DE102019206207A1 - 3D PRINTING METHOD AND 3D PRINTING DEVICE - Google Patents

Abstract

A 3D printing process includes depositing a modeling material in layers of material; Fusing the modeling material with an energy beam along a melting path in the respective material layer; Detecting a local material state of the fused modeling material with an imaging device along the melting path, wherein the imaging device detects the melted modeling material following the energy beam in the melting path locally along the melting path; simultaneous analysis of the detected local material condition of the fused modeling material in the melt path for quality defects with an analysis device; and remelting the modeling material with the energy beam in the melt path in the area of the quality defect if a quality defect is detected.

Description

The present invention relates to a 3D printing method and a 3D printing apparatus.

In generative or additive manufacturing processes, also generally referred to as “3D printing processes”, starting from a digitized geometric model of an object, one or more starting materials are sequentially stacked in layers and cured. In selective laser melting (SLM), for example, a component is built up in layers from a modeling material, for example a plastic or a metal, by applying the modeling material in powder form to a base and deliquely liquefying it through local laser irradiation, whereby a solid connected component results. 3D printing offers exceptional freedom of design and, among other things, allows objects to be produced with manageable effort that could not be produced using conventional methods or only with considerable effort. For this reason, 3D printing processes are currently widespread in industrial design, in the automotive industry, the aerospace industry or in general in industrial product development, in which a resource-efficient process chain is used for the needs-based small and large-scale production of individualized components.

To ensure that the printed components meet the specified quality requirements, they can be examined using different methods.

Frequently, however, such methods are only used after the component has been completed in order to sort out defective components that do not meet the specified requirements or specifications. Recently, however, real-time and / or online monitoring methods have also increasingly been proposed in order to obtain an assessment of the respective component already during the manufacturing process.

For example, the document describes WO 2016/183210 A1 the use of optical coherence tomography to monitor an object layer by layer during additive manufacturing. If a quality defect or a defect is discovered in a layer, the respective layer can be reprinted. For this purpose, the defective point can first be removed with a laser beam.

Against this background, the present invention is based on the object of finding improved solutions for the detection and elimination of quality defects already during additive manufacturing.

According to the invention, this object is achieved by a 3D printing method with the features of claim 1 and a 3D printing device with the features of claim 10.

Accordingly, a 3D printing process is provided. The 3D printing process includes depositing a modeling material in layers of material; Fusing the modeling material with an energy beam along a melting path in the respective material layer; Detecting a local material state of the fused modeling material with an imaging device along the melting path, wherein the imaging device detects the melted modeling material following the energy beam in the melting path locally along the melting path; simultaneous analysis of the detected local material condition of the fused modeling material in the melt path for quality defects with an analysis device; and remelting the modeling material with the energy beam in the melt path in the area of the quality defect if a quality defect is detected.

A 3D printing device is also provided. The 3D printing device is designed to deposit modeling material in material layers and to fuse the deposited modeling material with an energy beam along a melt path in the respective material layer. The 3D printing device comprises an imaging device which is designed to follow the energy beam in the melt path and to detect a local material state of the melted modeling material locally along the melt path; and an analysis device which is designed to analyze the detected local material state of the fused modeling material simultaneously in the melt path for quality defects, wherein the 3D printing device is further configured to re-fuse the modeling material with the energy beam in the melt path in the area of the quality defect if a quality defect is found.

An idea on which the present invention is based is to use the imaging device to check the fused or welded modeling material for defects immediately after exposure to the respective energy beam, e.g. a laser beam, by checking the condition of the material in a spatially limited area within the beam path is evaluated. For this purpose, the analysis device examines the local material condition detected with the imaging device simultaneously with the printing process, ie in real time. If a problem is discovered, the corresponding area can be corrected immediately afterwards. For this purpose the Energy beam applied again to the problematic location in the present invention.

For example, in selective laser sintering (SLS) or selective laser melting (SLM) or similar processes, after a problematic point has been identified, a laser beam can first be stopped, moved back a corresponding distance and then re-beamed onto the point with reduced beam energy. In the case of SLS, the defective area can thus be re-sintered, for example. This can ensure that the modeling material is sufficiently fused at the defective location. The laser beam can then be moved further along the melt path. If the corresponding point does not yet meet the specified quality requirements even after the repair, the above process can be repeated several times until the point is found to be good or a maximum number of correction attempts is reached. In the latter case, the printing process can be paused or canceled completely.

From a structural mechanical point of view, the solution according to the invention offers considerable advantages over known approaches from the prior art, since the correction can be carried out immediately after the first application of energy and the heated modeling material therefore does not have time to cool completely. In conventional solutions, a current layer is first completely completed before individual defects are corrected. In the present case, temperature-related stresses or the like can now be practically completely avoided. In addition, no exact position or direction data is required for the defects. The energy beam only needs to be moved back in the melt path by the corresponding amount and reapplied (with changed parameters if necessary). The approach according to the invention can be implemented as a closed control loop, for example for the additive manufacturing of metal and / or plastic components. In principle, however, other materials could also be printed with the device according to the invention, e.g. fiber-reinforced composite materials, etc. The information or image data recorded by the imaging device can, for example, be displayed in real time on a screen and examined, evaluated and / or monitored by an operator. Alternatively or additionally, however, the 3D printing device can also print a component fully automatically and monitor its quality and correct any defects.

Quality defects within the meaning of the invention include, in particular, material consolidation defects and / or fusing deficits in the fused, welded and / or sintered modeling material. Further quality defects include, for example, thermal cracks, gas or air inclusions, other cavities and / or defects, etc.

3D printing processes are particularly advantageous because they enable the production of three-dimensional components in primary molding processes without the need for special production tools that are tailored to the external shape of the components. This enables highly efficient, material-saving and time-saving manufacturing processes for parts and components. Such 3D printing processes are particularly advantageous for structural components in the aerospace sector, since there a large number of different components are used that are tailored to special purposes and that are used in such 3D printing processes with low costs, short production lead times and with low complexity in the Production required manufacturing facilities can be produced.

3D printing processes in the sense of the present application include all generative or additive manufacturing processes in which, on the basis of geometric models, objects of a predefined shape made from shapeless materials such as liquids and powders or shape-neutral semi-finished products such as strip or wire-shaped material using chemical and / or physical Processes are produced in a special generative manufacturing system. 3D printing processes within the meaning of the present application use additive processes in which the starting material is sequentially built up in layers in predetermined shapes.

Advantageous refinements and developments emerge from the further subclaims and from the description with reference to the figures.

According to a development, the imaging device can be designed and arranged in relation to the energy beam in such a way that the imaging device follows the energy beam at a predetermined distance in the melt path. In this way, the exact position of the defect point relative to the energy beam can be traced at any time, since the direction and course of the melt path are known from the control data of the energy beam. For example, it is not necessary to record the coordinates of one or more defective melting points.

According to a development, the 3D printing device can be designed to move the energy beam back by the specified distance in the melt path in order to achieve the To re-fuse modeling material in the event of a quality defect. In this particularly simple embodiment of the invention, the energy beam and the imaging device are thus simply moved back by the corresponding distance along the melt path. The energy beam can then be moved over the point again - if necessary with changed parameters such as beam power or beam speed - in order to repair it.

According to a development, the imaging device can be designed to record an internal spatial structure of the fused modeling material along the melt path in the respective material layer in order to detect the local material state. Precise and comprehensive information about the quality of the material consolidation and / or material fusion can thus also be obtained in the interior of the respective layer. For example, defects, cracks, cavities and / or porous areas can be identified in this way.

According to a development, the imaging device can be designed as a tomograph. In particular, the imaging device can be designed as a computer tomograph, i.e. Use x-rays.

According to one development, a type and / or a criticality of the quality defect can be determined and the energy beam can be controlled based on this. For example, the type of quality defect can indicate a material consolidation defect, a fusion deficit, voids, etc. The criticality of the quality defect can, for example, include information about whether the defect can be repaired at all or whether it turns out to be so serious that the partially manufactured component may have to be sorted out. On the other hand, the defect may be minor, so it may not be necessary to fix it. The criticality of the defect or defect can depend on the particular application. Some components may have stricter quality requirements than others. If a repair based on the ascertained type or the evaluated criticality of the quality defect is considered sensible or necessary, the energy beam can again be guided over the problematic point in the melt path with an adapted control strategy. For example, a poorly sintered point can be re-sintered with reduced beam power.

According to a further development, the re-merging can take place with changed printing parameters. Such printing parameters can be, for example, an energy beam power, a scanning speed, a position of a work platform, an orientation angle of the work platform or the like. The printing parameters can, for example, be adapted depending on the type of quality defect, the modeling material used and / or the energy beam used.

According to a further development, the 3D printing device can be designed as a powder bed device. Accordingly, the modeling material can be deposited in powder form.

According to a development, the modeling material can be selected from the group of metallic materials, plastics and composite materials.

The above configurations and developments can be combined with one another as desired, provided that it makes sense. Further possible configurations, developments and implementations of the invention also include combinations, not explicitly mentioned, of features of the invention described above or below with regard to the exemplary embodiments. In particular, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the present invention.

• 1 schematische Ansicht einer 3D-Druckvorrichtung zur Durchführung eines 3D-Druckverfahrens gemäß einer Ausführungsform der Erfindung;
• 2 schematisches Ablaufdiagramm des 3D-Druckverfahrens, welches von der 3D-Druckvorrichtung in 1 durchgeführt wird; und
• 3 bis 6 schematische Ansichten aufeinanderfolgender Verfahrensschritte des Verfahrens aus 2.

The present invention is explained in more detail below with reference to the exemplary embodiments specified in the schematic figures. It shows:

• 1 schematic view of a 3D printing device for performing a 3D printing method according to an embodiment of the invention;
• 2 schematic flowchart of the 3D printing process, which is used by the 3D printing device in 1 is carried out; and
• 3 to 6th schematic views of successive process steps of the process 2 .

The accompanying figures are intended to provide a further understanding of the embodiments of the invention. They illustrate embodiments and, in conjunction with the description, serve to explain principles and concepts of the invention. Other embodiments and many of the advantages mentioned emerge with a view to the drawings. The elements of the drawings are not necessarily shown to scale with one another.

In the figures of the drawing are identical, functionally identical and identically acting elements, features and components - unless otherwise is executed - each provided with the same reference numerals.

1 shows a schematic view of a 3D printing device 1 for performing a 3D printing process M. according to one embodiment of the invention.

A schematic flow diagram of the 3D printing process M. is in 2 shown.

The 3D printing process M. is used for the additive manufacturing of components 14th . This includes the 3D printing process M. under M1 Depositing a modeling material 2 in material layers 3 and under M2 Fusion of the modeling material 2 with an energy beam 4th along a melt path 5 in the respective material layer 3 .

The modeling material 2 can be a plastic or, for example, be selected from the group of metallic materials, metallic material combinations and metallic alloys. For example, it can be the modeling material 2 be titanium, aluminum, nickel, steel and / or an alloy or material combination of these. Likewise, however, the modeling material can be a composite material made of several of these or other materials; reinforcement elements such as fibers or the like can also be provided if necessary. Basically, the modeling material 2 can also be supplied and deposited in powder, wire or tape form. In the example explained in more detail below, a powdery modeling material is used 2 used.

In principle, the present invention provides a wide range of possibilities for the modeling material 2 to liquefy, at which heat is targeted locally in deposited modeling material 2 can be initiated. The use of lasers and / or particle beams, for example electron beams, is particularly advantageous, since heat can be generated in a very targeted and controlled manner. The 3D printing process M. can thus be selected, for example, from the group of selective laser sintering, selective laser melting, selective electron beam sintering and selective electron beam melting or the like. In principle, however, any additive method can be used in which an energy beam is used. The following is the 3D printing process M. exemplified in connection with selective laser melting (SLM), in which the modeling material 2 in powder form on a work platform 11 is applied and targeted by local laser irradiation with an energy beam 4th from a laser 9 is liquefied, creating a solid, coherent component after cooling 14th results.

The 3D printing process M. is made with the 3D printing device 1 in 1 carried out. A source of energy in the form of a laser 9 , for example a Nd: YAG laser, sends a beam of energy 4th location-selective on a certain part of a powder surface of the respectively most recently deposited material layer 3 of the powdery modeling material 2 , which in a working chamber 12th on a work platform 11 rests. The laser can do this 9 have a corresponding adjustable optical lens through which the energy beam 4th on a certain part of the powder surface of the modeling material 2 can be distracted. At the point of impact of the energy beam 4th becomes the modeling material 2 heated so that the powder particles are melted locally and form an agglomerate when cooled. Depending on a digital production model provided and possibly processed by a CAD system (“computer-aided design”), for example, the energy beam scans or travels 4th the powder surface along a melt path 5 in every material layer 3 from. After the selective melting and local agglomeration of the powder particles in the surface layer of the modeling material 2 can use excess, non-agglomerated modeling material 2 be weeded out. Then the work platform 11 by means of a working piston 13 lowered (see arrow in 1 ) and with the help of a material feeder 10 such as a shovel or other suitable device, becomes new modeling material 2 from a material chamber 16 in the working chamber 12th convicted. This is done in the material chamber 16 a corresponding feed piston 17th provided that the powdery modeling material 2 gradually up to the material feeder 10 transported. The modeling material 2 can accelerate the melting process by using infrared light to just below the melting temperature of the modeling material 2 lying working temperature are preheated. In this way, a three-dimensional sintered or “printed” component is created in an iterative generative build-up process 14th made of agglomerated modeling material 2 . The surrounding powdery modeling material 2 can provide support for the part of the component that has been built up until then 14th serve. Due to the continuous downward movement of the work platform 11 the component is created 14th in layered model generation.

The 3D printing process M. also includes under M3 Detection of a local material condition of the fused modeling material 2 with an imaging device 6th the 3D printing device 1 along the melt path 5 . The imaging facility followed 6th the energy beam 4th in the melting line 5 gradually and captures the fused modeling material 2 locally along the melting line 5 . The imaging facility 6th is designed for this purpose and based on the energy beam 4th arranged that the imaging device 6th the Energy beam 4th at a given distance 8th in the melting line 5 follows.

At the imaging facility 6th In this exemplary embodiment, it is a computer tomograph that uses X-rays 15th Conclusions about an internal spatial structure and thus the local material condition of the fused modeling material 2 along the melt path 5 in the respective material layer 3 enables. A depth of penetration of the imaging device 6th into the deposited modeling material 2 can depend on the thickness of the material layers 3 be adjusted. For example, exactly a single layer of material can 3 are recorded. A scanning width of the imaging device can also be used 6th on the material layer 3 to the width of the energy beam 4th generated melt path 5 be adjusted.

The imaging facility 6th and the laser 9 are in the embodiment shown together on a holder 19th attached over the two devices together along the melting path 5 can be moved. Specifically, the two facilities are at a given distance 8th from each other on the holder 19th arranged. The relative position of the imaging device 6th is therefore related to the laser 9 set. The imaging facility 6th follows the laser 9 in the direction of movement or the alignment of the melt path 5 after, ie the imaging device 6th is related to the direction of movement behind the laser 9 and thus also behind the energy beam 4th arranged. The default distance 8th can for example be several centimeters tall.

The 3D printing process M. includes under M4 furthermore simultaneous analysis of the detected local material condition of the fused modeling material 2 in the melting line 5 on quality defects 18th with an analysis device 7th of the 3D printing device 1. The analysis device 7th with the imaging facility 6th and the laser 6th be communicatively connected, for example via a wireless or wired connection. The analysis facility 7th can for example be part of a control device of the 3D printing device 1 or at least be in communication therewith. Furthermore, the analysis device 7th for example have a microprocessor or the like which, with the aid of appropriate software, analyzes algorithms for evaluating the with the imaging device 6th can execute recorded data. In principle, a display, a monitor or the like can also be provided (not shown) via which both the data from the imaging device 6th as well as the evaluation results of the analysis device 7th can be displayed and checked and / or monitored, for example, by an operator. Of course, the 3D printing device 1 can also partially or fully automate or autonomously the method M. run without human input.

The analysis facility 6th is designed, among other things, to identify a type and / or a criticality of the quality defect 18th ascertain. The analysis facility 6th can thus different quality defects 18th identify and separate from one another, for example material consolidation defects, fusion deficits, thermal cracks, gas inclusions, cavities and / or defects, etc. Furthermore, the analysis device 6th assess whether a repair of the quality defect 18th is required or whether the quality defect 18th in extreme cases cannot be remedied and the component 14th is to be sorted out. For example, one or more defect thresholds can be defined which define acceptable sizes for defects, for example cavities or pores, with a repair of the corresponding point being automatically initiated when these defect thresholds are exceeded. It can be provided here that these error thresholds can be adapted to the corresponding application, for example by an operator and / or in an automated manner by the 3D printing device 1.

In the event that a quality defect 18th is detected and this can be remedied, includes the 3D printing process M. under M5 re-fusing of the modeling material 2 with the energy beam 4th in the melting path, the remelting with changed printing parameters according to the type of quality defect 18th he follows. For this purpose the energy beam 4th by the specified distance 8th in the melting line 5 set back in such a way only the last energized area in the melt path 5 again with the energy beam 4th to edit. Here the energy beam can 4th be operated with adapted parameters that are tailored to a subsequent improvement. For example, in typical applications it can be sufficient if the faulty point is in the melt path 5 is irradiated with lower power or energy in order to improve it, for example to close existing pores, cracks or the like.

The 3D printing device 1 thus moves in every material layer 3 Production continues until cavities, pores, etc. occur that are greater than a predefined limit value. In this case, the 3D printing device 1 stops moving forward. The holder 19th moves the specified distance 8th backwards until the laser is 6th is above the faulty location. The modeling material 2 is now melted or welded again with reduced energy or power. Then the holder moves 19th further forward and the The patched area is reassigned by the imaging facility 6th appraised. Several repair passes may be necessary. If, however, the error could be eliminated, the owner can 19th further along the material layer 3 to complete the component 14th be moved.

3 to 6th show an example of such a process sequence. First, in 3 a new material layer 3 of the powdery modeling material 2 upset. Then the new material layer 3 in 4th with the energy beam 4th along a melt path 5 scanned, the modeling material 2 is merged (dark hatching). At the same time, the state of the fused modeling material 2 from the imaging facility 6th locally behind the energy beam 4th recorded and assessed. In 5 becomes an example of a quality defect 18th found, for example, the modeling material 2 in this case not properly merged (light hatching). The energy beam 4th is now stopped and the holder 19th with the laser 9 and the imaging device 6th will move the specified distance 8th between the energy beam 4th and the imaging device 6th pulled back. The faulty location is then displayed in 6th again with the energy beam 4th machined to the modeling material 2 to fuse sufficiently.

Any quality defects, defects and / or printing errors that occur are thus immediately after the application of the energy beam 4th corrected so that temperature-related stresses or the like are avoided, which could occur, for example, when the component 14th or at least the current material situation 3 would initially cool down in the run-up to repair work. From a structural mechanical point of view, the process offers considerable advantages. At the same time, the reject rate due to defective components can be drastically reduced. The procedure described M. can be implemented as a closed control loop, on the basis of which the 3D printing device 1 automatically creates a component 14th finished and relevant quality defects 18th can at least largely clean up independently.

In the preceding detailed description, various features have been summarized in one or more examples in order to improve the stringency of the presentation. It should be clear, however, that the above description is merely illustrative and in no way restrictive in nature. It serves to cover all alternatives, modifications, and equivalents of the various features and exemplary embodiments. Many other examples will be immediately and immediately apparent to those skilled in the art on the basis of their technical knowledge in view of the above description.

The exemplary embodiments were selected and described in order to be able to present the principles on which the invention is based and their possible applications in practice as well as possible. As a result, those skilled in the art can optimally modify and use the invention and its various exemplary embodiments with regard to the intended use. In the claims and the description, the terms “including” and “having” are used as neutral terms for the corresponding terms “comprising”. Furthermore, the use of the terms “a”, “an” and “an” should not fundamentally exclude a plurality of features and components described in this way.

List of reference symbols

1

3D printing device

2

Modeling material

3

Material position

4th

Energy beam

5

Melting line

6th

Imaging facility

7th

Analysis facility

8th

specified distance

9

laser

10

Material feeder

11

Work platform

12

Labor Chamber

13

Working piston

14th

Component

15th

X-ray

16

Material chamber

17th

Feed piston

18th

Lack of quality

19th

holder

M.

3D printing process

M1-M5

Process step

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• WO 2016/183210 A1 [0005]

Claims (15)

3D printing process (M), with: Depositing (M1) a modeling material (2) in material layers (3); Fusing (M2) the modeling material (2) with an energy beam (4) along a melting path (5) in the respective material layer (3); Detection (M3) of a local material state of the fused modeling material (2) with an imaging device (6) along the melt path (5), the imaging device (6) following the melted modeling material (2) after the energy beam (4) in the melt path (5) detected locally along the melt path (5); simultaneous analysis (M4) of the detected local material condition of the fused modeling material (2) in the melt path (5) for quality defects (18) with an analysis device (7); and renewed melting (M5) of the modeling material (2) with the energy beam (4) in the melt path (5) in the area of the quality defect (18) if a quality defect (18) is detected. 3D printing process (M) according to Claim 1 , wherein the imaging device (6) follows the energy beam (4) at a predetermined distance (8) in the melt path (5). 3D printing process (M) according to Claim 2 , wherein the energy beam (4) is set back by the predetermined distance (8) in the melting path (5) in order to remelt the modeling material (2) in the event of a quality defect (18). 3D printing process (M) according to one of the Claims 1 to 3 , wherein the imaging device (6) records an internal spatial structure of the fused modeling material (2) along the melt path (5) in the respective material layer (3) in order to detect the local material state. 3D printing process (M) according to Claim 4 wherein the imaging device (6) detects the local material state of the fused modeling material (2) on the basis of a tomographic method. 3D printing process (M) according to Claim 5 , the tomographic technique using X-rays. 3D printing process (M) according to one of the Claims 1 to 6th , whereby a type and / or a criticality of the quality defect (18) is determined and the energy beam (4) is controlled based on this. 3D printing process (M) according to one of the Claims 1 to 7th , the renewed merging (M5) taking place with changed printing parameters. 3D printing process (M) according to one of the Claims 1 to 8th , wherein the modeling material (2) is deposited in powder form. 3D printing device (1), which is designed to deposit modeling material (2) in material layers (3) and to fuse the deposited modeling material (2) with an energy beam (4) along a melting path (5) in the respective material layer (3) , wherein the 3D printing device (1) comprises: an imaging device (6) which is designed to follow the energy beam (4) in the melt path (5) and to detect a local material state of the melted modeling material (2) locally along the melt path (5); and an analysis device (7) which is designed to analyze the detected local material state of the fused modeling material (2) simultaneously in the melt path (5) for quality defects (18), the 3D printing device (1) also being designed to To fuse the modeling material (2) again with the energy beam (4) in the melt path (5) in the area of the quality defect (18) when a quality defect (18) is detected. 3D printing device (1) Claim 10 , the imaging device (6) being designed and arranged in relation to the energy beam (4) in such a way that the imaging device (6) follows the energy beam (4) at a predetermined distance (8) in the melt path (5). 3D printing device (1) Claim 11 , wherein the 3D printing device (1) is designed to move the energy beam (4) back by the predetermined distance (8) in the melt path (5) in order to melt the modeling material (2) again in the event of a quality defect (18). 3D printing device (1) according to one of the Claims 10 to 12th , wherein the imaging device (6) is designed to record an inner spatial structure of the fused modeling material (2) along the melt path (5) in the respective material layer (3) in order to detect the local material state. 3D printing device (1) Claim 13 , wherein the imaging device (6) is designed as a tomograph, in particular a computer tomograph. 3D printing device (1) according to one of the Claims 10 to 14th , wherein the 3D printing device (1) is designed as a powder bed device.

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