Method and system for controlling a manufacturing process for additively manufacturing a component

Abstract

The invention relates to a method for controlling a manufacturing process for additively manufacturing a component (2) in an apparatus (1), wherein build-up material (13) is solidified on a build-up field (8) in a process chamber (3) by irradiating the build-up material (13) with at least one energy beam (22), and wherein a process gas (G) loaded with impurities (A) is discharged from the process chamber (3) through a gas line (9), filtered, and returned to the process chamber (3), the method comprising the steps: - using a contamination measuring unit (18) to record a number of measured values (M), each measured value (M) permitting a conclusion to be drawn about a degree of contamination, at the time of recording, in the process gas (G) flowing through the gas line (9), - evaluating the number of measured values (M), - depending on the evaluation of the number of measured values (M), controlling the apparatus (1) and / or an output device (39) which is connected to the manufacturing process via a data link. The invention also relates to a corresponding system and to a manufacturing apparatus.

Description

[0001] Method and system for controlling a manufacturing process for the additive manufacturing of a component

[0002] The invention relates to a method and a system for controlling a manufacturing process for the additive manufacturing of a component in a device, wherein build-up material is built up layer by layer on a build-up field, in particular between the application of two material layers of build-up material, by a, in particular selective, solidification of build-up material by irradiation of the build-up material with at least one energy beam.

[0003] Additive manufacturing processes are becoming increasingly relevant in the production of prototypes and, more recently, in series production. In general, "additive manufacturing processes" refers to manufacturing processes in which a finished product ("component") is built up by depositing material (the "build material"), usually based on digital 3D design data. The build-up is usually, but not necessarily, layered. The term "3D printing" is often used as a synonym for additive manufacturing. The production of models, samples, and prototypes using additive manufacturing processes is often referred to as "rapid prototyping," the production of tools as "rapid tooling," and the flexible production of series components as "rapid manufacturing."As mentioned at the beginning, a key aspect is the selective solidification of the build-up material. In many manufacturing processes, this solidification can be achieved by irradiation with radiant energy, e.g., electromagnetic radiation, in particular light and / or thermal radiation, but possibly also with particle radiation such as electron beams. Examples of processes that use irradiation are "selective laser sintering" or "selective laser melting." In this process, thin layers of a build-up material, usually in powder form, are repeatedly applied one on top of the other. In each layer, the build-up material is selectively solidified by spatially limited irradiation of the areas that are to become part of the component after production, in a "welding process." The powder grains of the build-up material are partially or completely melted using the energy locally introduced by the radiation at that location.During cooling, these powder grains then solidify into a solid. Typically, the energy beam is guided across the build area along solidification paths, and the remelting or solidification of the material in the respective layer occurs in the form of "weld paths" or "weld beads," so that ultimately, the component contains a multitude of such layers formed from weld paths. In this way, components with very high quality and fracture strength can now be manufactured.

[0004] The manufacturing process often takes place in a protective gas atmosphere. For this purpose, a process gas, e.g. argon, flows through the process chamber. As a rule, the process gas is not released into the environment afterwards, but is fed back into the process chamber. Particularly in additive manufacturing with metallic build-up material, the process gas within this gas circuit becomes contaminated with particles. These can be particles of the build-up material, but also particles that arise during the solidification process. Furthermore, additional particles can be introduced into the process gas stream, e.g. a passivating agent such as lime, which, in the case of a metallic build-up material, can be added to the process gas flowing out of the process chamber for fire protection reasons.

[0005] To purify the process gas, it is usually filtered. However, it can still happen, e.g., due to a filter breakage, that the process gas fed into or returned to the process chamber is contaminated with particles, which leads to a reduction in the quality of the manufactured components. In general, permeability at the filter stage can have significant detrimental effects on the quality of the manufactured components, as well as cause machine damage, especially because it can remain undetected for a long time.

[0006] To reduce the risk of contamination due to filter breakthroughs, process gas is filtered, for example, through a two-stage filter system. Filter breakthroughs in the main filter (or pre-filter) can be compensated for and indirectly detected with the help of a downstream fine filter (often a non-cleanable storage filter), as this becomes clogged relatively quickly in the event of a breakthrough, leading to increased differential pressure across the filter, which a differential pressure sensor can detect or which can activate a pressure switch, which in turn can lead to production being stopped. During trouble-free operation, the first filter stage allows a small proportion of particles to pass through. The fine filter reduces this proportion, for example to a minimum of very fine particles (condensate), which reaches the clean gas side of the process gas circuit.

[0007] In another commonly used filter unit, the filtrate is first mixed with lime powder just upstream of the filter, omitting a downstream fine or storage filter. This creates the problem that if the filter is permeable, lime can also enter the clean gas side of the process gas circuit unnoticed and be introduced into the process chamber during the ongoing construction process. The lime can settle as dust on the powder bed or on the solidified areas and become integrated into the structure of a component. This can impair component properties such as its strength.

[0008] It is an object of the present invention to provide a method and a system for controlling a manufacturing process for the additive manufacturing of a component, which overcomes the disadvantages of the prior art and in particular allows automatic detection of filter breakthroughs.

[0009] This object is achieved by a method according to claim 1, a system according to claim 10 and a device according to claim 13.

[0010] A method according to the invention serves to control a manufacturing process for the additive manufacturing of a component in a device, wherein build material is solidified on a build area in a process chamber by irradiating the build material with at least one energy beam, and wherein a process gas laden with impurities is removed from the process chamber through a gas line, filtered, and returned to the process chamber. The method comprises the following steps:

[0011] - Recording a number of measured values ​​using a contamination measuring unit, whereby each measured value allows a conclusion to be drawn about the degree of contamination of the process gas flowing through the gas line at the time of recording,

[0012] - Evaluation of the number of measured values,

[0013] - Control of the device and / or an output device connected to the production process by data technology depending on the evaluation of the number of measured values.

[0014] As already indicated, in a manufacturing process, build-up material is built up layer by layer in a build area, i.e. one after the other in several material application levels or material layers. The build-up material is preferably a metal powder. However, the invention is not limited to this, but can also be used with other, preferably powdered, build-up materials, such as plastics or ceramics or mixtures of the various materials. In this case, build-up material is solidified (in particular selectively), in particular between the application of two material layers, by irradiating the build-up material with at least one energy beam generated by an irradiation unit of the manufacturing device (this means an energetic beam of photons or particles, e.g. a light beam or an electron beam).Not only is the build-up material in the top, freshly applied material layer captured and melted or remelted by the energy beam, but the energy beam usually goes a little deeper into the material bed and also reaches the underlying, already remelted material from previously applied material layers.

[0015] "Contaminant" essentially refers to any solid or liquid particles that contaminate the process gas. This includes, in particular, discharge materials or other contaminants from the process chamber, but can also include contaminants that arise downstream of the process chamber, particularly from added passivating agents. For example, contaminants can include smoke particles, particles of the build-up material (discharge material) or lime (passivating agent), or mixtures of these particles.

[0016] The degree of contamination refers to the amount of impurities in the process gas. This degree can generally be expressed as a percentage of particles or "contaminant elements," but the materials that contaminate the process gas can also be broken down by their proportions.

[0017] Contamination of the process gas can be caused by a variety of processes, for example the contamination depends on the flow velocity, in particular on the injection or extraction of the process gas, but also on the dosing process (powder can trickle out of the doser if the roller is rotated for too long or if the powder seal is defective), the coater run (powder that has not yet settled on the powder bed after coating is caught by the gas flow and further stirred up), the build process or laser activity, a collision between coater and component (stirring up of powder), defects or design flaws (dust collects on the coater and is stirred up by injection), operating errors (e.g. forgetting to fit the sealing lip on the doser) or even disregarding cleaning cycles (dust settling on surfaces).

[0018] A contamination measuring unit is used to record measured values, which can be, for example, a dust sensor known in the art. Measurements can be taken, in particular, optically, e.g. via turbidity according to the smoke detector principle, acoustically, e.g. via ultrasound, e.g. triboelectrically according to the principle of ionization smoke detectors, electrochemically, or electromagnetically, e.g. using a microwave Doppler sensor. Preference is also given to the use of any thermo-optical measuring devices available for process monitoring with regard to characteristic measured values ​​caused by the interaction of a laser beam with an impure process atmosphere, or by changes in processes in the melt pool due to this interaction. Also preferred is the monitoring of optical images taken through a possibly cloudy process atmosphere, particularly with regard to their brightness and contrast ratio.A preferred measuring unit is minimally invasive, easy to integrate into a system, wear-free, reliable and cost-effective.

[0019] The contamination measuring unit measures the particle load of the passing process gas, in particular on the clean gas side of the process gas circuit, i.e. between a filter and the inlet to the process chamber. The measurement can be carried out continuously or intermittently. A preferred arrangement of a sensor of the contamination measuring unit in the machine is such that the sensor can detect almost the entire internal diameter of the pipe in which it is arranged. If it is arranged in an area of ​​the outlet pipe, the sensor should be located where this pipe runs straight for as long as possible, in particular if the area is divided into thirds, preferably two-thirds of the distance downstream of the nearest bend and one-third of the distance upstream of the nearest bend. When measuring, the flow in the pipe should be as homogeneous and free as possible.Regarding the orientation of the sensor to the pipe cross-section (360°), the sensor is preferably positioned at 90° to the main flow direction and detects the widest possible spectrum of loading mass flows, ie it should be positioned along the maximum diameter of the pipe.

[0020] The measured values ​​recorded by the contamination measuring unit should allow conclusions to be drawn about the degree of contamination of the process gas flowing through the gas line at the time of recording. This means that each measured value directly indicates this respective degree of contamination or represents a value with which the degree of contamination can be determined, e.g. based on powder bed monitoring. Preferred measured values ​​indicate, for example, the total number of particles per time, but can also indicate a mass or electrical charge of the individual particles, whereby an additional measurement of the flow velocity could also be helpful here. In addition, it can also be advantageous to measure the homogeneity or heterogeneity of the flow, i.e. whether largely the same or different flow velocities prevail across the internal cross-section of the pipe.Other preferred measurements indicate the distribution of particles in the flow across the pipe's internal cross-section. For example, after a bend, in a wall area with the greatest bend length, the concentration of particles, especially heavier particles, may be higher due to the effect of centrifugal force. In short, all measurements that provide information about how many particles flow back into the process chamber along with the process gas are preferred.

[0021] It should be noted that the degree of contamination can certainly be measured solely at the gas outlet of the process chamber (in the raw gas line). However, it is preferable to measure the degree of contamination in the clean gas line (at the gas inlet into the process chamber or the process gas after filtering). However, it can also be very advantageous to measure both in the raw gas line and in the clean gas line, as this allows differential values ​​to be calculated, which can provide valuable information about changes in the filters.

[0022] The evaluation of the number of measured values ​​is preferably carried out with regard to the quality of the components. If the contamination of the process gas is too great, this should be counteracted so that this contamination does not unduly affect the process chamber and the components to be manufactured therein. For example, it is easy to check whether the level of contamination in the process gas lies above a predetermined limit, in particular for the lime content of the particles. However, other indicators are also possible, e.g. a sudden increase in the level of contamination or an increase in a certain concentration of certain particles, e.g. larger particles or lime particles. The contamination measuring unit can be integrated into a diagnostic system in which, for example, the measured values ​​are combined with measured values ​​from another sensor (e.g. as part of a "differential diagnostics").For example, the measured values ​​could be linked to control data from the activation of all moving elements in the process chamber (coater including individual parts, etc.) as well as the gas injection or gas extraction, or a temporal correlation could be created between an increase in powder discharge and a specific event or activity of a specific component. Relationships between error events can also be created using other sensors, or signals can be weighted and interpreted, thereby narrowing down the components or events causing the error. With regard to the control of the device or the output device, a production process can be interrupted until the level of contamination returns to a tolerable level. A warning can also be issued, e.g. that a filter breakage is likely.For example, a warning signal is issued if a threshold is exceeded, e.g., if the total amount of powder discharged is too high or if defined limits for local maximums / minima or curve gradients are exceeded. An error diagnosis can also be performed between the control and the evaluation unit to determine where the error might be.

[0023] A system according to the invention serves to control a manufacturing process for the additive manufacturing of a component in a device, wherein build material is solidified on a build area in a process chamber by irradiating the build material with at least one energy beam, and wherein a process gas laden with impurities is removed from the process chamber through a gas line, filtered, and returned to the process chamber. The system is particularly designed for carrying out the method according to the invention and comprises the following components:

[0024] - A contamination measuring unit designed to record a number of measured values, each of which allows a conclusion to be drawn about the respective degree of contamination in the process gas flowing through the gas line,

[0025] - an evaluation unit designed to evaluate the number of measured values,

[0026] - a control unit designed to control the device and / or an output device connected to the manufacturing process in terms of data technology depending on the number of measured values.

[0027] The invention has the advantage that particle-contaminated process gas can be detected and, if necessary, a process shutdown can be initiated or a warning can be issued. This prevents component defects caused by a poorly filtered process atmosphere, which could potentially remain undetected for a long time. Contamination can both directly impair the manufacturing process by disrupting the laser beam and lead to contaminated powder, which, even if subsequently sieved, can cause difficult-to-detect damage to manufactured parts. In particular, minimal filter penetrations that would not lead to a job abort based on other control mechanisms (e.g., due to an abrupt, significant drop in backpressure independent of a cleaning process) can be reliably detected by the invention.This prevents any impairment of component quality, particularly due to excessive limescale (passivating agent), from occurring over a longer period of time during which the process gas cleaning system appears to be functioning perfectly.

[0028] A device according to the invention (“manufacturing device”) for the additive manufacturing of a component in a manufacturing process in which build material is solidified on a build area in a process chamber by irradiating the build material with at least one energy beam, comprises the following components:

[0029] - a gas line for guiding a process gas from the process chamber through a filter unit and back into the process chamber,

[0030] - a system according to the invention, wherein the contamination measuring unit of the system is arranged in the gas line, preferably on a clean gas side of the gas line.

[0031] The filter unit is preferably configured with at most two stages, preferably at most one stage. "Single-stage" means that the filter unit can comprise filter elements connected in parallel, but not in series. It is preferred that at least one filter element, preferably all filter elements of the filter unit, is / are configured to be cleaned before, during, or after a manufacturing process. This means that the filter is not a storage filter. A particle separation unit is preferably arranged upstream of the filter unit.

[0032] It should be noted at this point that the device according to the invention can also comprise multiple irradiation devices, which are then controlled in a coordinated manner using the control data, as mentioned above. It should also be mentioned again that the energy beam can also consist of multiple superimposed energy beams, or that the energy beam can be either particle radiation or electromagnetic radiation, such as light or, preferably, laser radiation.

[0033] A control device according to the invention serves to control a device for a manufacturing process for the additive manufacturing of a component, wherein build material is solidified on a build area in a process chamber by irradiation with at least one energy beam, and wherein a process gas laden with impurities is discharged from the process chamber through a gas line, filtered, and returned to the process chamber. The control device is designed to control the manufacturing device according to the method according to the invention, or it comprises a system according to the invention.

[0034] The system according to the invention can be implemented in particular in the form of a computer unit, in particular in a control device, with suitable software. For this purpose, the computer unit can, for example, have one or more cooperating microprocessors or the like. In particular, it can be implemented in the form of suitable software program components in the computer unit. A largely software-based implementation has the advantage that even previously used computer units, in particular in control devices of manufacturing equipment, can be easily retrofitted with a software or firmware update to operate in the manner according to the invention.In this respect, the object is also achieved by a corresponding computer program product with a computer program that can be loaded directly into a memory device of a computer unit, with program sections to carry out all steps of the method according to the invention when the program is executed in the computer unit. Such a computer program product can, in addition to the computer program, optionally comprise additional components such as documentation and / or additional components, including hardware components such as hardware keys (dongles, etc.) for using the software. A computer-readable medium, for example a memory stick, a hard disk, or another portable or permanently installed data storage device, on which the program sections of the computer program that can be read and executed by a computer unit are stored, can be used for transport to the computer unit and / or for storage on or in the computer unit.

[0035] Further, particularly advantageous embodiments and developments of the invention emerge from the dependent claims and the following description, wherein the independent claims of one claim category can also be developed analogously to the dependent claims and embodiments of another claim category and, in particular, individual features of different embodiments or variants can be combined to form new embodiments or variants.

[0036] According to a preferred method, if the evaluation of the number of measured values ​​shows that the degree of contamination in the process gas flowing through the gas line is greater than a predetermined maximum contamination (a limit value for the degree, e.g. a particle concentration), at least one of the following steps is carried out:

[0037] - Output of information on the output device, in particular a warning message (a message) or a warning signal (e.g. an acoustic or optical signal),

[0038] - Interrupting (i.e. stopping or pausing) the manufacturing process,

[0039] - automatic entry of information on the degree of contamination in the process gas flowing through the gas line, determined from the number of measured values, into a quality data log,

[0040] - Determination of the condition of a number of components manufactured in the production process and estimation of which of the number of components is / are usable and which is / are not.

[0041] According to a preferred method, the number of measured values ​​is evaluated to control the device, taking into account a number of process parameters of the device that are characteristic of the additive manufacturing of a component. This is done, in particular, under the assumption that the detected impurities are process-related discharge material (in particular powdered application material) and / or passivating agents (in particular lime). Alternatively or additionally, the device is controlled by means of a, in particular automatic, control or regulation of the number of process parameters depending on the evaluation of the number of measured values, wherein, with regard to the control or regulation of the number of process parameters, optimization and / or error detection with regard to at least one process parameter is preferably carried out on the basis of the evaluation of the number of measured values. An optimization orError detection with respect to at least one process parameter can be achieved through targeted tests or based on estimates. For example, when measuring build-up material in the process gas stream, the flow of the process gas through the process chamber can be specifically altered, or when measuring smoke particles, the energy beam can be regulated.

[0042] According to a preferred method, one of the process parameters is characteristic of at least one of the following criteria:

[0043] - a throughput, a flow rate, a direction, an effective range and / or a speed of the process gas in the process chamber, in particular in each case relative to an uppermost layer of the build-up material, - a geometric and / or temporal uniformity of a throughput, a flow rate, a direction, an effective range and / or a speed of the process gas in the process chamber, in particular in each case relative to an uppermost layer of the build-up material,

[0044] - an area, thickness, position and / or shape of an area to be solidified on the construction site for the production of the component,

[0045] - feeding and / or selective solidification of the build-up material,

[0046] - distribution (especially layered application) of the build-up material,

[0047] - the at least one energy beam which causes the selective solidification of the building material, in particular its wavelength, intensity, intensity distribution, beam diameter, beam cross-section, deflection direction, direction of movement or speed of movement within the building field,

[0048] - filling and / or overfilling of an overflow container intended to collect excess build-up material in the process chamber,

[0049] - an increased or uncontrolled discharge of build-up material into the atmosphere of the process chamber.

[0050] According to a preferred method, the evaluation determines whether a measured value or a progression of a plurality of measured values ​​lies within a predetermined value range. Preferably, the number of measured values ​​is evaluated in a special way, e.g., by

[0051] - a measured value is compared with at least one predefined threshold value and / or

[0052] - a change in a number of measured values ​​is compared with at least one predefined threshold value and / or

[0053] - a plurality of measured values ​​are checked for a repeating measured value pattern, wherein the checking of the number of measured values ​​for the repeating measured value pattern preferably comprises detecting repeatedly occurring measured value anomalies (e.g., temporary measured value fluctuations), in particular those that occur briefly compared to the predetermined period of measured value acquisition. The evaluation of the number of measured values ​​preferably comprises establishing a temporal correlation between a result of an acquisition of the number of measured values ​​and at least one process parameter of the device that is characteristic of additive manufacturing of a component. Examples of such process parameters are mentioned above.According to a preferred method, the acquisition of a number of measured values, and preferably also the control or regulation of the process parameter, takes place during additive manufacturing of a component, preferably continuously or at regular intervals.

[0054] According to a preferred method, the building material is at least partially powdery and preferably comprises a metal powder.

[0055] According to a preferred method, a passivating agent, preferably lime particles, is added to the process gas flowing through the gas line downstream of the process chamber and / or upstream of the filter unit. As mentioned above, this passivating agent can lead to quality losses if it enters the process chamber. Therefore, the application of the method according to the invention is particularly advantageous here.

[0056] According to a preferred method, the build material is fed into the process chamber for manufacturing a component. A dosing device and / or a coater is arranged in the process chamber for this purpose, which applies the build material layer by layer within a build field. In the course of controlling the device, depending on the number of measured values, the build material is preferably dosed by means of the dosing device and / or the coater, which may optionally also be carried out in a modified manner based on the measured values ​​(i.e., deviating from a previously specified manner). Alternatively or additionally, the dosing device and / or the coater is preferably moved, optionally also in a modified manner.

[0057] Preferably, the contamination measuring unit comprises a filter breakage sensor, in particular based on the triboelectric effect, and / or an optical turbidity sensor, and / or a camera, which in particular monitors the brightness of images taken by the process atmosphere, and / or a thermo-optical measuring device and / or a system designed for powder bed monitoring and / or a measuring device for comparatively measuring a pressure (the differential pressure) at two parallel filter stages.

[0058] A filter break sensor is normally arranged downstream of a particulate filter to test or document its cleaning effectiveness. Such a filter break sensor often works according to the principle of triboelectricity, i.e. the electrical charging of particles through friction. Such a sensor can be designed as a metal rod that penetrates a line in the gas circulation system carrying the process gas. The penetration can occur at just one point on the wall. Contact between the metal rod and the metal pipe can be prevented by insulation. Electromagnetic shielding of the sensor is very advantageous to avoid interference. Electrically charged metal particles that have been charged through friction touch the electrically conductive metal rod and transfer their charge to the metal. For example, a cumulative charge can be measured as an electrical current (“total mass flow”).

[0059] The invention will be explained in more detail below with reference to exemplary embodiments in the accompanying figures. In the various figures, identical components are provided with identical reference numerals. They show:

[0060] Figure 1 is a schematic, partially sectioned view of an embodiment of an apparatus for additive manufacturing,

[0061] Figure 2 shows a block diagram of a possible process sequence of an embodiment of a method according to the invention,

[0062] Figure 3 shows a recirculating air filter system according to the state of the art,

[0063] Figure 4 shows a production device with recirculating air filter system and particle separator.

[0064] The following exemplary embodiments are described with reference to a device 1 for the additive manufacturing of components in the form of a selective laser sintering or laser melting device. It should be explicitly noted that the invention is not limited to selective laser sintering or laser melting devices. The device will therefore be referred to below—without limiting its generality—as "manufacturing device" 1.

[0065] Such a manufacturing device 1 is shown schematically in Figure 1. The device has a process chamber 3 or a process space 3 with a chamber wall 4, in which the manufacturing process essentially takes place. Located within the process chamber 3 is an upwardly open container 5 with a container wall 6. The upper opening of the container 5 forms the current working plane 7. The area of ​​this working plane 7 lying within the opening of the container 5 can be used to build the object 2 and is therefore referred to as the construction field 8.

[0066] The container 5 has a base plate 11 which is movable in a vertical direction V and is arranged on a carrier 10. This base plate 11 closes off the container 5 at the bottom and thus forms its base. The base plate 11 can be formed integrally with the carrier 10, but it can also be a plate formed separately from the carrier 10 and fastened to the carrier 10 or simply mounted thereon. Depending on the type of specific build material, for example the powder used, and the manufacturing process, a build platform 12 can be attached to the base plate 11 as a build base, on which the object 2 is built. In principle, however, the object 2 can also be built on the base plate 11 itself, which then forms the build base.

[0067] The basic construction of object 2 occurs by first applying a layer of build material 13 to the build platform 12. Then, as explained later, the build material 13 is selectively solidified using a laser beam 22 as an energy beam at the points that are to form parts of the object 2 to be manufactured. Then, with the aid of the carrier 10, the base plate 11, thus the build platform 12, is lowered, and a new layer of build material 13 is applied and selectively solidified, etc. In Figure 1, the object 2 constructed in the container on the build platform 12 is shown below the work plane 7 in an intermediate state. It already has several solidified layers, surrounded by unsolidified build material 13.Various materials can be used as the building material 13, preferably powder, in particular metal powder, plastic powder, ceramic powder, sand, filled or mixed powders or also pasty materials and optionally a mixture of several materials.

[0068] Fresh build material 15 is located in a storage container 14 of the production device 1. With the aid of a coater 16 movable in a horizontal direction H, the build material can be applied in the form of a thin layer in the working plane 7 or within the build area 8.

[0069] Optionally, an additional radiant heater 17 is located in the process chamber 3. This can be used to heat the applied build material 13, so that the irradiation device used for selective solidification does not have to introduce too much energy. This means, for example, that with the help of the radiant heater 17, a certain amount of basic energy can be introduced into the build material 13, which is naturally still below the energy required for the build material 13 to melt or sinter. An infrared radiator or VCSEL radiator, for example, can be used as the radiant heater 17.

[0070] For selective solidification, the production device 1 has an irradiation device 20, or more specifically, an exposure device 20 with a laser 21. This laser 21 generates a laser beam 22, which is deflected by a deflection device 23 in order to traverse the exposure paths or tracks (hatch lines) provided according to the exposure strategy in the respective layer to be selectively solidified and to selectively introduce the energy. Furthermore, this laser beam 22 is appropriately focused onto the working plane 7 by a focusing device 24. The irradiation device 20 is preferably located outside the process chamber 3, and the laser beam 22 is guided into the process chamber 3 via a coupling window 25 mounted on the top side of the process chamber 3 in the chamber wall 4.

[0071] The irradiation device 20 can, for example, comprise not just one but several lasers. These can preferably be gas or solid-state lasers or any other type of laser, such as laser diodes, in particular VCSELs (Vertical Cavity Surface Emitting Lasers) or VECSELs (Vertical External Cavity Surface Emitting Lasers), or a row of these lasers. Very particularly preferably, one or more unpolarized single-mode lasers, e.g., a 3 kW fiber laser with a wavelength of 1070 nm, can be used within the scope of the invention.

[0072] The production device 1 contains a gas line 9, which carries process gas G into and out of the process chamber 3, and a contamination measuring unit 18, which measures the degree of contamination in the process gas G flowing through the gas line 9. The gas flow flows through the gas-filled space above the container 5, which the energy beam 22 passes through during operation. Opposite the gas inlet (left) is a gas outlet (right), so that the gas flow completely crosses the construction area and can be recirculated if necessary (not shown). Here, a contamination A of a process gas G flowing out of the process chamber 3 is measured with the contamination measuring unit 18, but contamination of the inflowing process gas G can also be measured. The contamination measuring unit 18 can, for example,a filter breakage sensor, an optical turbidity sensor, a camera, a thermo-optical measuring device or a system designed for powder bed monitoring.

[0073] The measured values ​​M recorded by the contamination measuring unit 18, which allow a conclusion to be drawn about the respective degree of contamination in the process gas G flowing through the gas line 9, are transferred here to a control device 30 of the manufacturing device 1, which also serves to control the various components of the manufacturing device 1 for the overall control of the additive manufacturing process.

[0074] To record the measured values ​​M, the control device 30 has an evaluation unit 32 which is designed to evaluate the measured values ​​M. A control unit 29 of the control device 30 serves to control the device 1 depending on the number of measured values ​​M. The control unit 29 is designed to control the components of the irradiation device 20, namely here the laser 21, the deflection device 23 and the focusing device 24, and for this purpose transmits to them corresponding irradiation control data BS which are designed according to the measured values ​​M.

[0075] The control unit 29 also controls the radiant heater 17 by means of suitable heating control data HS, the coater 16 by means of coating control data ST and the movement of the carrier 10 by means of carrier control data TS and thus controls the layer thickness.

[0076] The control device 30 is coupled, here, for example, via a bus 60 or another data connection, to an output device 39, e.g., a terminal with a display or the like. It can send warning messages to an output device 39 via this bus 60 if the degree of contamination is too high. An operator can also control the control device 30 and thus the entire production device 1 via the terminal, e.g., by transmitting process control data PS.

[0077] It should also be noted again at this point that the present invention is not limited to such a manufacturing device 1. It can be applied to other methods for the generative or additive production of a three-dimensional object by layer-by-layer application and selective solidification of a building material, wherein an energy beam is emitted onto the building material to be solidified. Accordingly, the irradiation device can be not only a laser, as described here, but any device could be used with which energy can be selectively applied to or into the building material as wave or particle radiation. For example, another light source, an electron beam, etc., could be used instead of a laser.

[0078] Even though only a single object 2 or component 2 is shown in Figure 1, it is possible and generally common practice to produce multiple objects in parallel in the process chamber 3 or container 5. For this purpose, the build material is scanned layer by layer by the energy beam 22 at locations that correspond to the cross-sections of the objects in the respective layer.

[0079] Figure 2 shows a block diagram of a possible method sequence of an embodiment of a method according to the invention for controlling a manufacturing process for the additive manufacturing of a component 2 in a device 1, as shown, for example, in Figure 1. For this purpose, build-up material 13 is solidified on a build field 8 in a process chamber 3 by irradiating the build-up material 13 with at least one energy beam 22. A process gas G laden with impurities A is discharged from the process chamber 3 through a gas line 9, filtered, and returned to the process chamber 3. The build-up material 13 is at least partially in powder form and preferably comprises a metal powder. If a metal powder is processed, a filter unit 40 is often provided downstream of the process chamber 3 and / or upstream of a filter unit 40 (seeFollowing figures), a passivating agent, preferably lime particles, is added to the process gas G flowing through the gas line 9. All powdered materials can be present as contaminants in the process gas. In particular, in the event of a crack or break in a filter or other component intended to separate clean gas from contaminated gas (e.g., a seal), significant amounts of contaminants are reintroduced into the process chamber 3 with the process gas G, leading to quality losses in the manufactured components 2.

[0080] In step I, a number of measured values ​​M are recorded by means of the contamination measuring unit 18, wherein each measured value M allows a conclusion to be drawn about the degree of contamination of the process gas G flowing through the gas line 9 at the time of recording. A measured value M can indicate this respective degree of contamination directly or represent a value with which the degree of contamination can be determined, e.g., based on the turbidity of optical images, e.g., from the powder bed monitoring system. The measured values ​​M are recorded here during additive manufacturing of a component 2, preferably continuously or at regular intervals.

[0081] In step II, the measured values ​​M are evaluated. During the evaluation, it is determined whether a measured value M or a curve of a plurality of measured values ​​M lies within a predefined value range. The measured values ​​M can be evaluated in different ways. For example, a measured value M or its change is compared with at least one predefined threshold value. A plurality of measured values ​​M can also be checked for a repeating measured value curve pattern, whereby this check can, for example, include detecting repeatedly occurring measured value anomalies (e.g. temporary measured value fluctuations). The evaluation can also include forming a temporal correlation between a result of recording the number of measured values ​​M and at least one process parameter P of the device 1 that is characteristic of additive manufacturing of a component 2.

[0082] A process parameter P can, for example, be characteristic of one of the following criteria: a) A throughput, a flow rate, a direction, an effective range and / or a speed of the process gas G in the process space 3, in particular in each case relative to an uppermost layer of the build material 13, b) a geometric and / or temporal uniformity of a throughput, a flow rate, a direction, an effective range and / or a speed of the process gas G in the process space 3, in particular in each case relative to an uppermost layer of the build material 13, c) an area, thickness, position and / or shape of an area to be solidified on the build field 8 for the production of the component 2, d) a feeding and / or a selective solidification of the build material 13, e) a distribution (e.g.layer-by-layer application) of the building material 13, f) the at least one energy beam 22 which effects the selective solidification of the building material 13, in particular its wavelength, intensity, intensity distribution, beam diameter, beam cross-section, deflection direction, direction of movement and / or.

[0083] Movement speed within the construction area 8, g) filling and / or overfilling of an overflow container provided for collecting excess build material 13 in the process space 3, or h) an increased or uncontrolled discharge of build material 13 into an atmosphere of the process space 3.

[0084] In the step shown here, the evaluation of the number of measured values ​​M is carried out taking into account a number of process parameters P of the device 1 which are characteristic for an additive manufacturing of a component 2, in particular under the assumption that the detected impurities are process-related discharge material and / or passivating agents.

[0085] In step III, the device 1 and / or an output device 39 connected to the production process via data technology is controlled as a function of the evaluation of the number of measured values ​​M. In this example, the device 1 is controlled by means of an automatic control or regulation of the number of process parameters P as a function of the evaluation of the number of measured values ​​M, wherein an optimization and / or error detection with regard to at least one process parameter can take place based on the evaluation of the number of measured values ​​M. For example, to manufacture a component 2 using a device according to Figure 1, a dosage of the building material 13 by means of the coater 16 or its movement can be controlled based on the measured values ​​M.

[0086] In the event that the evaluation of the measured values ​​M shows that the degree of contamination in the process gas G flowing through the gas line 9 is greater than a predetermined maximum contamination, a warning message is output on the output device 39, for example. In addition, the production process can be interrupted until the degree of contamination has decreased again and information about the degree of contamination can be automatically entered into a quality data log.

[0087] Figure 3 shows a recirculating air filter system 40 with a pre-filter stage 42, a particle collection container 44, a fill level sensor 43 for measuring the fill level in the particle collection container 44, a fine filter stage 41, and a blower 45. As indicated by the arrows, process gas G flows from the process chamber 3 to the pre-filter 42 and is filtered there. Filtrate (particles) are separated into the particle collection container 44 when the pre-filter 42 is cleaned at specific intervals. The pre-cleaned process gas G then flows through the fine filter stage 41 before being returned to the process chamber 3 by means of the blower 45. Such a recirculating air filter system 40 is known in the prior art. In the event of a crack or break in the fine filter stage 41, which may not necessarily be noticed, impurities may remain in the process gas G and re-enter the process chamber 3. This may endanger the production of components 2.With the method according to the invention, damage to a filter can be detected at an early stage and countermeasures or warnings can be initiated automatically.

[0088] Figure 4 shows a production device 1 with a recirculating air filter system 40 and a particle separator 50. Process gas G is discharged from the production device 1 (see, for example, Figure 1) as raw gas, i.e., loaded with impurities, through a raw gas line 48 (upper arrow). It flows past a first contamination measuring unit 18 (top). It can then be fed directly into a pre-filter stage 42 and cleaned there (dashed arrow). In this example, however, it first flows through a particle separator 50, which uses a cyclone to remove particles from the process gas G and collects them in a particle collection container 44. Only then does the process gas G flow through the pre-filter stage 42 and a fine filter stage 41 through a clean gas line 49 back to the process chamber 3 of the production device 1. It flows past a second contamination measuring unit 18 (bottom).By simple measurements with the second contamination measuring unit 18 or a comparative measurement of both contamination measuring units 18, the degree of contamination of the process gas G returned through the clean gas line 49 can now be determined and, if necessary, measures can be initiated according to the method according to the invention.

[0089] Finally, it should be noted once again that the devices described in detail above are merely exemplary embodiments that can be modified in a variety of ways by those skilled in the art without departing from the scope of the invention. For example, solidification could be carried out using other energy beams instead of laser light. Furthermore, the use of the indefinite articles "a" or "an" does not exclude the possibility that the respective features may be present in multiple instances. Likewise, the term "unit" does not exclude the possibility that it consists of several interacting subcomponents, which may also be spatially distributed. The expression "a number" is to be understood as "at least one."

[0090] List of reference symbols

[0091] 1 device for additive manufacturing / manufacturing device

[0092] 2 Component / Object

[0093] 3 Process room / process chamber

[0094] 4 chamber wall

[0095] 5 containers

[0096] 6 Container wall

[0097] 7 Working level

[0098] 8 Construction site

[0099] 9 Gas pipeline

[0100] 10 carriers

[0101] 11 Base plate

[0102] 12 Construction platform

[0103] 13 Construction material (in container 5)

[0104] 14 storage containers

[0105] 15 assembly material (in storage container 14)

[0106] 16 coaters

[0107] 17 Radiant heating

[0108] 18 Contamination measuring unit

[0109] 20 Irradiation device / exposure device

[0110] 21 lasers

[0111] 22 Laser beam / energy beam

[0112] 23 Deflection device / scanner

[0113] 24 Focusing device

[0114] 25 coupling windows

[0115] 29 Control unit

[0116] 30 Control device

[0117] 31 Irradiation control interface

[0118] 32 Evaluation unit

[0119] 39 Terminal / Output device

[0120] 40 recirculation filter system

[0121] 41 fine filter stage

[0122] 42 Pre-filter stage

[0123] 43 Level sensor

[0124] 44 Particle collection container 45 Blower

[0125] 48 raw gas line

[0126] 49 Clean gas line

[0127] 50 Particle separator 60 Bus

[0128] A Contamination

[0129] BS control data / exposure control data

[0130] G Process gas

[0131] H horizontal direction HS heating control data

[0132] M measured value

[0133] P Process parameters

[0134] PS process control data

[0135] ST coating control data TS carrier control data

[0136] V vertical direction

Claims

Patent claims 1. Method for controlling a manufacturing process for the additive manufacturing of a component (2) in a device (1), wherein build material (13) is solidified on a build area (8) in a process chamber (3) by irradiating the build material (13) with at least one energy beam (22) and wherein a process gas (G) loaded with impurities (A) is discharged from the process chamber (3) through a gas line (9), filtered and returned to the process chamber (3), the method comprising the steps: Recording a number of measured values ​​(M) using a contamination measuring unit (18), wherein each measured value (M) allows a conclusion to be drawn about a degree of contamination of the process gas (G) flowing through the gas line (9) prevailing at the time of recording, Evaluation of the number of measured values ​​(M), Control of the device (1) and / or an output device (39) connected to the manufacturing process via data technology, depending on the evaluation of the number of measured values ​​(M).

2. The method of claim 1, wherein, in the event that the evaluation of the number of measured values ​​(M) reveals that the degree of contamination in the process gas (G) flowing through the gas line (9) is greater than a predetermined maximum contamination, at least one of the following steps is carried out: Output of information on the output device (39), in particular a warning message or warning signal, Interrupting the manufacturing process, automatically entering information about the degree of contamination in the process gas (G) flowing through the gas line (9), determined from the number of measured values ​​(M), into a quality data protocol, Determining the condition of a number of components (2) manufactured in the manufacturing process and estimating which of the number of components (2) is / are usable and / or which is / are not.

3. Method according to claim 1 or 2, wherein, for controlling the device (1), the evaluation of the number of measured values ​​(M) is carried out taking into account a number of process parameters (P) of the device (1) that are characteristic for an additive manufacturing of a component (2) and The device (1) is controlled by means of a control or regulation of the number of process parameters (P), in particular automatic control or regulation, depending on the evaluation of the number of measured values ​​(M), wherein, preferably with regard to the control or regulation of the number of process parameters (P), optimization and / or error detection with respect to at least one process parameter is carried out on the basis of the evaluation of the number of measured values ​​(M).

4. The method of claim 3, wherein a process parameter (P) of the number of process parameters (P) is characteristic of at least one of the following criteria: a flow rate, a flow rate, a direction, an effective area and / or a velocity of the process gas (G) in the process chamber (3), in particular relative to an uppermost layer of the build-up material (13), a geometric and / or temporal uniformity of a flow rate, a flow rate, a direction, an effective area and / or a velocity of the process gas (G) in the process chamber (3), in particular relative to an uppermost layer of the build-up material (13), an area, thickness, position and / or shape of an area to be solidified on the build-up area (8) for the production of the component (2), a supply and / or a selective solidification of the build-up material (13), a distribution of the build-up material (13), the at least one energy jet (22),which causes the selective solidification of the build material (13), in particular its wavelength, intensity, intensity distribution, beam diameter, beam cross-section, deflection direction, direction of movement and / or speed of movement within the build area (8), a filling and / or overfilling of an overflow container intended to collect excess build material (13) in the process chamber (3), an increased or uncontrolled discharge of build material (13) into an atmosphere of the process chamber (3).

5. A method according to any of the preceding claims, wherein the evaluation determines whether a measured value (M) or a series of measured values ​​(M) lies within a predetermined range, preferably wherein the number of measured values ​​(M) is evaluated by comparing a measured value (M) with at least one predefined threshold value and / or a change in a number of measured values ​​(M) is compared with at least one predefined threshold value and / or a plurality of measured values ​​(M) is checked for a recurring measured value pattern, wherein preferably the checking of the number of measured values ​​(M) for the recurring measured value pattern includes the detection of repeatedly occurring measured value anomalies, in particular those that occur briefly compared to the predetermined period of the measured value acquisition, preferably wherein the evaluation of the number of measured values ​​(M) includes the formation of a temporal correlation between a result of an acquisition of the number of measured values ​​(M) and at least one process parameter (P) of the device (1) that is characteristic for an additive manufacturing of a component (2).

6. Method according to one of the preceding claims, wherein the acquisition of a number of measured values ​​(M), and preferably also the control or regulation of the process parameter, takes place during an additive manufacturing of a component (2), preferably continuously or at regular time intervals.

7. Method according to any of the preceding claims, wherein the build-up material (13) is at least partially powdered and preferably comprises a metal powder.

8. Method according to claim 7, wherein a passivating agent, preferably lime particles, is added to the process gas (G) flowing through the gas line (9) downstream of the process chamber (3) and / or upstream of the filter unit (40).

9. Method according to one of the preceding claims, wherein for the production of a component (2) the build material (13) is fed into the process chamber (3) and a dosing device and / or a coater (16) is arranged in the process chamber (3) which applies the build material (13) layer by layer within a build area, and wherein, in the course of controlling the device (1), the build material (13) is dosed by means of the dosing device and / or the coater (16) or is dispensed in a modified manner depending on the number of measured values ​​(M) and / or the dosing device and / or the coater (16) is moved or is dispensed in a modified manner.

10. System for controlling a manufacturing process for the additive manufacturing of a component (2) in a device (1), wherein build material (13) is solidified on a build area (8) in a process chamber (3) by irradiating the build material (13) with at least one energy beam (22), and wherein a process gas (G) loaded with impurities (A) is discharged from the process chamber (3) through a gas line (9), filtered, and returned to the process chamber (3), the control system comprising: a contamination measuring unit (18) designed to record a number of measured values ​​(M), wherein each measured value (M) allows a conclusion to be drawn about the respective degree of contamination in the process gas (G) flowing through the gas line (9), an evaluation unit (32) designed to evaluate the number of measured values ​​(M),a control unit (29) designed to control the device (1) and / or an output device (39) connected to the manufacturing process via data technology, depending on the number of measured values ​​(M), wherein the system is designed in particular to carry out a method according to one of the preceding claims.

11. System according to claim 10, which is designed as a retrofit kit for a device (1) for the additive manufacturing of a component (2) and is designed such that the contamination measuring unit (18) can be arranged in a gas line (9) of the device (1) and the evaluation unit (32) and the control unit (29) can be arranged or implemented in a control device (30) of the device (1).

12. System according to claim 10 or 11, wherein the contamination measuring unit (18) comprises a filter breakage sensor, in particular based on the triboelectric effect, and / or an optical turbidity sensor, and / or a camera which in particular monitors the brightness of images taken through the process atmosphere, and / or a thermo-optical measuring device, and / or a system designed for powder bed monitoring, and / or a measuring device for comparatively measuring a pressure at two parallel filter stages.

13. Device (1) for the additive manufacturing of a component (2) in a manufacturing process in which build material (13) is applied to a build area (8) in a process chamber (3) by means of The device (1) comprises: a gas line (9) for guiding a process gas (G) from the process chamber (3) through a filter unit (40) and back into the process chamber (3), a system according to one of claims 10 to 12, wherein the contamination measuring unit (18) of the system is arranged in the gas line (9), preferably on a clean gas side of the gas line (9).

14. Device according to claim 13, wherein the filter unit (40) is designed to be at most two-stage, preferably at most one-stage, and / or wherein at least one filter element, preferably all filter elements of the filter unit (40) is / are designed to be cleaned before, during, or after a manufacturing process, preferably wherein a particle separation unit is connected upstream of the filter unit (40).

15. Computer program that can be loaded into a programmable control device (30) comprising program code to execute all steps of a method according to any one of claims 1 to 8 or 9 when the computer program is executed on the control device (30).

Images