Method for ascertaining a concentration of at least one material in a powder for an additive production method

Abstract

A method for ascertaining the concentration of at least one material in a powder mixture used as starting material for the production of a component in an additive production method, comprising: providing the powder mixture having at least two different materials; guiding a high-energy beam generated by a radiation source over the surface of the powder mixture; detecting by a detection unit at least one brightness value of at least one subregion of the surface irradiated by the high-energy beam during the irradiation; ascertaining by an analysis unit the concentration of at least one material in the powder mixture depending on the detected at least one brightness value and at least one predetermined reference brightness value for a concentration and/or a concentration range of the material.

Claims

1. A method for ascertaining a concentration of at least one material in a powder mixture used as a starting material for producing a component in an additive production method, wherein the method comprises: providing a powder mixture comprising at least two different materials selected from one or more of metals, metal alloys, metal oxides and ceramic materials; guiding a high-energy beam generated by a radiation source over a surface of the powder mixture; detecting by a detection unit at least one brightness value of radiation in a visible and/or infrared spectral range emerging from at least one subregion of the surface, which is irradiated by the high-energy beam, during irradiation with the high-energy beam; ascertaining the concentration of the at least one material in the powder mixture based on the detected at least one brightness value and at least one predetermined reference brightness value for a concentration and/or a concentration range of the material.

2. The method of claim 1, wherein a local concentration of the at least one material in the powder mixture is ascertained on the basis of brightness values of respective exposed pixels of the detection unit.

3. The method of claim 1, wherein respective brightness values of radiation in at least the infrared spectral range are detected by the detection unit.

4. The method of claim 3, wherein a CMOS sensor is used as a sensor for detection of the brightness value.

5. The method of claim 1, wherein an averaged concentration of the at least one material in the powder mixture is ascertained by averaging at least two brightness values and a comparison to the at least one predetermined reference brightness value for a concentration and/or a concentration range of the material.

6. A method of operating a manufacturing device for additive production of a component, wherein a concentration of the at least one material in the powder mixture as a starting material for the additive production of the component is ascertained by the method of claim 5 and a control parameter of the manufacturing device is set depending on the ascertained concentration of the at least one material.

7. The method of claim 1, wherein after the high-energy beam is guided further out of the irradiated subregion of the surface, further brightness values of the subregion are furthermore detected over a predetermined duration by the detection unit.

8. The method of claim 1, wherein respective brightness values and/or concentrations are stored in a database.

9. The method of claim 1, wherein at least one imperfection in the surface of the powder mixture is ascertained on the basis of brightness values characteristic for the imperfection, and brightness values associated with the ascertained imperfection are not taken into consideration in a calculation of the concentration of the at least one material.

10. The method of claim 9, wherein, to ascertain imperfections, a shape and/or a size of a detected brightness range is compared to a predetermined shape and/or a predetermined size of a reference brightness range and/or exceeding of a predetermined minimum or maximum brightness value of the detected brightness value and/or a difference of respective brightness values between at least two adjacent measurement points to at least one predetermined difference threshold value.

11. The method of claim 1, wherein the component is a component of a turbomachine.

12. A method of operating a manufacturing device for additive production of a component, wherein a concentration of the at least one material in the powder mixture as a starting material for the additive production of the component is ascertained by the method of claim 1 and a control parameter of the manufacturing device is set depending on the ascertained concentration of the at least one material.

13. The method of claim 1, wherein the powder mixture comprises at least one ceramic material.

14. The method of claim 13, wherein the powder mixture comprises at least one metal alloy.

15. The method of claim 1, wherein the powder mixture comprises at least one metal alloy.

16. The method of claim 1, wherein detected brightness values are read as grayscale values.

17. The method of claim 1, wherein the detection unit is an optical tomograph.

18. A method for ascertaining a concentration of at least one material in a powder mixture used as a starting material for producing a component of a turbomachine in an additive production method, wherein the method comprises: providing a powder mixture comprising at least two different materials selected from one or more of metals, metal alloys, metal oxides and ceramic materials and comprising at least one ceramic material; guiding a high-energy beam generated by a radiation source over a surface of the powder mixture; detecting by a detection unit at least one brightness value of radiation in at least an infrared spectral range emerging from at least one subregion of the surface, which is irradiated by the high-energy beam, during irradiation with the high-energy beam; ascertaining the concentration of the at least one material in the powder mixture based on the detected at least one brightness value and at least one predetermined reference brightness value for a concentration and/or a concentration range of the material.

19. The method of claim 18, wherein an averaged concentration of the at least one material in the powder mixture is ascertained by averaging at least two brightness values and a comparison to the at least one predetermined reference brightness value for a concentration and/or a concentration range of the material.

20. The method of claim 18, wherein at least one imperfection in the surface of the powder mixture is ascertained on the basis of brightness values characteristic for the imperfection, and brightness values associated with the ascertained imperfection are not taken into consideration in a calculation of the concentration of the at least one material.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The single FIGURE shows a schematic sectional view of a manufacturing device for additive production of a component.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

(2) The FIGURE shows a schematic sectional view of a manufacturing device 10 for additive production of a component 28, in particular a component of a turbomachine. The manufacturing device 10 comprises at least one powder distribution device 12 in this case for dispensing a powder mixture 14 onto a vertically adjustable construction platform 26. The powder mixture 14 comprises in this case at least two different materials as the starting material for the additive production of the component 28. Furthermore, the manufacturing device 10 comprises a radiation source 16, by means of which a high-energy beam 20, which can be guided over a surface 18 of the powder mixture 14, can be generated. The high-energy beam 20 is focused in this case by means of a focusing unit 22 and guided by means of a deflection device 24 over the surface 18 of the powder mixture 14. Alternatively, for example, the radiation source 16 itself could also be moved to guide the high-energy beam 20. By guiding the high-energy beam 20 over the surface 18 of the powder mixture 14, the component 28 is produced layer by layer by melting and/or sintering the powder mixture 14. A guide vane of a turbomachine, which is already partially produced, is schematically shown as the component 28 in the FIGURE.

(3) The high-energy beam 20 is a laser beam in the illustrated exemplary embodiment. However, electron beams can also be used, for example. The component 28 can be produced, for example, in the so-called selective laser melting method by means of the manufacturing device 10.

(4) In the illustrated exemplary embodiment, the powder mixture 14 comprises two different powdered materials, which are stored in two depots 30 and 32. The materials are supplied to the powder distribution device 12 from the depots 30, 32 and mixed therein. For example, a metallic material such as a nickel-based alloy can be stored in the depot 30 and a ceramic material or a ceramic starting material can be stored in the depot 32. The powder distribution device 12 additionally comprises a scraper 34 for dispensing the powder mixture onto the construction platform 26. Alternatively, the powder mixture 14 can also be supplied already mixed to the powder distribution device 12. Of course, the powder mixture 14 can also be formed from three or more different materials.

(5) In both cases, irregularities can occur during mixing of the materials of the powder mixture 14. For example, the two separate powders or the two materials cannot be mixed uniformly everywhere. Different concentrations of the materials in the powder mixture 14 can thus exist locally in an undesired manner. These deviations from the desired uniform concentration distributions have an influence on the quality of the finished component 28. In particular, the powder mixture 14 can react differently to the irradiation using the high-energy beam 20 at different concentrations of the individual materials. For example, the powder mixture 14 can fuse excessively strongly or not enough in the event of a concentration of the materials which deviates from a predefined and advantageous concentration distribution. The finished component can thus have local inhomogeneities, in particular density variations, locally differing strengths, and/or an unplanned and/or irregular shrinkage. An increased discard rate occurs, because the produced component has a reduced component quality. Costly and complex reworking can also become necessary in this way.

(6) The manufacturing device 10 shown in the FIGURE additionally comprises a detection unit 36 for detecting at least one brightness value of the surface 18 during the irradiation thereof using the high-energy beam 20, and also an analysis unit 38, by means of which a concentration or a concentration range of at least one of the materials in the powder mixture 14 can be calculated depending on the detected respective brightness values and at least one reference brightness value for a concentration and/or a concentration range of the material. The manufacturing device 10 can be controlled depending on this ascertained concentration of the at least one material or the concentrations of some or all materials. For example, the analysis unit 38 can control a power of the radiation source 16 and/or an activation of the deflection device 24 depending on the detected concentrations. Respective irregularities during the mixing of the powder mixture 14 can thus be at least partially compensated for during the additive manufacturing, for example. The concentration of the materials in the powder mixture 14 can thus be monitored and/or regulated in the manufacturing device 10 via a so-called online process control.

(7) The fact that a change of the powder composition or the material concentrations in the powder mixture 14 has a significant effect on process radiation is made use of in this case. Process radiation refers to the generated light or the generated radiation as a result of irradiation, heating, and the occurring fusing of the powder mixture 14 using the high-energy beam 20. Thermal radiation is thus emitted during the heating and/or during the fusing of the powder mixture 14. Vaporization and/or ionization of parts of the powder mixture 14 can occur at the same time. The powder mixture 14 can also at least partially reflect the high-energy beam 20.

(8) The detected brightness values can be read as grayscale values in this case. For example, at a 10% proportion of aluminum oxide in the powder mixture 14, a grayscale value of 15,000 can be measured, and at a 20% proportion of aluminum oxide in the powder mixture 14, a grayscale value of 20,000 results. Ascertaining the concentration of this material within the powder mixture 14 is therefore possible very accurately. Intermediate values can be ascertained by interpolation.

(9) The detection unit 36 can be designed as a so-called optical tomograph, for example. This optical tomograph can detect light in the visible and/or in the near infrared spectral range, for example. In particular, the detection of respective brightness values which are correlated with the concentration of the materials can be limited in this case by suitable filters. For example, respective reflections of the high-energy beam 20 are to be filtered out during the detection. The illustrated manufacturing device 10 additionally comprises a database device or memory device 40, in which respective measured values can be stored for later analysis and/or further comparison. At the same time, respective reference brightness values can be stored in the database device 40. For example, the concentration of a material in the powder mixture 14 can be compared by means of a comparison of the measured brightness values with brightness reference values in a table and/or from values stored during previous manufacturing. These brightness reference values can be saved, for example, for respective different concentrations of different materials and/or different powers and deflection speeds of the high-energy beam 20.

(10) During the processing of so-called multi-material powders, maintaining a defined composition, i.e., a defined and predetermined concentration of the individual components, is of decisive significance for the desired properties of the powder mixture 14 and the quality of the component 28 produced therefrom. The concentrations have to correspond to the set specifications both in the buildup direction and also in the construction plane. These concentrations can be monitored and/or even regulated via a suitable process control. That is to say, the powder distribution device 12 can also be controlled depending on the ascertained concentrations. In this case, the composition of the powder mixture 14 can be set again upon the dispensing of a new powder layer, to be able to compensate for deviations in the previous component layer, for example. Optical tomography can be used in this case as a monitoring method.

LIST OF REFERENCE NUMERALS

(11) 10 manufacturing device

(12) 12 powder distribution device

(13) 14 powder mixture

(14) 16 radiation source

(15) 18 surface

(16) 20 high-energy beam

(17) 22 focusing unit

(18) 24 deflection device

(19) 26 construction platform

(20) 28 component

(21) 30 depot

(22) 32 depot

(23) 34 scraper

(24) 36 detection unit

(25) 38 analysis unit

(26) 40 database device