阅读说明：本技术 在三维部件的增材制造中监控制造精度的系统和方法 (System and method for monitoring manufacturing accuracy in additive manufacturing of three-dimensional parts ) 是由 比阿特里斯·本德朱斯 乌拉纳·西卡洛娃 迈克·罗里 于 2019-01-11 设计创作，主要内容包括：本发明涉及一种用于在三维部件的增材制造中监控制造精度的系统,其中,设置有装配有二维检测器阵列(1)和至少一个激光辐射源(4)的组合的照明和检测元件(12),通过所述至少一个激光辐射源,将电磁辐射引导到粉末状或糊状材料的区域上,通过所述材料由于局部限定的能量输入而产生三维部件的至少一个区域。所述检测器阵列(1)被布置和设计成使得以空间分辨的方式检测在由所述激光辐射源(4)辐射的表面中/表面上出现的散斑。使用所述检测器阵列以空间分辨的方式感测的散斑信号能够被馈送到电子评估和控制电路(3)。所述电子评估和控制电路(3)连接到被设计成影响制造过程的电子开环和闭环控制装置。能够使用单独的能量束(10)或用于以局部限定的方式将能量输入到所述粉末状或糊状材料上以进行三维增材制造的能量束来实现热散斑激发。(The invention relates to a system for monitoring the manufacturing accuracy in the additive manufacturing of three-dimensional components, wherein an illumination and detection element (12) is provided which is equipped with a combination of a two-dimensional detector array (1) and at least one laser radiation source (4) by means of which electromagnetic radiation is directed onto a region of a powdery or pasty material, by means of which at least one region of the three-dimensional component is produced as a result of a locally defined energy input. The detector array (1) is arranged and designed such that speckles occurring in/on the surface irradiated by the laser radiation source (4) are detected in a spatially resolved manner. Speckle signals sensed in a spatially resolved manner using the detector array can be fed to an electronic evaluation and control circuit (3). The electronic evaluation and control circuit (3) is connected to electronic open-loop and closed-loop control devices designed to influence the manufacturing process. Thermal speckle excitation can be achieved using a separate energy beam (10) or an energy beam for inputting energy in a locally defined manner onto the powdery or pasty material for three-dimensional additive manufacturing.)

1. A system for monitoring manufacturing accuracy during additive manufacturing of a three-dimensional part, wherein,

the combined illumination and detection element (12) is formed by a two-dimensional detector array (1) and at least one laser radiation source (4), by means of which electromagnetic radiation is directed onto a region of the powdery material or material in paste form, by means of which at least one region of the three-dimensional component is produced as a result of a locally defined energy input, and

the detector array (1) is arranged and implemented such that speckles occurring in/on the surface irradiated by the laser radiation source (4) can be detected in a spatially resolved manner; wherein the content of the first and second substances,

speckle signals captured in a spatially resolved manner by the detector array (1) can be fed to an electronic evaluation and control circuit (3), and

said electronic evaluation and control circuit (3) being connected to electronic open-loop and closed-loop control means implemented to influence the manufacturing process; and is

Thermal speckle excitation can be achieved using a separate energy beam (10) or an energy beam for introducing energy in a locally defined manner into the powdery material or material in paste form for three-dimensional additive manufacturing.

2. System according to claim 1, characterized in that it is directly attached to a feeding or smoothing device (8) for the powdery material or material (7) present in paste form and is movable together with the feeding or smoothing device (8).

3. The system according to claim 1 or 2, characterized in that the two-dimensional detector array (1), the at least one laser radiation source (4) and the electronic evaluation circuit (3) are arranged together on one circuit carrier.

4. The system according to any one of the preceding claims, characterized in that a separate energy beam (10) is incident on a reflective element (11) and the energy beam (10) reflected by the reflective element is incident in a region of the powdery material or material (7) present in paste form, which region is not irradiated by the laser radiation source (4) and/or is not detected by the detector array (1).

5. System according to any one of the preceding claims, characterized in that the reflecting element (11) is attached to the feeding or smoothing device (8) for the powdery material or material (7) present in paste form, and the incident element is movable together with the feeding or smoothing device (8).

6. The system according to any of the preceding claims, wherein the laser radiation source (4) is a laser diode or a laser diode array and/or the detector array (1) is a CCD or CMOS array.

7. The system according to any one of the preceding claims, wherein the feeding device of material is a droplet application device, in particular a printing device, a device for laser cladding or a powder feeding device for an additive manufacturing process, and the smoothing device (8) is a doctor blade.

8. The system according to any of the preceding claims, characterized in that a filter (1a) and/or a beam shaping element (1b), in particular an optical lens, is arranged between the material (7) and the laser radiation source (4) and/or the detector array (1).

9. Method for monitoring the manufacturing accuracy during the additive manufacturing of three-dimensional components using a device according to one of the preceding claims, characterized in that a laser radiation source (4) is used for directing electromagnetic radiation into a region of a powdery material or a material in paste form, by means of which at least one region of a three-dimensional component is produced as a result of a locally defined energy input, and

the detector array (1) is arranged and implemented such that speckles occurring on a surface irradiated by the laser radiation source (4) are detected in a spatially resolved manner; wherein the content of the first and second substances,

the speckle signals captured in a spatially resolved manner by the detector array (1) are fed to an electronic evaluation and control circuit (3), and

-sending said speckle signals evaluated by said electronic evaluation and control circuit (3) to an electronic open and closed loop control device implemented to influence the manufacturing process; and

thermal speckle excitation is achieved using a separate energy beam (10) or an energy beam for introducing energy in a locally defined manner into the powdery material or material in paste form for three-dimensional additive manufacturing, and

terminating the manufacturing process using the electronic open and closed loop control device, or influencing the manufacturing process in view of the captured and evaluated speckle signals, in the following manner:

if a deviation from a predetermined speckle signal on a correctly applied material (7) is determined, a manufacturing error, in particular an error during the application of the material (7), is compensated.

Technical Field

The present invention relates to a system and method for monitoring manufacturing accuracy during additive manufacturing of three-dimensional parts.

Background

A method called additive manufacturing or generative manufacturing can produce parts in a time and effort saving manner with almost unlimited freedom of design and construction. Due to their functional manufacturing advantages, they are particularly appreciated and promoted. In particular in the field of tool inserts (tool inserts), aerospace, medical engineering, and lightweight construction and general prototyping, which offers great innovation and application potential, for example, in the manufacture of custom implants or turbine blades that are cooled to the vicinity of a contour.

Despite the continuous further development of manufacturing processes and the increasing presence in media (mainly characterized by the term "3D printing"), measures are still very much needed in terms of quality assurance and process stability. A faulty setting of process parameters or fluctuations in process conditions can deteriorate the performance of the resulting mechanical technical component or lead to a process termination. Subsequent failure handling of the component is only possible in certain cases and the advantages of Additive Manufacturing (AM) are offset. Thus, there is a clear need for a solution for factory integrated process monitoring that allows the detection of a defect immediately upon its occurrence and allows the stopping of the assembly of the parts in order to save material, but above all time the time and costs that would arise in further assembly and processing. It should also be possible to perform anomaly detection in order to be able to control the manufacturing process and to perform closed-loop control of parameters without having to terminate the process.

For this reason, previous methods include molten pool monitoring, in which the construction process is monitored by thermal imaging and image-based methods that are not suitable for controlling high-speed processes in a small space.

With the ever-increasing demand for adequate solutions for process monitoring and product documentation, various approaches have been taken in recent years. Therefore, a system for monitoring the weld pool area similar to that already used in the field of laser welding is known. Here, a beam splitter is used to capture the radiation emitted from the melt bath by means of a photodiode. Based on the radiation intensity and using another CMOS camera, the range of the puddle can be captured and subject to closed loop control. A separately attached CCD camera was used to optically monitor the powder application. The image of the powder layer is used to detect wear and damage of the coating mechanism by striation marks that may be present in the powder.

In the extended method, additional illumination has been integrated into the system, so that recording with high time resolution is also possible. In this respect, it is also known practice to express the intensity of the bath radiation as a function of the position of the laser beam in x and y coordinates by means of a mapping algorithm. This process makes it possible to create a composite image of the bath temperature, giving the impression of an image record. Here, the black spots in the recording are interpreted as signs of process heat flow deviation, so that in the case of overhanging geometries, local component-over-height can be signaled due to internal stresses and heat accumulation.

Disclosure of Invention

It is therefore an object of the present invention to provide an option for online monitoring of manufacturing accuracy during additive manufacturing of three-dimensional components, which has a simple and low-cost embodiment and allows monitoring with improved accuracy and miniaturization.

According to the invention, this object is achieved by a system having the features of claim 1. A method is defined in claim 9. Advantageous embodiments and further examples of improvements of the invention can be achieved by the features described in the dependent claims.

In the system according to the invention there is a combined illumination and detection element. The combined illumination and detection element is equipped with a two-dimensional detector array and at least one laser radiation source by means of which electromagnetic radiation is directed onto a region of the powdery material or of a material present in paste form, by means of which at least one region of the three-dimensional component is produced as a result of a locally defined energy input.

The detector array is arranged and implemented such that speckle occurring in/on the surface area irradiated by the laser radiation source can be detected in a spatially resolved manner.

Speckle signals captured by the detector array at spatial resolution are fed to an electronic evaluation circuit. The electronic evaluation circuit is connected to electronic open-loop and closed-loop control means implemented to influence the manufacturing process.

Thermal speckle excitation is achieved using a separate energy beam or an energy beam for introducing energy in a locally defined manner into a material in powder form or in paste form for three-dimensional additive manufacturing.

In the case of a detector array useful in the present invention, the individual detectors or sensors should be arranged in rows and columns in order to spatially resolve and simultaneously capture the speckle obtained by the excitation with supplied energy. Here, spatially resolved speckle captured at the same time and at subsequent times separated by a predetermined time interval may be evaluated. Optical sensors capable of capturing the intensity of electromagnetic radiation impinging on the various sensors may be used. This may be the case for a single wavelength or range of wavelengths of electromagnetic radiation incident on the optical detector or sensor, or in a wavelength-resolved (spectrally-resolved) manner. The measurement signals captured by the detector or sensor in a spatially and, where appropriate, also advantageously in a time-resolved manner can be used to achieve the desired monitoring of the manufacturing accuracy.

The principle of Laser Speckle Photometry (LSP) can therefore be applied within the scope of the present invention.

The LSP is suitable for real-time monitoring and has high sensitivity to out-of-plane and in-plane displacements. In contrast to other techniques that focus on distortion of the overall speckle pattern or interference pattern (fringes), the LSP measures the spatiotemporal dynamics of the speckle due to variations in the intensity of each individual pixel of the detector array.

If a rough surface is illuminated by a coherent light source, a speckle pattern can be formed after speckle excitation. Scattered waves from different points of the illumination area interfere on a rough surface in the viewing plane and create a speckle pattern therein, as a spatial structure, with random distributions of maximum and minimum intensities that can be detected by a CCD/CMOS chip as a detector array. The speckle pattern carries fingerprint information about the 3D properties of the surface. In order to be able to derive information about scattering objects, it is customary to work in the near field range. Structural information can be obtained primarily from sequential statistics of speckle intensity and speckle phase or amplitude. In addition to structural information, speckle images captured by the detector array in a spatially resolved manner can also convey important information over time, for example, information about the diffusion process of the object under examination. Similarly, based on the motion of the material captured in the speckle images, the activity of the material motion can be determined by a suitable algorithm for dynamic, time-continuous captured speckle images. For example, a specific correlation function (autocorrelation difference) can be used to determine the interaction between speckle dynamics and the state or process of the respective surfaces of the sample. The basic LSP algorithm is based on thermal diffusivity calculations solved using heat transfer equations.

Since only one beam path is used, the process is substantially more robust. The measuring structure is simple, and therefore, the size can be effectively reduced.

The system may be directly attached to a feeding device or smoothing device for powdered material or material in paste form and may move with the feeding device or smoothing device. The system can therefore also follow the advancing movement synchronously during the material application or during the smoothing of the applied material, and no special drive is required for this purpose. Here, the system may be arranged such that capturing speckle signals at a layer previously processed with an energy beam for solidifying the material results in detection being performed simultaneously with the motion for material application or smoothing.

The feeding device of the material may be a droplet application device, in particular a printing device, a device for laser cladding or a powder feeding device for an additive manufacturing process, and the smoothing device may be a doctor blade.

A variety of metals and their alloys or ceramic materials may be used as materials for additive manufacturing. Components produced using at least two different materials can also be additively manufactured.

Advantageously, the two-dimensional detector array, the at least one laser radiation source and the electronic evaluation circuit and optionally other required components such as a power supply unit and reflective elements can be arranged together on a circuit carrier. This can further improve miniaturization. The circuit carrier may be multilayered. The electrically conductive connection may be formed by printed electrical conductor tracks and vias. At least one laser radiation source and a detector array are to be arranged on the surface of the circuit carrier facing the component or the material from which the component is produced.

The individual energy beams should be incident on the reflective element and the energy beams reflected by the reflective element should preferably be incident in areas of the powdered material or material present in paste form which are not irradiated by the laser radiation source and/or not detected by the detector array. The separate energy beam may likewise be a laser beam.

As already indicated, the reflective element should likewise be attached to the feed device or smoothing device for the powdery material or the material present in paste form, and it should be movable together with the feed device or smoothing device. This can be achieved without additional measures to achieve thermal excitation at a location where detection of speckle signals is convenient.

In the present invention, the laser radiation source may be a laser diode or a laser diode array, and/or the detector array may be a CCD or CMOS array.

A filter and/or a beam shaping element, in particular an optical lens, may be arranged between the material and the laser radiation source and/or the detector array. During detection and evaluation, the use of filters can avoid or at least suppress interfering components of electromagnetic radiation, e.g. reflected or scattered radiation. Furthermore, monochromatic electromagnetic radiation can be better used for the radiation if a filter is arranged upstream of the at least one laser radiation source. Using at least one optical element, the size and shape of the area to be irradiated and/or detected, respectively, on the applied or distributed material can be influenced.

In the method, a process is used in which electromagnetic radiation is directed using a laser radiation source into a region of a powdery material or a material present in paste form, by means of which material at least one region of the three-dimensional component is additively manufactured as a result of a locally defined energy input.

The detector array is arranged and embodied in such a way that speckle occurring in the surface region irradiated by the laser radiation source is detected in a spatially resolved manner.

Speckle signals captured with spatial resolution by the detector array are fed to an electronic evaluation circuit. The electronic evaluation circuit is connected to an electronic open and closed loop control device implemented to affect the manufacturing process and sends an evaluated speckle signal to the electronic open and closed loop control device.

Thermal speckle excitation is achieved using a separate energy beam or an energy beam for introducing energy in a locally defined manner into a material in powder form or in paste form for three-dimensional additive manufacturing.

The manufacturing process is terminated using electronic open and closed loop control means or is influenced after taking into account the captured and evaluated speckle signals, so that manufacturing errors, in particular errors during the application of the material, are compensated if deviations from the predetermined speckle signal on the correctly applied material have been determined.

This can avoid waste products wasting unnecessary material and energy consumption.

The energy beam used for curing the applied material, in particular for sintering or fusing, may in particular be an electron beam or a laser beam. Such an energy beam may additionally be used for thermal excitation that may be used to generate speckle. In this case, a separate energy beam for the excitation can be omitted, if applicable.

In contrast to the methods specified above (thermal imaging and molten bath monitoring), miniaturized monitoring systems based on speckle sensor systems are able to detect specific material parameters (e.g. porosity, but possibly other parameters) and surface defects during the additive 3D manufacturing process. Furthermore, the individual components of the system according to the invention can be integrated in a very small space compared to previously known solutions, in particular facilitating retrofitting existing equipment that can be used for additive manufacturing. A sensor array constructed from multiple miniaturized LSP sensor units can also be used to map material parameters simultaneously.

This allows monitoring of a rapidly executing manufacturing process.

The present invention will be described in more detail below by way of examples. The features shown in the drawings and described in the description can be combined with one another independently of the respective drawings and the respective examples.

Drawings

Fig. 1 shows two diagrams of an example of a system according to the invention.

Fig. 2 shows an example of a system according to the invention for use on an apparatus implemented for selective laser sintering or selective laser melting.

Fig. 1 shows two different views of an example.

Detailed Description

The inventive combined illumination and detection element 12 may be used for LSPs. Here, in this example, in addition to the combination of a high-resolution image converter (CMOS/CCD) as detector array 1 with optical filter 1a and optical lens/objective lens 1b, a circuit carrier 5 (e.g. a printed circuit board) is attached with an energy-saving electronic evaluation and control circuit 3 (e.g. a chip set/electronic unit) for controlling the measuring range and image processing in the vicinity of the detector and a laser diode array as laser radiation source 4 for exciting the speckle pattern. These elements can be connected to one another via interference-free, low-current electrical interfaces via electrical conductor tracks and vias (not shown here) printed on the circuit carrier 5. On/at the circuit carrier 5 there may also be a power supply unit 6 flexibly adapted to the respective place of use.

By way of example, a multilayer or multiple structure of the circuit carrier 5 can be recognized, in particular in the lower side sectional view.

Advantageously, the dimensions of the individual components, in particular the detector array 1 and the laser diode array as laser radiation source 4, can be used in a multilayer circuit carrier 5 with optimal line/space conditions and minimized holes. Here, the structure may be expanded in the z-axis direction as desired. Thus, thicker circuit carriers 5 or circuit carriers 5 having more than two layers may be used.

The combined illumination and detection element 12 is fixed to a machine unit embodied to apply and smooth the powdery material 7, which powdery material 7 is applied layer by layer onto a powder bed and processed by an energy beam. This can be done on a scraper 8 which serves to keep the powdered material 7 in a certain layer thickness and to smooth it. As shown in fig. 2. The doctor blade 8 is moved to form a powder bed so as to distribute the powdered material 7 evenly over the entire area of the layer, i.e. in particular to distribute the material evenly with a constant layer thickness.

Using the combined illumination and detection element 12, each layer of the additively manufactured component 9 can be measured at one point or line by line during production of the component. In this case, for example, an inhomogeneous distribution of the powdery material 7 in the layers, particles or impurities present in the individual layers having a particle size which deviates from the specification can be detected and then taken into account accordingly.

However, after or during the processing of the individual layers made of the powdery material 7 with the energy beam to solidify the respective material 7, it is also possible to detect by means of LSP using the combined illumination and detection element 12 and possibly other components belonging to the system, and in the process also to identify errors occurring during the additive manufacturing when forming at least one layer. If an error is identified, electronic open and closed loop control devices (not shown) implemented to affect the manufacturing process may be used to intervene in the manufacturing process, as has been described in the general part of the specification.

In this example, the thermal excitation is carried out with a separate energy beam 10, which energy beam 10 is emitted by a photodiode/laser diode 10.1 and directed onto an element 11 reflecting the energy beam 10. The energy beam 10 and the reflective element 11 are arranged and aligned relative to one another in such a way that the focal point of the energy beam 10 impinges on the surface of the powdery material 7 and causes a thermal excitation. Here, the focal spot should be directed to a position that is not directly located in the detection area that can be captured by the detector array 1.

The left diagram of fig. 3 schematically shows how a laser beam 10 is directed onto the surface of a component 9 to be additively manufactured in order to excite speckle. The detector array 1 is arranged here on the doctor blade 8 and moves together with the doctor blade. The doctor blade 8 is used to achieve a layer-by-layer powder distribution as is customary in selective laser welding or laser sintering.

The right-hand figure clearly shows that the detector array 1 is formed by a plurality of optical sensors arranged in rows and columns. On the detector array 1 there is a reflective element 11, by means of which reflective element 11 a laser beam 10 is directed onto the surface of the uppermost layer of the powder bed for the additive manufactured part 9 in order to excite speckle.

The optical sensor captures the speckle excited by the laser beam 10 in a spatially resolved manner.