EP3183109A1

EP3183109A1 - Device and method for the production of three-dimensional objects

Info

Publication number: EP3183109A1
Application number: EP15753673.1A
Authority: EP
Inventors: Frank Herzog; Florian DR. BECHMANN; Fabian Zeulner; Tobias BOKKES; Marie-Christin EBERT
Original assignee: CL Schutzrechtsverwaltung GmbH
Current assignee: CL Schutzrechtsverwaltung GmbH
Priority date: 2014-08-22
Filing date: 2015-08-18
Publication date: 2017-06-28
Also published as: WO2016026853A1; US20170274592A1; DE102014012286B4; CN110239091A; DE102014012286A1; CN107073838B; CN107073838A

Abstract

The invention relates to a device (1) for the production of three-dimensional objects (9) by successive solidification of layers of a construction material (7) which can be solidified by means of radiation at the points corresponding to the respective cross section of the object (9), comprising a construction chamber (4) in which a support device (8) is arranged for supporting the object (9), the support device comprising a height adjustable carrier (22), a radiation device (13) for irradiating layers of the construction material (7) at the points corresponding to the respective cross section of the object (9), and an image acquisition device (17) for acquiring at least one image data set imaging the construction chamber (4), wherein at least one position mark (20, 24) is present in the construction chamber (4) for calibrating the image acquisition device (17). The invention further relates to a method for executing a calibration.

Description

DESCRIPTION

Device and method for producing three-dimensional objects

The invention relates to a device for producing three-dimensional objects by successively solidifying layers of a radiation-hardenable building material at the locations corresponding to the respective cross-section of the object, with a building chamber in which a carrying device for carrying the object is arranged with a height-adjustable support Irradiation device for irradiating layers of the building material at the locations corresponding to the respective cross-section of the object and an image recording device for receiving at least one image data set which images the construction chamber.

When referred to above as an image pickup device, so are also including devices that use a C-MOS or CCD technique, i. Devices in which an image is generated from individual pixel data. The term "image pickup device" should therefore be understood to include such electronic devices as well.

Forming methods are known in which a material is solidified in layers at predetermined locations so as to build a three-dimensional object. Basically, fluids such as in stereolithography or powders such as laser sintering (SLS) or laser melting (LSM) can be solidified. The already processed layers are lowered in layers and a new layer applied to solidify the building material in the desired places.

In the case of a layered order, incorrect applications may occur. Furthermore, the different heating of the building material is a problem because it may affect the strength of the created three-dimensional object.

It is therefore still known to use a camera for monitoring the installation space or the building chamber. EP 2 032 345 B1 teaches a device for selective laser powder processing in which the camera or the photodiode array or the CCD array is guided to the laser beam for solidifying the powder.

It is also known, based on the image data, the irradiation energy or the Retention of the laser to modify so that the energy input per area section is controlled. As a result, multiple melting of the same surface area can be avoided. Despite all the improvements, there is the problem that the image data taken from the camera or the data derived therefrom do not have the required accuracy in the prediction of the derived data such as the temperature of the melt pool, ie the melted and not yet re-solidified building material have too much tolerance.

It is therefore an object of the present application to provide a device of the type mentioned, in which the processing quality of the recorded image data is increased. To solve this problem, a device having the features of claim 1 is proposed. Advantageous developments emerge from the subclaims.

As the core of the invention, it is considered that the image recording device can be calibrated by means of position marking or position markings in the construction chamber. It has been found that the inaccuracies in the further use of the image data of the image recording device are position-dependent and thus a dependence of information from the place in the image is present. Accordingly, this position-dependent measurement inaccuracy of the image pickup device is compensated by calibration.

Thus, in the present application, a calibration is an acquisition of information in such a way that measurement inaccuracies in image data records recorded during the construction process can be compensated. These inaccuracies of measurement depend on the construction and can not be eliminated by repositioning the image pickup device.

Accordingly, the position marking is not intended to mark a specific position in the construction chamber, but rather marks a specific image position. By evaluating the image area depicting the position marker, data for compensating the measurement inaccuracies can be obtained.

For a calibration, any value should be used as normal. Deviations from this standard are used by one or more calibration dates To obtain calibration data. The normal may be the intensity value in the center of an image data set taken by the camera. Alternatively, it may be the brightest or darkest intensity value of the image data set in the entire image or a predefinable image area. Further embodiments will be described below.

A mirror arrangement with at least one mirror can be arranged between the image recording device and the construction chamber. This mirror arrangement serves for deflecting the laser beam output by the laser device for solidifying the building material. However, the building chamber can also be used to record at least partially imaging image data via this mirror arrangement.

Advantageously, the at least one position marking may be arranged at the bottom of the building chamber or at a bottom plate at the bottom of the building chamber. The position-dependent measurement inaccuracies relate to the layer of construction material that lies in the so-called building level and is or is to be irradiated with a laser beam. The building level is a plane parallel to the floor and floor slab. Therefore, optimal calibration can be achieved by means of ground-based position markers.

Preferably, a light-permeable heat protection device, in particular made of glass ceramic, can be arranged above the position marking. If the position markings are sensitive to heat, they are protected by the glass-ceramic layer, since this shields the thermal energy introduced by the laser beam and passed on via the build-up tetarial from the position markings.

It is preferably provided that the position markings simulate a uniform emission behavior of the build-up material installed in the construction chamber, at least regionally or in support sites. It is thus pretended that the building material has a given heat radiation, which is constant throughout the construction plane. The emitted electromagnetic radiation is simulated by the position markers. In extreme cases, the position marking is a lighting device that impacts the bottom or the bottom plate in whole or in part.

In order to realize the position markings cost-effectively, these can be used as LED Lamp is designed. These preferably emit light in the visible and infrared wavelength range from 700 nm to 1100 nm, in particular at a wavelength between 800 nm and 900 nm. This is the wavelength or that wavelength range which is also emitted by the heated build material. By simulating the radiation of the building material under idealized conditions, in particular with respect to the temperature considered constant, it can be achieved that deviations in the representation of an image area of the image data set representing the position marking or position markings from another image area alone affect the position-dependent measurement inaccuracies of the image recording device can be returned, whereby they are correctable.

In principle, it does not matter whether the homogeneous light emission is realized over a region of the bottom or the bottom plate with a single position marking or with a multiplicity of position markings. However, it is preferred to provide a plurality of position markers. This has the advantage that in case of failure of a position marker still a calibration of the image pickup device is possible. Then it is preferred that the position markings each have a predetermined light emission angle, which is in particular parallel. The image recording device then forms parallel light beams, as a result of which position-dependent measurement inaccuracies can be ascertained and corrected particularly easily.

When using a plurality of position markers, the position marks form support points. Intermediate areas can be interpolated.

An image data record which maps at least one position marking is therefore used to obtain at least one calibration information item or one calibration data item. This happens before a construction process. The calibration data then corrects the image data sets that represent the construction level in the construction chamber during a construction process, so that the data derived therefrom, such as temperature data, are corrected for the position-dependent measurement inaccuracies. The device for producing three-dimensional objects is preferably a laser melting or laser sintering device.

The image pickup device is preferably designed as a photo or camera. she can So record individual images or image data sets or continuous image data sets. The image recording device is preferably designed for recording in the visible light range or in the infrared range.

In addition, the invention relates to a method for producing a three-dimensional component by a generative construction method, wherein the component takes place by successively solidifying defined areas of individual layers by the action of a radiation source on the solidifiable building material, wherein the areas are solidified in spaced individual sections, and wherein a Image recording device for receiving at least one image data set of the building material receiving the building chamber is provided. This is characterized in that the image recording device records at least one image data record as a reference image data record with at least one light-emitting position marker and makes use of the at least one reference image data record to correct an image data record taken during a construction process.

Further advantages, features and details emerge from the figures and exemplary embodiments described below. Showing:

1 shows an apparatus for producing three-dimensional objects,

2 shows the structure in the bottom region of the building chamber in cross section,

3 shows position markings of a first embodiment,

4 shows position markings of a second embodiment,

5 shows position markings of a third embodiment,

6 shows a calibration data record, and

Fig. 7 is a flowchart for performing a calibration.

FIG. 1 shows a device 1 for producing three-dimensional objects by successively solidifying layers of a pulverulent, solidifiable material Building material. In this case, all not essential to the invention elements such as the gas supply for the supply of inert gas, which are always provided, not explicitly shown in the figures. Shown is a building module 2 with a metering chamber 3, a building chamber 4 and an overflow chamber 5. About the metering chamber 3 and the building chamber 4 is an applicator 6 for transporting building material 7 from the metering chamber 3 to the building chamber 4 movable. The building material is a powdery, solidified material made of metal or plastic. In the building chamber 4 is a carrying device 8. By means of the support device 8, the three-dimensional object 9 is height adjustable. The topmost layer of building material 7 in the building chamber 4 forms the building level 10. The building material 7 in the building level 10 is solidified by means of laser radiation at the appropriate locations. Once a layer of building material 7 is solidified in the building chamber 4 at the desired locations, the support device 8 is lowered and transported with the applicator 6, a new layer or layer of building material 7 from the metering chamber 3 to the building chamber 4. For lifting the building material 7 in the metering chamber 3, this also has a carrying device 1 1.

Above the building module is a mirror arrangement 12 with which the laser beam 14 emitted from a laser beam device 13 can be deflected so that the respective desired areas of the building surface 10 are irradiated. In the beam path of the laser beam 14 is still a lens assembly 15 and a beam splitter 16. With the lens assembly 15, the laser beam 14 is focused while the beam splitter 16 on the one hand for the laser beam 14 is transparent and on the other hand deflects light to the camera 17 as an image pickup device. Thus, the camera 17 can map the building level 10. The camera 17 is connected to a control device 18. This may be a control device 18 assigned to the camera 17, but it may also be the control device 18 of the device 1, which carries out a multiplicity of control tasks and, for the laser beam device 13 and / or the mirror assembly 12 controls.

The mirror assembly 12 and the lens assembly 15 may each include one or more mirrors or lenses. On the support device 8 of the building chamber 4, which forms the bottom of the building chamber 4, there is a bottom plate 19. In the bottom plate 19 recesses are provided, in which LED lamps 20 are arranged as position markings. On the bottom plate 19 is still a glass ceramic plate 21 as heat protection for the LED lamps 20. When building the first layers, a large amount of heat is emitted to the LED lamps 20 through the laser beam 14. By the glass ceramic plate 21, the LED lamps 20 are protected from it.

Figure 2 shows a cross section through the structure at the bottom of the building chamber 2. In this, the support 22 of the support device 8, the bottom plate 19 with the therein arranged LED lamps 20 and the glass ceramic plate 21 are shown. Not shown is the electrical connection of the LED lamps 20. This may be e.g. pass through the carrier 22. Also not shown is the spindle drive of the carrying device 8, which raises and lowers the carrier 22.

FIG. 3 shows a plan view of a base plate 19 for illustrating a possible distribution of the LED lamps 20. These and the distributions shown in FIGS. 4 and 5 are suitable for all kinds of position markings, not only for LED lamps 20.

FIG. 3 shows a lattice structure of the LED lamps 20. In the embodiment shown, the center points of the LED lamps 20, of which only three are provided with reference numerals for reasons of clarity, each have the same spacing, furthermore the connecting lines of the lattice are at right angles , But it is alternatively possible to use other grating structures such as, for example, diamond pattern etc.

FIG. 4 shows a further alternative arrangement of the LED lamps 20. These are arranged on concentric circles 23. The circles 23 are shown in dashed lines and intended only for orientation. The LED lamps 20, of which in turn only a few are provided with reference numerals by way of example, are represented by circles with closed lines.

The spacing of the circles is determined, inter alia, on the basis of the size of the LED lamps, the number to be achieved per area, the required wall thickness of the bottom plate 19 between the LED lamps 20, etc.

The LED lamps 20 may be arranged as threaded on spokes as shown be, wherein the number of spokes increases with increasing circular diameter also. The LED lamps 20 can also be arranged relatively arbitrarily on the circles 23. In a calibration, as described above, any value should be taken as normal. This can be the intensity value of the LED lamp 20 in the center of an image data record taken by the camera 17. Alternatively, it can be the brightest or darkest intensity value of an LED lamp 20 or a general position marker in the entire image or a predefinable image area. The choice of the normals depends on the framework conditions and may differ from the proposed designs.

FIG. 5 shows a further embodiment of a position marking as a planar lighting device 24. Preferably, the light output of the lighting device 24 is homogeneous over the entire surface, but it is finally sufficient if the distribution of the light output is known. This is then to be considered in the calibration of the camera 17. By way of example, the lighting device 24 can be obtained by providing a light-distributing plate above the LED lamps 20 in a structure as in FIG. This is preferably used below a glass ceramic plate 21.

The light output of the LED lamps 20 or the lighting device 24 is detected before the start of construction and by the camera 17 in at least one image data set. Based on this image data set and regardless of the design of the position markers at least one calibration date is obtained, in which case a date is understood as a singular of "data", that is to say information in particular in the form of numbers or numbers.

Preferably, a calibration data record 25 is determined from an image data record which maps the light emission of the position markings, in particular of the LED lamps 20 or the lighting device 24, by obtaining a normal value from a picture element, also referred to as pixel, or an image area by averaging over several picture elements , All further pixels are then divided by this normal value and the inverse is taken from this. This happens pixel by pixel. A calibration data set 25 is shown in FIG. Since these values are "contaminated" by noise, 25 areas 26, 27, 28, 29, 30 and 31 can be found in the calibration data set which differ only in noise, in these areas 26, 27, 28, 29, 30 and 31 In each case an average value can be formed in order to suppress or reduce the noise.

After creating the calibration data set 25, it is simply multiplied by pixels with the image data records recorded during the construction of the three-dimensional object 9 in order to eliminate the position-dependent measurement inaccuracies.

It is also apparent from FIG. 6 that the measurement inaccuracies do not have to occur symmetrically around the center of the image. With the described device and the described method, it is rather possible to eliminate any measurement inaccuracies.

7 shows a flowchart for carrying out a calibration of an image recording device, that is to say the camera 17. In step S1, a bottom plate 19 with LED lamps 20 is placed on the carrier 22 in a construction chamber 4 and an electrical connection to the LED lamps is established. Preferably, corresponding contacts are present on the carrier 22, so that a simple placement is sufficient. In step S2, the carrier 8 is moved to a height so that the lamps are at the level and emit light as the building level 10 is later.

In the following step S3, an image data record is taken with the camera 17. From this, a calibration data record 25 is determined in step S4. In this case, all current and described process steps, such as consideration of the distribution of the light output of the LED lamps 20 or the lighting device 24, averaging, selection of the norms, etc., can be used. For calculation, the control device 18 is used. The calibration data set 25 is then stored as step S5 in a memory device, not shown.

This calibration and creation of a calibration record 25 can be done before each Construction process done. But it can also be done once for commissioning the camera 17. In particular, LED lamps 20 having different wavelength outputs may be used to generate a respective calibration data set for a building material 7, respectively. The LED lamps with different wavelength outputs can also be arranged on a building board 19 and controlled separately. Alternatively, a separate bottom plate 19 or a separate bottom can be provided for each predetermined wavelength or each wavelength range. In this case, the distribution of the LED lamps 20 and the generation of calibration data or data records is independent of each other.

REFERENCE LIST

1 device

2 building module

3 dosing chamber

4 construction chamber

5 overflow chamber

6 application device

7 construction material

8 carrying device

9 three-dimensional object

10 construction levels

11 carrying device

12 mirror arrangement

13 laser beam device

14 laser beam

15 lens arrangement

16 beam splitters

17 camera

18 control device

19 base plate

20 LED lamp

21 glass ceramic plate

22 carriers

23 circle

24 lighting device

25 calibration data set

26 area

27 area

28 area

29 area

30 area

31 area

Claims

PAT E N TAN S P R O C H E

Device (1) for producing three-dimensional objects (9) by successively solidifying layers of a radiation-hardenable building material (7) at the locations corresponding to the respective cross section of the object (9), with a building chamber (4) in which a carrying device (FIG. 8) for carrying the object (9) with a height-adjustable support (22) is arranged, an irradiation device (13) for irradiating layers of the building material (7) at the respective cross-section of the object corresponding locations and an image pickup device (17) for receiving at least one image data set which images a section of the construction chamber or the entire construction chamber, characterized in that at least one position marking (20, 24) for calibrating the image recording device (17) is present in the construction chamber (4).

Apparatus according to claim 1, characterized in that the at least one position marking (20, 24) is arranged at the bottom of the building chamber (4).

3. Device according to claim 1, characterized in that the at least one position marking (20, 24) on a bottom plate (19) at the bottom of the building chamber (4) is arranged.

4. Device according to one of the preceding claims, characterized in that above the position marking (20, 24) a light-permeable heat protection device (21), in particular made of glass ceramic, is arranged.

Device according to one of the preceding claims, characterized in that the at least one position marking is designed as an LED lamp (20).

Device according to one of the preceding claims, characterized in that the position marker (20, 24) emits light in the visible and in the infrared wavelength range.

Apparatus according to claim 6, characterized in that the position marker (20, 24) emits light of a wavelength in the range between 800 nm and 900 nm.

Device according to one of the preceding claims, characterized in that a plurality of position markings (20) is provided, each having a predetermined Lichtabstrahlwinkel.

9. Apparatus according to claim 8, characterized in that the position markings (20) substantially

Have main emission directions.

10. Device according to one of claims 8 or 9, characterized in that the position markings (20, 24) radiate substantially to a mirror arrangement above the building chamber out.

1 1. Device according to one of the preceding claims, characterized in that at least one of the image recording device (17) recorded image data set by means of at least one calibration data set (25) is changeable.

12. Device according to one of the preceding claims, characterized in that at least one of the image recording device (17) recorded image data set by means of at least one plurality of light signals from LED lamps (20) having image data set is changeable.

13. Device according to one of the preceding claims, characterized in that at least one image data set recorded with the image recording device (17) can be used to determine a calibration data set (25).

Device according to one of the preceding claims, characterized in that the device (1) has a memory for storing a calibration data record.

Method for producing a three-dimensional object (9) by a generative construction method, in which the object (9) is formed by successively solidifying defined areas of individual layers by the action of a radiation source (13) on the solidifiable building material (7), the areas being spaced apart from one another An image pickup device (17) for receiving at least one image data set of the building material (17) receiving the building chamber (4) is provided, characterized in that the image recording device (4) at least one image data set as a reference image data set with at least one light emitting Position mark (20, 24) is recorded and based on the at least one reference image data set at least one calibration date, in particular a calibration data set (25) for correcting a recorded during a construction process image data set is determined.

A method according to claim 15, characterized in that a light-emitting position marker (20, 24) is used which emits light at a wavelength or in a wavelength range which is the same Wavelength or corresponds to the wavelength range, which gives the building material used for building (7).

17. The method according to any one of claims 15 or 16,

characterized in that

Light is emitted in the visible and infrared wavelengths.

18. The method according to any one of claims 15 to 17,

characterized in that

as the position marker an LED lamp (20) is used.