Apparatus and method for manufacturing parts taking into account in-line determined injectability properties of powders - Patents.com

Abstract

The invention relates to an apparatus for the layer-by-layer production of parts by local selective solidification of a material powder in a process area by electromagnetic or particle radiation. The apparatus comprises a powder supply for feeding a powder P to the process area. The powder supply comprises a powder conduit connected to a funnel 1 and at least one controllable shut-off valve V1, V2 arranged downstream of the funnel 1 in the powder flow direction R. The apparatus allows an in-line determination of the injectivity properties of the powder actually used.

Description

[Technical field]

[0001] The present invention relates to an apparatus for the layer-by-layer production of a part by local selective solidification of a material powder, comprising a powder supply. The present invention also relates to a method for producing a part by local selective solidification of a material powder.

[0002] The machine according to the invention is in particular a machine for producing shaped parts according to the principle of selective laser melting or selective laser sintering, in particular material powders made of metals, metal alloys, plastics or ceramic materials can be used and processed. [Background technology]

[0003] In the selective laser melting or laser sintering process, molded parts such as machine parts, tools, prostheses, jewelry, etc. can be produced according to corresponding geometric shape description data (e.g. CAD data) of the molded part by forming layer by layer from metal or ceramic material powder or plastic powder. In the production method, the material powder to be solidified is applied layer by layer to a workpiece table and is exposed to electromagnetic or particle radiation, in particular focused laser radiation, according to the geometric shape description data. The radiation causes heating and thus melting or sintering of the material powder of the powder layer, so that certain areas of the powder layer are solidified. The solidified areas correspond to the cross-section of the molded part of the applied material powder layer to be produced. After the cross-section of the molded part has solidified in the material layer, the workpiece table is lowered by the layer thickness and a new material powder layer is applied. This allows the cross-section of the molded part to be consolidated. This process is repeated until the molded part is formed layer by layer. Teachings of laser melting can be found, for example, in WO 2019 / 211 476 A1.

[0004] For example, Japanese Patent Publication No. 2019 039010 discloses a method for printing a three-dimensional part using an electrophotographic additive manufacturing system, which includes creating layers of the three-dimensional part from fill part material using an electrophotographic drive device.

[0005] US 2019 / 0105843 discloses depositing a powder mound in a first step to identify features related to the spreading behavior of the powder. The powder pile is generally provided from a dispenser as a fill or charge of material deposited prior to a spreader. A light source is arranged to illuminate one side of the powder pile, thereby resulting in a shadow of the powder pile as the powder pile is being dispensed by the spreader. Also, a sensor is provided for detecting and evaluating the cast shadow. Summary of the Invention [Problem to be solved by the invention]

[0006] In conventional systems, to accurately determine the powder properties, especially the injectivity properties of the powder, a sample must be removed. Thus, the powder is removed from the powder or feed circuit of the machine and examined by external analysis. [Means for solving the problem]

[0007] Detailed Description of the Invention In order to solve the above mentioned problems, the features of the independent claims are provided. The dependent claims relate to preferred embodiments of the invention.

[0008] An apparatus is provided for layer-by-layer manufacturing of parts by local selective solidification of a material powder in powder form in a process area by electromagnetic or particle radiation. The apparatus may comprise a powder supply for supplying the powder to the process area. The powder supply may further comprise a feed line or powder conduit that can be connected to the funnel and a controllable shut-off valve that can be arranged downstream of the funnel in the powder flow direction. In order to directly determine the injectability properties of the powder, at least one sensor, in particular a mass sensor, may be provided for the determination of the time dependence of the mass (and / or weight) of the powder that is (directly) placed in or (directly) removed from the funnel. Thus, an in-line determination of the injectability properties of the powder placed in the feeder can be achieved without the need to remove a powder sample from the feeder circuit or the powder circuit. The in-line determination of the injectability properties allows a fast and accurate determination of the actual powder properties in the feed line and the powder supply, so that time-consuming removal of the powder sample from the circuit is not necessary. The direct inline determination of the injectivity properties allows the process parameters to be directly controlled during the layer-by-layer production of the component, which results in a precise adaptation of the production method to the powder properties (e.g. (real-time) monitoring of the production method).

[0009] The injectivity properties of the powder can be determined in-line, and therefore in particular directly in the powder feed circuit, without removing a powder sample from the circuit. The powder for which the injectivity properties are determined passes through the powder circuit and is used for the manufacture of the part. Particularly preferably, the injectivity properties are further determined in the powder feed direction (and / or in the powder circuit), so that the feed section of the powder feed circuit is directly used to determine the properties of the powder. This is achieved by providing a container with a funnel-shaped outlet as part of the powder feed line. Based on the flow rate of the powder from the funnel, the injectivity properties of the powder can be determined by determining the time. Preferably, the determined values ​​(time values ​​or weight and / or mass) of the discharged powder can be compared with reference values ​​from a table to determine the injectivity properties.

[0010] The funnel or funnel section can thus be provided with a controllable shut-off valve arranged below it, as well as a device for mass determination for in-line determination of the injectability properties of the powder (especially SLM powder; selective laser melting (SLM)). In a special further development, a defined funnel shape borrowed or adopted from Hall (ISO 4490) or Carney measurement method (ASTM B964) can be used to directly introduce the powder into the powder circuit at a suitable point. Preferably, a controllable shut-off valve is arranged downstream of the funnel shape. The funnel shape containing the powder and held by the shut-off valve is arranged so that it can be metered. Furthermore, another device can be arranged downstream of the shut-off valve, which also makes it possible to meter the material (powder) arranged therein as a whole.

[0011] Advantageously, two methods can be used to determine the injectivity characteristics. According to the first method, the valve is opened and closed for a defined time. The mass of powder passed, in combination with the time, offers the possibility of determining the injectivity characteristics of the powder. According to the second method, the valve is opened until a defined amount / mass of powder passes through the funnel and the time the valve is open is measured.

[0012] A controllable shut-off valve may be provided for selectively shutting off the powder flow from the funnel. For example, the shut-off valve may be controlled via a control unit, in particular a central control unit, to rapidly open and close the shut-off valve. Advantageously, pinch valves are used for this purpose, which respond essentially without delay. Preferably, at least one regulating means (to disconnect the conduction from the mass sensor) may be arranged downstream of the shut-off valve. Particularly preferably, a regulating means is arranged downstream of each of the shut-off valves, the regulating means being made, in particular, of an elastic material.

[0013] It is particularly advantageous if an inert gas atmosphere is provided in the powder supply, so that the powder conduit is made gas-tight.

[0014] Further, a determination device may be provided for determining the injectability characteristics based on the weight change of the powder placed in the powder supply section based on at least the weight (or mass) determined by the mass sensor and / or the predetermined time required for a certain amount of powder to be removed from the funnel section. When the shut-off valve is opened, the powder leaves the funnel section, preferably by gravity, through the funnel outlet and the corresponding vertical configuration of the adjacent conduit section. Thus, preferably, the funnel section is disposed above (particularly directly above) the adjacent conduit section so that the powder can pass vertically from the funnel section into the conduit section.

[0015] The determination device may be configured to determine the injectability characteristics based on a weight (or mass) change of the powder disposed in the funnel over a predetermined period of time. Alternatively or additionally, the injectability characteristics may be determined based on a period of time required for a predetermined weight (or mass) change in the funnel. The injectability of the powder may be determined based on the time required for a predetermined amount of powder to be removed from the funnel of the powder supply of the device.

[0016] Preferably, the apparatus may be configured such that the shut-off valve is opened for a predetermined period of time and the mass sensor determines the mass of powder removed during that period. Preferably, the injectability characteristics of the powder in the powder supply are determined by comparing the determined value (mass removed) with a reference value.

[0017] Advantageously, at least a first mass sensor may be provided to determine the weight (and / or mass) of the powder placed in the funnel, and at least a second mass sensor may be provided to determine the weight (and / or mass) of the powder removed from the funnel. The dual mass sensor configuration may further increase the accuracy and sensitivity of this determination.

[0018] Further advantageously, the first and second cut-off valves may be arranged in succession with each other in the powder flow direction, preferably downstream of the funnel for selectively cutting off the powder flow direction, thus further increasing the accuracy and sensitivity of the determination.

[0019] The funnel may be (directly) interchangeably arranged in the powder supply section to replace or exchange with a funnel having a different funnel inner wall shape. Thus, depending on the powder being used, an adapted or optimized funnel with a corresponding funnel inner wall shape can be directly replaced in the powder supply section for an optimized powder flow, so that the accuracy and sensitivity of the determination can be further increased. For this purpose, the funnel may be equipped with a conical (inner) powder retention area. Advantageously, the inside of the funnel, along which the powder passes, can have an at least partially (preferably completely) polished surface.

[0020] Preferably, at least one powder removal means can be provided downstream of the shut-off valve for removing powder in the feed direction. The powder removal means particularly advantageously comprises an ultrasonic exciter, which is arranged such that the powder in the powder supply can be fed by ultrasonic excitation in the direction of the process area or directly to the powder application unit. According to an advantageous embodiment, the powder removal means is only activated when removing powder from the funnel in order to improve the discharge of powder from the funnel.

[0021] Particularly preferably, the funnel is provided with a further sensor, in particular at least one moisture sensor for determining the moisture of the powder placed in the funnel.

[0022] The shut-off valve may preferably be arranged downstream (particularly vertically directly below) the funnel, and the powder may preferably be removed from the funnel by gravity (or preferably by applied gas pressure) when the shut-off valve is open. Thus, in particular, constant conditions are provided for the determination, so that the accuracy and sensitivity of the determination can be further increased.

[0023] Furthermore, the apparatus may comprise a powder application unit for applying a powder layer of the supplied powder in the process area (to the part to be manufactured). The powder supply may thus comprise a powder application unit at one end of a powder conduit, so that the powder metered by the at least one mass sensor is (preferably automatically) supplied to the powder application unit for use in the manufacture of the part. At the other end, in particular, a powder reservoir or a powder main storage may be provided, which serves as a reservoir for making the powder available to the manufacturing method. Between these ends, a funnel may be provided for this determination. Furthermore, the funnel may preferably be arranged directly below the powder reservoir.

[0024] Advantageously, the funnel may be a container having a funnel outlet (intermediate container) in communication with a feed passage for supplying powder to the powder application unit. In particular, the powder supply may form a powder circuit. Advantageously, the powder supply may also be set up for automatic powder supply.

[0025] The powder bed based additive manufacturing method having the powder circuit described above can include determining an injectivity characteristic of a powder disposed in the powder supply by determining a weight change of the powder in the funnel as a function of time, and determining the injectivity characteristic of the powder based on the determined weight change. Further, the method can include adjusting the manufacturing method based on the determined injectivity characteristic of the powder in the powder supply.

[0026] The method may therefore comprise a step of (directly) determining the injectability properties of the powder placed in the powder supply by determining (in particular time-dependently) the mass (and / or weight) of the powder placed in or removed from the funnel. A comparison of the value (e.g. mass or weight) determined by the determination may then be carried out with a predefined value for determining the injectability properties. The predefined value may advantageously be powder-specific and / or funnel-shape specific and may have been previously determined by carrying out experiments or tests.

[0027] The step of determining the injectability characteristics can be performed during the production of the part, in particular without removing the powder from the powder supply, so that the determination does not interrupt the production process and the measured powder (or the powder used for the determination) can be used directly in the production process to produce the part, since no powder is removed from the feed circuit for the determination.

[0028] The injectivity characteristics of the powder placed in the funnel can be determined directly by determining the weight change of the powder in the funnel. It is therefore possible to determine the injectivity of the powder directly in the feed line (in-line in the feed line) without the need to remove the powder from the circuit.

[0029] Advantageously, an apparatus may be provided in such a way that the powder is reprocessed if it is determined that the powder does not correspond to the predetermined properties. In particular, an additional drying section can be provided (directly) in the powder supply section so that the moisture content of the powder can be adjusted. For example, drying of the powder can be achieved by the introduction of heat. Said drying can preferably be used if it is determined that the injectability of the powder does not meet the specifications for manufacturing a particular part. Preferably, said drying section is provided downstream of the funnel section in the flow direction of the powder.

[0030] Preferably, a mass sensor may be provided for weighing the powder placed at least directly in the funnel. For a more accurate weight determination, at least two opposing mass sensors may be provided for this purpose. The mass sensor is preferably provided directly in the funnel, so that the most unbiased measurement results can be obtained.

[0031] To be able to guarantee a stable method and a consistently high quality product, a continuous (e.g. constant) monitoring of important process and quality parameters can be carried out. Measurements of samples in the laboratory are usually not fast enough to be able to intervene in the process in case of an error and to save the process. Furthermore, all laboratory procedures are only momentary evaluations. Continuous measurements, which are carried out directly in the process and under the same conditions, are more suitable for process control.

[0032] At least one adjusting means may be provided, which may be arranged downstream of the shut-off valve to disconnect the line path from the mass sensor. The adjusting means may advantageously be made of an elastic material. The adjusting means is suitable for applications in which inaccurate or misaligned parts must be positioned accurately, or in which inaccuracies in the positioning of parts must be compensated for and jamming of opposing parts must be reduced.

[0033] The proposed device can be easily integrated into various positions in the powder circuit (e.g. below the main (powder) reservoir). Moreover, it offers the possibility to easily and quickly determine physical properties in existing circuit systems that can be used to determine the process quality of the powder. Moreover, it is still possible to intervene in the powder circuit at an appropriate point if the process quality of the powder does not meet the requirements. Process improvements can also be achieved, since only suitable powders that meet the requirements are introduced into the process chamber to manufacture the part. [Brief description of the drawings]

[0034] [Figure 1] The configuration of the device incorporated in the powder circuit is shown. [Figure 2A] A method for determining the injectability of a powder is presented. [Figure 2B] A method for determining the injectability of a powder is presented. [Figure 2C] A method for determining the injectability of a powder is presented. [Diagram 3] 1 shows a further device configuration integrated into the powder circuit. [Figure 4A]A method for determining the injectability of a powder is presented. [Figure 4B] A method for determining the injectability of a powder is presented. [Figure 4C] A method for determining the injectability of a powder is presented. [Diagram 5] 1 shows a further device configuration integrated into the powder circuit. [Figure 6A] A method for determining the injectability of a powder is presented. [Figure 6B] A method for determining the injectability of a powder is presented. [Figure 7] 1 shows an advantageous further development of the device. [Figure 8] The advantageous funnel 1 is shown. [Figure 9] Advantageous powder circuits are shown. [Figure 10] A further advantageous powder circuit is shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. The features of the embodiments may be combined in whole or in part, and the present invention is not limited to the described embodiments.

[0036] In contrast to the known prior art, the present invention provides an optimized method for determining the injectivity properties of powders, in particular SLM powders, directly in the powder circuit, without the need for inspection of powder samples outside the respective apparatus.

[0037] Especially in the process of selective laser melting, the quality of the parts achieved is highly directly related to the quality and properties of the powder used. Since external powder sampling to determine the powder injectability as well as other powder properties involves, on the one hand, delays in the manufacturing process and, on the other hand, process inaccuracies due to the delays, the inventors propose an optimized system that allows the determination of the powder properties to be integrated into the powder circuit, so that the removal of powder outside the powder circuit can be omitted.

[0038] Thus, as shown in FIG. 1, according to the invention an injectivity measuring module M0 is proposed, which is installed directly in the powder circuit of the machine. The term machine is to be understood in particular as an apparatus for selective laser melting or laser sintering, with which molded parts such as machine parts, tools, prostheses, jewellery, etc. can be produced by layer-by-layer formation from metal or ceramic material powder or plastic powder. In the production process, the material powder is applied layer-by-layer on a workpiece table in a process chamber PK and exposed to electromagnetic or particle radiation, but in particular to focused laser radiation according to a given geometric shape. The radiation causes heating and thus melting or sintering of the material powder of the powder layer, as a result of which certain areas of the powder layer are solidified. In this way, the desired cross-section of the molded part to be produced can be generated from the material powder. In subsequent process steps, further material powder layers can be applied and solidified accordingly, until the desired molded part is built up layer-by-layer.

[0039] The modular part shown in FIG. 1 can be inserted directly into the powder supply circuit of the machine, so that powder extraction for determining the physical properties can be performed without actually removing the powder from the powder circuit, so that interruptions to the powder supply can be reduced as much as possible or even avoided. As shown in FIG. 1, a funnel part 1 is provided in which the powder P is arranged. The funnel part 1 can be formed as a container with a funnel-shaped side, in particular a funnel-shaped bottom side, into which the powder can be filled. The funnel part 1 is in particular mounted in such a way that a mass determination or weight determination of the powder P arranged in the funnel part 1 can be achieved precisely via the mass sensors M1 and M2. As shown in FIG. 1, two mass sensors M1 and M2 are preferably used for this purpose, which are arranged in particular opposite each other, for example directly in the region of the support point of the funnel part. Advantageously, the funnel part 1 can also be mounted in a floating manner.

[0040] The funnel section 1 has at its lower end, i.e. at the end of the tapered section through the funnel, a funnel outlet 2 along which the powder P can be led to the shut-off valve V1. The shut-off valve V1 in particular serves to shut off the powder flow from the funnel section 1. When the shut-off valve V1 is open, the powder P leaves the funnel section 1 at a constant speed due to gravity and the funnel shape. As the powder P leaves the funnel section 1, the weight of the powder P in the funnel section 1 becomes less and less and consequently decreases. By closing the shut-off valve V1, the powder flow is stopped and the weight loss of the powder P placed in the funnel section 1 can be directly prevented. A pinch valve has been found to be particularly advantageous as the shut-off valve V1.

[0041] In order to make it possible to determine as accurately as possible the weight of the powder P placed in the funnel section 1, in particular to achieve a vertical separation of the funnel section 1 from the continuous powder line, regulating means 3 are provided downstream of the shut-off valve V1, which in particular are able to compensate for vertical fluctuations. Both the funnel outlet 2 and the shut-off valve V1 as well as the regulating means 3 are preferably arranged below the funnel section 1. Particularly preferably, the system is made gas-tight so that a protective gas can be placed inside the powder circuit, which is subjected to a given internal pressure.

[0042] The internal shape of the funnel part 1 is preferably formed according to a precisely defined shape and has in particular a polished surface. Particularly advantageously, the funnel shape can be based on or adopted from the Hall (ISO 4490) or Kearney (ASTMB964) measurement methods. By defining the funnel shape and using a known material powder, the injectability properties of the powder can be determined. In particular, by using predefined characteristic values ​​that can be predetermined, specific to the powder and the funnel, conclusions can be drawn about the actual injectability properties of the powder used by comparing the actually determined values.

[0043] FIG. 1 also shows the powder flow direction R, in which the powder flows due to gravity when the shut-off valve is open. Advantageously, two different methods can be used to determine the injectability characteristics. According to the first method, the valve V1 is opened and closed for a defined time. The mass of powder passed, in combination with the time, offers the possibility of determining the injectability characteristics of the powder. According to the second method, the valve is opened until a predefined amount / mass of powder passes through the funnel and the time the valve is open is measured. This also offers the possibility of determining the injectability characteristics of the powder. Thus, the state of the shut-off valve V1 is detected so that the period of the state change of the valve can be detected, i.e. from the closed position to the open position or vice versa. Preferably, this is done by a control device, which can be provided accordingly and connected to the shut-off valve. Alternatively, the time detection can also be achieved via the change in the measured values ​​of the mass sensors M1 and M2, so that, for example, it can be determined that the valve is closed if the measured values ​​of the mass sensors do not change over time. The mass sensors can also have time-related measuring points that correlate with the opening and closing times of the valve, so that, for example, measurements can be made only when the state of the valve changes.

[0044] Alternatively, the mass sensor can measure continuously and record the measured values ​​accordingly. The injectivity properties of the powder used change, for example, depending on the humidity and / or temperature or the quality of the powder. The powder P placed in the funnel 1 can initially be fed directly from a powder reservoir, which can also be fed simultaneously to the coater B. After the initial state of the funnel has been reached and the powder P has been filled in the funnel, the measurement of the injectivity properties of the powder can be started directly. Preferably, the determined powder quality values ​​can be fed directly to the control system of the machine, thereby in order to influence the workpiece manufacturing process, for example to change the behavior of the laser or to change the layer thickness and / or application speed of the powder layer of the manufacturing process and optimally adapt it to the powder placed. Alternatively and / or additionally, it is also possible to rework the powder according to the determined powder quality or injectivity properties, for example to carry out a reworking via a heating unit or a drying unit, in order to improve the properties of the powder and thus optimize the manufacturing quality of the part.

[0045] In FIG. 1, downstream of the shut-off valve V1 and the regulating means 3 in the powder flow direction R1 there is a first conduit section 4, which is formed via associated mass sensors M3 and M4 for determining the mass or weight of the powder placed in the conduit section 4. Advantageously, the determination of the weight of the powder P placed in the conduit section 4 is made possible via corresponding mass sensors M3 and M4 at the fulcrum of the first conduit section 4. The first conduit section 4 can be closed via a shut-off valve V2. The shut-off valve V2 is arranged downstream of the first conduit section 4 in the powder flow direction R. The first conduit section 4 can be tubular with parallel sides. By determining the weight of the powder P placed in the first conduit section 4 in combination with a controlled shut-off valve V1 and determining the weight based on the measured values ​​of the mass sensors M1 and M2, the accuracy of the determined injectability properties of the powder can be significantly increased.

[0046] Downstream of the shut-off valve V2 there is a further regulating means 5 which separates the first conduit section 4 and thus allows a highly accurate measurement of the powder P placed in the first conduit section 4. Further in the powder flow direction R there is a second conduit section 6 as part of the powder circuit. This conduit section can for example lead to a feed section which feeds the coater B or lead via a line to a main storage section or powder reservoir PS in which the majority of the powder in the powder circuit is stored. The proposed solution can therefore be easily integrated at various points in the powder circuit, in particular below the powder reservoir. Moreover, this offers the possibility to easily and quickly determine the physical properties of the powder in an existing powder circuit system in order to determine the process quality of the powder. Moreover, it is still possible to intervene at the appropriate points in the powder circuit if the process quality of the powder does not meet the desired requirements. Advantageously, only the appropriate powder is fed into the process chamber.

[0047] FIG. 1 shows the funnel outlet shape through which the powder is fed, whereby a shut-off valve, for example a pinch valve, is arranged below the funnel opening. A mass sensor is used to determine the mass or weight of the powder in the funnel section. Downstream in the powder flow direction R, a first conduit section 4 is provided, which can also be formed as a container or a pipe and has a further shut-off valve V2 in the lower area and makes it possible to meter the received powder. The system is connected to a powder circulation system via a second conduit section 6. Advantageously, adjustment means are provided so that the metering in the individual sections is not affected. Advantageously, the system is also operated with inert gas and is subject to internal pressure, so that the characterization and the powder flow are further improved. Thus, according to the invention, an inline determination of the injectability of powders, in particular of SLM powders, is provided.

[0048] In Figures 2A, 2B and 2C three different time points T1, T2 and T3 are shown to illustrate an advantageous process for determining the injectability of the powder P used.

[0049] At time T1, powder P is in the funnel and mass sensors M1 and M2 indicate a corresponding value, shut-off valve V1 is in the closed position, there is no powder in the first conduit section 4 and mass sensors M3 and M4 detect the weight of the corresponding empty conduit section.

[0050] At time T2, the shutoff valve V1 is closed after opening for a certain time or depending on the fact that a certain amount of powder or mass has flowed out. The residual powder amount P# in the funnel section therefore corresponds to the powder amount by time T1 minus the removed powder amount P*. The mass sensors M1 and M2 detect the residual powder in the funnel section. The removed powder amount P* can then be weighed via the mass sensors M3 and M4 when the shutoff valve V2 is closed, as shown in FIG. 2B. This double determination allows to achieve a very accurate determination of the discharged powder or mass and weight via the funnel section 1 and the first conduit section 4, as well as the determination of the injectability characteristics of the powder to be used as a result. Finally, at time T3, as shown in FIG. 2C, the shutoff valve V2 is opened to empty the conduit section 4 and prepare it for further measurement processes. The funnel section 1 contains the residual powder P#.

[0051] FIG. 3 shows another advantageous embodiment. Powder P is fed into the funnel section 1 and metered via at least two mass sensors M1 and M2. Downstream of the funnel outlet in the powder flow direction there is a shutoff valve V1. Downstream of the shutoff valve V1 there is a regulating means 3, which leads to a vibratory feeder F1. The vibratory feeder F1 essentially comprises a horizontally arranged pipe section, to which powder is fed from the regulating means 3 via a vertical inflow. Furthermore, a motor MF1 of the vibratory feeder is provided for driving the vibratory feeder and thus conveying the powder arranged in the vibratory feeder F1 to a powder outlet of the vibratory feeder, which advantageously leads to a regulating means M5. The body of the vibratory feeder F1, for example a tube section, is metered via mass sensors M3 and M4. Advantageously, these mass sensors are used when supporting the body of the vibratory feeder F1 in order to allow an accurate determination of the powder arranged in the vibratory feeder F1. The powder thus fed into the vibratory feeder below the valve V1 is metered there and then discharged via the vibratory feeder. The vibratory feeder outlet is located at the end of the body and is connected to the powder circuit via an adjusting means, i.e. the metering in the individual sections remains unaffected.

[0052] 4A, 4B and 4C show an example of injectability determination using the device shown in FIG. 3. FIG. 4A shows the initial position in which the powder P is placed in the funnel 1 and metered via the mass sensors M1 and / or M2. The shut-off valve V1 is closed. The body of the vibratory feeder is empty of powder and is preferably also metered to determine the starting value. As shown in FIG. 4B, a powder quantity P* is removed from the funnel 1 through the opening of the shut-off valve V1, for example as a function of a certain time or as a function of certain measured values, for example as a function of the mass sensors M1 and / or M2 and thus of the residual powder mass P#. The removed powder quantity P* can be metered in the vibratory feeder F1 and the powder is placed in the body of the vibratory feeder. After activation of the vibratory feeder, in particular the corresponding motor MF1, the removed powder quantity P* can be completely discharged from the vibratory feeder F1, so that the vibratory feeder F1 is substantially empty of powder. Advantageously, as already mentioned above, the system can also be operated with an inert gas and subjected to internal pressure. By using a vibratory feeder, the second shut-off valve can be omitted, which preferably allows even more accurate measurements to be performed.

[0053] Figure 5 shows a simplified example in which only the shut-off valve V1 is provided to measure the powder P placed in the funnel 1 by the mass sensors M1 and M2. The adjustment means 3 can be used to directly connect the device to the powder circuit via the outlet A. In this embodiment, the injectability characteristic is therefore determined only by determining the weight or mass of the powder P placed in the funnel 1 before and after the shut-off valve V1 opens, and the measured values ​​are compared with predefined predetermined values ​​for a characteristic powder and a characteristic funnel.

[0054] The determination of the powder mass P is further illustrated in Figures 6A and 6B, where Figure 6A shows the initial state and Figure 6B shows the state after a quantity of powder has been removed from the funnel 1 by opening the shut-off valve V1. By comparing the determined mass by the mass sensors M1 and / or M2 of the initial powder quantity P in Figure 6B with the residual powder quantity P#, the reduction in mass can be determined and at the same time a determination of the injectability properties of the powder placed in the funnel 1 can be achieved via a time recording of the opening time of the shut-off valve V1. To enable the measurement of the powder P placed in the funnel 1, adjustment means 3 are provided, preferably arranged downstream of the shut-off valve V1.

[0055] FIG. 7 shows an advantageous further development of the aforementioned embodiment. In addition to the mass sensors M1, M2, which determine the mass of the powder P placed in the funnel 1, a moisture sensor 1B and a removal means 1A are provided. Preferably, both the removal means and the moisture sensor are provided directly in the funnel 1. The moisture sensor 1B can be used to determine the moisture of the powder P placed in the funnel 1. The removal means 1A can be provided to improve the discharge of the powder, which promotes the flow of the powder P, for example by introducing vibrations into the funnel 1. By determining different time and / or weight values ​​for different powder qualities, a database can be created in which the corresponding injectability or injectability characteristics are recorded. If a known powder with an unknown powder quality is used, the injectability characteristics of the powder used can be estimated by comparing the values ​​recorded in the database with the current measured or determined values ​​of the mass sensors M1 or M2, as well as the opening times of the closing valves and the removed powder masses. By additionally using a moisture sensor, even more precise determinations are possible regarding the injectability characteristics of the powder used. The removal means used may preferably be an ultrasonic exciter, which is only activated during the measurement or in case of possible blockage of the funnel. Preferably, the funnel shape used has the shape of the funnel used in the Hall or Carney measurement method, or another standardized funnel shape for measurements. Such a preferred funnel shape is shown by way of example in FIG. 8.

[0056] The advantageous funnel 1 shown in FIG. 8 has a large receiving opening 11, by which the powder feed into the funnel 1 can take place, in particular from a powder reservoir or a powder main store. The upper side 12 is thereby connected directly to a pipe and / or to the main store. Advantageously, a flange 13 is used for this purpose. The body 14 has a funnel shape 10. The funnel shape 10 is preferably selected according to standardized funnel shapes for determining the injectability of material powders. Advantageously, the funnel shape has an opening angle of 60 degrees ± 0.5 degrees and a predefined funnel outlet diameter D. The funnel outlet 2 leads to an opening 17, which can be connected to a shut-off valve V1. The shut-off valve V1 thus faces the funnel bottom 15. Preferably, the inside of the funnel, i.e. the funnel shape 10, is a polished surface. Advantageously, therefore, a calibrated funnel is used, for example according to DIN-EN-ISO 4490 or ASTMB 964.

[0057] FIG. 9 shows an exemplary powder circuit. The powder is mainly stored in a powder reservoir PS, which can be closed by a suitable valve. The powder from the powder reservoir can be made available directly, preferably simultaneously, to the injectivity measurement module M0 and to the coater B. The powder used for the injectivity measurement by the injectivity measurement module M0 is then returned directly to the powder reservoir PS via the powder preparation PA, as is the powder discharged from the process chamber PK via the bleeder U. As an example, the optical module OP carries a laser for solidifying the respective powder layer. It can thus allow an injectivity determination of the powder actually used in parallel to the powder supply to the coater B, as shown. Furthermore, the embodiment also allows the reuse of the measured powder, by directly connecting the injectivity measurement module M0 to the powder preparation PA. Furthermore, as already explained, the powder circuit can be provided with adjustment means, such as a drying unit or a heating unit, in order to optimize the powder properties.

[0058] Another advantageous embodiment is shown in Fig. 10, in which a powder separation unit Pab is provided, which receives powder from the powder preparation Pa. Via a corresponding valve, the powder of the powder separation unit can be fed to an injectivity measurement module M0 and simultaneously to a powder reservoir PS (main store). The powder reservoir feeds powder to a coater B, which provides a layer in a process chamber PK. Excess powder is returned to the powder preparation via a bleeder U. Thus, an optical module OP is also provided.

[0059] Existing features, components, and specific details can be interchanged and / or combined to create further embodiments, depending on the required purpose of use. Modifications that are within the knowledge of those skilled in the art are implicitly disclosed herewith.

Claims

1. 1. An apparatus for the layer-by-layer production of parts by local selective solidification of a material powder in a process area by means of electromagnetic or particle radiation, comprising: A powder supply unit for supplying powder (P) to the process area, the powder supply unit comprising: a powder conduit connected to the funnel (1); and controllable shut-off valves (V1, V2) arranged downstream of the funnel (1) in the powder flow direction (R), wherein at least one sensor is provided for determining the time dependence of the mass of the powder (P) arranged in or removed from the funnel (1) in order to determine the injectability characteristics of the powder (P).

2. a determining device is provided for determining the injectability characteristics of the powder (P) placed in the powder supply based on at least the weight determined by the sensor; 10. The apparatus of claim 1.

3. the at least one sensor is a mass sensor (M1, M2, M3, M4), the mass sensors (M1, M2, M3, M4) being arranged such that the determination of the injectivity properties of the powder (P) is carried out in-line, in the powder feed direction and / or in the powder circuit, 3. The device according to claim 1 or 2.

4. the determining device is configured to determine the injectability characteristics based on a weight change of the powder (P) placed in the funnel (1) during a predetermined time period (T1) and / or a time period (T2) required for a predetermined weight change in the funnel (1), 4. The apparatus of claim 3.

5. the controllable shut-off valves (V1, V2) are provided to selectively shut off the powder flow from the funnel (1); At least one regulating means (3, 5) is arranged downstream of the shut-off valve.

3. The device according to claim 1 or 2.

6. the device is configured to open the shut-off valves (V1, V2) for a predetermined period of time, determine the powder mass removed by the mass sensors (M1, M2, M3, M4), and determine the injectability characteristics of the powder (P) placed in the powder supply by comparison with a reference value.

4. The apparatus of claim 3.

7. at least a first mass sensor (M1, M2) is provided for determining the weight of the powder (P) placed in the funnel and at least a second mass sensor (M3, M4) is provided for determining the weight of the powder (P*) removed from the funnel; 3. The apparatus of claim 2.

8. the shut-off valve (V1) and the second shut-off valve (2) are arranged in succession relative to one another in the powder flow direction, 3. The device according to claim 1 or 2.

9. The funnel (1) is replaceably arranged in the powder supply unit to replace a funnel having a different funnel inner wall shape.

3. The device according to claim 1 or 2.

10. the shut-off valves (V1, V2) are disposed below the funnel portion (1), and the powder (P) is removed from the funnel portion (1) by gravity when the shut-off valves (V1, V2) are opened; 3. The device according to claim 1 or 2.

11. a powder application unit is provided for applying a powder layer of the supplied powder, the funnel portion (1) comprising a container having a funnel outlet communicating with a feed passage for supplying the powder to the powder application unit; 3. The device according to claim 1 or 2.

12. at least one powder removal means is provided downstream of the shut-off valves (V1, V2) for removing the powder in the feed direction, and at least one moisture sensor is provided for measuring the powder (P) disposed in the funnel (1); 4. The apparatus of claim 3.

13. the inside of the funnel along which the powder passes is at least partially polished; 3. The device according to claim 1 or 2.

14. - determining the injectability characteristics of the powder placed in the powder supply by determining the mass of the powder (P) placed in or removed from the funnel (1) as a function of time; - comparing said determined value with a predetermined value for determining the injectivity characteristic; 3. A powder bed based additive manufacturing method comprising the powder supply of claim 1 or 2, comprising:

15. 15. The method of claim 14, wherein determining the injectability characteristics is performed during continuous production of a part without removing powder from the powder supply.

16. - determining the mass of powder placed in the funnel by one or more mass sensors; - opening the shut-off valves (V1, V2) to remove at least a portion of the powder placed in the funnel; - after a predetermined time, closing the shut-off valves (V1, V2) and determining the mass of powder remaining in the funnel, or - continuously determining the mass of powder removed from the funnel (1) and determining the time required to remove said mass after reaching a predetermined removed mass; and - determining the powder flow by comparing the determined mass or the determined time with a predetermined value; 15. The method of claim 14, comprising:

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