DE102015224395A1 - Device and method for producing a component in a layered construction, use of a detection device in a layer construction method - Google Patents

Abstract

The invention relates to a device and a method (10) for producing components (16) in a layer construction method comprising: a container (18) which defines a construction space (19) in which a powder bed (29) of a powdery starting material ( 19) is producible,
an exposure device (21) for generating a light beam (22) with which regions of a layer of pulverulent starting material are solidifiable, a coating device (26) for producing an uppermost layer of powdery starting material on the underlying powder bed (29), characterized by a detection device (27 ), for detecting surface irregularities on the powder bed (29). Moreover, the invention relates to the use of a detection device (27).

Description

The present invention relates to an apparatus and a method for producing components in layered construction according to the type specified in the preamble of the independent claims, as well as a use of a detection device in a layer construction method.

For the production of prototypes or of components which are needed only in small numbers, one uses in today's vehicle construction of the so-called rapid prototyping. This is a manufacturing process in which three-dimensional pattern components are generated based on design data. In this master-molding process, of shapeless material, e.g. powdered plastic or metal, a workpiece produced in layers. As a component while a tool and / or a prefabricated component can be realized. The term "rapid prototyping" particularly includes electron beam melting, laser deposition welding, beam melting, 3D printing, stereo lithography and selective laser sintering.

In these methods, the component is produced from the source material layer by layer on a construction platform. In this case, coating steps and exposure steps are alternately carried out. In a coating step, a new layer of powdered material is produced. Subsequently, a predetermined area is solidified in the powder layer in an exposure step. During solidification, the powder material is melted by energy input, for example by means of a laser beam or an electron beam, and bonded cohesively to adjacent powder material. This can lead to errors or impurities in an already solidified layer. These impurities can be, for example, spatters of sweat, which arise when the predetermined areas solidify and lead to secondary defects in overlying layers which are later produced. Such impurities can also result, for example, from thermal distortion of component regions which lie in already solidified layers. Such a distortion causes the already generated component area bulges, which parts of the manufacturing device can be damaged.

To circumvent these disadvantages, the prior art has attempted to monitor generative methods by optical control. Here, an operator of the device takes a sense of control of the individual powder layers. The result of this control is highly dependent on the subjective assessment of the monitoring operator and only to a limited extent as a measure of the quality of the powder layer to use.

Starting from this prior art, it is the object of the present invention to provide an improved apparatus, an improved method and a use with which the disadvantages of the prior art are overcome. It is another object of the invention to provide a device, an improved method and a use, with the components can be produced in the layer construction process, which are characterized by a high production quality.

To solve this problem, the invention proposes a device for the production of components in a layer construction process. The apparatus may be a container which defines a space in which a powder bed of a powdery starting material is generated in layers, an exposure device for generating a light beam with the areas of a layer of powdery starting material are solidified and a coating device for producing an uppermost layer of powdery starting material on the underlying powder bed. Furthermore, a detection device may be provided for detecting surface irregularities on the powder bed. This offers the advantage that the entire manufacturing process is actively monitored in order to detect defects in the layer order can.

For the purposes of this invention, the surface of the powder bed has areas with non-solidified starting material and areas in which the powdery starting material has been solidified by energy input. The surface of the powder bed thus corresponds to the surface of an uppermost layer of powder material, which has already been solidified in sections by an exposure step. For the purposes of this invention, a solidification of the starting material in the broadest sense can be carried out by energy input. Accordingly, an exposure device is to be understood as a solidification device. The light beam is to be understood as an energy beam and in particular comprises formations in the form of a laser beam or an electron beam.

According to one embodiment, the scanning of the surface can be carried out with an optically based detection device and comprise a line laser with which a line-shaped light spot can be generated on the surface of the powder bed. Advantageously, even the smallest differences in the quality of the layer structure can be detected, so that a much better quality than in a monitoring with the naked eye can be achieved. The detection device may have a camera for detecting the line-shaped light spot.

Furthermore, in a control device based on a triangulation method, the presence of unevenness on the surface of the powder bed can be evaluated. The triangulation method is particularly suitable for easily determining the distance of a point from a reference point. As a result, a height difference on the surface of the powder bed can be detected in a particularly simple manner.

Alternatively, in another embodiment, the detection means may scan the surface of the powder bed by means of an electromagnetic wave. The detection device is radio-based, in particular designed as a radar system. Such radar systems provide in the near field range, a detailed resolution and a very high speed in information processing.

The detection device can be movable across the surface of the powder bed. This offers the advantage that a height profile of the powder bed surface can be created.

In one embodiment, the detection device can be arranged on the coating device. This results in the advantage that immediately before the production of a coating, the powder bed surface is examined for unevenness.

The detection device can advantageously be generated during a movement of the coating device in which the coating device has an uppermost layer which precedes the coating device. Thus, in the sense of functional integration, a very efficient device can be provided, wherein the method steps of detecting unevenness and generating a powder layer take place simultaneously or secondarily in parallel.

Furthermore, the detection device can be designed in particular as a line laser scanner or as a radar sensor.

As an alternative to the variant described above with a mobile detection device, a static or stationary detection device can also be used. In this case, a strip light projection scanner is preferably used. This offers the advantage that the surface of the powder bed can be completely monitored at the same time. Thus, a height profile of the entire surface can be detected in a short time.

The invention also relates to the use of a detection device for detecting surface irregularities on the surface of a powder bed in a layer-building process.

Advantageously, all the variants of detection devices described above can be used as detection device in order to detect a distance of individual surface points to the detection device.

Furthermore, a control device can be used which evaluates the presence of surface unevenness on the basis of a triangulation method.

According to a first embodiment of the invention, a detection device is used which can be moved across the surface of the powder bed. Preferably, the detection device is arranged on a coating device. During a movement (F) of the coating device in which the uppermost layer can be produced by the coating device, the detection device leads the coating device.

• – Erfassen des Abstandes zwischen einer Erfassungseinrichtung und einzelner Punkte der Oberfläche,
• – Ermitteln von Unebenheiten auf der Oberfläche, auf Basis der erfassten Abstände, und
• – Abgleich der ermittelten Unebenheiten mit Referenzunebenheiten.

In a further aspect, the invention relates to a method for monitoring a surface of a powder bed with the steps:

• Detecting the distance between a detection device and individual points of the surface,
• - Determine surface imperfections based on the detected distances, and
• - Adjustment of the determined unevenness with reference unevenness.

In a method step, first a line-shaped light spot can be generated on the surface.

Furthermore, the detection of the distance can be done by means of a triangulation method.

• – in einem Beschichtungsschritt eine obersten Schicht aus pulverförmigen Ausgangsmaterial auf dem darunter liegenden Pulverbett erzeugt wird und
• – in einem Belichtungsschritt mit einem Lichtstrahl Bereiche einer Schicht aus pulverförmigen Ausgangsmaterial verfestigt werden, wobei die beiden Schritte bis zur Fertigstellung des Bauteils abwechselnd ausgeführt werden, dadurch gekennzeichnet, dass
• – vor jedem Belichtungsschritt eine Oberfläche des Pulverbetts mit einem im vorhergehenden beschriebenen Verfahren überwacht wird.

Moreover, the invention relates to a layer construction method for the production of components wherein in a container which defines a space, a powder bed of a powdery starting material is produced in layers, wherein

• - In a coating step, an uppermost layer of powdery starting material is produced on the underlying powder bed and
• In an exposure step with a light beam, regions of a layer of powdery starting material are solidified, wherein the two steps are carried out alternately until completion of the component, characterized in that
• - Before each exposure step, a surface of the powder bed is monitored by a method described above.

The invention primarily offers the advantage that the topography of the powder bed is monitored in terms of irregular quality of the layer. The topography of the powder bed surface is thus a quality feature for the quality of the layer formed and thus of the powder bed. It can be the smallest irregularities in the powder bed detect, which are reflected as small bumps on the surface. This improves the quality of the manufacturing process. On the other hand, by deriving suitable control measures in the event of the detection of an impurity, the component properties of the manufactured products can also be improved. Not least, a high reproducibility of the Bauresultate is achieved. Through continuous monitoring of the powder bed throughout the process, countermeasures can be taken immediately to detect any irregularities.

The invention is explained in more detail below with reference to the description of the figures. The claims, the figures, and the description include a variety of features that will be discussed below in conjunction with exemplary embodiments of the present invention. The person skilled in the art will also consider these features individually and in other combinations to form further embodiments that are adapted to corresponding applications of the invention.

In a schematic representation:

1 a device for producing components in the layer construction method,

2 a detailed view of the device 1 , and

3 an apparatus for producing components in the layer construction method according to another embodiment.

In the following, the basic structure of the device as well as the basic sequence of the method during the manufacture of components in the layer construction method will first be explained with reference to FIG 1 ,

The 1 shows a rapid prototyping device 10 , with the in the layer construction process components 16 can be produced. The device comprises an exposure device 21 , For example, a laser, the Energierstrahl eg in the form of a laser beam 22 sending out. This laser beam 22 is via a deflection device 20 , for example, a mirror, distracted. The device 10 further comprises a container 18 with side surfaces and a bottom surface that provides a space 19 lock in. In the container 18 is a building platform 23 provided, via an adjusting device such as a lifting ram 21 in the vertical direction Z is movable. On one of the installation space 19 facing surface of the building platform 23 is a substrate 14 intended. On the substrate 14 becomes a first layer of powdery starting material 17 applied. This is from a memory, not shown, the interior of the container 18 fed. With the help of a coating device 26 , such as a wiper device, the powdered starting material 17 on the surface of the substrate 14 be spread evenly and thinly to produce a first layer in this coating step. Subsequently, the laser beam 22 on the layer of the powdery starting material 17 passed, whereby this solidifies to a first region of the component 16 ,

Depending on the desired component geometry, it may be prior to the production of individual areas of the component 16 first a support structure 15 be produced by powdered starting material 17 is solidified. In the 1 Two areas are shown in which a support structure 15 is needed. In the middle, intermediate area is on a support structure 15 has been omitted, since the slope of the component contour with an horizontal line forms an angle of more than 45 °. In these cases, it is possible to build directly onto the previous solidified component layer (component area) without a support structure for this purpose 15 is needed.

After the applied layer with the help of the laser beam 22 was solidified in an exposure step, the building platform 23 lowered by a predetermined amount. In a further subsequent coating step, a new layer of the powdery starting material 17 applied in a further exposure step. again solidified by laser energy to the parts of the starting material 17 melt and other areas of the component 16 train. Alternating exposure and coating steps make the component 16 generated in layers. At the beginning of the procedure is the construction platform 23 in the upper area of the installation space 19 and is successively lowered down. 1 thus represents the end point of a layer construction process in which the component 16 is being completed.

In 2 is the detail D off 1 shown enlarged. At the coating device 26 is a detection device 27 provided with the the surface 28 of the powder bed 29 can be sampled. The powder bed 29 For the purposes of this invention, all layers which have been solidified at least in sections in previous exposure steps. In the powder bed 29 are therefore already finished component areas of the component 16 formed by unconsolidated starting material 17 are surrounded. The detection device 27 can be designed in particular as a laser line scanner. This sends a laser beam 25 and creates a line on the surface 28 of the powder bed 29 , Experiments have shown that the use of a line laser with a sampling rate of 200 Hz, about 60 mm above the surface 28 of the powder bed 29 is positioned, provides good scanning results.

The course or the geometric contour of the line through the line laser on the surface 28 is generated, is detected by means of an optical camera. With the aid of a triangulation method, the distance of each point illuminated by the laser at the surface over the entire length of the line becomes the detection device 27 determined. Defects described above 30 , as they arise, for example, by welding spatter, have a particle size whose order of magnitude is in the range of about 200 microns. Such defects 30 make an elevation or a roughness on the surface 28 of the powder bed 29 This unevenness can be detected by the detection device 27 be well recognized, since the grain size of the powder material in the range of 20μm to 50μm and thus is much smaller. In other words, with the detection device 27 a height difference between different surface points of the surface 28 of the powder bed 29 measured.

To create a height profile of the surface 28 , the capture device becomes 27 over the surface 28 away. According to the in 2 the embodiment shown is the detection device 27 at the coating device 26 arranged. In other embodiments, not shown, the detection device can also be independent of the coating device 26 at the device 10 be educated. Preferably, the line length produced by the line laser on the surface corresponds to the width of a new powder layer or the width of a powder layer portion coming from the coater 26 is produced. During a translatory movement of the coating device 26 in the direction of arrow F, a new layer or layer of powdered material is applied to the powder bed 29 Applied and at the same time the surface 28 of the powder bed 29 scanned for bumps.

Once an unevenness, ie a height difference is detected which is greater than a predetermined maximum tolerable height difference, a control device checks whether the unevenness is an impurity which could disturb the function of the device. For this purpose, an adjustment of the height of the unevenness with a predetermined maximum allowable height. When exceeding this height, for example, the coating device 26 get in touch with the unevenness. As a result, damage to the coating device could occur 26 or on the device 10 result. Such unevenness can, for example, have the so-called "curling" as a cause. Upon determination that the amount of unevenness exceeds the maximum allowable height, the manufacturing apparatus is stopped. This emergency stop function ensures that no malfunction of the device due to curling occurs.

Further, the controller performs a check to determine whether the unevenness is an impurity or a tolerable unevenness. Unevenness, the height of which is smaller than the maximum permissible height, does not pose a risk to the correct functioning of the device. However, such unevenness, such as that caused by welding splashes, can lead to pore formation in the Z direction above the unevenness in overlying layers. In the area of these pores occurs a faulty exposure of the powder material, which causes errors in the finished component. For this purpose, the control device checks whether the component to be manufactured 16 , Has areas that are above the detected unevenness. If this is true, the recorded unevenness is an impurity. In order to prevent the already partially produced component from becoming a reject part, the control device issues a corresponding error message.

To eliminate the source of error then come various regulatory measures into consideration. In a first variant, a new layer can be created. Alternatively, by adjusting the build platform in the Z direction, the defect can be corrected. In a further alternative, the elevation or unevenness can be removed with the aid of, for example, a milling device. Alternatively, by appropriate application of energy (e.g., laser beam, electron beam), the cant can be reflowed and corrected. Last but not least, an operator can also eliminate the detected defect manually.

Alternatively, only the processing of individual components can be switched off. This offers advantages when several components are simultaneously produced in a powder bed. If above an already generated component portion of a component an impurity is detected, this component is considered scrap and their further processing is suppressed and only the non-defective components processed further. So not the whole process succumbs. In addition, it is also prevented that due to curling damage to the coating device comes through which the entire construction process is suppressed and thus all components become rejects.

If the component to be manufactured 16 has no areas that are located above the defect, the detected unevenness is classified as non-critical. The manufacturing process is then continued without interruption.

In 3 is a device 10 for producing component 16 shown in layer construction process. Same reference numerals as in the 1 and 2 describe the same components. Notwithstanding the in the 1 and 2 shown embodiment in which the detection device 27 is designed to be movable, the embodiment has 3 a stationary detection device 27 ' , The detection device 27 ' is static and has a detection range, which essentially corresponds to the entire surface of the powder bed, so that can be dispensed with a translational movement. The stationary detection device 27 ' offers the advantage that the topography of the surface is recorded simultaneously. In other words, a height profile of the surface of the powder bed is created substantially simultaneously, wherein the height of all surface points is detected. This can speed up the construction process.

LIST OF REFERENCE NUMBERS

10

 Laser sintering device

14

 substratum

15

 support structure

16

 component

17

 Powdered starting material

18

 container

19

 space

20

 mirror

21

 exposure means

22

 beam of light

23

 building platform

24

 lifting ram

25

 laser beam

26

 coater

27

 monitoring device

28

 surface

29

 powder bed

30

 unevenness

Claims (20)

Contraption ( 10 ) for the production of components ( 16 ) in a layering process comprising: - a container ( 18 ), which has a space ( 19 ) in which in layers a powder bed ( 29 ) from a powdery starting material ( 19 ), - an exposure device ( 21 ) for generating a light beam ( 22 ) are solidifiable with the areas of a layer of powdery starting material, - a coating device ( 26 ) for producing a topmost layer of powdery starting material on the underlying powder bed ( 29 ) characterized by - a detection device ( 27 ), for detecting surface irregularities on the powder bed ( 29 ). Apparatus according to claim 1, characterized in that the detection device ( 27 ) - a line laser, with a line-shaped light spot on the surface of the powder bed ( 29 ) is producible and - has a camera for detecting the line-shaped light spot. Device according to one of the preceding claims, characterized in that in a control device based on a Triangulationsmethodik be present can be evaluated by uneven floors. Device according to one of claims 1 or 3, characterized in that the detection device ( 27 ) the surface ( 28 ) of the powder bed ( 29 ) detected by means of an electromagnetic wave, in particular radio-based and in particular designed as a radar system. Device according to one of the preceding claims, characterized in that the detection device ( 27 ) over the surface ( 28 ) of the powder bed is movable across. Apparatus according to claim 5, characterized in that the detection device ( 27 ) on the coating device ( 26 ) is arranged. Device according to one of the preceding claims, characterized in that the detection device ( 27 ) during a movement (F) of the coating device ( 26 ) in the with the coating device ( 26 ) an uppermost layer can be generated, the coating device ( 26 ) hastens. Device according to one of the preceding claims, characterized in that the detection device ( 27 ' ) is stationary. Use of a detection device ( 27 ), for detecting surface irregularities on the surface ( 28 ) of a powder bed ( 29 ), in a layer construction process. Use according to claim 9, characterized in that the detection device ( 27 ) comprises a line laser or a radio device with which a distance of individual surface points to the detection device ( 27 ) is measurable. Use according to one of claims 9 or 10, characterized in that the detection device ( 27 ) has a camera for detecting the line-shaped light spot. Use according to one of the preceding claims, characterized in that in a control device based on a Triangulationsmethodik be present from bumps is evaluable. Use according to one of the preceding claims, characterized in that the detection device ( 27 ) over the surface ( 28 ) of the powder bed is movable across. Use according to claim 13, characterized in that the detection device ( 27 ) on a coating device ( 26 ) is arranged. Use according to one of the preceding claims, characterized in that the detection device ( 27 ) during a movement (F) of the coating device ( 26 ) in the with the coating device ( 26 ) an uppermost layer can be generated, the coating device ( 26 ) hastens. Use according to one of the preceding claims, characterized in that the detection device ( 27 ) is designed as a line laser scanner. Method for monitoring a surface ( 28 ) of a powder bed ( 29 ) comprising the steps of: - detecting the distance between a detection device ( 27 ) and individual points of the surface ( 29 ), - determination of surface irregularities ( 28 ), based on the recorded distances, - adjustment of the determined unevenness with reference unevenness. A method according to claim 17, comprising the steps of: - producing a line-shaped light spot on the surface ( 28 ). Method according to one of claims 17 or 18, characterized in that takes place for detecting the distance by means of a triangulation method. Layer construction method for the production of components, wherein in a container ( 18 ), which has a space ( 19 ), layer by layer a powder bed ( 29 ) from a powdery starting material ( 19 ), wherein - in a coating step, an uppermost layer of powdery starting material on the underlying powder bed ( 29 ) and - in an exposure step with a light beam ( 22 ) Areas of a layer of powdery starting material are solidified, wherein the two steps are carried out alternately up to the completion of the component, characterized in that - before each exposure step , a surface ( 28 ) of the powder bed ( 29 ) is monitored by a method according to claims 17 to 19.

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