SIMULATION METHOD FOR DEVELOPING A PRODUCTION PROCESS

Abstract

A method for developing a production process where a component is built up layer by layer by melting on powder material using a radiation source, and the melted-on powder material is subsequently solidified; in a first phase of the method, material-specific properties of a material being ascertained as a function of process parameters in a multiscale, physically based simulation chain independently of a component geometry; and, in a second phase of the method, taking into account the process parameters and the material-specific properties, an additive build-up of the component using this material being simulated which ensures minimal distortions and internal stresses. Also described is an installation for the generative production of components that includes a processing unit that is adapted for implementing a method for developing a production process.

Claims

1-13. (canceled)

14: A method for manufacturing a component comprising: in a first phase, only ascertaining material-specific properties of a material as a function of process parameters independently of a geometry of the component in a multiscale simulation chain; and, in a second phase, taking into account the process parameters and the material-specific properties of the first phase, performing a simulation of an additive build-up of the component using the material to generate a computer model of the additive build-up of the component; in a third phase, melting on powder material layer by layer using a radiation source, and subsequently solidifying the melted-on powder material in accordance with the generated computer model.

15: The method as recited in claim 14 wherein the method is at least partially implemented by a computer.

16: The method as recited in claim 14 wherein the first phase of the method includes: a)—ascertaining a temperature field on the basis of a melt pool movement and a melt pool solidification curve; b)—ascertaining a local solidification rate on the basis of the temperature field and segregations; c)—ascertaining a grain structure of the material on the basis of the temperature field and the local solidification rate; d)—ascertaining a precipitate structure of the material on the basis of the temperature field, the grain structure, and a thermal treatment; and e)—ascertaining local, mechanical properties on the basis of the temperature field, the grain structure, and the precipitate structure.

17: The method as recited in claim 16 wherein the second phase includes a sixth step (f) in which internal stresses, respectively distortions or deformations, are simulated in the component to be manufactured on the basis of material models.

18: The method as recited in claim 17 wherein process parameters optimized in sixth step (f) are fed back to the first phase.

19. The method as recited in claim 16 wherein a viewing plane in second step (b) is smaller than other viewing planes in first step (a) and third step (c).

20. The method as recited in claim 18 wherein a viewing plane in sixth step (f) is greater than in preceding steps (a) through (e).

21: An installation for additively manufacturing components, the installation comprising: a device for melting on powder material layer by layer using the radiation source; and one or more processing units adapted for implementing the method as recited in claim 14.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Preferred exemplary embodiments of the present invention will be described in greater detail below with reference to the drawings. It is understood that the schematically illustrated individual elements and components may be combined and/or designed in ways other than those described, and that the present invention is not limited to the variants presented.

[0031] Schematically, in the drawings,

[0032] FIG. 1: shows a greatly simplified flow chart of an exemplary method according to the present invention; and

[0033] FIG. 2 illustrates an installation according to the present invention.

DETAILED DESCRIPTION

[0034] FIG. 1 shows method 1 according to the present invention on the basis of a greatly simplified flow chart. It is intended that a component be additively manufactured layer by layer by melting on powder material using a radiation source, and that the melted-on powder material be subsequently solidified. The powder material is metal-based, for example, and a laser is used as a radiation source. It is intended that a production process for additively manufacturing the component with optimal strength properties be developed prior to the physical manufacture of the component. To this end, specific properties of a material are ascertained in a first phase 2 of the method as a function of process parameters, independently of a component geometry. In a second phase 4 of the method, a component is then built up using this material, taking into account the process parameters and the specific properties.

[0035] The first phase of the method includes a multiscale, physically based modeling. In the exemplary embodiment shown here, it includes the following five steps:

a)—ascertaining a temperature field on the basis of a melt pool movement and a melt pool solidification curve;
b)—ascertaining a local dentritic solidification rate on the basis of the temperature field;
c)—ascertaining a grain structure of the material on the basis of the temperature field and the solidification rate;
d)—ascertaining a precipitate structure of the material on the basis of the temperature field, the grain structure, and a thermal treatment; and
e)—ascertaining local, mechanical properties on the basis of the temperature field, the grain structure, and the precipitate structure.

[0036] The five steps a) through e) optimize the process parameters and the material for the optimal strengths of the base material as a function of specific requirements placed on the macroscopic component or on individual component zones.

[0037] A component geometry and scan/manufacturing strategy of the additive manufacturing are optimized to minimize internal stresses and distortions to enable near net shape manufacturing.

[0038] In first step a), parameters, such as energy, scanning rate, layer thickness are derived and identified, via which a high volume density in the component and a negligible roughness in the boundary contour may be achieved or ensured. A viewing plane is preferably approximately 1 mm.sup.2.

[0039] In second step b), material-specific, dendritic solidification rates are ascertained as a function of the thermal conditions, such as the temperature field and temperature gradient field from first step a), segregation coefficients and the like for the individual elements on the basis of the computation results from step a) mentioned in the preceding phase. Here, the phase field method may be used, for example. A viewing plane preferably ranges from nm.sup.2 to μm.sup.2 or nm.sup.3 to μm.sup.3.

[0040] A local rapid solidification is ascertained on the basis of the temperature field/temperature gradients from first step a). Moreover, a segregation or chemical inhomogeneity is ascertained on the basis of the temperature field/temperature gradients. The particular computation is preferably only performed for various small increments of first step a).

[0041] In third step c), it is ascertained which grain structure (morphology, such as grain size and elongation ratio, as well as texture) may be achieved using the respective, specific energy source and the selected/potential parameters, respectively may be attained in the potential parameter window. Examples are a columnar or rod-shaped grain structure or a globulitic grain structure, respectively an equioriented grain structure. Further examples include graded transitions between both grain structures that may be selectively adjusted in different zones of the component in order to satisfy the particular strength requirements. Third step c) is preferably achieved using the cellular automaton method. A viewing plane is preferably approximately 1 mm.sup.2 and thus within the range of the preferred viewing plane of first step a). The computation results from first step a) and second step b) mentioned in the preceding section form the basis.

[0042] Fourth step d) ascertains which particle sizes, proportion by volume, and which phases exist at all following the process, and what influence the thermal treatment has on the development thereof. A suitable method in this case is a CALPHAD based method for describing thermokinetic precipitation reactions. This method allows viewing planes in the preferred range of nm.sup.3 to 1 mm.sup.2. However, a viewing plane larger than 1 mm.sup.2 is also conceivable. A precipitation kinetics under the influence of the parameter window and temperature field from step a), the grain structure from step c), and the thermal treatment subsequent to a production process are computed.

[0043] In fifth step e), local strengths are derived from the grain structure (morphology and texture) and precipitation state (particle size, volumetric proportion of the phase, and the like) for different component regions. A crystal plasticity method may be used to model fifth step e). A viewing plane is preferably in the mm.sup.3 range. A computation of the local strength in crystal physical terms is performed for all possible and useful combinations from the preceding four steps a) through d).

[0044] Second phase 4 of the method relates to the modeling of the component plane. It includes a sixth step f) in which an internal stress simulation and a deformation are carried out in the component to be manufactured on the basis of material models. In sixth step f), internal stresses and distortions that result from the process are computed using the input from the scan strategy stored in the build order. Optimization measures are derived for the component geometry, scan strategy and the like to reduce internal stresses and distortions and to make possible a near net shape production. In sixth step f), a viewing plane is preferably in the cm.sup.3 range and is thus larger than in preceding steps a) through e).

[0045] Here, second phase 4 of the method has an interface to first step a); and, more specifically, the abstract thermal coupling, respectively the alternative heat source used from method step 4 may be calibrated and optimized using the data from the highly resolved, physically based melt pool simulation from step a), without any further experimental outlay. In addition, the second phase of the method has an interface to fifth step e); and, more specifically, the calibration of the simplified material laws stored or used in phase 4 of the method on the basis of the highly resolved, physically based local strength calculation from step e). In other words: it is the aim of the interface to improve the abstract, simplified models using steps a) and e).

[0046] As a function of a sensitivity decision, respectively a deviation assessment 6, a feedback 8 of parameters may take place from second phase 4 of the method to first phase 1 of the method and, thus, to the user of the particular installation, respectively to a design department. The process development may be hereby constantly optimized.

[0047] FIG. 2 is an exemplary specific embodiment of an inventive installation 100 for additively manufacturing components. The illustrated installation includes a device 10 for melting on powder material layer by layer using a radiation source 11 in order to manufacture a component 20 in this way. Furthermore, installation 100 includes a processing unit (respectively, a computer) 30 that is adapted for implementing a method according to the present invention to develop a production process in accordance with one of the specific embodiments described in this document and for thereby simulating, in particular, an additive building up of the component. Illustrated processing unit 30 includes a screen display 31 for displaying a computer model 21 of component 20 generated in the course of the simulation. Parameters, such as the particular material and/or an energy input, may be specified via input means 32.

[0048] Processing unit 30 is preferably adapted to ascertain whether defined, load-oriented, nominal requirements suffice for computer model 21 prior to manufacture of component 20, or whether there are deviations therefrom, as well as to display consequences, potentially resulting from the deviations, for the properties and quality of the component, for example, on screen display 31.

[0049] In the illustrated example, data determining the generated computer model are stored on a mobile data carrier 50 and thus transmitted to a processing unit 40 that is associated with device 10. Alternatively, the data could be transmitted via a wireless communication connection or via a data transmission cable from processing unit 30 to processing unit 40. Processing unit 40 is adapted for controlling device 10 for melting on powder material layer by layer on the basis of generated computer model 21.

[0050] In accordance with an alternative specific embodiment, a processing unit 30 that carries out an inventive method (for simulating, in particular, the additive building up of the component) is connected to device 10 to melt on powder material layer by layer (wirelessly or via a data transmission cable) and adapted for controlling the melting on of powder material on the basis of generated computer model 21. Thus, the need for a second, external processing unit is eliminated in accordance with this specific embodiment.

[0051] Instructions for implementing the method according to the present invention may be stored on a machine-readable medium, for example, and be made available to a processing unit of this kind linked to device 10.

[0052] A method is described for developing a production process where a component is built up layer by layer by melting on powder material using a radiation source, and the melted-on powder material is subsequently solidified; in a first phase of the method, material-specific properties of a material being ascertained as a function of process parameters independently of a component geometry in a multiscale, physically based simulation chain; and, in a second phase of the method, taking into account the process parameters and the material-specific properties, an additive build-up of the component using this material being simulated, which ensures minimal distortions and clampings internal stresses. Also described is an installation for manufacturing a component that includes a processing unit that is adapted for implementing a method for developing a production process, and a device for melting on powder material layer by layer using a radiation source on the basis of a computer model generated in the course of the method.

LIST OF REFERENCE NUMERALS

[0053] 1 method [0054] 2 first phase of the method [0055] 4 second phase of the method [0056] 6 sensitivity decision, respectively deviation assessment [0057] 8 feedback [0058] a) ascertaining a temperature field [0059] b) ascertaining a local dentritic solidification rate [0060] c) ascertaining a grain structure [0061] d) ascertaining a precipitate structure [0062] e) ascertaining local, mechanical properties [0063] f) internal stress and deformation simulation [0064] 10 device for melting on powder material layer by layer [0065] 11 radiation source [0066] 20 component [0067] 21 computer model [0068] 30 processing unit [0069] 31 screen display [0070] 32 input means [0071] 40 processing unit [0072] 50 data carrier [0073] 100 installation for additively manufacturing components