Additive manufacturing method for parts that produces parts by depositing at least one material in the form of droplets

Abstract

The present method is a method for creating a part by depositing at least one material in the form of droplets, wherein the droplets are arranged in a parallel arrangement and / or in an upper and lower layered arrangement, and immediately after individual droplets are deposited, a step of smoothing the surface by applying a laser beam to the ridges of each ply to smooth the surface, thereby removing material from the ridges so that the surface roughness is reduced to a predetermined level, and / or lowering the viscosity and / or surface tension of each material in the area surrounding the pinch-shaped depressions to flow the material for at least partial filling of the depressions. Alone or in addition thereto, locally defined material removal may be performed to set surface characteristics in a targeted manner or to form a structure of lower dimensions than the resolution capability of the additive process for deposited droplets having a larger diameter, and curing, melting, degreasing, and / or sintering are performed to complete a specific part.

Description

Technology Field

[0001] The present invention relates to an additive manufacturing method for producing a part by depositing at least one material in the form of a droplet. This falls under the field of additive manufacturing and is suitable for the production of parts manufactured using various materials, such as composite parts. Background Technology

[0002] To date, methods for producing parts by arranging individual droplets in parallel and / or vertical directions have been known. Droplets with appropriate consistency and viscosity are deposited drop by drop from a nozzle or through a pressure device, and a three-dimensional part can be obtained after curing or sintering.

[0003] Typical droplet sizes range from 200 μm to 500 μm, which limits resolution in additive manufacturing using droplets. Due to the individual deposition process, the viscosity of individual droplets, and surface tension, gussets are formed between adjacent and / or overlapping droplets by depressions at the edges of individual droplets and ridges between droplets, which degrades surface quality and results in the finished part having a relatively rough surface.

[0004] To address these drawbacks, mechanical post-processing performed after drying, curing, or sintering is time-consuming, typically requires additional plant technology at a different location, and necessitates the removal of solid materials, resulting in high costs. Some areas of parts manufactured in this manner may be inaccessible or extremely difficult from the outside, making surface finishing impossible or highly complex. These may be cavities or undercut areas. The problem to be solved

[0005] Therefore, the objective of the present invention is to reduce the effort associated with the process by specifying the possibility of improving / targeting the surface quality of parts produced using an additive manufacturing process in which material is deposited drop by drop. Additionally, it is to produce part structures having finer and more sophisticated dimensions and structural elements. means of solving the problem

[0006] This objective is achieved according to the invention by a method having the features of claim 1. Advantageous embodiments and improvements of the invention may be implemented by features described in dependent claims. Specific details for implementing the invention

[0007] In this method, droplets are arranged in parallel and / or in upper and lower layered arrangements. Immediately after individual droplets are deposited, the surface is smoothed using the energy of a laser beam focused on the ridges formed on the droplets. The sidewalls of the deposited droplets may also be smoothed.

[0008] Therefore, the laser beam is focused immediately after deposition, before additional processing, particularly drying, hardening, melting, or sintering, is performed.

[0009] Smoothing can be performed in the following ways.

[0010] Material is removed from the raised area so that the surface roughness is reduced to a specified level. Material removal can preferably be achieved by ablation or sublimation.

[0011] Either alone or in addition to material removal, the individual materials are flowed for at least partial filling of the depression by lowering the viscosity and / or surface tension of each material in the regions surrounding the pinch-shaped depression formed between parallel individual droplets, through the energy of a laser beam focused on the regions of droplets arranged parallel to the depression adjacent to it, so that the surface roughness is reduced to a predetermined level. Thus, the material can be flowed through a locally defined temperature rise to reduce the droplet depth and volume of the depression and smooth the surface.

[0012] As another alternative according to the present invention, which may be performed in combination with at least one of the previously mentioned alternatives, locally defined material removal is performed to finely adjust surface characteristics or to form a structure of lower dimensions than the decomposition capability of the deposition process for deposited droplets having a larger diameter.

[0013] Then, hardening, melting, or sintering is performed to complete each part.

[0014] The material used to form the droplets may be a polymer and / or solid-containing suspension. Polymers include numerous organic compounds, including copolymers and monomers. Suspensions may be formed with a liquid containing solid particles or fibers and one or more organic binders. Viscosity and surface tension must be maintained at the corresponding processing temperature during droplet deposition so that droplets can form and the material does not flow out.

[0015] Droplets of different materials can be arranged in parallel directions and / or in the up and down directions.

[0016] In the raised area, after droplets are deposited in at least one ply forming each layer, fluidization of the material may be performed for the removal of the material and / or at least partial filling of the depression. However, this may also be performed after a predetermined number of plies (e.g., 3 or 5 plies) have been stacked.

[0017] Advantageously, material removal from the ridge and / or fluidization of the area surrounding the depression can be performed in a controlled manner. The surface topography can be detected by at least one optical sensor and may be influenced by a spatially resolved height value, a deflection shift of the laser focus, and preferably the power density of the laser beam focus. The deflection shift of the focus may be caused by the relative movement of the laser beam having an optical axis with respect to the surface of each part, i.e., at least two-dimensional movement of the building platform manufactured by adding each part. However, the laser beam may also be deflected using appropriate optical elements and, if necessary, its shape may be changed.

[0018] Since the locations of the ridges and depressions can be determined when recording the surface topography, a biased movement of the material can be performed to the area surrounding each ridge and / or pinch-shaped depression from which the material is to be removed, and this can be performed in one or more dimensions using a so-called scanner.

[0019] In particular, the surface topography can be determined by at least one optical sensor and used for control. The temperature is measured additionally, preferably non-contactually, for the focal application area, and the measured temperature influences the retention time at a specific location, the power density of the focal point, and the size of the instantaneous focal area. This is not only advantageous when removing material. It can also be used to smooth the surface by inducing fluidization to fill depressions, by influencing the determination of the advantageous temperature for each droplet material area.

[0020] The temperature must be determined locally or selectively so that locally defined control can be performed.

[0021] In particular, for materials that are difficult to impart fluidity to due to their consistency characteristics, the material of the droplet can be softened using laser beam energy, and then mechanical deformation can be achieved by applying or attaching a forming tool to achieve the desired plastic deformation, and the surface can also be smoothed during this process.

[0022] After creating layers or applying material to each layer, green processing can be performed directly through laser removal ablation or fluidization treatment. Surface roughness can be significantly reduced, and the surface can be smoothed.

[0023] If necessary, specific geometric features much smaller than the resolution limit of the drop-by-drop application process can be generated by forming contour elements smaller than 50 μm instead of smaller than 500 μm through locally defined material removal.

[0024] Furthermore, direct integration of green processing is possible by machining all surfaces, including the internal surfaces of each component. By processing immediately after the first material is deposited without significant time delay, boundaries between different individual deposited droplets, as well as boundaries between different materials when droplets of different substances are deposited, can be designed more precisely.

[0025] Significantly improved surface quality and interface geometry can be formed at droplet interfaces with minimal additional effort required to integrate laser processing.

Claims

Claim 1 An additive manufacturing method for forming a part by depositing at least one material in the form of droplets, wherein the droplets are arranged in an adjacent and vertical layered arrangement, comprising: a step of smoothing the surface using the energy of a laser beam focused on the ridges of each ply immediately after individual droplets are deposited, the step of removing material from the ridge regions so that the surface roughness is reduced to a predetermined level; a step of flowing the materials to at least partially fill the ridges by lowering the viscosity and surface tension of each material in the regions surrounding the pinch-shaped depressions formed between the adjacent individual droplets through the energy of the laser beam focused on the regions of droplets arranged in an adjacent direction adjacent to the depressions so that the surface roughness is reduced to a predetermined level; and a locally defined material removal step to specifically adjust surface characteristics or to form a structure with dimensions lower than the resolution of the additive droplet deposition process for deposited droplets having a larger diameter. An additive manufacturing method in which, after a step of smoothing the surface, a step of hardening, melting, or sintering is performed to complete each part. Claim 2 A method for manufacturing additively according to claim 1, wherein a polymer and / or solid-containing suspension is used as the material forming the droplets. Claim 3 A method for manufacturing additively, wherein the step of removing material from the raised region and the step of fluidizing material for at least partial filling of the recessed region are performed after at least one layer of droplets for forming each layer has been deposited. Claim 4 A method for manufacturing additively, wherein, in paragraph 3, the step of removing material from the raised region and the step of fluidizing the material for at least partial filling of the recessed region are performed after a predetermined number of layers forming a layer have been deposited. Claim 5 delete Claim 6 An additive manufacturing method according to any one of claims 1 to 4, wherein the step of removing material from the raised region and the step of fluidizing the material for at least partial filling of the depression are performed in a controlled manner, and the surface topography is detected by at least one optical sensor and is influenced by a spatially resolved height value, a deflection movement of the laser beam focus, and additionally the power density of the laser beam focus. Claim 7 In claim 6, for the above control, the temperature is determined by a spatially resolved method or selectively determined, an additive manufacturing method.