Multi-laser systems for additive manufacturing

Abstract

A multi-laser system (100) for additive manufacturing is described, consisting of multiple laser sources in an environment with an inert gas atmosphere and multiple optics and / or optical system scanning required to generate and transmit electromagnetic radiation beams within a given processing sector, used in a working chamber capable of removing fumes and / or contaminants resulting from the selective powder melting process as close as possible to the molten layer or layers, and of locally introducing process gases required for powder bed fusion or processing of the powder bed within the same chamber.

Description

[Technical Field]

[0001] The present invention relates to a multi-laser system for additive manufacturing according to the preamble of claim 1. In particular, a multi-laser system for additive manufacturing with powder bed fusion or powder bed technology is depicted.

[0002] Additive manufacturing (AM) is a series of additive manufacturing processes that starts from a digital model, in contrast to traditional subtractive techniques (machining, cutting, drilling to remove chips); a 3D CAD model that is divided into layers by software integrated into the machine control system, or an online service, which obtains the scheme of the resulting layers that are processed by machine tools for deposition processes or sintering of various types of materials, especially metal, plastic, or composite components.

[0003] The main feature of this technology is that it is a manufacturing process that can produce parts with a geometry very close to that of the final part required by the project design. Within the AM family, several different techniques can be identified, such as selective melting / sintering of a powder bed using a laser beam (selective laser beam melting - SLBM, or selective laser beam sintering - SLBS, or also known as powder bed fusion bonding or PBF), metal deposition by laser beam (laser beam metal deposition - LBMD), and selective electron beam melting - SEBM.

[0004] In powder bed or PBF technology, a laser beam is used as a heat source with a high power density, necessary to melt metal powder only in specific zones or predetermined areas where compact material is needed to create three-dimensional parts. The advantage associated with using a laser beam is that it can be focused to a small size or spot, typically around 30 μm in diameter, ensuring high power density, resulting in rapid melting of the powder and a good level of precision in terms of the surface finish of the produced part. These characteristics have enabled powder bed technology to enter the industrial market for the production of parts in a variety of fields, from aerospace to medical, automotive to jewelry. In particular, the greater flexibility of powder bed technology compared to traditional manufacturing techniques allows for a very high level of part customization to be achieved.

[0005] In manufacturing processes, there is a time interval between the melting of one layer and the melting of the next layer that limits the productivity of the system, as the doctor blade or recoater must wait to complete the drafting of the new powder bed before the subsequent process can begin.

[0006] The manufacturing process mainly depends on the interaction between radiation and matter, the material's absorption characteristics of electromagnetic radiation energy, and the temperature of the powder bed. In particular, the material's absorption characteristics, including parameters such as density, thermal conductivity, specific heat, and emissivity, vary with the temperature of the material itself, and in additive manufacturing techniques using powder beds or powder bed fusion, determine the material processing process.

[0007] The choice of process parameters such as laser power, laser scanning speed over the powder bed, shape of the laser beam, material used etc. influences the structure and surface quality of the manufactured parts, the productivity of the system, and thanks to advantages such as high spatial resolution, capillary process control, the ability to carry out pre-treatment of the powder bed and post-treatment of the freshly molten material, they are decisive for the use of this type of machine in industrial fields, especially in the fields today encompassed by casting and / or thermoforming and / or die casting.

[0008] The melting process is carried out by one or more laser sources in a working chamber, under an inert gas atmosphere (e.g., nitrogen, argon, etc.), with the help of several optical and / or scanning systems, inside which there are several processing devices that control the addition of powder, thus ensuring the realization of the part, allow the aspiration of fumes derived from the selective melting process, and allow the injection of gases to support the manufacturing process.

[0009] Many multi-laser systems for additive manufacturing are known in the art, such as those disclosed in EP 3083254, which relates to a system consisting of a set of lasers adapted to scan a working area for the 3D manufacturing of an object; CN 112248436, which relates to a system with multiple lasers, which reduces the number of scans performed on the object being built, thereby improving the quality of the build; CN 111842886, which relates to a system for powder bed technology, in which there are multiple scanning systems of laser beams and air blowing and suction systems between the working area and the laser beam delivery system; CN 209063559, which describes a system including four galvanometers, two air inlets, two air outlets, and a filtration system, in which two exhaust ports are located at the lower ends of the left and right side plates of the chamber, respectively; and EP 3050648, which relates to a gas inlet and suction system above the working area, with inlet and outlet nozzles arranged to form a gas flow that passes partially over at least the working area and the joining area.

[0010] The main drawbacks of the known techniques are related to systems in which devices with multiple lasers cannot operate autonomously on specific sectors of the work surface, or in which the number of scans is reduced even when multiple laser sources are used, which leads to a drawback in the production speed, and also to systems in which the extraction of process fumes and the introduction of support gases are not localized but are restricted to the boundary walls of the working chamber or to structures that can introduce uncontrollable vibrations into the dust bed, and are not localized in the vicinity of the process carried out in the powder layer by the lasers used, which is a limitation in the melted material and thereby introducing defects and / or inclusions in the final part with small and / or large dimensions. Furthermore, these are devices that are not easily scalable in terms of laser sources, especially in terms of the local processing of layers in the powder bed.

[0011] The objective of the present invention is to solve the above-mentioned problems of the prior art by providing a multi-laser system for additive manufacturing, with a scalable system that allows the use of multiple laser sources generating electromagnetic radiation beams arranged along pre-established processing sectors, each capable of operating autonomously in its own capacity, ensuring high production speeds and high quality of the objects produced. Another objective is to use a mechanical system that is free from the possibility of uncontrolled vibrations in the powder bed, by using a system fixed above the working area that moves perfectly to the right / left with respect to the working area during the doctor blade's passage. This ensures that the layer deposited on the working surface is not subject to fluctuations and / or turbulence with respect to the drawing of subsequent layers.

[0012] As will become apparent from the following description, these and other objects and advantages of the present invention are achieved by a multi-laser system for additive manufacturing as set forth in claim 1. Preferred embodiments and non-obvious modifications of the invention form the subject of the dependent claims.

[0013] It will be understood that all appended claims form an integral part of this specification.

[0014] It will be readily apparent that numerous variations and modifications (e.g., as to shape, size, arrangement, and functionally equivalent parts) may be made to what has been described without departing from the scope of the invention, as evidenced by the appended claims. [Brief explanation of the drawings]

[0015] The invention will now be explained in more detail by means of some preferred embodiments, given as non-limiting examples, with reference to the accompanying drawings, in which:

[0016] [Figure 1] FIG. 1 shows a multi-laser system (100) for additive manufacturing according to the present invention. [Figure 2] FIG. 2 shows a diagram of the overlap area of a multi-laser system (100) for additive manufacturing according to the present invention. [Figure 3] FIG. 3 shows a diagram of the continuous overlap region of a multi-laser system (100) for additive manufacturing according to the present invention. [Figure 4] FIG. 4 shows a top view of the laser trajectories in the corresponding working area of a multi-laser system (100) for additive manufacturing according to the present invention. [Figure 5] FIG. 5 shows the gas suction and aspiration system (105) according to the invention in a translational movement phase in the direction (X+). [Figure 6] FIG. 6 shows the gas intake and suction system (105) according to the invention in a translational movement phase in the direction (X-). [Figure 7] FIG. 7 shows an off-work surface gas suction and aspiration system (105) according to the present invention.

[0017] The multi-laser system (100) for additive manufacturing is designed to be used in a working chamber in an environment of an inert gas (e.g., nitrogen, argon, etc.) atmosphere, and consists of several laser sources and several optical and / or scanning systems required to generate and transmit electromagnetic radiation beams within a given processing sector, making it possible to remove fumes and / or contaminants resulting from the selective powder fusion process as close as possible to the molten layer or layers, while allowing the process gases required for powder bed fusion or powder bed treatment to be introduced locally in the same chamber, said multi-laser system (100) being scalable and able to operate autonomously in each specialized field, ensuring a high quality of the manufactured objects combined with a high production rate. As can be seen in FIG. 1, a multi-laser system (100) for additive manufacturing comprises a matrix (103) of independent optical systems designed to transmit electromagnetic radiation beams (107) to a predetermined area of a work surface (101), i.e., a matrix (103) of independent optical systems capable of 100% overlap of the electromagnetic radiation beams (107) in the predetermined area of the work surface (101), the matrix (103) of independent optical systems being connected to the upper surface of a machine tool; and a work surface (101) designed to accommodate a powder bed (102), operably connected to a piston (106).

[0018] Advantageously, as can be seen from FIG. 1, the matrix (103) of independent optical systems is scalable and modular in a number of modules (111) of laser and optical systems and / or galvanometric scanning systems, in particular the modules (111) can be constituted by at least four laser and optical and / or galvanometric scanning systems, the modules (111) being able to be increased in increments of four corresponding to the working area required to carry out the additive manufacturing process, depending on the production volume, the dimensions of the parts to be manufactured and the process speed.

[0019] Furthermore, the modules (111) of the laser and optical system and / or galvanometric scanning system can operate autonomously to perform additive manufacturing processes within each work sector (112), in particular, each laser source emits a beam of electromagnetic radiation (107), i.e., when two laser sources are operating as shown in Figures 2 and 3, the additive manufacturing process can be performed in corresponding areas (119) within each work sector (112) with a total overlap of 100%, and in corresponding areas (115), (116), (117), and (118) within each work sector (112) with a partial overlap of 50%.

[0020] In the areas 115, 116, 117, and 118, the two laser sources of the first module 111 work together with two laser sources of the second module 111 to perform 100% processing in the area 219 and 50% processing in the areas 215, 216, 217, and 218, so that the overlap of the two laser sources can cover 100% of the entire peripheral area with the help of two laser sources of said module 111, as shown in Figure 3. Thus, as can be seen in Figure 3, in the area denoted as AA, given by the combination of areas 215 and 118, four laser sources work, and each of the areas 215 and 118 is covered by the laser sources of the two adjacent modules 111. This management of the overlap area allows the optical system and / or galvanometric scanning system to be closer to the work area, allowing additive manufacturing operations to be performed using a smaller spot diameter of the electromagnetic radiation beam (107), resulting in benefits to the final part produced, such as a greater surface finish, better final surface accuracy, and a reduced probability of containing manufacturing defects.

[0021] As can be seen from Figures 5, 6 and 7, the multi-laser system (100) for additive manufacturing of the present invention is equipped with a fume extraction and support gas injection system (105) that defines the working sector (112) by a central diffusion element (108) suitable for introducing process gases into said specific processing sector (112), and two suction side elements (109) designed to remove fumes resulting from the process from said sector (112), said central diffusion element (108) and said suction side elements (109) being movable laterally relative to said working surface (101) and operably connected to said working surface (101).

[0022] In particular, with the help of electromechanical actuators designed to expose the working sectors (113) and (114) to the electromagnetic radiation (107) of the corresponding module (111), by means of a translation system along the X-axis, the fume extraction and support gas injection system (105) can ensure maximum layer performance of the flow, thereby making it possible to complete the additive manufacturing process in the working sectors (113) and (114), in order to produce an object free from residual stresses, internal defects and inclusions in layers or within layers (for example porosity or structural interruptions in the area of the welded surface) that contribute to impairing the structural integrity and performance of the final part, and the fume extraction and support gas injection system (105) can locally introduce the gases required for the process onto the working surface (101) and locally suck out process fumes from the working surface (101).

[0023] The translation process is performed in combination with a doctor blade or recoater (104) located at one end of the work surface (101) and equipped with optical or capacitive proximity sensors necessary to control the relative movement between said doctor blade (104) and the system for sucking fumes and introducing support gas (105), these movements being managed by a control unit (120) operatively connected to the machine tool.

[0024] Advantageously, as can be seen from FIG. 7, the fume suction and support gas injection system (105) is designed to translate in the X direction from the work surface (101) towards the edge and in the opposite direction relative to the doctor blade (104) to enable the passage of said doctor blade (104) within said work surface (101) and said doctor blade (104) to spread the powder.

[0025] Furthermore, the system (105) for suction of fumes and introduction of support gas is designed to translate in the X direction towards the edge of the working surface (101) and in the opposite direction to the doctor blade (104) to allow the passage of the doctor blade (104) over the working surface (101) and to allow the dispersion of powder by the doctor blade (104).

[0026] The multi-laser system (100) for additive manufacturing is designed to be versatile depending on production needs and includes: directing a doctor blade (104) along a work surface (101) in the X direction, spreading the powder bed (102) over the edge of said work surface (101); positioning a gas suction and suction system (105) above the powder bed (102) on the work surface (101); arranging the laser source and the independent optical system (103) or a separate module (111) to be switched on, and directing the laser beam (107) to a working sector (112) located between the central diffusing element (108) and the two suction side elements (109); translating the gas intake and suction system (105) along the X-axis above the powder bed (102) and exposing the working sectors (113) and (114) to electromagnetic radiation (107) for additive manufacturing applications; translating the gas suction and suction system (105) in the X direction towards the end of the working surface (101) in the opposite direction to the doctor blade (104) and moving the piston (106) downwards in the Z direction; turning off the laser source during the passage of the doctor blade (104) to spread the powder on the work surface (101); positioning a gas intake and suction system (105) on said work surface (101) and activating a laser source; Includes.

Claims

1. A work surface (101) operably connected to a piston (106) and designed to accommodate a powder bed (102); a matrix of independent optical systems (103) designed to transmit electromagnetic radiation beams (107) to a predetermined area of the work surface (101), the matrix of independent optical systems (103) being capable of overlapping the electromagnetic radiation beams (107) in a range of 50% to 100% in the predetermined area of the work surface (101), the matrix of independent optical systems (103) being connected to an upper surface of the machine tool; a system (105) for suction of fumes and introduction of a support gas, the system (105) for suction of fumes and introduction of a support gas being designed to translate in an X direction from the work surface (101) towards the edge and in the opposite direction relative to a doctor blade (104) to allow passage of the doctor blade (104) over the work surface (101) and to allow the doctor blade (104) to spread powder in the powder bed (102); A multi-laser system (100) for additive manufacturing, comprising:

2. 2. A multi-laser system (100) for additive manufacturing according to claim 1, characterized in that the matrix (103) of independent optical systems is scalable and modularized in a number of modules (111) of laser and optical systems and / or galvanometric scanning systems corresponding to the working area required to perform the additive manufacturing process.

3. 2. A multi-laser system (100) for additive manufacturing according to claim 1, characterized in that the autonomous module (111) is designed with at least four lasers, each of which emits a beam of electromagnetic radiation (107) capable of carrying out additive manufacturing in a corresponding area (119) of each working sector (112) with a total overlap of 100%.

4. 2. A multi-laser system (100) for additive manufacturing according to claim 1, characterized in that the autonomous module (111) is designed with at least four lasers, each of which emits a beam of electromagnetic radiation (107) capable of carrying out additive manufacturing in corresponding areas (115), (116), (117) and (118) of each working sector (112) with a partial overlap of 50%.

5. 2. The multi-laser system (100) for additive manufacturing according to claim 1, characterized in that work sectors (112) are delimited by a system (105) for suction of the fumes and introduction of a support gas, the system (105) for suction of the fumes and introduction of a support gas being operatively connected to the work surface (101).

6. A multi-laser system (100) for additive manufacturing as described in claim 1, characterized in that the system (105) for suction of fumes and introduction of support gas comprises a central diffusion element (108) suitable for the process gas in the working sector (112) and two suction side elements (109) designed to remove fumes resulting from the process from the working sector (112), the central diffusion element (108) and the suction side elements (109) being operably connected to the working surface (101).

7. A multi-laser system (100) for additive manufacturing as described in claim 1, characterized in that the system (105) for suction of fumes and introduction of support gas is designed to perform a translational movement along the axis X necessary to expose the working sectors (113) and (114) to electromagnetic radiation (107) for additive manufacturing applications.

8. A multi-laser system (100) for additive manufacturing as described in claim 1, characterized in that the system (105) for suction of fumes and introduction of support gases is capable of locally introducing gases necessary for the process at the work surface (101) and locally extracting process fumes from the work surface (101).

9. 1. An additive manufacturing method performed using an additive manufacturing multi-laser system (100), wherein the additive manufacturing multi-laser system (100) is the additive manufacturing multi-laser system (100) of claim 1; The additive manufacturing method comprises: directing the doctor blade (104) along the work surface (101) in the X direction to spread the powder bed (102) over the edge of the work surface (101); positioning a system (105) for suction of the fumes and introduction of a support gas above the powder bed (102) on the work surface (101); arranging to switch on the laser source and the independent optical system (103) or separate modules (111) and directing the electromagnetic radiation beam (107) to a working sector (112) located between the central diffusing element (108) and the two suction side elements (109); translating the system for suction of fumes and introduction of support gas (105) along the X-axis above the powder bed (102) and exposing working sectors (113) and (114) to electromagnetic radiation (107) for additive manufacturing applications; translating the system for suction of fumes and introduction of support gas (105) towards the edge of the work surface (101) in the X direction, opposite to the doctor blade (104), and moving the piston (106) downwards in the Z direction; turning off the laser source during the passage of the doctor blade (104) to spread the powder on the work surface (101); placing a system (105) for suction of the fumes and introduction of a support gas on the work surface (101) and activating a laser source; 1. An additive manufacturing method comprising:

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