MANUFACTURING METHOD WITH ADDITIVE COMPONENT PRODUCTION AND POST-PROCESSING

Abstract

The invention relates to a method of manufacturing components, comprising the steps of: a) manufacturing a component blank in an additive manufacturing process, comprising: a1) determining component regions of the component blank to be cured in an electronic planning process and generating a component blank data set defining the component regions to be cured, a2) arranging a raw material and selectively curing and joining the raw material in the component regions to be cured on the basis of the component blank data set to form the component blank, wherein the curing and joining of the raw material on the basis of the component blank data set is carried out such, that the component blank has a component blank density which is less than 99.5% of the density theoretically achievable with the raw material, b) compacting and solidifying the component blank to form a component in a hot isostatic pressing process, in which the component blank is heated in a furnace chamber to a temperature below the melting temperature of the raw material and is pressed by generating an overpressure in the furnace chamber by means of a furnace chamber pressure of at least 50 bar.

Claims

1. A method for manufacturing components, comprising the steps: producing a component blank in an additive manufacturing process, comprising: determining, in an electronic planning process, component regions of the component blank which are to be cured and generating a component blank data set defining said component regions to be cured, and dispensing a raw material and selectively curing and joining the raw material in said component regions to be cured based on the component blank data set of said component blank, wherein the curing and joining of the raw material is performed using the component blank data set such that the component blank has a component blank density which is less than 99.5% of the density theoretically achievable with the raw material; and compacting and solidifying the component blank to form a component in a hot isostatic pressing process, in which the component blank is heated in a furnace chamber to a temperature below the melting temperature of the raw material and is pressed by generating an overpressure in the furnace chamber by means of a furnace chamber pressure of at least 50 bar.

2. The method of claim 1, wherein generating the component blank data set comprises the steps of determining an outer geometry of the component blank; defining an envelope region and a core region of the component blank, the envelope region enclosing the core region; determining a first value of a first manufacturing parameter for the core region; and determining a second value of said first manufacturing parameter for the envelope region, the second value being different from the first value, and wherein the selective curing and joining of the raw material is performed in the core region using the first value of the first manufacturing parameter and hereby generates a first density in the core region, and is performed in the envelope region using the second value of the first manufacturing parameter and hereby generates a second density in the envelope region which is higher than the first density.

3. The method according to claim 1, wherein generating of the component blank dataset comprises determining an outer geometry of the component blank; defining a first envelope region and a core region of the component blank, the first envelope region partially or completely enclosing the core region; defining at least one second envelope region enclosing a partial volume of the core region, the second envelope region lying within the first envelope region; determining a first value of a first manufacturing parameter for the core region: determining a second value of said first manufacturing parameter for the first envelope region, the second value being different from the first value; determining a third value of said first manufacturing parameter for the partial volume, the third value preferably being the same as the first value, and optionally determining a fourth value of said first manufacturing parameter for the second envelope region, the fourth value preferably being the same as the second value, and wherein the selective curing and joining of the raw material is performed in the core region using the first value of the first manufacturing parameter and generates a first density in the core region, is performed in the first envelope region using the second value of the first manufacturing parameter and produces a second density in the first envelope region which is higher than the first density, is performed in the partial volume using the third value of the first manufacturing parameter and produces a third density in the partial volume which is preferably identical to the first density, and optionally is performed in the second envelope region using the fourth value of the first manufacturing parameter and produces a fourth density in the second envelope region that is preferably identical to the second density.

4. The method of claim 3, wherein the third value of the first manufacturing parameter defines that no raw material is placed in the partial volume during the additive manufacturing process, or the raw material is placed in the partial volume during the additive manufacturing process and is removed again in a subsequent step, or a different raw material is arranged in the partial volume than in the core region, or the raw material is arranged in the partial volume during the additive manufacturing process, is removed again in a subsequent step, and the partial volume is filled with a second raw material which is different from the raw material in the core region, wherein preferably during or after the filling of the second raw material into the partial volume a compression of the second raw material takes place in the partial volume, in particular by means of a vibrating process of the second raw material.

5. The method according to claim 3, wherein the component regions determined to be cured comprise a pressure equalization channel which extends from the first envelope region to the second envelope region and connects the partial volume to the environment of the component blank for fluid pressure transfer.

6. The method according to claim 2, wherein said manufacturing parameter is a travel speed of a collimated electron beam and the first value is smaller than the second value or the third value is smaller than the fourth value, or said manufacturing parameter is a radiation intensity of a collimated electron beam and the first value is greater than the second value or the third value is greater than the fourth value, or said manufacturing parameter is a path spacing between two adjacent raster paths of a collimated electron beam and the first value is smaller than the second value, or the third value is smaller than the fourth value, or said manufacturing parameter is a duration of an energy impact on the raw material leading to curing and bonding, and the first value is greater than the second value or the third value is greater than the fourth value, or said manufacturing parameter is a layer thickness or a drop size when applying the raw material, and the first value is smaller than the second value, or the third value is smaller than the fourth value, or said manufacturing parameter is a material definition and the first value, the second value and/or the third value each define different raw materials.

7. The method according to claim 1 wherein generating of the component blank data set comprises determining an outer geometry of the component blank defining an envelope region and a core region of the component blank, the envelope region completely or partially enclosing the core region, and wherein during the selective curing and joining of the raw material the raw material in the envelope region undergoes processing leading to curing and joining, and the raw material in the core region does not undergo any processing leading to curing and joining, and wherein compacting and consolidating the component blank comprises curing and joining of the raw material in the core region.

8. The method of claim 3, wherein when generating the blank data set one of the two values selected from the first and the third value defines that the raw material does not undergo a processing leading to curing and joining, and the other of the first and third values defines that the raw material undergoes processing leading to curing and joining, and wherein during the selective curing and joining of the raw material the raw material in the region which is cured and joined with one of the two values does not undergo any processing leading to curing and joining, and the raw material in the region to be cured and joined with the other of the two values undergoes processing leading to curing and joining, and wherein compacting and consolidating the component blank comprises curing and joining of the raw material in the region that is cured and joined with one of the two values.

9. The method according to claim 1 wherein the raw material behaves homogeneously during curing and joining, and/or the raw material has such a temperature resistance, and the hot isostatic pressing process is carried out with such process parameters that the weight of the component blank does not change during the hot isostatic pressing process.

10. The method according to claim 1 wherein a powder material is processed as the raw material, wherein the powder material comprises powder particles of different particle size, wherein a particle size lies between a lower powder particle size limit and an upper powder particle size limit and extends over a powder particle size bandwidth corresponding to the upper powder particle size limit minus the lower powder particle size limit, and wherein a weight fraction of small powder particles having a particle size lying within a range of 10% to 20% of the total powder particle size range from the lower powder particle size limit is at least 20% by weight of the powder material, and wherein a weight fraction of large powder particles having a particle size lying within a range of 10% to 20% of the total powder particle size range from the upper powder particle size limit is at least 20% by weight of the powder material.

11. The method according to claim 1 wherein a powder material is processed as the raw material, and the selective curing and joining of the raw material comprises the steps of a) applying a powder layer to a surface of a substrate plate or a prefabricated component by means of a powder application device; b) selective curing of the component regions to be cured in the applied powder layer and bonding of the component regions to be cured to the substrate plate underneath by the action of energy, in particular the action of electromagnetic radiation, to produce correspondingly cured component regions; c) applying of a further powder layer on top of the previously applied powder layer by means of the powder application device; and d) selective curing of the component regions to be cured in the applied further powder layer and bonding of the component regions to be cured to the cured component regions of the underlying powder layer by action of energy, wherein multiple repeats of steps c) and d) to build up the component layer by layer.

12. The method according to claim 1 wherein in generating the component blank data set, determining the external geometry of the component blank comprises determining a product geometry and a reference structure disposed on the product geometry said reference structure being added as an outer surface to the product geometry, determining a machining allowance volume that is attached to the product geometry in at least a partial region, connecting the product geometry, the machining allowance volume and the reference structure to the outer geometry of the component blank, and wherein after the step of compacting and solidifying the component, a precision mechanical machining step is carried out, comprising defined positioning of the compacted and solidified component in a machining space of a material-removing maching device, the reference structure being used as a measuring point or measuring surface for the defined positioning of the component in the machining space, or serving as a clamping spot or clamping surface of a clamping device of the material-removing maching device, removing material in the region of the machining allowance volume by means of a material-removing manufacturing method, in particular a cutting manufacturing method in the material-removing machining device, and wherein the reference structure is removed after the precision mechanical machining step.

13. The method according to claim 1 wherein during the compacting and solidifying of the component blank to form a component, the component blank is encased in a casing material, the casing material preferably being a metallic foil, such as a stainless steel foil.

14. The method according to claim 1 wherein in generating the component blank data set, determining the outer geometry of the component blank comprises determining a target geometry determining a shrinkage volume which defines a shrinkage occurring during the compacting and solidifying of the component blank as a blank volume to be added to the component blank geometry, by which the component produced from the component blank after the compacting and solidifying has the target geometry, and/or determining a distortion volume, which defines a distortion occurring during the selective curing and joining of the component blank and/or during the compacting and solidification of the component blank, as a blank volume to be added to the component blank geometry, by which the blank has the target geometry after the compacting and solidifying, one or more of the nominal geometry, a correction data set determined from the shrinkage volume, and/or the distortion volume is used to generate the component blank data set, wherein the correction data set is preferably determined by creating a component in a first manufacturing step in which the component blank data set corresponds to a nominal geometry data set describing the nominal geometry of a product, measuring the actual geometry of the component after compacting and solidifying the component produced in the first manufacturing step by means of an electronic measuring device and creating a three-dimensional actual geometry data set, calculating a difference geometry data set from a comparison of the measured actual geometry of the component and the nominal geometry data set, and calculating the correction data set from the difference geometry data set, wherein the difference geometry data set is preferably multiplied by a factor between 1 and 1.2, thereby determining the difference geometry data set.

15. The method according to claim 1 wherein during compacting and solidifying according the furnace chamber is charged with at least one raw component which has been produced according to one of determining and/or dispensing steps and which, in order to achieve compaction and solidification, requires a hot isostatic pressing operation with a first set of parameters comprising a first pressing pressure, a first pressing temperature and a first pressing duration, and wherein at least one component which has been produced by a casting process and which, in order to achieve compaction and solidification, requires a hot isostatic pressing operation with a second set of parameters comprising a second pressing pressure, a second pressing temperature and a second pressing duration, and wherein the compacting and solidifying is performed with a third set of parameters comprising as the pressing pressure the higher one of the first and second pressing pressures, as the pressing temperature the higher one of the first and second pressing temperatures, and as the pressing time the longer one of the first and second pressing times.

16. The method of claim 9 wherein the raw material is a powder material which consists of powder particles, wherein all the powder particles having the same melting temperature

17. The method of claim 9 wherein the lower powder particle size limit is 0, 10 or 20 □m and the upper powder particle size limit is 40, 50 or 75 □□m.

18. The method of claim 11 wherein the action of energy is electromagnetic radiation.

19. The method of claim 11 wherein after at least one step of applying a powder layer in step a) and step c), a compaction of the powder layer is performed after each step or every other step of applying the powder layer.

20. The method of claim 19 wherein compaction of the powder layer is performed by vibration.

Description

[0128] Preferred embodiments of the invention are described with reference to the figures. Showing:

[0129] FIG. 1a schematic flow diagram of the process according to the invention,

[0130] FIG. 2a-f The structure of a component according to the method according to the invention in a schematic representation.

[0131] The method according to the invention starts with the creation of a finished data set in step 1. Here, a data set, for example standardized in STL data format, is created on the basis of a desired target geometry of a component, which is done computer-aided by means of CAD programs. This three-dimensional data set is supplemented in step 1 with manufacturing parameters which define certain parameters of the manufacturing process for the component, which are to be applied in subsequent production in an additive manufacturing process. These manufacturing parameters can apply to the entire component, but can also be defined specifically for individual component regions and in this way define different manufacturing parameters for different component regions.

[0132] The creation of the manufacturing data set in step 1 further includes defining specific auxiliary structures, such as supports and the like, that are necessary or advantageous for the manufacturing process in certain additive manufacturing processes and that must subsequently be separated from the component.

[0133] Furthermore, step 1 defines the position in which the component is arranged in the production space of the device for additive manufacturing of the component. Particularly in the case of layer-by-layer additive manufacturing processes, attention must be paid to an advantageous alignment in order to achieve a high surface quality of certain surfaces.

[0134] Step 1 is followed as step 2 by the manufacture of the component in an additive manufacturing process. In this process, the component is built up automatically and produced layer by layer, point by point or line by line on the basis of the production data set. The production data set defines in each layer, which corresponds to a section through the component, the volume portions of the component lying in this section, corrected if necessary with geometric parameters which take into account shrinkage or warpage and, if necessary, plus production aids such as supports, reference structures or the like. These volume portions are cured in step 2 and bonded to previously cured volume portions of the component. This may be done, for example, by selectively scanning a powder layer, for example of a titanium alloy or titanium with a laser under the control of the manufacturing data set, or by masked exposure of a liquid layer of a photopolymerizing liquid, or by spot application of a curing material. The selective laser irradiation may be carried out in a controlled atmospheric environment, for example in an argon atmosphere.

[0135] Due to the only low density required for the component blank in the process according to the invention, the power of the laser used for selective irradiation may be lower than in such manufacturing processes aiming to achieve the required component strength already in the additive manufacturing process. For example, it is possible to selectively bond metallic powders to the component blank using a laser in the additive manufacturing process that has a power of less than 10 kw, or less than 5 kW, such as Yb fiber lasers and even excimer lasers with a power below 500 W can be used for metal powder processing.

[0136] Step 2 may be followed by a step 3 in which raw material is removed again from certain regions of the partially or completely built-up product in order to thereby create cavities. This step 3 may optionally be followed by a further step 4, in which cavities thus created are refilled with a raw material which is different from the original raw material. In this way, components can be produced which have regions with different raw materials.

[0137] In many additive manufacturing processes, in particular 3D printing processes, the product can also be built up directly in step 2 using different raw materials. Step 3 or step 4 can also be followed by a continuation of the additive manufacturing process in step 2 in order to further build up the product after the cavity has been created and, if necessary, filled.

[0138] The creation of the manufacturing data set and the manufacturing of the component in steps 2 and optionally 3 and 4 together form the additive manufacturing process 5 as a whole. This additive manufacturing process 5 is typically followed by a stress relief annealing, for example as a vacuum heat treatment, in a step 6. According to the invention, this step 6 is followed by a hot isostatic pressing process of the component in a step 7. This hot isostatic pressing process is carried out in a hot isostatic pressing furnace having a furnace chamber which can be pressurized to an elevated pressure and in which an elevated temperature can be set over a predetermined period of time. The temperature can be set as a constant temperature or as a temperature profile over time to set favorable heating and cooling phases for the product and to avoid unfavorable warping effects or microstructural changes. The furnace temperature is selected so that the component is heated to a sinterable temperature below the melting temperature of the material of the component. Typical values for carrying out the hot isostatic pressing process are an overpressure of 1000 bar, a temperature of 920° C. and a hot isostatic pressing time of 2 hours for the hot isostatic pressing of components that have previously been manufactured in an additive manufacturing process using a metallic raw material.

[0139] Optionally, the hot isostatic pressing in step 7 can be followed by mechanical finishing in step 8. Here, a mechanical machining process, for example a CAM-controlled milling process, is used to produce an exact geometry and surface quality of the component. The component can be machined on the basis of the CAD data used in step 1 for the creation of the manufacturing data set by creating the CAM manufacturing data for the mechanical machining from this CAD data and thereby correcting shrinkage and distortion effects caused by the previous steps.

[0140] FIGS. 2a-f show the sequence of manufacture of a component according to the method of the invention in an additive manufacturing process. The component is built up on a substrate plate 10, from which a plurality of supports 11, 12 extend, which serve as an auxiliary support structure to enable the component to be built up above the substrate plate without distortion. In individual cases, the component may also be directly connected to the substrate plate and must then subsequently be separated from the latter.

[0141] The supports 11, 12 also serve as a reference structure in the component manufactured according to the invention. On these supports, the component can be clamped in a mechanical machining process carried out after the hot isostatic pressing process and thereby placed and held in a predetermined, defined position for mechanical machining.

[0142] The component is built up in layers by applying a powder layer from above, curing the cross-sectional parts of the component that lie in this powder layer by the action of a laser and bonding them to parts of the component that lie underneath. In this process, the laser is selectively guided over the applied powder layer by computer control. In the laser focus, the powder material melts and bonds to the component section in this region. At the same time, the melted powder is bonded to an underlying portion of the component that lies in the previously selectively cured layer.

[0143] The component 20 has an outer envelope 21 which is circular in cross-section as shown. In this outer envelope region, the raw material is bonded in a gas-tight manner under the high energy effect of the laser beam.

[0144] The cladding region 21 encloses a core region 22, in which the raw material is bonded with reduced energy impact and therefore does not exhibit high mechanical stability. This reduced energy impact is achieved by guiding the laser with increased travel speed over the regions of this core region 22, thereby shortening the manufacturing process in terms of time. In principle, curing of the raw material by means of the laser could also be completely dispensed with in the core region, so that the raw material remains unchanged in the core region and is merely enclosed by the cladding region 21.

[0145] Within the core region, a second envelope region is built up which, like the first envelope region, is cured and bonded tightly by high energy impact. This second envelope region is formed in the cross-sectional contour of a double-T beam and serves to mechanically stiffen the component. A partial volume 24 of the core region is disposed within the second envelope region. This partial volume 24 is not subjected to curing and bonding, so that the raw material in the partial volume is unchanged in powder form.

[0146] A pressure equalization channel 30 connects the partial volume 24 with the environment outside the envelope region 21. Through this pressure equalization channel, the pressing pressure can be introduced into the partial volume in the subsequent hot isostatic pressing, so that the partial volume remains as a volume and is not compressed by the hot isostatic pressing process.

[0147] Shortly before the second enveloping region 23 is completely closed, in the step according to FIG. 2b the raw material arranged in the partial volume 2 is removed, for example by suctioning off the material. Instead of this raw material, another material is inserted into the partial volume, as can be seen in FIG. 2c. In principle, the filling of another raw material can also be dispensed with, so that the partial volume 24 remains as a cavity, filled with gas.

[0148] Continuing the manufacturing process in steps FIG. 2d to FIG. 2f, the second envelope region 23 is completely closed, thereby closing the hollow partial volume 24 or the partial volume 24 filled with the other raw material. Further, the core region is filled and the first envelope region 21 is also closed, whereby the component 20 has been completely manufactured in the additive manufacturing process.

[0149] The component thus produced is removed from the substrate plate by separating the supports 11, 12 from the substrate plate at their lower end and may then be subjected to a hot isostatic pressing (HIP) process. In this process, depending on whether the partial volume is hollow, or filled, the pressure equalization channel 30 may be maintained to supply the hollow volume to a pressure equalization of the hot isostatic pressing pressure, thereby maintaining it as a hollow space during the HIP process. The pressure equalization channel 30 may also be closed prior to the HIP operation to subject the partial volume to compression and solidification in the hot isostatic pressing operation, if a different feedstock material has been disposed therein.