Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
  • B29C64/10—Processes of additive manufacturing
  • B29C64/141—Processes of additive manufacturing using only solid materials
  • B29C64/153—Processes of additive manufacturing using only solid materials using layers of powder being selectively joined, e.g. by selective laser sintering or melting
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
  • B22F10/20—Direct sintering or melting
  • B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
  • B22F10/40—Structures for supporting workpieces or articles during manufacture and removed afterwards
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
  • B22F10/80—Data acquisition or data processing
  • B22F10/85—Data acquisition or data processing for controlling or regulating additive manufacturing processes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
  • B22F12/90—Means for process control, e.g. cameras or sensors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
  • B29C64/20—Apparatus for additive manufacturing; Details thereof or accessories therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
  • B29C64/30—Auxiliary operations or equipment
  • B29C64/386—Data acquisition or data processing for additive manufacturing
  • B29C64/393—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
  • B29C64/40—Structures for supporting 3D objects during manufacture and intended to be sacrificed after completion thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y10/00—Processes of additive manufacturing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y50/00—Data acquisition or data processing for additive manufacturing
  • B33Y50/02—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
  • G01N29/04—Analysing solids
  • G01N29/07—Analysing solids by measuring propagation velocity or propagation time of acoustic waves
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
  • B22F10/80—Data acquisition or data processing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N2291/00—Indexing codes associated with group G01N29/00
  • G01N2291/01—Indexing codes associated with the measuring variable
  • G01N2291/011—Velocity or travel time
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/25—Process efficiency

Definitions

• the invention is in the field of additive manufacturing and more particularly relates to a method and an ultrasonic inspection device for additive manufacturing processes.
• the additive manufacturing term designates according to the standard NF E 67-001, "the set of processes for making layer by layer by adding material a physical object from a digital object.” This term includes dozens of designations of manufacturing technologies, classified in seven categories of processes according to the standard NF ISO 17296-2 June 2015, among which is the category of melting on a powder bed having the abbreviation (PBF) of the English "Powder Bed Fusion”.
• PPF abbreviation
• the PBF processes have the common point of proceeding to a partial or total melting of static powder, the powder generally coming from metallic, ceramic or plastic materials.
• the PBF processes differ according to the nature of the energy source used to produce the fusion, which may be a laser (LMF process for "Laser Metal Fusion"), an electron beam or an infrared lamp to name just a few. these examples.
• LMF process Laser Metal Fusion
• electron beam or an infrared lamp to name just a few.
• Ultrasound has been the subject of various uses in additive manufacturing, especially as a source of energy for manufacturing (see patent application WO2015053644), to assist and optimize it (see patent application WO2015031453) or to reduce the level of residual stresses (see patent application US20150314373). Their use for control or characterization purposes remains very limited. Laser ultrasonic methods have been used several times in additive manufacturing, particularly in the case of powder bed processes (see EP1815936), mainly because of its implementation without contact. This approach nevertheless has limitations, which are: a weak ultrasound generation efficiency (in comparison with piezoelectric transducers); a high sensitivity to the surface state; high cost; and a subsurface inspection limited to the vicinity of the upper surface on the last layers.
• Patent Application WO 2015/109096 A1 describes a method of direct ultrasonic inspection of a part being manufactured in a powder bed, via the use of a multi-element sensor. This approach has limitations that make it very inefficient. Indeed, it requires the manufacture of a part directly on the support plate, in order to allow the transmission of the ultrasound beam therein. This important anchoring of the part renders its separation from the delicate plate even impossible without damaging it, and produces high stresses due to thermal expansions / retractions.
• the proposed method allows the analysis of only massive and very simple parts, because the powder-bed manufacturing processes are advantageous for geometrically complex parts having very thin thicknesses, many ramifications leading to parasitic echoes and a dispersion of the useful signal for which a usual ultrasonic inspection is poorly adapted.
• An object of the present invention relates to a method and an apparatus for ultrasonic inspection and control of additive manufacturing processes, and more particularly the family of powder bed melting processes.
• the general principle of the invention consists in producing ultrasound waveguides simultaneously with the additive manufacturing of one or more pieces in order to inspect the homogeneity in the powder bed and / or to inspect the part (s) in progress.
• the present invention makes it possible to overcome the major limitations of ultrasonic testing of high complexity parts during manufacture in a powder bed.
• Another object of the present invention is to provide a process and an additive manufacturing device which comprises an ultrasonic waveguide inspection system which makes it possible to probe during manufacture, that is to say process "according to the conspicuous Anglicism, the bed of powder and / or key areas of the piece or pieces in progress.
• the present invention aims to overcome the limitations of current inspection techniques by providing ultrasonic volume inspection in the powder bed.
• the invention will find advantageous applications in many technical fields such as the aeronautics, space or automotive industries, to name only these examples.
• the method of the invention by ultrasonic inspection carried out during manufacture provides access to various levels of information on the quality of the parts produced in the powder bed.
• a process for additive manufacturing of parts by melting on a powder bed comprising layer-by-layer manufacturing steps on a construction plate of at least one ultrasonic waveguide simultaneously with the production layer by layer of at least one piece in the powder bed, said at least one ultrasonic waveguide being integral with the construction plate to provide an acoustic connection with at least one translator under the construction plate, and having a minimum value of the smallest dimension of the upper section at the "c / f" ratio, where "c” designates the velocity of propagation of the ultrasonic wave in the controlled material and "f” is the main frequency of the ultrasonic wave, at least one waveguide being manufactured in isolation or integral with said at least one part, the method being characterized in that it simultaneously comprises the layer-by-layer inspection steps in order to inspecting the powder bed by said at least one isolated waveguide of the part and / or inspecting said at least one part by said at least one waveguide integral with said at least one part.
• the method consists in simultaneously producing a plurality of parts and a plurality of ultrasonic waveguides, the waveguides comprising waveguides integral with certain parts and isolated waveguides of all the parts.
• the method consists in simultaneously producing temporary supports for said at least one part, such that at least one ultrasonic waveguide is integrated in a temporary support.
• the invention also covers a powder bed additive manufacturing system comprising means for implementing the claimed additive manufacturing process.
• the means for implementing the manufacturing method comprise ultrasonic translators able to send and receive each at least one ultrasound beam in at least one waveguide to inspect during the manufacture of at least one part. the powder bed and / or said at least one part being manufactured.
• the translators are arranged under the construction plate so that each translator can emit an ultrasonic beam into a respective waveguide made in its view.
• the translators are piezoelectric transducers used in transmission-reception mode combined.
• said at least one waveguide is piezoelectric transducers used in transmission-reception mode combined.
• - has a predefined section, selected from the group of round, oval, square, triangular or rectangular base type sections.
• the claimed system includes means for analyzing received signals.
• the subject of the invention is also an inspection method for additive manufacturing of pieces on a bed of powder, the process comprising the steps of:
• the step of analyzing the received signal consists in determining whether there is a fault
• the step of analyzing the received signal consists in determining whether there is a defect in the part and / or in the powder bed;
• the step of analyzing the received signal further comprises a step of comparing the received signal with a signal from a digital simulation of ultrasonic control.
• the invention also relates to an inspection device for additive manufacturing of pieces on a powder bed, which comprises means for implementing the steps of the claimed method.
• Figure 1 is a simplified representation of an additive manufacturing system for implementing the device of the invention
• Figure 2 illustrates in a sectional view, a first embodiment of the device of the invention
• Figures 3a to 3c illustrate in a sectional view the dual functionality of the ultrasonic waveguide of the device of the invention in one embodiment
• Figures 4 to 6 illustrate in a sectional view, different embodiments of the device of the invention
• Figure 7 illustrates the flow of operations for implementing the additive manufacturing method of the invention
• Figure 8 illustrates a sequence of steps of the inspection method of the invention in one embodiment.
• FIG. 1 shows an additive manufacturing system (100) for implementing the device of the invention, comprising a construction plate (102) on which one or more pieces (104) are manufactured according to a additive manufacturing process on a bed of powder (106).
• the system comprises a powder reservoir (108) and a powder diffuser (1 10) for supplying a layer of powder from the reservoir to the support plate or under the effect of a heat source (1 12), the melting of the powder operates to produce a layer of the part or parts to be manufactured. The process is repeated layer by layer until the final piece (s) are obtained.
• the complete process is not described in more detail, and one skilled in the art can refer to the numerous literature on additive manufacturing processes and variant embodiments based on this same principle.
• Figure 2 is a sectional view of an additive manufacturing system according to a first embodiment of the invention. It should be noted that the identical elements between the figures bear the same references. For reasons of simplification of the description but not limiting, the figure shows a single piece arrived at the end of its manufacture according to a laser powder bed method. Those skilled in the art will extend the principles described to additive manufacturing cases of a plurality of parts that can be of identical or variable size and shape, having simple or complex geometries.
• the piece (202) is manufactured on a temporary support structure (204) for stabilizing it on a construction board (206).
• the general principle of the invention is to manufacture waveguides ultrasound (208-1 to 208-4, 210) according to the powder bed additive manufacturing process, simultaneously with the manufacture of the piece.
• the waveguides which may be referred to in the description by the acronym GO, are made by melting the powder, as are the temporary supports and parts. They are anchored on the upper face of the building board (206).
• the manufacture of GOs is carried out with a scan strategy similar or identical to that of adjoining parts, in particular in terms of laser power, laser speed and trajectories, making the GO inspection operation more representative of the quality of the adjoining rooms. or supported.
• the GOs may optionally have a slight reduction in section at their anchorage with the plate and, where appropriate, with the part, to facilitate their separation.
• the section reduction must be limited so as not to induce artifact on the emitted and reflected ultrasonic beams.
• the GOs preferably have a simple, solid and axial geometry without bifurcation throughout the inspection area. Their section is predefined to allow the passage of an ultrasonic inspection beam, while minimizing the consumption of powder and process time to achieve it.
• the waveguides are constructed as cylinders erected simultaneously with the workpiece (or batch of workpieces) and its support structure, layer after layer.
• the GOs may have other geometries of sections such as round, oval, square, triangular, rectangular, etc. bases.
• the minimum section of an GO is chosen based on the material inspected and the ultrasonic wave used for the inspection, particularly its type and frequency. Also, the diameter of a GO is always chosen greater than the "c / f" ratio, and preferably greater than "3 * c / f", where "c” designates the propagation velocity of the ultrasound wave in the inspected material and "f" the main frequency of the ultrasonic wave.
• the minimum preferential dimension of a GO is of the order of a millimeter.
• ultrasonic translators (212-1 to 212-4, 213) integral with the construction plate are arranged under the plate so that they can each emit an acoustic beam in a GO manufactured in its view.
• a translator (212-1 to 212-4) is positioned respectively under the platen at the place of manufacture of each GO (208-1 to 208-4) and similarly a translator ( 213) is positioned under the tray at the location of manufacture of the GO (210).
• the translator is a piezoelectric translator used in transmission-reception mode, called "pulse-echo" according to recognized anglicism.
• Each waveguide conveys an ultrasonic signal to the heart of the powder bed to perform a material health inspection.
• the beam propagates in the GO parallel to the GO axis.
• a preferred implementation is where the waveguides are orthogonal to the building board, i.e., vertical in the powder bed, to allow most of the signal reflective on the top face to move towards the receiver.
• the translator which is secured to the rear face of the construction plate is mounted to ensure the acoustic connection between the translator and the tray.
• a layer of coupling agent grey, oil, cellulosic glue, special gels
• the translator and couplant are selected to withstand the maximum temperature of the plate (which is a function of the merged material and the manufacturing strategy, typically of the order of a few tens of ° C).
• the diameter of a GO is preferentially defined as being that or slightly greater (eg + 10%) than the size of the piezoelectric pellet of the translator.
• the GOs for example have a diameter of the order of 1.6 mm for an opening sensor 1 / 1 6 inch, of the order of 3.4 mm for a 1/8 inch aperture sensor, or about 6.4 mm for a 1 ⁇ 4 inch aperture sensor.
• the diameter of the GOs for usual additive manufacturing devices does not exceed a few centimeters.
• the translator or translators are connected to an electronic acquisition system (214) that allows the digitization of the analog signals received from each translator.
• the electronic acquisition system sends at fixed time intervals of excitation pulses to the translator and receives any signal reflected by the GO in a time interval less than the interval between theinstalles.
• the digitized signal can be stored for viewing and data processing can be done for process abnormality detection.
• the processing may have the effect of triggering an alarm with respect to the manufacturing process and interrupting the current production cycle.
• two types of waveguides can be manufactured simultaneously with the manufacture of parts, each GO having a different location and functionality.
• the method makes it possible to manufacture:
• the GO-witnesses have no contact with the parts in production, they are isolated parts and are inserted in free locations of parts as witnesses of compliance.
• a GO-support is integrated into temporary supports for parts in production.
• a GO-support is integral with a workpiece, and depending on its location on the workpiece, it can be integral with the workpiece either as soon as the first layers of the workpiece are made, or become integral with a workpiece later during the manufacturing process.
• the integral waveguides of a room serve by routing an ultrasonic beam, to the inspection of the room itself.
• a first function of the GO-witnesses is to provide information on the absence of deviations or defects during manufacture in a powder bed, particularly when the parts constructed simultaneously have geometric complexities such that they limit or prohibit their direct control. .
• a control GO is located in the vicinity of a room, or each critical room.
• a control GO can be placed in a proximity of a room ranging from millimeters to a few centimeters in order to increase the representativity of the control by GO-control to qualify a room.
• a plurality of GO-witnesses can be placed in the vicinity of a room, for example all around it.
• a second feature of the GO-witnesses is to evaluate the homogeneity of the manufacturing within the powder bed.
• the powder beds have known variabilities, due for example to a variable compactness of the powder, to temperature heterogeneities or to a variation of the laser power according to its angle of incidence (higher angle at the edge of the plate by center report).
• the comparison of the ultrasonic signals of the different GO-controls in particular the comparison of the porosity or density ratio indicators, makes it possible to qualify the homogeneity on the plateau.
• a plurality of identical GO-controls is distributed within the powder bed, interposed between the different parts to be manufactured.
• the number of GO-witnesses can vary from at least one to several tens.
• a control GO differs from a simple control room in that its positioning is adapted, or even optimized, for inspection in the vicinity of a part or the entire surface of the plate.
• the anchoring on the GO-control panel does not reduce a disadvantage in that the GO-witnesses can be sacrificial, unlike control pieces.
• the GO-supports are integrated with the provisional supports of parts in manufacture, and serve to convey the ultrasonic beam in the room. They differ from the temporary supports in that they have larger sections than those of the usual elements.
• the section of the GO-supports is chosen of sufficient size to allow the passage of the ultrasonic inspection beam, while being minimized to firstly avoid excessive consumption of powder to achieve them and secondly avoid too high concentration constraints.
• GO-support will be arranged to route the beam in critical areas of the room. It may especially be regions in which the occurrence of defects is frequent or likely, such as the border zone between a contour laser scan and a filling scan, regions with a high thermal gradient or stress concentration (generally identified by simulation), the trajectories of lasers with high curvatures or high speeds of passage, where any region known to those skilled in the art as "defect-gene". They can also be areas critical to the reliability of the room where any imperfection can have significant consequences on the function of the room. It can also be areas that will be difficult to access any post-manufacturing control.
• a support GO integrated in the support structure advantageously has symmetry or periodicity to limit the asymmetry of deformations at the scale of the room.
• GO-support may be present on the entire support zone of the part, separated by "n" usual supports, "n” being constant between each GO-support.
• FIGS. 3a to 3c show, in sectional view, different stages of manufacture of a part (202) illustrating the manufacture of simultaneous manner of ultrasonic waveguides (208-1 to 208-4) according to the principle of the invention.
• Figure 3a which illustrates an early stage of manufacture, a single waveguide (208-2) reaches the room, then having GO-support functionality to inspect the room. It is apparent that three waveguides (208-1, 208-2, 208-4) that are also simultaneously manufactured do not reach the part. They can then be used during inspection as GO-witnesses to check the homogeneity of the powder bed.
• Figure 3b illustrates an intermediate fabrication step of the room where two waveguides (208-2, 208-3) reaching the room can be used as GO-support and where two waveguides (208-1, 208 -2) not reaching the room can be used as GO-witnesses.
• Figure 3c illustrates the final step where the part is manufactured with the four waveguides (208-1 to 208-4) manufactured simultaneously, which are used as GO-supports.
• Figure 3 is simplified, but does not limit the embodiments where control waveguides, independent of the room can also be manufactured simultaneously (as the GO-control 210 in Figure 2).
• the method of the invention allows during the same powder bed additive manufacturing cycle to combine inspection of the powder bed concomitantly with that of one or more parts in production.
• FIG. 4 shows in a sectional view an embodiment of the invention for which a single multielement translator (408) is used for several support waveguides (406-1, 406-2, 406-3) of the same piece (402) having temporary supports (404).
• the translator allows to inspect turn by sending an ultrasonic beam in each GO-support, the room in three localities, adapting well-known delay laws to direct the beam along the axis the desired translator.
• the device of the invention allows an inspection in several areas of a part in manufacture.
• the inclination of the waveguides (406-1, 406-3) is limited to the possibility of receiving an exploitable signal by the receiver.
• Variations where the GOs are not perpendicular to the building board may be:
• the axis of the GO-control preferably has an orientation identical to that of one of the axes or one of the main directions of the room, to be more representative of the quality of the piece.
• FIG. 6 illustrates an alternative embodiment of the invention in which a transmitting translator (608-1) is distinct from a receiver translator (608-2), a "pitch and catch" configuration.
• this configuration makes it possible to reduce the sensitivity to the orientation of the defect, in particular in the case of cracks.
• FIG. 7 illustrates the flow of the preparatory operations for the implementation of the additive manufacturing and inspection method of the invention.
• a first step (702) each part to be manufactured is modeled in a Computer Aided Design (CAD) system.
• CAD Computer Aided Design
• a second step (704) batches of parts are created by selecting files, making it possible to group parts that can be manufactured simultaneously on the same bed of powder.
• CAD models for the temporary supports and the support and control waveguides are designed.
• All CAD models - parts, media, GOs - are converted (708) into a file format that can be used by an additive manufacturing system, such as the STL format, where the models are described layer by layer.
• the last step (710) before starting the manufacturing and inspection process (800) is to determine the manufacturing strategy, i.e., for example, to define the parameters of the laser scan.
• the positioning of the GO-witnesses can be identical from one production batch to another, which makes it possible to avoid moving the translators from one impression to the other.
• the pieces are then arranged between them.
• the GO-controls and the GO-supports are integrated during the design of the powder bed, simultaneously with the design of the temporary supports, once the grouping of parts to be manufactured simultaneously, identified.
• Figure 8 illustrates a sequence of steps (800) of the implementation of the manufacturing and inspection method of the invention in one embodiment.
• the method performs the layer-by-layer fabrication of parts, temporary supports and waveguides (GO-media and GO-witnesses) according to the data received from the previously created files.
• An inspection (804) can be performed at various times during manufacture, since one or a few layers have been fabricated (802).
• an inspection step is started to probe cooled zones, where the temperature is below 300 ° C, preferably below 100 ° C, and where the thermal gradient is limited along the waveguide.
• an inspection can be launched at the end of the completion of each layer, or after the completion of all layers.
• an inspection may be performed in one region of the powder bed while the laser irradiates another region to manufacture the parts concomitantly.
• the ultrasonic inspection consists of sending an ultrasonic beam in transmission-reception mode in the control waveguide (s) and / or supports, and analyzing the received signal (s).
• the ultrasonic inspection frequency may be between 0.5 MHz to 20 MHz, preferably between 5 MHz and 20 MHz
• the sensor opening may range from 1.59 mm to 25.4 mm, preferably from 3.175 mm to 12.7 mm.
• the signal analysis can be done according to known ultrasonic analysis techniques. The analysis may include the comparison of ultrasound signals received from different GO-controls.
• Intervention / interruption of the process can be performed if faults are detected (yes branch of 808), otherwise the manufacturing process continues to manufacture the next layer (810).
• the ultrasonic signals received on the detectors associated with the GOs can be difficult to interpret. For example, it may be difficult to decorrelate an echo defect on the walls of the room or to quantify the density of the material.
• the analysis of the signals from the GO inspection of the invention can be coupled with that of signals from a digital simulation of the ultrasonic control.
• signals obtained by the commercial software CIVA of the applicant makes it possible to increase the possibility of interpretation and exploitation of the signals measured by the ultrasonic inspection of the invention.
• the additive manufacturing digital chain has the specificity of producing CAD files of a part or batch of sliced pieces, for each layer of their production, these CAD files can advantageously be used as input data (803 ) for a comparison (806) between the measured signals and the expected signals.
• the ultrasonic inspection of the invention provides access to various levels of information on the quality of the parts produced in the powder bed. It makes it possible to detect the appearance of point defects, such as non-fused powder particles or porosities.
• the size of the detectable defects is a function of the choice of the sensor used and the material inspected.
• the minimum size D min of individually identifiable defects is given by the equation:
• the inspection method of the invention makes it possible to detect localized defects of a size of several hundred micrometers.
• the cracking of the material for example under the effect of thermal origin stresses, can also be detected as soon as cracks of the same dimensions appear.
• the identification of such a defect is based on the detection of an echo resulting from the interaction of the ultrasonic wave with the defect, whose flight time makes it possible to locate said defect. This echo can be detected by subtracting the received signal at a previous time by the same GO.
• GO ultrasonic testing can be used to evaluate the quality of the fused material.
• Indicators of the porosity rate of the material or its density or the stiffness of the merged material may also be extracted from the measured signals, based in particular on the attenuation of the signal and / or its frequency spectrum and / or on the characteristics of the backscattered signal.
• a calibration by measuring a posteriori the porosity rate or the density of different GO-controls by conventional methods (tomography, double-weighing, microscopy and image processing ...) optionally makes it possible to convert these indicators into physical quantities in certain case.
• Another use of the ultrasound inspection method in the waveguides makes it possible to identify process deviations, characteristics of additive manufacturing in a powder bed, the first of which account the lack of layering. This defect resulting from a bad interpenetration during the fusion of two successive layers, this results in an interfacial discontinuity producing a reflection echo which is detectable.
• the proposed ultrasonic control also makes it possible to measure the thickness of the layers produced, by converting the time of flight from the surface echo to a distance, which can also be refined by a calibration of the propagation velocities in the material produced.
• the present description illustrates a preferred implementation of the invention, but is not limiting.
• An example was chosen for allow a good understanding of the principles of the invention, and a concrete application, but it is in no way exhaustive and should allow the skilled person to make changes and implementation variants retaining the same principles.
• the present invention preferably relates to the simultaneous manufacture of waveguides and parts, the method can be operated for the sole fabrication of isolated waveguides on a test plate in order to characterize the homogeneity of the bed. of powder.
• the invention has been described for metallic materials, but it can be applied to other materials sufficiently conducting ultrasonic waves at frequencies of interest, such as certain ceramics.
• the present invention has been described for a laser powder melting method, the method is transposable to other sources of fusion activation.

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• 2017
  • 2017-07-28 FR FR1757192A patent/FR3069468B1/fr active Active
• 2018
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