Combination printing for the additive manufacturing of a component made from a metal-plastic combination

Abstract

A combination printing process for producing a multi-component component comprising areas of both metal and plastic, wherein at least one metal is plasticized by means of a first extruder (5) and at least one thermoplastic material is plasticized by means of a second extruder (5) and selectively applied two-dimensionally in the x- and y-axis directions to a build surface (7) on a build platform (8) and cooled, after which the build platform (8) is lowered in the z-axis or the extruders (5) are raised in the z-axis and the steps are repeated until the component is completed, and the extruders (5) and the build platform (8) are arranged on a kinematic system (6), wherein, for the production of a positive-locking bond between the at least one metal and the at least one thermoplastic material, the at least one metal and the at least one thermoplastic material have similar melting and / or glass transition temperatures.

Description

The invention relates to a method and the corresponding plant setup for the additive manufacturing of components made from the combination of one or more low-melting or amorphous metals and one or more thermoplastics with similar melting temperatures. Over the past 30 years, various additive manufacturing processes have become established, distinguished primarily by the method of layer generation in conjunction with the starting material. The most important processes are stereolithography (STL), 3D printing (3DP), polymer printing, selective laser sintering / melting (SLS / SLM), electron beam melting (EBM), and fused deposition modeling (FDM). The operating principle of the different additive manufacturing processes is based on layer-by-layer construction, with the general distinguishing features being the variations in the states of matter and the bonding or solidification of the material to be used. Thermal sintering is mainly used for the additive manufacturing of metallic components.Melting processes are used, in which either a laser (SLS, SLM, DLMS) or an electron beam (EBM) selectively solidifies the metal powder in the powder bed. The layering of the metallic powder occurs similarly to 3D printing in a sealed build chamber under vacuum or protective gas. The high-energy beams are moved along the powder bed either via mirror mechanisms or electromagnets. This locally melts the powder bed and then resolidifies it. The powder bed is created by a doctor blade and covers the entire build chamber. In the SLM and EBM processes, the energy input is so high that the powder melts completely, resulting in very dense components. In the SLS process, the individual powder particles are merely sintered, leading to a more porous component. Components produced using melting processes exhibit very good mechanical properties.However, these methods currently do not allow for the simultaneous processing of different materials. Furthermore, due to the high melting point of most metals, it is inherently very difficult to process metals and plastics together in an additive manufacturing process, as the molten metal deforms or destroys the polymer. Known additive manufacturing processes pursue approaches that either involve the processing of composite materials (plastic-metal composites) or different materials within the same material group (e.g., plastics with different technical or optical properties). However, these methods cannot produce components that contain areas made of both metal and plastic.In German patent application DE 10 2014 018 080 A1, the inventors already described a method for the additive manufacturing of amorphous crystalline and / or semi-crystalline metal components (Selective Amorphous Metal Extrusion (SAME)). The invention relates to an additive manufacturing process for producing metal parts with amorphous, crystalline, and / or semi-crystalline structures for rapid prototyping, rapid tooling, and rapid manufacturing. The process can be used in all industries where additive manufacturing processes are employed, such as medical technology, aerospace for the production of lightweight components (closed honeycomb structures, etc.), and mechanical engineering for the direct production of custom-made parts and spare parts.Using an extrusion process, an amorphous, metallic starting material is heated in an extruder to above the glass transition range to create thermoplastic behavior, extruded and selectively applied two-dimensionally to a build platform in the form of an extruded metal thread and then cooled, whereby the two-dimensional application and cooling of the extruded material thread continues until the metal part is completed.The system for carrying out the process consists of a three-dimensionally movable kinematic unit, a build platform, and an extruder mounted on the three-dimensionally movable kinematic unit. The extruder is equipped with an extrusion screw for the amorphous metallic feedstock to be extruded, a heated or partially heated housing, and an interchangeable die mounted on the housing. Optionally, active cooling is directed below the die onto the extruded material exiting the die. A patent exists that describes a similar process. US 5,622,216 A describes a method and setup for an additive manufacturing process that conveys metals between the liquidus and solidus temperatures through a die, thus producing three-dimensional components. However, this patent is limited to crystalline eutectic metals.US 2009 / 0 263 582 A1 discloses a method for the layer-by-layer construction of a three-dimensional object, the method comprising: heating a build chamber of a digital manufacturing system, feeding a solid starting material of an amorphous metal alloy to a liquefaction assembly of the digital manufacturing system, heating the model material from the solid starting material in the liquefaction assembly to an extrudable state, and depositing the heated model material in the heated build chamber in a predetermined pattern to form the three-dimensional object. US 2012 / 0 258 190 A1 discloses a consumable for use in an extrusion-based digital manufacturing system, wherein the consumable has a length and cross-sectional profile that is axially asymmetric over at least a portion of its length. Furthermore, there are several hybrid processes that work with multiple materials simultaneously. US patent 2014 O 324 204 A1 describes a multi-material printer that can generate droplets from previously different plastics using piezoelectric printheads. German patent DE 10 2009 048 706 A1 discloses a process for the additive manufacturing of large-volume components made of metal and plastic. This process is a thermal spraying process in which metal and plastic powders are compacted layer by layer into solid bodies. However, the resolution of this process is very poor because the powder jet has a diameter of several millimeters and the application cannot be precisely controlled. Another approach is being pursued by the company WZR, in which a component made of metal and ceramic is produced using "inks." However, a subsequent sintering process is necessary to transform the ceramic into its final state.However, the production of metal-plastic components is not possible. Another approach taken by Northwestern Engineering involves using an "ink" filled with metal particles, which is printed into a ceramic powder bed. This selectively bonds the powder. The printed component then needs to be sintered. However, the solutions mentioned here do not individually offer the possibility of combining the material groups metal and plastic in a single construction process. The object of the invention is to develop a method that, for the first time, enables the combined processing of plastics and metals in an additive manufacturing process. By combining both material groups, components with specifically adjustable local functional properties can be produced. Possible applications include plastic housing parts with integrated metallic bearings or threaded bushings, plastic components with integrated electrical conductors, or mechanically robust plastic parts with lightweight metallic structural reinforcement. According to the invention, the problem is solved by a method (polymer metal printing, PMP) for producing a component by extruding a low-melting-point or amorphous metal and a thermoplastic polymer, wherein the component is built up layer by layer. Both the metal and the polymer are extruded from dies by a thermo-mechanical process. The extruded metallic and polymeric areas bond together to form a component. The low-melting-point or amorphous metal and the polymer must have similar melting or glass transition temperatures, and thus similar processing temperatures, so that deformation or destruction, in particular of the polymer, by the extruded metal due to thermal influences can be prevented.The process is a combination printing process for producing a multi-component component from one or more metals and one or more thermoplastic materials using two or more extruders (5), wherein at least one metal and at least one thermoplastic are plasticized by short-term thermal and mechanical action and selectively applied two-dimensionally in the x- and y-axis directions to a build surface (7) of a build platform (8) and cooled, after which the build platform (8) is lowered in the z-axis or the extruders are raised in the z-axis and the steps are repeated until the component is completed, and the extruders (5) and the build platform (8) are arranged on a kinematic system (6), and the metals and plastics to be extruded have similar melting and / or glass transition temperatures and are in thread and / or granule form.The metals used consist of low-melting or amorphous alloys with a melting point in the range of 300°C, in particular the low-melting or amorphous alloys MgxZkyCaz or MgxCuyYz. The thermoplastic polymers consist of high-melting polymers with melting points in the range of 300°C, in particular polyoxymethylene (POM), acrylonitrile butadiene styrene copolymer (ABS), polyetherimide (PEI), polyethersulfone (PES), polysulfone (PSU), or polyetheretherketone (PEEK). In a further embodiment of the invention, the metal is in granular form and the extruder (5) is designed as a screw extruder. The heating temperature for the extrusion of the different materials can be set independently, and the metal and the thermoplastic material can be in thread and / or granular form as starting materials. In a further embodiment of the invention, the extruded threads are actively or passively cooled, wherein the extruded threads are cooled during application to the component (7). In a further embodiment of the invention, the nozzle diameters of the extruders for extruding both materials can be the same or different. The temperature of both extruders can be the same or different and can be adjusted by a control system, whereby the heating temperature is set differently for extruding the different materials. The exit velocity of the extruded filaments from the nozzle is adapted to the travel speed of the build platform (8). The invention will now be explained in more detail using an example, wherein Fig. 1 shows a schematic representation of an extruder, Fig. 2 shows the kinematics (3) with two extruders (5) and Fig. 3 shows a component made of a metal and plastic combination. Reference symbol list 1 Extruder feed screw (5) 2 Heated extruder housing (5) 3 Extruder nozzle (5) 4 Material 5 Extruder 6 Kinematics 7 Component 8 Build platform A kinematic system (6) with linear drives movable in the x, y, and z axes accommodates at least two extruders (5) for extruding metal and plastic. In each extruder (5), at least one metal and at least one thermoplastic are briefly plasticized under thermal and mechanical stress and selectively deposited two-dimensionally in the x and y directions to form a component (7) on a build platform (8). The component is then cooled, and the build platform (8) is lowered in the z-axis, or the extruders (5) are raised in the z-axis. These steps are repeated until the component is complete. The extruders (5) consist of a feed screw (1), a heated housing (2), and a replaceable die (3) arranged on the housing (2). Metals and plastics with similar melting and / or glass transition temperatures are used as the material (4).A special magnesium alloy (Mg60Zn35Ca5) has already been successfully tested. This alloy has a relatively low glass transition temperature of 90°C and a melting point of 300°C, allowing a heating element to reach the required temperature in the extruder for extrusion. This extruder can also process many different alloys with low melting or glass transition temperatures, such as Ce58Cu20Al10Nb2, Mg65Cu25Y, or Au49Ag5Pd2.3Cu26.9Si6.3. The heat input brings the material into the thermoplastic range, and the mechanical force of the screw compacts it. The extruder must not become blocked or clogged, and it extrudes a continuous strand of material through the attached die. The material is characterized by its viscosity, which can be adjusted via temperature, so that a pasty state of the material can be created and extruded with the screw conveyor.A thermoplastic is used as the plastic, which has a similar melting point to the metal used (around 300°C). Due to these similar melting points, the two material groups can be joined. The extruded filament cools rapidly after exiting the die and hardens, creating a form-fitting composite between the metal and plastic. This process allows for the production of a component made from two different material groups (metal and plastic). By using additional extruders, support materials made of a thermoplastic material or other building materials (metals and plastics) can also be processed in a single operation. The parts can also be post-processed if necessary (e.g., surface finishing, machining of the metallic areas).The invention makes it possible for the first time to produce parts made of metal and plastic directly in an additive manufacturing process.

Claims

A combination printing process for producing a multi-component component comprising areas of both metal and plastic, wherein at least one metal is plasticized by means of a first extruder (5) and at least one thermoplastic material is plasticized by means of a second extruder (5) and selectively applied two-dimensionally in the x- and y-axis directions to a build surface (7) on a build platform (8) and cooled, after which the build platform (8) is lowered in the z-axis or the extruders (5) are raised in the z-axis and the steps are repeated until the component is completed, and the extruders (5) and the build platform (8) are arranged on a kinematic system (6), wherein, for the production of a positive-locking bond between the at least one metal and the at least one thermoplastic material, the at least one metal and the at least one thermoplastic material have similar melting and / or glass transition temperatures. Combination printing according to claim 1, characterized in that the low-melting or amorphous alloys consist of a plurality of elements, such as MgXZkyCaZ or MgxCuyYZ. Combination printing according to claim 1, characterized in that the high-melting-point plastics consist of POM, ABS, PEI, PES, PSU or PEEK. Combination printing according to claims 1 to 3, characterized in that the metal is in granular form and the extruder (5) is designed as a screw extruder. Combination printing according to claims 1 to 4, characterized in that the heating temperature for the extrusion of the different materials is adjustable differently. Combination printing according to claims 1 to 5, characterized in that the extruded threads are cooled passively or actively in a controllable manner. Combination printing according to claims 1 to 6, characterized in that at least a part of the component is produced as a complex multi-material structure by the method. Combination printing according to claims 1 to 7, characterized in that the nozzle diameters of the extruders for extruding the materials can be the same or different. Combined pressure according to claims 1 to 8, characterized in that the temperature of both extruders can be the same or different and can be adjusted by a control system. Combination printing according to claims 1 to 9, characterized in that the exit velocity of the extruded filaments from the nozzle is adapted to the travel speed of the build platform (8).

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