused for later processes. The accuracies of this method are + / -0.1 mm, and the layer thickness varies between 20 and 50 µm. The surface roughness is 8–10 µm, and the porosity is between 0.2 and 0.5%. Typical build volumes range from 250 x 150 x 150 mm to 500 x 280 x 360 mm, making them suitable for smaller components and assemblies.

[0005] An alternative process is metal extrusion (see FDM, BMD - Bound Metal Deposition). In this process, the material is applied layer by layer through an extruder nozzle, similar to the standard FDM process for plastics. The semi-finished product consists of metal powder embedded with a polymer. After printing, a "green part" is obtained, which must be post-processed by removing the polymer binder and sintering. During sintering, the polymer is removed, and the components consist entirely of metal. The components shrink by approximately 20% during the sintering process. The dimensional accuracy (after accounting for the 20% shrinkage) is + / - 0.5 mm. The layer thickness resolution is 50-200 µm, and the porosity is relatively high at 2-4%.

[0006] Another process is Direct Energy Deposition (DED), in which the component is printed using a powder or a wire. With powder feed systems, the semi-finished product (powder) is stored in material magazines and fed to the application head for the printing process, where it is melted by a heat source (laser, arc, or electron beam). The deposition rate can be adjusted within limits by varying the amount of powder fed or the feed rate. A protective gas is introduced at the deposition point to protect the material from oxidation and improve component quality.

[0007] One implementation of the DED process involves wire feeding systems where a wire with a fixed diameter is fed in (WAAM - Wire Arc Additive Manufacturing). The deposition rate can be adjusted by changing the process speed. At the lay-down point, the wire is melted by one or more heating sources (laser, electric arc, or electron beam), and a protective gas atmosphere is usually created in the weld area.

[0008] A major advantage of the DED process over SLM and BDM processes is the option of multi-axis manufacturing. The various end effectors (application heads) can be operated on robot kinematics with five or more axes. This enables the production of large and complex structures as well as the repair and enhancement of existing components. DED processes are also characterized by high deposition rates, which, however, usually come at the expense of surface roughness, tolerances, and layer thickness resolution.

[0009] To achieve the required component tolerances, parts produced using 3D wire printing are predominantly machined, which adds another process step and increases component costs. At very high deposition rates, the tolerance in the printing process can be so high that components and functional surfaces cannot be printed directly. In such cases, an additional process step would be necessary. High deposition rates can be achieved in 3D wire printing by using a large-diameter blank, but this comes at the expense of tolerance. Conversely, using smaller-diameter blanks reduces printing deviations, but this also reduces the deposition rate. Since the blank diameter must be determined before printing begins, a trade-off between accuracy and processing time must always be made.

[0010] From US patent 2010 / 0327479A1, a device for extruding a plastic material is known in which the plastic material is melted and mixed with other substances in order to modify the optical properties of the extruded material.

[0011] From CN 11 0 667 114 A, a device and a method for dispensing a filament is known, which is drawn through a molten plastic bath and thereby impregnated with plastic material.

[0012] A device for producing a high-temperature filament for 3D printing is known from CN 21 0 082 404 U. In this process, a supplied material is heated, shaped, cooled, and wound up.

[0013] It is therefore an object of the present invention to provide an improved 3D wire printing process that reduces the disadvantages known from the prior art.

[0014] The problem is solved according to the invention by the production plant according to claim 1 and the method according to claim 1. Advantageous embodiments of the invention are described in the corresponding dependent claims.

[0015] According to claim 1, a manufacturing system for the three-dimensional printing of components from a wire-like printing material is proposed, which produces a component using a 3D wire printing process. A wire-like printing material is fed into the manufacturing system and usually placed on a tool to build the component, particularly layer by layer. The manufacturing system can produce both entire components from the wire-like printing material and add components to existing components using the 3D wire printing process. In both cases, the term "production of a component" is used.

[0016] The production system features an application head to which the wire-shaped printing material is continuously fed during component manufacturing. The application head (end effector) dispenses this wire-shaped printing material, often involving relative movement between the tool on which the component is manufactured and the application head. For this purpose, the application head is, for example, mounted on a robot capable of moving it in various spatial directions. Advantageously, this robot is designed to allow the application head to move along all three translational and all three rotational axes.

[0017] The relative movement between the tool and the application head allows the entire component with its component geometry to be mapped layer by layer, in which the wire-shaped printing material is continuously dispensed through the application head during the relative movement.

[0018] During the dispensing of the wire-shaped printing material, thermal energy is introduced into the material using a thermal energy source. This heats the material to a temperature that allows it to be dispensed from the application head and enables plastic deformation. This allows for the reproduction of any component geometry without having to cut the wire-shaped printing material and restart the dispensing process. Instead, a continuous layer of material can be achieved.

[0019] Furthermore, the production system includes a material feeder to continuously supply the wire-shaped printing material from a material storage unit to the application head. The material feeder continuously conveys the wire-shaped printing material from the material storage unit to the application head, thus enabling continuous dispensing and depositing of the printing material.

[0020] According to the invention, such a generic manufacturing plant for carrying out a 3D wire printing process is characterized only in that a cross-section changing device is arranged in the material feed between the material storage and the application head, which is configured to change the wire-shaped printing material from a first cross-section to at least a second cross-section during the continuous feed.

[0021] This makes it possible to change the cross-section of the wire-like printing material during the output and placement of the printing material, so that changing cross-sections of the wire-like printing material can be fed to the application head without interrupting the printing process. The application head is designed so that it can continuously output and place different cross-sections of the wire-like printing material and / or changes to these cross-sections during the printing process, and, if necessary, also cut them.

[0022] The present invention makes it possible to adapt the cross-section of the wire-shaped printing material to the predetermined conditions of a complex component during the printing process, without having to interrupt the printing process and replace the wire-shaped printing material with another printing material with a different cross-section. Instead, the cross-section of the printing material can be changed in situ during the process.

[0023] This allows for the production of components optimized for accuracy and production rate. Extensive machining of the components is therefore unnecessary, especially at high production rates, because the accuracy can be locally increased by modifying the cross-section during the printing process at critical points on the component.

[0024] This allows areas of the component that have particularly high tolerance requirements to be printed with a cross-section of the wire-shaped printing material optimized for this purpose, while areas of the component with lower tolerance requirements can be printed with a different cross-section of the wire-shaped printing material to increase the production rate.

[0025] According to the invention, it is further provided that the cross-sectional changing device is configured to change the wire-shaped printing material from the first cross-section with a first cross-sectional area to at least one second cross-section with a second cross-sectional area different from the first cross-sectional area.

[0026] The cross-sectional changing device is now designed in such a way that the cross-sectional area of ​​the wire-shaped printing material can be changed, wherein the cross-sectional changing device can change the cross-section from the first cross-sectional area to at least one different second cross-sectional area.

[0027] For this purpose, it is provided that the second cross-sectional area is smaller than the first cross-sectional area.

[0028] Accordingly, the cross-sectional change device is set up to reduce the cross-sectional area of ​​the wire-shaped printing material from the first cross-sectional area to at least one second cross-sectional area.

[0029] By reducing the cross-sectional area, for example by decreasing the diameter of the wire-shaped printing material, areas of the component with high tolerance requirements and lower delamination rates can be printed, while areas with lower tolerance requirements can be printed with a larger cross-section and higher delamination rate. This reduction in cross-sectional area occurs during the printing process without interrupting the output of the printing material.

[0030] According to one embodiment, the cross-sectional changing device is designed to change the wire-shaped printing material from the first cross-section with a first cross-sectional shape to at least one second cross-section with a second cross-sectional shape different from the first cross-sectional shape.

[0031] By adjusting the shape of the cross-section, specific requirements for the component geometry can be met in situ during the printing process.

[0032] According to the invention, the cross-section changing device is further configured to change the wire-shaped printing material from the first cross-section to the second cross-section by means of a wire drawing process. For this purpose, the cross-section changing device is configured to carry out the cross-sectional change by means of a plurality of drawing dies arranged one behind the other in the feed direction.

[0033] The wire-shaped printing material can be drawn through several dies. The openings of the dies, through which the wire-shaped printing material is passed, are designed to change the cross-sectional shape and / or area during the printing process, thus achieving the desired change in cross-section. Alternatively, the dies can be designed so that, as needed, corresponding cross-sectional changes can be achieved by enclosing the wire-shaped printing material. Depending on the required diameter of the openings through which the wire-shaped printing material is to be drawn, the dies can be opened and closed to adjust the cross-section accordingly.

[0034] According to one embodiment, the manufacturing plant has a control device for controlling the thermal energy source, wherein the control device is configured to adjust the amount of energy depending on a change in the cross-section by the cross-section changing device.

[0035] Changing the cross-section also changes the amount of material dispensed per unit of time, allowing the thermal energy input to be adjusted accordingly by a control unit. For example, if the cross-sectional area is reduced, less energy is required to melt the wire-shaped printing material.

[0036] The task is also solved using the method for three-dimensional printing of components from a wire-shaped printing material using a manufacturing system, whereby the method comprises the following steps: - continuous feeding of a wire-shaped printing material from a material storage area to an application head of the production plant; - Ejecting the wire-shaped printing material fed to the application head to produce the component, - wherein, when the wire-shaped printing material is dispensed at the application head, a thermal energy input with a predetermined amount of energy occurs by means of a thermal energy source, and - Varying the cross-section of the wire-shaped printing material during continuous feeding by means of a cross-section changing device of the production plant, - wherein the cross-sectional area of ​​the wire-shaped printing material is varied during continuous feeding by means of a wire drawing process and by a plurality of drawing dies arranged one behind the other in the feeding direction, such that the cross-sectional area is reduced.

[0037] Advantageous embodiments of the process can then be found in the corresponding subclaims.

[0038] The invention is explained in more detail using the attached figures as examples. They show: Fig. 1. Schematic representation of a top view of two components manufactured according to the state of the art; Fig. 2 Schematic representation of a manufacturing plant according to the invention; Fig. 3 Schematic representation of a top view of a component with varying cross-sections of the wire-shaped printing material; Fig. 4 Schematic representation of a side view of two components with varying cross-sections of the wire-shaped printing material.

[0039] Fig. Figure 1 shows a schematic representation of a top view of two components 100, 102, which were manufactured using a 3D wire printing process according to the state of the art.

[0040] The component 100 on the left was printed using a wire-like printing material, with several material webs 110 having a very large diameter and thus a relatively large cross-sectional area. Since the actual component 100 has a circular shape, the material webs 110 must extend beyond the edge of the component 100. Due to the relatively large cross-sectional area, this results in a significant amount of waste at the overhanging edge areas 120.

[0041] Component 102 on the right, however, was printed with material webs 112, which have a relatively small diameter and therefore a relatively small cross-sectional area. Compared to component 100 on the left, it is evident that significantly more webs of the wire-like printing material had to be deposited, thus reducing the production rate. On the other hand, the waste from component 102 on the right is considerably less than that of component 100 on the left, because the smaller diameter results in less excess material.

[0042] According to the current state of the art, the only choice is between a high production rate with large amounts of waste and extensive post-processing, or a low production rate with small amounts of waste and less post-processing.

[0043] Fig. Figure 2 shows a schematic representation of a production plant 200 according to the invention, with which the in Fig. The tension field shown in 1 can be resolved.

[0044] The production system 200 has a rail-guided robot 210 with a motion kinematics 212, on which an application head 220 with a thermal energy source 222 is arranged as an end effector. The application head 220 is designed such that a wire-shaped printing material supplied to it is dispensed in such a way that a component 202 can be manufactured. The wire-shaped printing material 240 is deposited by the application head 220 onto a tool 230 or tool table, on which the component 202 is then built up layer by layer.

[0045] Thermal energy sources 222, for example, laser heating sources, arc welding, or electric current, are considered. The position of the beginning and end of the modified diameter is transmitted to the system control via rotary encoders and the fixed distances / path lengths and processed within the software. Therefore, according to the invention, the beginning and end of a material web with a predetermined modified cross-section can be calculated by measuring the path length of the wire-shaped printing material.

[0046] The wire-shaped printing material 240 is held in a material storage unit 242 and fed from the material storage unit 242 to the application head 220 by means of a material feeder 250. The application head 220 can be designed to automatically draw the wire-shaped printing material 240 from the material storage unit 242.

[0047] In the material feed 250, between the material storage 242 and the application head 220, there is a cross-section changing device 252, by which the cross-section of the wire-shaped printing material 240 can be changed in situ during the printing process.

[0048] For this purpose, the wire-shaped printing material is stretched, for example, using a wire-drawing process, which reduces the cross-section or cross-sectional area. It is also conceivable that the wire-shaped printing material is guided through one or more dies whose openings can be variably opened or closed to produce the desired cross-section.

[0049] The production plant 200 also includes a control device 260 for controlling the production plant. In particular, the thermal energy source 222 is controlled with regard to the amount of energy to be supplied, such that the amount of energy to be supplied depends on the currently applied cross-section, which is changed by the cross-section changing device 252. Thus, an optimal amount of energy can always be supplied to the wire-shaped printing material.

[0050] The cross-section changing device 252 can further include an additional heating source (not shown) to prepare the wire-shaped printing material 240 for a corresponding wire drawing process. This prevents stresses in the material and improves the drawing process with regard to the required drawing force.

[0051] Fig. Figure 3 shows the geometry of the component using an example. Fig. Figure 1 shows a top view of a component 300, which can be manufactured using the production system 200. It can be seen at the bottom edge that the individual printing webs 310, 312, and 314 of the wire-shaped printing material vary in their cross-sectional area or diameter, increasing in diameter from the outside to the inside. This minimizes waste and thus the excess material at the edge of the component 300 being manufactured, without reducing the production rate accordingly. The diameter was changed during the printing process and adjusted accordingly with each new printing web being applied.

[0052] In the upper right part of the component, three print bands 320, 322, and 324 are visible, each with a varied cross-section. The central print band 322 initially has a smaller cross-section, which then increases in the middle area during the printing process before decreasing again. This allows the cross-section of an individual print band to be changed during printing, thus enabling optimal adaptation to the component and its shape.

[0053] Fig. Figure 4 schematically shows in a side view 2 components 400, 402, which were built up layer by layer by a wire-shaped printing material which has a progressively smaller cross-section or cross-sectional area towards the top.

[0054] As the cross-sectional area of ​​the wire-shaped printing material decreases, the roughness on the surface of the respective component also decreases 400, 402.

[0055] Component 400 on the left showed a decreasing wall thickness as the cross-sectional area decreased. To compensate for this, several layers of the wire-like printing material with different cross-sections can be deposited per layer, so that a small cross-sectional area is chosen on the outside to minimize surface roughness, and a larger cross-sectional area is chosen on the inside. Reference symbol list 100 first component according to the state of the art 102 second component according to the state of the art 110 material webs of the first component 112 material webs of the second component 120 overhang 200 production plant 202 component to be printed 210 robots 212 Kinematics 220 application head 222 thermal energy source 230 tool table 240 wire-shaped printing material 242 material storage 250 material feed 252 Cross-section changing device 260 Control unit of the production plant 300 components with material webs of varying cross-section 310-314 Material webs 320-324 material webs 400 first component with varying cross-sections 402 second component with varying cross-sections

Claims

[1] Manufacturing system (200) for three-dimensional printing of components (202) from a wire-shaped printing material (240) with - an application head (220) which is configured to dispense a wire-shaped printing material (240) continuously supplied to the application head (220) for the production of a component (202), - a material feeder (250) to continuously feed the wire-shaped printing material (240) from a material storage unit (242) to the application head (220), and - a thermal energy source (222) which is set up to introduce a predetermined amount of thermal energy into the wire-shaped printing material (240) when it is dispensed through the application head (220), characterized by, that in the material feed (250) between the material storage (242) and the application head (220) a cross-sectional change device (252) is arranged, which is configured to change the wire-shaped printing material (240) during the continuous feed from a first cross-section with a first cross-sectional area to at least a second cross-section with a second cross-sectional area smaller than the first cross-sectional area by means of a wire drawing process, wherein the cross-sectional change device (252) has a plurality of drawing dies arranged one behind the other in the feed direction. [2] Manufacturing plant (200) according to claim 1, characterized by, that the cross-sectional changing device (252) is configured to change the wire-shaped printing material (240) from the first cross-section with a first cross-sectional shape to at least one second cross-section with a second cross-sectional shape different from the first cross-sectional shape. [3] Manufacturing plant (200) according to any one of the preceding claims, characterized by , that the manufacturing plant (200) has a control device (260) for controlling the thermal energy source (222), wherein the control device (260) is configured to adjust the amount of energy depending on a change in the cross-section by the cross-section changing device (252). [4] Method for three-dimensional printing of components (202) from a wire-shaped printing material (240) using a manufacturing system (200), the method comprising the following steps: - continuous feeding of a wire-shaped printing material (240) from a material storage (242) to an application head (220) of the production plant (200); - Ejecting the wire-shaped printing material (240) supplied to the application head (220) to produce the component (202), - wherein, when the wire-shaped printing material (240) is dispensed at the application head (220), a thermal energy input with a predetermined amount of energy is carried out by means of a thermal energy source (222), characterized by - Varying the cross-section of the wire-shaped printing material (240) during continuous feeding by means of a cross-section changing device (252) of the production plant (200), - wherein the cross-sectional area of ​​the cross-section of the wire-shaped printing material (240) is varied during the continuous feeding by means of a wire drawing process and by a plurality of drawing dies arranged one behind the other in the feeding direction such that the cross-sectional area is reduced. [5] Method according to claim 4, characterized by , that the cross-sectional shape of the cross-section of the wire-shaped printing material (240) is varied during continuous feeding. [6] Method according to claim 4 or 5, characterized by , that by means of a control device (260) the amount of energy of the thermal energy input is adapted to the varied cross-section of the wire-shaped printing material (240).

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