Inspection system and method for in situ detection of features in solidified powder materials

Abstract

The present invention relates to an inspection system (200) for in-situ detection of features (114, 116) in a solidified powder material (104) by a high-energy beam (128), the inspection system (200) being disposable on a moving unit (110), the inspection system (200) comprising an eddy current inspection unit (202) arranged and configured to detect material features of the solidified powder material (104) by eddy current inspection and capable of detecting electrical conductivity differences in the solidified powder material (104) to identify the features (114, 116) during additive manufacturing, the inspection unit (202) comprising a first eddy current sensor unit (210) arranged and configured to identify features having a first feature size equal to or greater than a size threshold, particularly a single defect, and a second eddy current sensor unit (230) arranged and configured to identify a collection of features having a second feature size smaller than the size threshold, particularly a porous defect region.

Description

[Technical Field]

[0001] The present invention relates to an inspection system and method for in-situ detection of properties in solidified powder materials, and to a manufacturing system. [Background technology]

[0002] Inspection systems for in-situ detection of properties in solidified powder materials are known in principle. During additive manufacturing of parts from powder materials, the powder material is solidified to produce the part layer by layer. The powder material can be solidified, for example, by a high-energy beam, in particular a laser beam, or by a binder.

[0003] Thermography can be used to detect defects, for example, but the amount of data is so large that real-time evaluation is impossible or only possible to a limited extent. Furthermore, repeatable testing is not possible. Furthermore, particles in the beam path can falsify the results. Another drawback of thermography is that the required test setup is relatively expensive.

[0004] Furthermore, it is possible to test solidified powder materials using ultrasound. One drawback of the ultrasonic method is that the achievable test resolution is usually insufficient. In addition, the ultrasonic probe can only be placed below the base plate, so limited accessibility must be taken into account.

[0005] Computed tomography can usually be used to accurately determine defects. However, computed tomography cannot be applied in the field, is relatively expensive, and requires radiation protection during testing.

[0006] Acoustic emission analysis can usually be used to detect defects, but the exact location of the defect can only be determined to a limited extent. Furthermore, repeat testing is usually not possible. Furthermore, hidden defects cannot be detected using optical methods.

[0007] US Patent Application Publication No. 2016 / 9215 discloses a system for non-destructive testing of parts produced by additive manufacturing, in which an electromagnetic field is applied. In this case, eddy current testing is performed, but a structure is proposed that provides limited spatial resolution, making it impossible to accurately determine defects of different configurations in the solidified powder material.

[0008] DE 102016201290 A1, DE 102011111818 A1, EP 3632595 A1 and US 2018 / 0264590 A1 disclose devices for the additive manufacturing of parts with an inspection unit. Summary of the Invention [Problem to be solved by the invention]

[0009] The industry demands additive manufacturing processes with low reject rates and high quality, especially to reduce downstream inspection efforts. In particular, computed tomography, currently often applied to components in medical or aerospace technology, entails high costs and / or time commitments. Furthermore, because additive manufacturing offers certain advantages in terms of resource utilization, there is a demand for increasing process stability in additive manufacturing to a level comparable to that of conventional manufacturing.

[0010] It is therefore an object of the present invention to provide an inspection system and method for in-situ detection of properties in solidified powder materials, and a manufacturing system, that reduces or eliminates one or more of the above-mentioned disadvantages. In particular, it is an object of the present invention to provide a solution that allows reliable in-situ detection of properties in solidified powder materials. [Means for solving the problem]

[0011] This problem is solved by an inspection system and a method according to the features of the independent claims. Further advantageous embodiments of these aspects are set out in the respective dependent claims. The features disclosed in the claims, the description and the drawings can be individually combined with one another in a technically meaningful way, thereby showing further embodiments of the invention.

[0012] According to a first aspect, the above problem is solved by an inspection system for in-situ detection of features in solidified powder material, comprising an eddy current inspection unit that can be arranged on a mobile unit and that is arranged and configured to detect electromagnetic material features of the solidified powder material by eddy current inspection, so that electrical conductivity differences in the solidified powder material can be detected in order to identify the features, the inspection unit comprising a first eddy current sensor unit that is arranged and configured to identify features having a first feature size greater than or equal to a size threshold, in particular a single defect, and a second eddy current sensor unit that is arranged and configured to identify a second feature size less than the size threshold, in particular a collection of features having a porous defect area.

[0013] The present invention is based on the discovery that single defects and clusters of micro-defects are the most common causes of scrap in powder-based additive manufacturing. Furthermore, the present invention is based on the discovery that different eddy current-based mechanisms are required to test the above-mentioned features to ensure reliable identification. This discovery can be technically and advantageously utilized by using two different eddy current sensor units, i.e., first and second eddy current sensor units, configured to identify features having different feature sizes.

[0014] Thus, the inspection system allows for on-site adjustment, particularly correction, of identified characteristics, as described in more detail below. Furthermore, during production and after characteristic detection, a construction sequence or part can be stopped, so that cost-intensive additive manufacturing is stopped after the production of an unadaptable or uncorrectable characteristic. Additionally, the inspection system offers the advantage that complex inspection steps are not required after the part is completed, which typically involves high costs with computed tomography.

[0015] Another advantage of eddy current methods is that the amount of data generated is so small that data evaluation can be performed during the additive manufacturing process, allowing process control systems based on the inspection system's results to be designed in real time. Furthermore, properties can be assigned layer by layer. Furthermore, on-site recording of properties can be used to derive correlations between properties and applied process parameters, as well as between process conditions determined by sensors in the manufacturing system, thereby optimizing the additive manufacturing process. This can be done, for example, using artificial intelligence. Furthermore, the process can be loop-controlled on-site, as described in more detail below. Additionally, process interruptions and cancellations are reduced by increasing process stability. Furthermore, such testing enables digital manufacturing documentation.

[0016] The inspection system is designed to detect characteristics in situ within a solidified powder material. A solidified powder material refers to any powder material whose powder particles are at least partially bonded together. For example, the solidified powder material can be formed by bonded and / or glued powder particles. The solidified powder material is particularly configured to be electrically conductive and / or ferromagnetic. In situ testing and detection of characteristics is particularly understood to refer to testing during the process of manufacturing a part from the powder material, for example, at one or more points between the production of the first and last layers of the part.

[0017] In principle, characteristics are understood to mean all properties of the solidified powder material. Characteristics may be, for example, inhomogeneities or anomalies. For example, characteristics may be incomplete melting, gas holes, microporosity, cavities due to material properties, delamination, geometric deviations, poor surface quality, discoloration, and / or other properties in the material structure. Furthermore, characteristics may be the geometry, edge, or contour of the solidified powder material or part.

[0018] The inspection system is particularly configured for powder bed-based additive manufacturing processes. The inspection system is particularly suitable for additive layer manufacturing processes, such as selective laser beam melting (L-PBF), selective electron beam melting (E-PBF) or metal binder jetting (MBJ). The powder material can be solidified, for example, using a high-energy beam and / or a binder. The high-energy beam is preferably a laser or an electron beam. Consolidated powder material is particularly understood to mean a powder material whose powder particles are at least partially bonded to one another, in particular fused to one another.

[0019] The inspection system comprises an eddy current inspection unit, which is understood to be essentially an inspection unit configured to detect properties based on eddy current inspection, preferably arranged and configured to generate an alternating magnetic field that penetrates the surface to be inspected, generate eddy currents in the material, measure the response of this eddy current and use it for material testing.

[0020] The generated eddy currents are countered by their own magnetic fields, and these differences can then be detected by the inspection unit. In particular, eddy current inspection units can be used to detect differences in electromagnetic properties within solidified powder materials. For example, pores have a different conductivity than the solidified powder material that surrounds them. The detected conductivity differences can then be used to draw conclusions about the properties.

[0021] When the inspection system is used as intended, the inspection unit can, for example, induce eddy currents in the solidified powder material. The response of these eddy currents is then measured. Furthermore, changes in the eddy currents can be detected, and based on this, differences in conductivity can be detected. A corresponding evaluation of the detected differences in conductivity allows conclusions to be drawn about characteristics, particularly defects. As an alternative to the inspection unit that induces eddy currents, an additional excitation unit can also be provided.

[0022] The inspection unit can be arranged on a moving unit, which means in particular that the inspection unit is designed to be arranged on a moving unit that can move over the powder bed.

[0023] The eddy current inspection unit is configured to detect electromagnetic material properties of the solidified powder material by eddy current inspection, and thus, differences in electrical conductivity within the solidified powder material can be detected to identify the properties. It is particularly preferred that changes in the electromagnetic material properties are detected.

[0024] The inspection unit includes a first eddy current sensor unit. The eddy current sensor unit is particularly positioned and configured to identify features having a first characteristic magnitude equal to or greater than a size threshold during intended operation. In particular, the first eddy current sensor unit is positioned and configured to detect a single defect, such as a single pore. The first eddy current sensor unit is preferably positioned and configured to measure a magnetic field at the eddy current sensor unit that is affected by the flow of eddy currents in the solidified powder material. The eddy current path, which is disturbed by the feature of the solidified powder material, results in a measurement effect at the sensor. In particular, the first eddy current sensor unit is configured to identify larger features. Therefore, the first eddy current sensor unit is configured to identify features equal to or greater than a size threshold. The first eddy current sensor unit is preferably miniaturized. Preferably, the first eddy current sensor unit includes one, two, or more eddy current sensors.

[0025] The inspection unit also includes a second eddy current sensor unit. The second eddy current sensor unit is configured to identify a set of characteristics. The set of characteristics may be, for example, porosity formed by micropores. The second eddy current sensor unit is preferably configured to measure the impedance of the eddy current coil to detect changes in impedance caused by the opposing magnetic field of the eddy current. The second eddy current sensor unit preferably has integral behavior so that it can advantageously identify areas of defects. The second eddy current sensor unit is preferably miniaturizable. Preferably, the second eddy current sensor unit includes one, two, or more eddy current sensors.

[0026] The inspection unit, the first eddy current sensor unit, and / or the second eddy current sensor unit are or are preferably configured to generate a characteristic signal representative of the characteristic. A signal is understood to mean any type of information carrier. The characteristic signal can be configured, for example, as a data set. The characteristic signal is preferably provided permanently, such that a change in the characteristic signal indicates the characteristic.

[0027] In particular, signal intensity, preferably a constant signal intensity, can be used to draw conclusions about the properties of the solidified powder material. An offset in signal intensity can characterize a decrease in material density. To maximize this value, parameters can be modified to obtain optimal values, particularly to maximize the density of the component.

[0028] Furthermore, the inspection unit, the first eddy current sensor unit, and / or the second eddy current sensor unit are preferably configured to provide a characteristic signal to a control device, which is preferably adapted to identify and classify the characteristic, as described in more detail below, based on which the characteristic can be adapted, in particular corrected, if technically possible, as is possible with an adaptation signal, as described in more detail below.

[0029] The first eddy current sensor unit and the second eddy current sensor unit particularly have individual sensors arranged and configured to generate and provide a test signal capable of detecting a conductivity difference, thereby allowing the detection of an electromagnetic material property.

[0030] Preferably, the sensor data from the first eddy current sensor unit and the second eddy current sensor unit can be evaluated in a combined manner to enable improved detection of characteristics based on the combined evaluation, preferably by overlapping the sensor data and / or by data fusion, thereby extending the test stability of the test system.

[0031] Preferably, the first eddy current sensor unit has a first control unit, and / or the second eddy current sensor unit has a second control unit, and / or the inspection system has a controller adapted to recognize conductivity differences in the solidified powder material and identify a characteristic based on test signals from the first eddy current sensor unit and / or the second eddy current sensor unit, and the first control unit and / or the second control unit and / or the controller are preferably adapted to generate and / or provide a characteristic signal representative of the identified characteristic.

[0032] A preferred further development of the inspection system is characterized in that the first eddy current sensor unit and / or the second eddy current sensor unit are arranged and configured to provide sensor movement in a secondary direction oriented non-parallel to the main direction of the movement unit, in particular the feed direction. The first eddy current sensor unit and / or the second eddy current sensor unit are preferably arranged to be movable in the secondary direction. Alternatively or additionally, individual sensors of the first eddy current sensor unit and / or the second eddy current sensor unit can be arranged to be movable in the secondary direction. For example, the magnetic field sensors of the first eddy current sensor unit can be moved back and forth laterally during testing by a drive, in particular a linear motor, resulting in a zigzag movement during testing. This, for example, improves geometric testing. The technical effect of the secondary movement is, among other things, reduced directional dependency of resolution and improved resolution.

[0033] In order to improve the identification of characteristics, the first eddy current sensor unit preferably has excitation elements arranged in multiple rows, e.g. excitation wires, arranged so that they can bring about excitation currents oriented at an angle to each other.

[0034] In a preferred embodiment of the testing system, the first eddy current sensor unit has a first test resolution and the second eddy current sensor unit has a second test resolution, the first test resolution being higher than the second test resolution, in particular several times higher.

[0035] The first and second inspection resolutions are to be understood in particular as measures of the level of detail of the inspection performed using the first and second eddy current sensor units. The higher the inspection resolution of the eddy current sensor units, the more precise the inspection can be and the smaller the distinguishable features can be. Furthermore, the inspection resolution can be understood to mean the maximum measuring point distance.

[0036] The first inspection resolution is preferably less than 100 micrometers, and the second inspection resolution may be preferably less than 1 millimeter.

[0037] Another preferred configuration of the inspection system is characterized by a size threshold of 15 micrometers to 100 micrometers, in particular 20 micrometers to 50 micrometers. The selection of the first and second eddy current sensor units, which are distinguished by this size threshold and / or their local inspection resolution, has been found to be particularly suitable for detecting different characteristics in solidified powder materials.

[0038] In a further preferred embodiment of the inspection system, the first eddy current sensor unit is or comprises a magnetic field sensor. Preferably, the first eddy current sensor unit comprises a plurality of magnetic field sensors. The magnetic field sensors can be arranged in an array. The magnetic field sensors can be, for example, magnetoresistive sensors, giant magnetoresistive (GMR) sensors, magnetic tunnel resistance (TMR) sensors and / or Hall sensors. Preferably, the magnetic field sensors can be miniaturized.

[0039] Furthermore, the second eddy current sensor unit may preferably be or include an eddy current coil. The eddy current coil may be, for example, a printed coil. It is further preferred that the second eddy current sensor unit has two or more eddy current coils. In the second eddy current sensor unit, an eddy current coil is preferably also used as an excitation unit.

[0040] In particular, the combination of a magnetic field sensor and an eddy current coil makes it possible to identify both primary and secondary characteristics in the form of micro-defect accumulation.

[0041] The magnetic field sensor is preferably located at a distance from the eddy current coil such that the eddy current coil does not physically affect the magnetic field sensor, or only slightly affects it. Furthermore, the effect of the eddy current coil on the magnetic field sensor may be affected by additional factors.

[0042] In a further preferred embodiment, it is envisaged that the inspection unit is arranged and configured to detect the electromagnetic material properties by eddy current inspection during solidification, in particular by exposure and / or stopping and / or movement of the movement unit. The inspection unit can, for example, be arranged in front of or behind the movement unit in the feed direction. The movement unit can, for example, be a coating unit.

[0043] Another preferred advanced development of the inspection system is characterized in that it comprises a control device coupled by a signal to the inspection unit and adapted to generate an adaptation signal, in particular a correction signal, which is representative of an adaptation strategy, in particular a correction strategy, of the manufacturing system for adapting, in particular eliminating, the characteristics, in particular single defects and / or porous defect areas.

[0044] The adaptation signal is understood to mean any type of information carrier suitable for implementing an adaptation strategy of the manufacturing system. For example, the adaptation signal can be structured as a data record and / or represent a command. Furthermore, the adaptation signal can be based on characteristics, in particular the identification and / or classification of individual defects and / or defect areas.

[0045] Furthermore, the controller is preferably adapted to optimize parameters of the manufacturing system based on the identified characteristic and / or based on the adaptation signal, such that generation of the characteristic is reduced or avoided.

[0046] The controller is preferably adapted such that the adaptation signal results in the adaptation of manufacturing and / or machine parameters and / or process conditions, for example, the adaptation signal can adapt process parameters such as scanner, exposure, bonding and coating parameters, gas flows, preheat and / or building chamber pressure.

[0047] Furthermore, the adaptive signal can cause a new exposure and / or combination of properties, in particular an adapted exposure and / or combination. The adaptive signal can also cause a change in the scanning strategy and / or scanning pattern, a change in the exposure sequence, a change in the temporal sequence of exposures, a new application of powder, an adaptation of the building platform stroke, or a layer thickness. Furthermore, the adaptive signal can represent or cause the cancellation of individual parts or the entire building sequence.

[0048] Thus, the inspection system allows for the adjustment, especially correction, of the properties of currently produced layers, whereas existing approaches typically only allow properties to be affected by additional layers that have already been produced. This allows for more direct and targeted influence on properties. Furthermore, the inspection system not only allows for identifying defects in the part, checking its integrity, and recording the state of material properties within the inspection depth, but also for deriving targeted countermeasures to proactively eliminate defects and check whether the elimination was successful. This is where the repeatability of the inspection comes into play. Other in-situ inspection systems do not allow for direct inspection, derivation of measurements, targeted repair, and verification of this repair.

[0049] A preferred training of the inspection system envisions that the control device is configured to control the inspection unit so that a predetermined number of layers, particularly predetermined layer positions, are inspected. For example, an inspection system configured in this manner could inspect layers 50-500 of a build job, while the remaining layers are not inspected because they are irrelevant to the quality of the part. This may be the case, for example, when the first layer is intended to attach the part to the build platform and therefore its characteristics are not relevant. This further reduces the amount of data generated.

[0050] A preferred embodiment of the inspection system is characterized in that the inspection unit is configured to identify an adaptive characteristic based on the adaptation signal. Further, it may be preferred that the control device is adapted to generate a second adaptation signal based on the identified adaptive characteristic, the second adaptation signal representing a second adaptation strategy of the manufacturing system for further adapting the adaptive characteristic.

[0051] A further preferred embodiment of the inspection system provides that it comprises an excitation unit for inducing eddy currents in the solidified powder material, and that in normal operation one excitation unit or two excitation units on either side of the first eddy current sensor unit are positioned at equal distances from the test surface.

[0052] This configuration allows the eddy current sensor unit to be positioned particularly close to the test surface, in particular the powder bed surface, thereby enabling good eddy current testing. The excitation unit is preferably positioned and configured to induce eddy currents with a penetration depth of more than 100 micrometers, preferably more than 200 micrometers.

[0053] During normal operation, the eddy current sensor unit is positioned between the powder bed and the excitation unit and / or in the same plane as the excitation unit parallel to the surface of the powder bed.

[0054] A further preferred embodiment of the inspection system comprises a topography measurement system for determining the topography of the solidified powder material, in particular the surface of the solidified powder material, the topography measurement system being adapted to generate topography signals characterizing a topography image representative of the distance of the solidified powder material to the inspection unit, the features being further identified based on the topography image.

[0055] The topography measuring system may be, for example, a unit for stripe light projection, a line scanner and / or a light field camera. The distance between the solidified powder material and the inspection unit is determined, in particular between the surface of the solidified powder material and the first and / or second eddy current sensor units, in particular their respective sensors.

[0056] Another preferred embodiment of the inspection system is characterized in that the first eddy current sensor unit and the second eddy current sensor unit are arranged offset from each other. For example, they can have a pitch or distance. Furthermore, they can be arranged in several rows. It is particularly preferred that the first eddy current sensor unit and the second eddy current sensor unit are arranged horizontally offset from each other in the intended operation. In particular, the individual sensors of the second eddy current sensor unit are arranged offset from each other. In the intended use, the individual sensors can be arranged offset from each other so as to be perpendicular to the main direction of movement of the moving unit, in particular the feed direction.

[0057] In a further preferred embodiment of the inspection system, the first eddy current sensor unit and / or the second eddy current sensor unit have individual sensors, in particular magnetic field sensors and / or eddy current coils, which are arranged and configured so that they can be supplemented by at least one further individual sensor. Such an arrangement and design of the eddy current sensor units allows them to be individually expanded, thereby addressing various requirements of additive manufacturing.

[0058] In another preferred embodiment, the inspection system is signal coupled to the inspection unit and has an application specific integrated circuit adapted to amplify, digitize, filter and / or provide signals recorded by the first eddy current measurement unit and / or the second eddy current measurement unit for further processing.

[0059] One advantage of application specific integrated circuits is their high integration density, which allows the test unit to be miniaturized, as it occupies only a small amount of space.

[0060] In a further preferred embodiment of the inspection system, the control device is adapted to identify edges and / or contours of a part, in particular a part made of consolidated powder material, based on output signals from the first and / or second eddy current sensor units. The inspection system is advantageous for detecting edges and contours of a part because loose powder material acts as an insulator when the first and / or second eddy current sensor units are measuring. This allows both signals to be efficiently superimposed and processed.

[0061] According to a further aspect, the problem mentioned in the beginning is solved by a manufacturing system for additively manufacturing a part by consolidating a powder material, the manufacturing system comprising a build chamber in which the powder material can be disposed, a consolidation unit arranged and configured to consolidate the powder material, in particular with a high-energy beam or a binder, a movable transfer unit arranged above the powder material to be consolidated, and an inspection system according to one of the above-mentioned embodiments, wherein the inspection unit is arranged on the transfer unit.

[0062] The manufacturing system may preferably be controlled by a control device of the above-mentioned test system. Alternatively, the manufacturing system may have a control unit that receives and / or generates the above-mentioned adaptation signals, and the manufacturing system may be controlled by the adaptation signals. The manufacturing system may be controlled in parallel or loop-controlled by the above-mentioned inspection system so that detected features of the currently manufactured layer and / or one of the previously manufactured layers are adapted, particularly modified, or the part or build job is aborted.

[0063] The solidification unit is preferably configured as an exposure unit for exposing the powder material. Alternatively or additionally, the solidification unit is configured for applying a binder.

[0064] In a preferred embodiment of the manufacturing system, the transfer unit is configured as a coating unit for forming a powder bed surface. The coater unit, for example, has a smoothing function to form a flat powder bed surface. This function can be configured, for example, using a coater lip. Furthermore, the coater unit can have a powder material supply section or be connected to a powder material storage section so that powder material can be supplied to the coater unit. Arranging the inspection unit on the coater has the advantage that the coater passes over the powder bed periodically, thus enabling a complete inspection of the consolidated powder material in parallel with the process. In particular, in the case of unidirectional layer coating, it is preferable that the inspection unit perform a first inspection on the outward path and a second inspection on the return path to the starting position.

[0065] In a further preferred embodiment, the moving unit is configured as at least one handling system, in particular a robot, for example at least one robot arm. The handling system is preferably arranged and configured to test accessible sections while the powder material is still solidifying. The testing process is partially or completely parallel to the solidification process. Furthermore, the moving unit is preferably a solidification unit or includes a solidification unit.

[0066] According to a further aspect, the problem stated at the beginning is solved by a method for in situ detection of features in solidified powder material, in particular by an inspection system according to one of the above-mentioned design variants, which method comprises detecting an electromagnetic material property of the solidified powder material by eddy current inspection, i.e. detecting a conductivity difference in the solidified powder material to identify the property, wherein a first eddy current sensor unit is used to identify a feature having a first feature size greater than or equal to a size threshold, in particular a single defect, and a collection of features, in particular a porous defect region, having a second feature size less than the size threshold are identified by a second eddy current sensor unit.

[0067] Preferably, a test signal is generated based on which conductivity difference is detected so that an electromagnetic material property is detected. The detection of the material property is preferably performed using a first control unit of the first eddy current sensor unit and / or a second control unit and / or controller of the second eddy current sensor unit. Furthermore, the identification of the property is preferably performed using the first control unit and / or the second control unit and / or controller.

[0068] According to a preferred embodiment of the method, this comprises the steps of generating an adaptation signal, in particular a correction signal, based on the identified characteristics, in particular single defects and / or porous defect areas, generating an adaptation signal, in particular a correction signal, representative of an adaptation strategy, in particular a correction strategy, to a manufacturing system for adapting the characteristics, and driving the manufacturing system with the adaptation signal, in particular the correction signal, in order to adapt the characteristics.

[0069] For further advantages, embodiments and details of the individual aspects and their possible further developments, reference is also made to the descriptions given of the further aspects, corresponding features and further developments. [Brief explanation of the drawings]

[0070] Preferred embodiments are illustrated by the accompanying drawings shown below. [Figure 1] 1 is a schematic two-dimensional view of an exemplary embodiment of a manufacturing system. [Figure 2] FIG. 2 is a schematic two-dimensional plan view of the manufacturing system shown in FIG. [Figure 3] FIG. 2 is a further schematic two-dimensional view of an exemplary embodiment of a manufacturing system. [Figure 4] FIG. 2 is a further schematic two-dimensional view of an exemplary embodiment of a manufacturing system. [Figure 5] 2 is a schematic two-dimensional view of an exemplary embodiment of a first eddy current sensor unit. [Figure 6] 1 is a schematic two-dimensional diagram of an exemplary embodiment of a connection between a magnetic field sensor and an application specific integrated circuit. [Figure 7] FIG. 2 is a schematic two-dimensional view of an exemplary embodiment of a second eddy current sensor unit. [Figure 8] FIG. 1 is a schematic diagram of an exemplary method. [Figure 9] FIG. 10 is a schematic diagram of a further exemplary method. DETAILED DESCRIPTION OF THE INVENTION

[0071] In the drawings, identical or substantially identical or similar elements are designated by the same reference numerals.

[0072] 1 to 3 show a manufacturing system 100 for additively manufacturing a part 102 by exposing a powder material 104. The part 102 is formed by solidifying powder material 104. The powder material 104 is solidified using a high-energy beam 128, which may be, for example, a laser beam. The part 102 is manufactured in a powder bed 106. For this purpose, a moving unit 110 configured as a coater 112 applies the powder material 104 in layers, the thickness of which is in the micrometer or millimeter range. The moving unit 110 moves in a feed direction 118.

[0073] After the layer of powder material 104 is applied, it is selectively exposed to light by exposure unit 108, whereby it is typically melted. Next, table 124 with adjustment unit 126 is lowered vertically by one layer thickness to allow coater 112 to create a new layer of powder material 104. The system is disposed on frame 122.

[0074] Exposing the powder material 104 to the high-energy beam 128 also periodically creates features 114, 116. Feature 114 is shown as a single defect, and feature 116 is shown as a porous defect region with numerous micro-defects. This process takes place in the construction chamber 107.

[0075] 3 shows that a mirror element 120 is positioned in the beam path of a high-energy beam 128, which may be part of a scanner, for example. Using the mirror 120, the high-energy beam 128 can be directed to any location on a test surface configured as a powder bed surface 130.

[0076] Manufacturing system 100 also includes inspection system 200. Inspection system 200 is configured for in-situ detection of characteristics 114, 116 in solidified powder material 102. Inspection system 200 comprises an eddy current-based inspection unit 202 disposed on motion unit 110. Inspection unit 202 is configured to detect electromagnetic material properties of solidified powder material 102 by eddy current inspection, thereby detecting electrical conductivity differences in solidified powder material 102 for identifying characteristics 114, 116 during additive manufacturing. Eddy currents 204 are induced by inspection system 200 with excitation unit 242 or an excitation unit not included in inspection system 200.

[0077] The inspection unit 202 includes a first eddy current sensor unit 210 positioned and configured to identify features 114 having a first feature size, particularly a single defect, that is equal to or greater than a size threshold. Additionally, the inspection unit 202 includes a second eddy current sensor unit 230 positioned and configured to identify a collection of features 116 having a second feature size, particularly a porous defect region, that is smaller than a size threshold.

[0078] The inspection system 200 further comprises a controller 240 signal-coupled to the inspection unit 202 adapted to generate, based on the identified characteristics 114, 116, a correction signal representative of a correction strategy of the manufacturing system 100 for repairing the characteristics 114, 116.

[0079] The inspection system 200 further comprises a topography measurement system 244 for determining the topography of the solidified powder material 104. The topography measurement system 244 is adapted to generate a topography image representative of the distance of the powder bed surface 130 to the inspection unit 202, and the characteristics 114, 116 are further identified based on the topography image. The placement of the topography measurement system 244 on the coater 112 is optional, since the latter can be positioned, for example, from obliquely above the construction plane so that the topography of the entire construction plane can be measured.

[0080] 4 shows a manufacturing system 100 essentially similar to that of FIG. 3, where the solidification unit is configured as a binder unit 246 for applying a binder 248, thereby allowing the inspection system 200 described above to be used to inspect powder material 104 solidified by the metal binder jetting method.

[0081] 5 shows that the first eddy current sensor unit 210 comprises a plurality of magnetic field sensors 212. The magnetic field sensors 212 are connected in pairs to an application specific integrated circuit 214. This connection is particularly shown in FIG. 6, where these connections are made by connecting surfaces 222 and connecting wires 224.

[0082] The application specific integrated circuit 214 is further connected to an FPGA 216, a control element 218, and a memory element 220. The FPGA 216 can be used, for example, for pre-analysis and intermediate storage of data generated by the magnetic field sensor 212, as well as for specifying test frequencies. The FPGA serves as an interface converter between the ASIC and other units of the system.

[0083] The control element 218 is also coupled to the computing unit 206 by a data connection 207 .

[0084] 7 shows details of the second eddy current sensor unit 230. The second eddy current sensor unit 230 is similar to the first eddy current sensor unit 210. The second eddy current sensor unit 230 comprises an eddy current coil 232, which is shown only schematically, coupled to an FPGA 234, a control element 236, and a memory element 238. The second eddy current sensor unit 230 preferably has several, preferably a plurality of, eddy current coils 232.

[0085] 8 illustrates a method for in-situ detection of features 114, 116 in a solidified powder material 102 using a high-energy beam 128. The method includes step 300 of detecting electromagnetic material properties of the solidified powder material 102 by eddy current inspection, such that electrical conductivity differences within the solidified powder material 102 are detected to identify the features 114, 116 during additive manufacturing. A first eddy current sensor unit 210 is used to identify a feature having a first feature size, and a second eddy current sensor unit 230 is used to identify a set of features. In step 302, the feature 114 and / or the set of features 116 are recognized based on the detected electromagnetic material properties.

[0086] 9 illustrates a preferred embodiment of the above-described method. In step 304, a correction signal is generated based on the identified characteristics 114, 116, particularly single defects and / or porous defect regions, and the correction signal represents a correction strategy for the manufacturing system 100 to remove the characteristics 114, 116. In step 306, the manufacturing system 100 is controlled using the correction signal to correct the characteristics 114, 116.

[0087] The inspection system 200 and corresponding methods described above enable particularly advantageous detection of features 114, 116 in parts manufactured from powder material 104. In particular, different feature sizes can be reliably distinguished. Furthermore, the inspection system and method enable process-parallel control or adjustment of additive manufacturing processes, as the amount of data generated and required is very small, allowing for real-time control. [Explanation of symbols]

[0088] 100: Manufacturing Systems 102: Parts 104: Powder material 106: Powder bed 107: Construction Chamber 108: Exposure unit 110: Mobile unit 112: Recoater 114: Characteristics 116: Characteristics 118: Recoater feed 120: Mirror element 122: Frame 124: Table 126: Adjustment unit 128: High energy beam 130: Powder bed surface 200: Inspection system 202: Eddy current inspection unit 204: Eddy current 206: Computational unit 207: Data connection 210: First eddy current sensor unit 212: Magnetic field sensor 214: ASIC (Application Specific Integrated Circuit) 216: FPGA (Field Programmable Gate Array) 218: Control element 220: Memory element 222: Connection surface 224: Connecting wire 230: Second eddy current sensor unit 232: Eddy current coil 234:FPGA 236: Control element 238: Memory element 240: Control device 242: Excitation unit 244: Topography measurement system 246: Binder unit 248: Binder

Claims

1. 1. An inspection system (200) for in-situ detection of a characteristic (114, 116) in a solidified powder material (104), comprising: an eddy current inspection unit (202) disposable on a moving unit (110), the eddy current inspection unit (202) being arranged and configured to detect electromagnetic material properties of the solidified powder material (104) by eddy current inspection, thereby detecting electrical conductivity differences within the solidified powder material (104) to identify the properties (114, 116); the inspection unit (202) comprising a first eddy current sensor unit (210) arranged and configured to identify features having a first feature size equal to or greater than a size threshold; The inspection system (200) includes: the inspection unit (202) comprising a second eddy current sensor unit (230) configured to identify a set of features having a second feature size less than the size threshold.

2. 2. The inspection system (200) of claim 1, wherein the first eddy current sensor unit (210) has a first inspection resolution and the second eddy current sensor unit (230) has a second inspection resolution, the first inspection resolution being higher than the second inspection resolution, in particular by an order of magnitude.

3. Inspection system (200) according to any one of the preceding claims, wherein the size threshold is between 15 μm and 100 μm, in particular between 20 μm and 50 μm.

4. the first eddy current sensor unit (210) is or comprises a magnetic field sensor (212), and / or 10. The inspection system (200) of any preceding claim, wherein the second eddy current sensor unit (230) is or comprises an eddy current coil (232).

5. 10. The inspection device (200) according to any of the preceding claims, wherein the inspection unit (202) is arranged and configured to detect the electromagnetic material characteristics by eddy current inspection during the solidification, in particular by exposure and / or stopping and / or moving the moving unit (110).

6. 10. The inspection system (200) according to any of the preceding claims, comprising a control device (240) coupled to the inspection unit (202) by a signal and adapted to generate an adaptation signal based on the identified characteristics, in particular single defects and / or porous defect areas, wherein the adaptation signal represents an adaptation strategy of the manufacturing system for adapting the characteristics.

7. the inspection unit is arranged and configured to identify an adaptation characteristic based on the adaptation signal; and / or 10. The inspection system (200) of any preceding claim, wherein the controller (240) is adapted to generate a second adaptation signal based on the identified adaptive characteristic, the second adaptation signal representing a second adaptation strategy of the manufacturing system for further adapting the adaptive characteristic.

8. 10. The inspection system (200) of claim 1, further comprising an excitation unit (242) for causing eddy currents to flow in the solidified powder material (104), wherein in normal operation, a first eddy current sensor unit (210) and / or a second eddy current sensor unit (230) are disposed between the excitation unit (242) and the test surface (130).

9. 10. The inspection system (200) of any preceding claim, comprising a topography measurement system for determining a topography of the solidified powder material (104), and adapted to generate a topography signal characterizing a topography image representative of a distance from the solidified powder material (104) to the inspection unit (202), the characteristic being further identified based on the topography image.

10. 10. The inspection system (200) of any preceding claim, wherein the first eddy current sensor unit (210) and the second eddy current sensor unit (230) are positioned offset from each other.

11. 10. The inspection system (200) of any preceding claim, wherein the first eddy current sensor unit (210) and / or the second eddy current sensor unit (230) have individual sensors arranged and configured such that they can be supplemented by at least one further individual sensor.

12. 10. The test system (200) of any preceding claim, comprising an application specific integrated circuit (214) signal-coupled to the test unit (202) and adapted to provide amplification, digitization, filtering, and / or further processing.

13. 10. The inspection system (200) of any preceding claim, wherein the control device (240) is adapted to identify a component edge of the component based on output signals of the first and / or second eddy current sensor units (210).

14. 1. A manufacturing apparatus (100) for additively manufacturing a part by means of solidifying a powder material (104), comprising: a build chamber (107) in which said powder material (104) can be placed; a solidification unit (108, 146) positioned and configured to solidify the powder material (104); a moving unit (110) movably arranged above the powder material to be solidified; and the inspection system (200) according to any one of claims 1 to 13, wherein the inspection unit (202) is disposed on the moving unit (110).

15. 15. The manufacturing system (100) of claim 14, wherein the transfer unit (110) is a coating unit (112) for forming a powder bed.

16. A method for in situ detection of a characteristic (114, 116) in a solidified powder material (104), in particular using an inspection system according to any one of claims 1 to 13, comprising: detecting electromagnetic material properties of the solidified powder material (104) by eddy current inspection, such that electrical conductivity differences within the solidified powder material (104) are detected to identify the properties (114, 116); a first eddy current sensor unit (210) used to identify first feature sizes above a size threshold, particularly features (114, 116) having a single defect; A method in which a second eddy current sensor unit (230) is used to identify a set of features having a second feature size, particularly porous defect regions, that are smaller than a size threshold.

17. generating an adaptation signal based on the identified characteristics, in particular single defects and / or porous defect regions, said adaptation signal representing an adaptation strategy of the manufacturing system for adapting said characteristics; 17. A method according to any preceding claim, comprising the step of: controlling a manufacturing system using the adaptation signal to adapt the characteristic.

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