Method for the generative production of a 3-dimensional component

Abstract

A method and apparatus for the generative production of a three-dimensional component in a processing chamber are disclosed. The method performs the steps of providing a metal starting material in the processing chamber and melting the starting material by inputting energy, which are repeated multiple times. A process gas is passed through the processing chamber in a circuit. Hydrogen is added to the circulating gas, then the circulating gas is heated to a temperature above 500 C. and then cooled to a temperature below 60 C.

Claims

1. A method for the generative production of a three-dimensional component in a processing chamber, comprising: (a) providing a metal starting material in the processing chamber, and (b) melting the starting material by inputting energy, wherein (a) and (b) are repeated multiple times, wherein a process gas is provided in the processing chamber, and wherein a portion of the process gas is extracted, forwarded in a circuit as a circulating gas, and returned to the processing chamber, said method further comprising: adding hydrogen to the circulating gas, heating the circulating gas to a temperature above 500 C., and then cooling the circulating gas to a temperature below 60 C.

2. The method according to claim 1, wherein the circulating gas is then cooled to a temperature below 0 C.

3. The method according to claim 1, wherein the oxygen content of the process gas or circulating gas is determined and that the quantity of hydrogen fed into that circulating gas is calculated on the basis of the determined oxygen content of the process gas or circulating gas.

4. The method according to claim 3, wherein a hydrogen substance quantity fraction introduced into the circulating gas does not exceed twice the determined oxygen content of the process gas or circulating gas.

5. The method according to claim 4, wherein the hydrogen substance quantity fraction introduced into the circulating gas is less than twice the determined oxygen content of the process gas or circulating gas.

6. The method according to claim 4, wherein the hydrogen content and the oxygen content in the circulating gas are determined, and then an amount of hydrogen is added to the circulating gas that does not exceed twice the determined oxygen content in the circulating gas is added to the circulating gas.

7. The method according to claim 1, wherein the hydrogen is added to the circulating gas together with an inert gas.

8. The method according to claim 1, wherein water condensing out of the circulating gas during cooling is removed from the circulating gas.

9. The method according to claim 1, wherein the heating of the circulating gas and/or the cooling of the circulating gas is regulated as a function of the oxygen content in the process gas.

10. The method according to claim 1, wherein the heating of the circulating gas and/or the cooling of the circulating gas is regulated as a function of the dewpoint of the circulating gas.

11. The method according to claim 5, wherein the hydrogen substance quantity fraction introduced into the circulating gas is less than 90% of the determined oxygen content.

12. The method according to claim 1, wherein the circulating gas is heated to a temperature above 600 C.

13. The method according to claim 1, wherein the circulating gas is heated to a temperature above 700 C.

14. The method according to claim 1, wherein the circulating gas is cooled to a temperature below 40 C.

15. The method according to claim 1, wherein the circulating gas is cooled to a temperature below 20 C.

16. A method for the generative production of a three-dimensional component in a processing chamber, comprising: (a) providing a metal starting material in the processing chamber, and (b) melting the starting material by inputting energy, wherein (a) and (b) are repeated multiple times, wherein, during (a) and (b), a process gas is provided in the processing chamber, and a portion of the process gas is extracted, forwarded in a circuit as a circulating gas, and returned to the processing chamber, said method further comprising: adding hydrogen to the circulating gas, heating the circulating gas to a temperature above 500 C., and then cooling the circulating gas to a temperature below 60 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention and further details of the invention will be explained in greater detail in the following text with reference to an embodiment thereof represented schematically in the drawing. In the drawing:

(2) The FIGURE shows an apparatus according to the invention for three-dimensional manufacturing. The FIGURE is a schematic representation of an apparatus for carrying out the method according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) In the following text, an apparatus for generative production of a three-dimensional component is described. As noted earlier, however, the method according to the invention is not limited to the apparatus represented for generative production of three-dimensional components.

(4) The apparatus is a laser melting apparatus. The laser melting apparatus comprises a processing chamber 1 which serves as the construction space for the three-dimensional component 2.

(5) A structuring platform 3 for supporting the component 2 to be produced is arranged inside processing chamber 1. Structuring platform 3 is equipped with a height adjustment device 4, by means of which the height of structuring platform 3 may be adjusted vertically.

(6) Apparatus 1 further comprises a reservoir 5. Reservoir 5 is designed to hold a powder starting material which can be solidified.

(7) Additionally, an application device 6 is provided for depositing the starting material on structuring platform 3. Such an application device 6 is movable horizontally, parallel to work level 10.

(8) A laser 7 for generating a laser beam is also provided. A laser beam generated by laser 7 is deflected via a deflection mechanism 8 and focused through a focusing device (not shown) on a predetermined point immediately below or in work level 10. The path of the laser beam may be altered by deflecting mechanism 8 in such manner that it melts the locations of the deposited layer that correspond to the cross section of the object 2 that is to be produced.

(9) A process gas feed device 9 is also provided, by means of which processing chamber 1 may be charged with a process gas.

(10) Process gas feed device 9 is equipped with one or more reservoirs for the process gas or individual constituents of the process gas, wherein the process gas reservoir (not shown) is connected via one or more line segments to inlets (not shown) which open into the processing chamber. The inlets, e.g., one or more nozzles for introducing process gas are arranged in a lower region of processing chamber 1. The quantity of gas that is introduced may be regulated by means of a control valve 20. At least one nozzle of the process gas feed device is preferably arranged in the bottom region of processing chamber 1 or at a height equivalent to one fifth, one quarter, one half, two thirds or three quarters of the height between the bottom of processing chamber 1 and work level 10 or approximately level with work level 10.

(11) An inert gas such as argon having greater density than air at the same temperature is preferably provided as the process gas.

(12) A fan device (not shown) is also arranged in a bottom region of the processing chamber. Multiple fan devices may also be provided.

(13) A circulating line 14 for a portion of the process gas is also provided. A portion of the process gas may be extracted from processing chamber 1 through an outlet 15, forwarded through circulating line 14 and returned to processing chamber 1 again through inlet 16. The circulation of the process gas is effected for example by means of a blower or compressor 23. A control valve 17 is also provided inside circulating line 14, by means of which the quantity of gas that is returned to processing chamber 1 is controllable. A line 18 is also provided which branches off from circulating line 14 and which makes it possible to draw off the process gas which is transported through circulating line 14. Line 18 is also fitted with a control valve 19.

(14) The apparatus further comprises a controller 11 for controlling control valve 20 of process gas feed device 9 and control valves 17 and 19. Controller 11 may comprise one or preferably two regulating devices (not shown) with a closed control circuit. The regulating devices may also comprise a P-regulator, an I-regulator, a D-regulator and combinations thereof, such as a PID-regulator.

(15) A measurement sensor 12 for determining the hydrogen content of the process gas circulating through circulating line 14 and a lambda probe 13 for determining the oxygen content of the process gas circulating through circulating line 14 are also provided. A further sensor 21 serves to determine the water vapor content or the dewpoint of the process gas circulating in the circuit. Measurement sensor 12, lambda probe 13 and sensor 21 are connected to controller 11.

(16) A hydrogen feed 24 opens into circulating line 14, through which feed a gas mixture of inert gas and hydrogen may be fed into circulating line 14. Hydrogen feed 24 is fitted with a control valve 28, via which the quantity of gas introduced may be adjusted. Control valve 28 is also connected to controller 11.

(17) A heating device 25 is provided downstream of the opening of hydrogen feed 24 to heat the circulating gas. Finally, a cold trap 26 is provided still further downstream to cool the circulating gas. Both the heating device 25 and the cold trap 26 are connected to controller 11 and may be actuated by controller 11.

(18) The following text describes a method according to the invention with reference to an embodiment thereof.

(19) Argon is fed into a bottom region of processing chamber 1 as the process gas. Since process gas feed device 9 introduces the process gas at the height of work level 10 or lower, processing chamber 1 is filled with the process gas from the bottom up.

(20) Consequently, the heavier gaseous argon forces the lighter air into the top region of processing chamber 1, in which an outlet (not shown) is provided to allow the air to escape.

(21) The process gas in processing chamber 1 may optionally be agitated by means of a fan device inside processing chamber 1. The turbulence has the effect of removing impurities from dead spaces in the processing chamber. It also creates a homogeneous gas composition throughout the entire volume of the processing chamber. Clean process gas may also be introduced into processing chamber 1 via process gas feed device 9.

(22) A metal starting material is deposited or provided on structuring platform 3 in the form of a powder bed by application device 6. Alternatively, the metal starting material may also be introduced via a powder feed or a wire feed.

(23) Then, the starting material is melted by means of laser 7. The two steps providing a metal starting material on structuring platform 3 and melting the starting material are repeated multiple times so that the component is constructed layer by layer.

(24) It has been found that the energy introduced with the laser 7 for melting the starting material decomposes water or water vapor present in the process gas into hydrogen and oxygen.

(25) However, the oxygen content of the process gas should not exceed a predetermined maximum value throughout the manufacturing process in order to avoid undesirable oxidation reactions. The oxygen content of the process gas is therefore monitored according to the invention. For this, a sample of the process gas circulating through circulating line 14 is passed to lambda probe 13, and the oxygen content of the sample is determined by lambda probe 13. The oxygen content value obtained thereby is transmitted to controller 11.

(26) Besides measuring the oxygen content, the hydrogen content of the process gasi.e. the process gas circulating in the circuitis determined. For this purpose, a second sample is drawn from the process gas and the hydrogen content therein is determined by means of a measuring sensor 12.

(27) The second sample may be taken upstream or downstream of the point where the sample for determining the oxygen content is taken. It is also possible to use to the same sample for determining both the oxygen content and the hydrogen content.

(28) The value for the hydrogen content calculated by measuring sensor 12 is also transmitted to controller 11. Then in controller 11, the additional quantity of hydrogen that would have to be fed to the circulating gas to achieve the right stoichiometry for converting hydrogen and oxygen into water is determined. Controller 11 adjusts control valve 28 so that no more than the quantity of hydrogen needed to achieve stoichiometric balance is introduced via hydrogen feed 24. The substance quantity fraction of hydrogen introduced via hydrogen feed 24 preferably consists of between 50% and 95% or between 60% and 90% or between 70% and 90% of the quantity of additional hydrogen required calculated beforehand.

(29) The circulating gas enriched with hydrogen is then forwarded to heater 25 and heated to a temperature above 650 C. In this temperature range, hydrogen and oxygen react almost completely to form water vapor. The circulating gas 14 that exits heater 25 is thus essentially free from oxygen and hydrogen, but it does contain the water vapor which was formed during the conversion reaction.

(30) Accordingly, circulating gas 14 is led to cold trap 26, where it is cooled vigorously enough to ensure that the water vapor in the circulating gas condenses out. Advantageously, circulating gas 14 is cooled to a temperature below 60 C., below 40 C. or below 20 C. The water which is condensed out is then separated from circulating gas 14 and removed from the circuit.

(31) Moreover, some or all of the parameters including oxygen content, hydrogen content, water vapor content, and other parameters such as temperature, carbon content etc. may be determined in circulating line 14, either downstream or upstream of heater 25 and cold trap 26, or even directly inside processing chamber 1. The one or more measured values are advantageously also forwarded to controller 11 and used to regulate hydrogen feed 24, heater 25, cold trap 26, process gas feed device 9, control valve 17 and/or control valve 19.

LIST OF REFERENCE SIGNS

(32) 1 Processing chamber 2 Component 3 Structuring platform 4 Height adjustment device 5 Reservoir 6 Application device 7 Laser 8 Deflecting mechanism 9 Process gas feed device 10 Work level 11 Controller 12 Measuring sensor 13 Lambda probe 14 Circulating line 15 Outlet 16 Inlet 17 Control valve 18 Line 19 Control valve 20 Control valve 21 Water vapor measurement 22 Sensor 23 Blower 24 Hydrogen feed 25 Heater 26 Cold trap 28 Control valve