Additive manufacturing process for a component marked with at least one individual marking

Abstract

Additive manufacturing process for a component (10) provided with at least one individual marking (20), comprising at least the following steps: a) Creation of an electronic volume model (1) for the component (10); b) Defining a base plane (3) on the volume model (1) and dividing the volume model (1) into a plurality of layers, each having a manufacturing layer height h0; c) Generation of a sequence of layer data sets (4.1,..., 4.n) wherein in each of the layer data sets (4.1,..., 4.n) at least one area to be filled by an additive manufacturing device is defined; d) Transfer of the sequence of layer data sets (4.1,..., 4.n) to the additive manufacturing device and manufacturing of the component by sequential processing of the layer data sets in the manufacturing device, wherein at least one marking area (2) for applying the at least one individual marking (20) is determined on the volume model (1) of the component (10), and wherein, based on the position and / or orientation of the marking area (2) with respect to the base plane (3) and the extent of the marking area (2), the marking layers touching the marking area (2) are determined from the set of all layers; characterized in that, - that a suitable marking area (2) is preselected using software on the volume model (1), wherein a software-supported preselection is based on a comparison of the angle α between a normal vector of a build platform (44) on the manufacturing machine and the respective normal vectors of the individual facets of an STL data set, wherein this comparison: ▪ preferred areas (41) with 5° < α ≤ 90° or -5° > α ≥ - 90°, ▪ Offered areas (42) with 0° < α ≤ 5° or 0° > α ≥ -5° and ▪ Neglected regions (43) with 90° < α ≤ 180° or -90° > α ≥ -180° are formed - that in the respective layer data set (4.4, 4.5) at least one data change is made for the addition or subtraction of a partial area to or from the layer of each of the marking layers, and an individual marking layer data set (5.4, 5.5) is formed from this; - that in the sequence of layer data sets (4.1,..., 4.n) to be transferred to the additive manufacturing device, the layer data sets (4.4, 4.5) assigned to the marking layers are exchanged for the marking layer data sets (5.4, 5.5) and - that additive manufacturing is carried out with the modified sequence of layer data sets (5.1, ..., 5.6).

Description

[0001] The invention relates to an additive manufacturing process for a component provided with at least one individual marking, comprising the features of the preamble of claim 1.

[0002] Many components are individually marked, whether to prevent counterfeiting, to apply legally required markings for a specific sales region, or to guarantee traceability in case of defects. These markings are typically applied in a downstream process step, such as by affixing a label, printing, or altering the surface using laser marking, engraving, etching, etc., to create a visible mark on the component. This downstream direct marking requires several process steps for handling and product identification itself. Each process step inherently carries a risk of errors, inevitably increasing the overall error rate of the entire process chain and thus jeopardizing added value.Furthermore, the product is not marked from the very beginning of its creation, meaning that guaranteed end-to-end traceability is not possible, nor is there secure, legally admissible documentation of the manufacturing process chain. In particular, markings intended for authentication, such as those embedded inside the component, are no longer feasible in subsequent process steps. The disadvantages of the aforementioned marking solutions consist primarily of additional effort, an increased error rate, and limited functionality.

[0003] In an additive manufacturing process, also known as 3D printing, it is advantageous to create a so-called additive direct marking directly during component production.

[0004] A manufacturing process of the type mentioned above, as described for example in DE 10 2018 204 510 A1, is characterized by the fact that a marking is created directly during the additive manufacturing process together with the component and is inseparably connected to it, without the need for subsequent process steps for marking.

[0005] Up to now, additive direct markings have been created by embedding the markings into the digital 3D CAD data, provided this data exists as a solid model or as a complete description of the surface of the planned component. This requires further steps for manufacturing preparation, such as the generation of layer data. For example, for a serialized small series of 100 components, 100 individualized data sets exist. Their individuality, or deviation from the solid model created for component manufacturing, consists solely of the additional marking elements, which as such form at least one body that is merged with the component body by adding or subtracting volume elements. If the components are to be manufactured using a process that requires support structures, a solid model or a complete description of the surface of the planned component is required for each of the 100 data sets.Another electronic component description is generated as a support structure. Subsequently, for each individual volume model, a sequential series of layer data sets is calculated in a process called "slicing" and transferred to the manufacturing machine for the additive manufacturing of the component, including the direct marking. The disadvantages of this method of applying a direct marking to a component therefore lie in the significant resource requirements in terms of storage space, computing power, and time.

[0006] To illustrate the problem, the following examples are provided: A component measuring 40 mm × 40 mm × 40 mm is manufactured using an extrusion deposition process, divided into 400 layers, each 100 µm thick. If a serialized code measuring 7 mm × 7 mm and 0.2 mm deep needs to be integrated—that is, embossed, stamped, or underprinted—onto a vertically oriented surface within the build space, this serialization only affects 7 of the 40 mm component height, and thus only 70 of the 400 layers. Therefore, calculating the adaptation of the entire solid is unnecessary. - Laser beam melting of metals often involves layer thicknesses between 20 and 50 µm, so that while the ratio between the layers relevant for component identification and the entire component remains identical, the effort required for calculation increases many times over due to the high number of layers.

[0007] DE 10 2018 212 496 A1 discloses a method for manufacturing individually marked components. The identifying element is formed as a surface contour, in particular with raised areas and / or recesses. A computer program used for manufacturing components is modified so that an individually identifying element is formed on each individual component. By creating the encoding for the individual identifying elements and implementing it in an (STL) file for the creation of new (STL) files, an individual identifying element can be achieved for each component. This involves a data modification to generate a marking layer dataset. The modification of the STL file also entails the insertion or modification of vectors. However, the user must specify how and where the marking is to be placed.

[0008] The object of the invention is therefore to improve an additive manufacturing process for a component bearing an individual marking in such a way that the manufacturing can be carried out faster and / or with less computing power and storage space.

[0009] This problem is solved by an additive manufacturing process for a component bearing an individual marking and having the features of claim 1.

[0010] In the present invention, the term "volume model" is used as a generic term for all electronic data suitable for describing and, if necessary, visualizing the overall geometric structure of the component body and which has not yet been prepared with regard to a specific machine intended for manufacturing. This includes volume models in the narrower sense of CAD technology as well as mesh models that enclose the surface of the component to be manufactured.

[0011] A "layer" or "slice" refers to the section of a component that can be produced in a single manufacturing plane of an additive manufacturing machine, also known as a "3D printer," without moving the machine's vertical Z-axis. This section is parallel to the reference plane and has a height corresponding to the layer thickness achievable in a single manufacturing plane using the given manufacturing process. The sum of all layers produced on top of each other results in the creation of the complete component.

[0012] The invention provides for a direct influence on the manufacturing process by redirecting layer contours generated generically for the component and the resulting hatching. "Hatching" refers to those areas within a manufacturing plane that are filled with the material during additive manufacturing, while the remaining areas remain unfilled.

[0013] An individual marking produced according to the invention significantly reduces the subsequent process steps required in digital manufacturing preparation. Nevertheless, traceability from the physical product to its digital twin is enabled from the very first moment of component production. The creation of a marking according to the invention can be described as component identification, e.g., through serialization, and authentication, e.g., through hidden markings.

[0014] A further advantage of the manufacturing process according to the invention is that the individual marking on the component is more precise in shape and position than when merging a volume model for the component with another volume model for the marking, as is conventionally practiced, because errors can occur during the merging, especially in the edge areas of the marking.

[0015] According to the invention, however, markings are always implemented as multiples of a layer thickness and therefore always have sharp boundary edges, which can also be visualized beforehand.

[0016] In contrast, the serialization of the layered basic data is fully automated. An algorithm generates the layers affected by product identification ("marked") for each component and combines them with the "non-marked" areas of the basic data.

[0017] According to the invention, identifying and / or authenticating direct markings can be embedded in the component. Identifying features serve to transmit information, for example, a serial or batch number or a manufacturing date. These markings replace a printed label, a sticker, or a laser marking.

[0018] Authentication markings serve to guarantee the authenticity of the component. Any module geometry can be used to represent machine-readable matrix codes that are not feasible with conventional manufacturing processes and are not readily apparent to the user, thus providing a novel form of anti-counterfeiting protection. These markings can be, in particular, raised features that would be impossible to demold using conventional casting methods for plastics and metals.

[0019] The authenticating features do not necessarily have the same reference plane as is possible according to the prior art. The layer-by-layer generation of the individual module geometries provided for in the invention allows elements to be placed on different reference planes or even on curved surfaces without negatively affecting readability.

[0020] Because the invention allows direct control over each individual point in a layer intended for marking, not only does the contour of the markings applied externally to the component appear sharper, but it also enables a sharply defined marking within the filled component volume that is invisible from the outside and only visible through special analysis methods. For example, in a manufacturing machine that allows layer production with more than one component, a marking containing ferromagnetic particles can be applied. To read a hidden serial number, the component can be partially magnetized and coated with iron powder.

[0021] It is also possible to place a marking very close to the component surface and / or to apply several markings directly on top of each other or with a separating layer only a few layer thicknesses high. If, for example, a surface-visible marking is mechanically removed, e.g., by grinding, another marking appears underneath. Overlapping markings can also combine to form a motif, as on counterfeit-proof banknotes, if transparent or semi-transparent markings are applied to the outside, or if the outermost marking consists of a subtraction, i.e., a recess that reveals the layer behind it.

[0022] Such a double marking cannot be subsequently altered on an original component. Even with a replica component manufactured using an original template and the inventive manufacturing process, or with a different support structure, it cannot be precisely reproduced unless the original volume model or the original sequential sequence of layer data sets can be accessed. Minute dimensional deviations that occur during reverse engineering may not change the appearance or function of the component, but at least lead to minimal shifts and changes in the markings, with these errors becoming particularly visible when two markings complement each other. This results in a high level of counterfeit protection, for example, for safety-relevant vehicle parts.Before installation, the internal marking, similar to a ruble ticket, can be exposed by removing a thin outer layer to verify the authenticity of the component.

[0023] If an interface exists between an electronic work preparation device and a manufacturing machine that allows direct access to the memory of the manufacturing machine, the marking-specific layer data sets can be selected directly in the memory of the manufacturing machine and exchanged for the marking layer data sets generated individually for each component to be manufactured, before production is started.

[0024] If no such interface exists, the exchange of individual layer data sets for the marking layer data sets is carried out in advance, and before each start of component production, the modified sequential sequence of layer data sets is completely transferred to the manufacturing machine.

[0025] The invention is explained in more detail below with reference to an exemplary embodiment and the drawings. The figures each show a schematic representation of: Fig. 1 a sequence of manufacturing steps; Fig. 2A, Fig. 2B each one stack of shift data records; Fig. 3 an illustration of the software-supported selection of a marking area and Fig. 4A, Fig. 4B each a block diagram to describe the process flow;

[0026] Fig. Figure 1 shows a schematic sequence of the steps provided for in the method according to the invention. First, an electronic volume model 1 is created for the component to be manufactured. A base plane 3 is then defined on this model. The base plane 3 corresponds to the plane of the receiving surface on the manufacturing machine intended for additive manufacturing. The marking area 2 is selected for applying an individual component marking.

[0027] In a subsequent calculation step, the volume model 1 is decomposed into a multitude of layer data sets 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, each with a height h0. Each of these layer data sets 4.1,..., 4.6 contains data to produce a single layer in the additive manufacturing machine, the so-called 3D printer, by material deposition or material curing. The Z-axis of the manufacturing machine is then adjusted so that the tool head is positioned above the previously produced layer and builds the next layer upon it.

[0028] By means of the marking area 2 on the volume model 1, two of the layer data sets 4.4, 4.5 are selected and shown schematically in the diagram. Fig. 1 is marked by a thick border line. Only these layer data sets 4.4 and 4.5 enter the manipulation process illustrated in the middle, in order to directly insert data for creating the desired component marking into the respective layer data set.

[0029] An example of a single layer data set 4.4 is shown. According to the CLI / SLI protocol, widely used in additive manufacturing, layer data set 4.4 contains at least one vector that defines a contour to be manufactured. For illustrative purposes, the vector here describes a rectangular contour that is part of the cuboid modeled in volume model 1. By definition, material is then applied either to the left of the vector or omitted to the right.

[0030] According to the invention, at least one vector 6.4 is inserted into the data of layer data set 4.4, or at least one vector is modified, to create the data for forming the individual marking. This results in the formation of a new marking layer data set 5.4. The same applies to layer data set 4.5, which is generated for the next layer located in marking area 2; a new marking layer data set 5.5 is also formed from this. The two modified marking layer data sets 5.4 and 5.5 are inserted into the stack as replacements for the original layer data sets 4.4 and 4.5. The other layer data sets 4.1, 4.2, 4.3, and 4.6 lie outside marking area 2 and are incorporated unchanged into the new sequence of layer data sets 5.1, ..., 5.6.

[0031] The sequence of layer data sets 5.1, ..., 5.6 is processed in the additive manufacturing machine, producing a component 10 corresponding to the original volume model 1, which additionally contains an integrated individual marking 20.

[0032] The Fig. 2A and Fig. Figure 2B shows, in schematic view, a stack of 7', 7" layer data records each, containing information for a concave, impressed mark ( Fig. 2A) or a raised, convex marking ( Fig. 2B), where the marking on the finished component is hemispherical.

[0033] The representation in Fig. Figure 3 illustrates how a suitable marking area 42 can be selected on the volume model 40 using software.

[0034] For components where the placement of the marking is not limited by optical or functional constraints, this selection allows the marking area to be chosen so that only a few layer data records need to be converted into marking data records.

[0035] The semi-automatic selection process is algorithmically supported in that surfaces suitable for the selected marking type and the build direction within the additive manufacturing system are pre-selected after checking the space requirements and only need to be approved by the user. A fully automated process is not advantageous here, as the marking itself can introduce weak points into the component, and therefore the surface selection must only be made taking the load cases into account.

[0036] The software-supported pre-selection is based on a comparison of the angle α between a normal vector of a build platform 44 on the manufacturing machine and the respective normal vectors of the individual facets of an STL dataset. This comparison generates: - preferred ranges 41: 5° < α ≤ 90° ∨ -5° > α ≥ -90° - Offered ranges 42: 0° < α ≤ 5° ∨ 0° > α ≥ -5° - neglected regions 43: 90° < α ≤ 180° ∨ -90° > α ≥ -180°

[0037] The Fig. 4A and Fig. Figures 4B each show a block diagram illustrating a preferred embodiment of the method, wherein in Fig. 4A the preparatory steps are shown and in Fig. 4B those who describe the manufacturing of the component including at least one individual marking.

[0038] The preparation process essentially determines: - the orientation of the volume model in relation to the base level 3 on the additive manufacturing machine; - the location of the marking area 2 on the volume model 1 and - Form and content of the individual marking.

[0039] According to the described and in Fig. The preparatory steps shown in 4A lead to the transition to the steps described in Fig. The steps shown in Figure 4B are described. The invention provides for marking, during the subdivision of the CAD base data into a sequence of layer data sets, the so-called "slicing," areas of layer data sets that actually need to be modified to form the marking. For this purpose, the lower and upper limits of the marking area are determined with respect to the base plane, and then each layer data set is checked to see if it lies within these limits. Layer data sets lying outside these limits are categorized as "non-marked" and remain unchanged.

[0040] Layer datasets lying within the boundaries are modified and / or supplemented with additional data (see vector 6.4 in Fig. 1) to marking layer datasets. In vector-based formats such as the STI / CLI format, intersection points are determined between a vector that is part of the individual marking and the vector describing the basic contour of the component.

[0041] As in Fig. As illustrated in Figure 1, the vector 4.4 describing the base contour is essentially opened between these intersection points and supplemented by the vector 6.4 describing the marking. This process is repeated as long as marking data is available for the layer that needs to be incorporated. Only then is the marking layer data set 5.4 complete, which is then inserted into the sequence of layer data sets 5.1, ..., 5.6.

[0042] Before the combined layer data sets (slices) are transferred and the additive manufacturing process begins, a check routine can be performed to determine whether all vectors in the layer are closed again after the marking data has been incorporated, thus preventing interruptions during component production. If necessary, the healing can be achieved automatically by connecting any exposed ends, or an error message can be displayed and user input awaited.

Claims

[1] Additive manufacturing method for a component (10) provided with at least one individual marking (20), comprising at least the following steps: a) creating an electronic volume model (1) for the component (10); b) defining a base plane (3) on the solid model (1) and dividing the solid model (1) into a plurality of layers, each having a manufacturing layer height h0; c) generating a sequence of layer data sets (4.1,..., 4.n), wherein in each of the layer data sets (4.1,..., 4.n) at least one area to be filled by an additive manufacturing device is defined; d) transferring the sequence of layer data sets (4.1,..., 4.n) to the additive manufacturing device and manufacturing the component by sequentially processing the layer data sets in the manufacturing device, wherein at least one marking region (2) for applying the at least one individual marking (20) is determined on the volume model (1) of the component (10), and wherein the marking layers touching the marking region (2) are determined from the set of all layers based on the position and / or orientation of the marking region (2) with respect to the base plane (3) and the extent of the marking region (2); characterized by , - that a suitable marking area (2) is preselected on the volume model (1) with the aid of software, wherein a software-supported preselection is based on a comparison of the angle α between a normal vector of a construction platform (44) on the production machine and the respective normal vectors of the individual facets of an STL data set, wherein by means of this comparison: ▪ preferred areas (41) with 5° < α ≤ 90° or -5° > α ≥ - 90°, ▪ offered ranges (42) with 0° < α ≤ 5° or 0° > α ≥ -5° and ▪ Neglected areas (43) with 90° < α ≤ 180° or -90° > α ≥ -180° are formed - that in the respective layer data set (4.4, 4.5) of each of the marking layers, at least one data change is made to add or subtract a partial area to or from the layer, and an individual marking layer data set (5.4, 5.5) is formed therefrom; - that in the sequence of layer data sets (4.1,..., 4.n) to be transferred to the additive manufacturing device, the layer data sets (4.4, 4.5) assigned to the marking layers are exchanged for the marking layer data sets (5.4, 5.5) and - that additive manufacturing is carried out with the modified sequence of layer data sets (5.1, ..., 5.6). [2] Manufacturing method according to claim 1, characterized by that the sequence of layer data sets (4.1,..., 4.6) is transferred to a memory of the production machine and before each production of a component (10) the layer data sets (4.4, 4.5) assigned to the marking layers are exchanged in the memory for individual marking layer data sets (5.4, 5.5). [3] Manufacturing method according to claim 1, characterized bythat before each production of a component (10), the layer data sets (4.4, 4.5) assigned to the marking layers are exchanged for individual marking layer data sets (5.4, 5.5) and the thus modified sequence of layer data sets (5.1,...,5.n) is transferred to the production machine. [4] Manufacturing method according to one of claims 1 to 3, characterized by that a concave, embossed mark or a raised, convex mark is formed.

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