Method for additively manufacturing three-dimensional components by means of process parameter monitoring

Abstract

The invention relates to a method for additively manufacturing a three-dimensional component by applying a construction material layer by layer and locally selectively consolidating the construction material by means of at least one beam impinging on the construction material, wherein the beam is guided on the basis of a plurality of process parameter values, the method comprising the following steps: a) measuring at least one state value relating to a construction process, in particular within a process chamber, more preferably state values of the component, preferably the temperature, more preferably the surface temperature, by means of at least one measuring device, more preferably during the construction process; b) determining a process status on the basis of the at least one measured state value in step a); c) comparing the at least one measured state value with comparison data, the comparison data being preferably stored in a database; d) adapting at least one process parameter on the basis of the comparison in step c), preferably in order to realise at least one target variable.

Description

[0001] Meissner Bolte 1 M / EOSG-061-PC

[0002] Method for the additive manufacturing of three-dimensional components with process parameter monitoring

[0003] Description

[0004] The invention relates to a method for the additive manufacturing of three-dimensional components and to a system for the additive manufacturing of three-dimensional components. Furthermore, the present invention relates to a computer-readable storage medium.

[0005] Manufacturing devices and corresponding methods for the additive manufacturing of three-dimensional components by layer-by-layer application and locally selective solidification of a build material are generally known from the prior art. For the locally selective solidification of the build material, at least one corresponding irradiation unit (e.g., comprising at least one laser) is usually provided, which emits a beam onto the build material, which typically consists of a powder, in order to melt and thereby solidify the powder at the point where the beam strikes.

[0006] After an initial layer has solidified on the original powder bed in this way, another layer of build material is typically applied, and the solidification process by blasting or sintering is repeated. This process is repeated until a finished component has been produced, from which unsolidified build material can easily be removed.

[0007] Often, several elements that are to be spatially separated in a later application can be manufactured as components of a single component, which is later cut at the relevant points to increase production efficiency.

[0008] Many of the physically relevant properties of the build-up material, as well as the solidified material, are not constant during a manufacturing process, but change with time and / or temperature, as well as other external influences. For example, the successive heating of layers leads to the external dimensions of components becoming smaller with increasing layer thickness. Furthermore, it is comparatively difficult to estimate the extent to which different Meissner Bolte 2 M / EOSG-061-PC

[0009] Layer temperatures and geometries will have an effect on the crystalline structures of the solidified material.

[0010] This leads to a situation where, even with constant parameter settings or parameter values ​​according to which the solidification jet is guided, and constant application of new build-up material, a distortion of the component occurs during manufacturing that is difficult to estimate, in particular shrinkage, which means that individual elements or components cannot be manufactured with consistent manufacturing tolerances.

[0011] To remedy this problem, it is therefore desirable to specify a procedure that captures the actual existing construction conditions and takes them into account when setting the process parameters in order to achieve the desired target values.

[0012] The problem according to the invention is solved by a method according to claim 1, as well as a system according to claim 11 and a computer-readable storage medium according to claim 12.

[0013] The inventive method for the additive manufacturing of a three-dimensional component consists of layer-by-layer application of a build-up material and locally selective solidification of the build-up material by means of at least one beam impacting the build-up material, wherein the guidance of the beam is carried out on the basis of a plurality of process parameter values, comprising the following steps:

[0014] a) Measuring at least one state value relating to a construction process, in particular within a process chamber, further preferably of state values ​​of the component, preferably the temperature, further preferably the surface temperature, by means of at least one measuring device, further preferably during the construction process;

[0015] b) Determining a process status based on at least one state value measured in step a);

[0016] c) Comparing the at least one measured state value with reference data, the reference data preferably being stored in a database;

[0017] d) Adjusting at least one process parameter based on the comparison in step c), preferably to achieve at least one target variable.

[0018] Process parameters are, in particular, parameters that describe the manufacturing conditions during the production of the component. Meissner Bolte 3 M / EOSG-061-PC

[0019] In particular, process parameters are all parameters that can be adjusted to influence the manufacturing process. Examples of process parameters include the beam power, beam diameter, irradiation time of individual sections of the component, beam guidance, composition, density and / or thickness (etc.) of the build material.

[0020] A state value is, in particular, a value that represents a property of the component or a part of the component (preferably current, determined during the construction process). This property can be geometric, thermal, and / or chemical. Examples of state values ​​include the surface or core temperature of the component, the size and / or dimensions of a component section (e.g., wall thickness), gray values, electrical conductivity, density, composition, etc.

[0021] The process status indicates, in particular, the extent to which the process has resulted in a component with the desired properties. Specifically, the process status indicates whether the manufacturing process, with the measured state value, has led to a component with the desired target parameters. Determining the process status involves ascertaining whether the manufactured component exhibits the desired intrinsic and / or extrinsic properties, given the measured state value.

[0022] For example, the process status could be the surface temperature of a part of the component. The process status then indicates whether the desired target values ​​were achieved during the manufacturing of the component under these conditions, and preferably by what amount these values ​​were missed.

[0023] The target parameter here is understood to be, in particular, a property of the component after completion and / or (immediately) after the solidification step. This can be an extrinsic property, such as dimensions, surface roughness and / or diameter (and / or similar), as well as an intrinsic property, such as crystal structure, electrical or thermal conductivity and / or flexibility (and / or similar).

[0024] The measured condition value and preferably also the process status are then compared with reference data. This reference data includes previously measured condition values ​​from earlier construction processes with recorded process parameters, preferably relating to the same quantity, as well as further information regarding the outcome of the corresponding construction operations. Particularly preferably, the reference data includes corresponding process statuses for the measured condition values. The reference data can also include, for example, Meissner Bolte 4 M / EOSG-061-PC.

[0025] Correlations between process status and state values, or models, are included.

[0026] A model, in particular, comprises a set of known relationships that connect state values ​​and / or process parameter values ​​with target variables. These relationships can be either deterministic or statistical in nature. A deterministic approach would involve specifying a target variable as a (continuous) function of a state value, at least over a certain interval (e.g., the density of the finished component as a function of radiation intensity). However, the model can also include statistical relationships, such as correlations between state values ​​and / or process parameter values ​​on the one hand, and target variables (e.g., a correlation coefficient between exposure time and the external dimensions of the component) on the other. Similarly, the model can include tables that list the realized target variables observed in experiments for a (varying) set of state values.The model therefore reflects, in particular, the amount of theoretical and / or empirical information available about the effects of state values ​​and / or process parameter values ​​on the target variables.

[0027] The described method allows for the determination, particularly across multiple component generations, of the state values ​​that lead to components with the desired properties. Specifically, this method captures the actual manufacturing conditions, not merely those "set" by process parameters. This is particularly advantageous because crucial process conditions often cannot be directly controlled by process parameters. For example, the component temperature in a specific manufacturing step cannot be directly set but depends on numerous process parameters such as laser power, exposure time, build area size, etc. This eliminates the need for complex derivations of the relationships between process parameters and manufacturing conditions, allowing for their empirical determination.

[0028] An important point is that the process parameters are changed / adjusted (possibly during the process). A feedback loop can be implemented in the build job (manufacturing process), but this is not mandatory. Temperature measurement, as an example of a status value, serves as a control to reduce deviations / irregularities. A key aspect is data correlation between real-time measurement data and measurement data from previous build jobs. This can be achieved, for example, by evaluating / analyzing the temperature measurement curve over time and / or layer heights. Meissner Bolte 5 M / EOSG-061-PC

[0029] The process parameters can be changed, or other process parameters can be selected from a set of data parameters from previous construction processes, depending on the results of the comparison (e.g., analysis of the temperature curve).

[0030] Particularly preferably, the measurement of the state value according to the inventive concept takes place for each voxel of the process chamber in order to obtain as complete a picture as possible of the process conditions, which is also spatially resolved.

[0031] According to a preferred embodiment, the method further comprises a step of updating the comparison data based on the state values ​​measured in step a).

[0032] By iteratively adjusting the comparison data with each new component generation, the desired target parameters and / or state values ​​can be controlled or regulated more precisely. This ensures that the information newly acquired in each manufacturing process is taken into account when evaluating and / or executing the next build process. This results in a feedback loop, at least between (some) component generations, preferably until the desired process conditions (state values, target parameters, process parameters) are achieved.

[0033] In a further preferred embodiment, the method comprises determining a correlation between at least one target variable and at least one process parameter, preferably based on the measured state values.

[0034] Determining correlations allows for a better understanding of the relationships between process parameters and / or state values ​​with target variables and / or process status. In particular, this enables the consideration of diverse influences that cannot be directly represented analytically.

[0035] Preferably, the adjustment of at least one process parameter is carried out by selecting a new process parameter from the comparison data.

[0036] If a status value closer to a desired value was already recorded in a previous construction process, it can be useful to directly set the corresponding process parameter as a new process parameter. This avoids unnecessary adjustments to process parameters that do not produce the desired result. Meissner Bolte 6 M / EOSG-061-PC

[0037] generate, reduce. In addition, it is easy to revert to previous construction processes that have already led to satisfactory results.

[0038] According to a further preferred embodiment, the at least one state value comprises at least one gray value and / or the at least one measuring device comprises an optical tomography camera.

[0039] By recording gray values ​​within the process chamber, for example using an optical tomography camera, a correlation between gray values ​​and target parameters can be determined by comparing them with previous manufacturing processes and preferably also with corresponding incoming goods inspections. In particular, it has been shown that there is a high correlation between gray values ​​and electrical conductivities in

[0040] Thin-walled components can be manufactured using this method. The gray values ​​can qualitatively describe the coating of the powder bed (e.g., good, medium, and other gradations) or the exposure temperature of the weld pool. Based on the exposure temperature and the amount of energy applied, conclusions can be drawn about the weld thickness, quality, and electrical conductivity, preferably even before the component has been removed from the laser beam melting system.

[0041] This is particularly the case when the structure consists of a large number of layers in a vertical direction, because the residual heat from the previously solidified layers below causes the temperature to increase steadily in the vertical direction if no adjustments are made to the process parameters (such as exposure times).

[0042] According to a further preferred embodiment, the adjustment of the at least one process parameter is based on a correlation between a gray value and a target quantity, preferably an electrical conductivity.

[0043] By adhering to certain limit values ​​within a process band (min / max), the gray values ​​provide a direct indicator of component overheating.

[0044] This results, for example, in an increase in wall thickness due to increased energy input, and thus changes the electrical conductivity or the geometry of the wall thicknesses of the component. Meissner Bolte 7 M / EOSG-061-PC

[0045] In a further preferred embodiment, adjusting the at least one process parameter leads to a, preferably temporary, shutdown of the beam.

[0046] The energy input can be adjusted, for example, by changing the laser power input, which would then be the process parameter to be changed. Alternatively, specifically adjusted waiting times can be implemented in a build process (exposure times) to, for example, reduce the temperature as a state value.

[0047] Temporarily switching off the irradiation allows the temperature inside the process chamber to be reduced effectively and easily. This can be used, for example, to prevent overheating of layers of the component that are located high up in the vertical direction.

[0048] Preferably, adjusting the at least one process parameter includes adjusting the laser power, preferably by implementing a waiting time.

[0049] In particular, the process can be switched off for a predetermined time at a predetermined layer height to ensure a more uniform temperature of the component parts during manufacturing. For example, after completing a layer, a waiting period can be observed before irradiating the next layer to allow the underlying layer to cool sufficiently. The necessary waiting time can be determined by comparing and / or interpolating with reference data.

[0050] In a further preferred embodiment, the at least one state value in step a) is an average value which is formed from a plurality of individual measurements, preferably averaged over time and / or location.

[0051] According to the corresponding embodiment, several individual measurements are averaged to obtain a more meaningful result. This reduces the total volume of data to be evaluated while simultaneously increasing its significance.

[0052] For example, when measuring temperature voxels, it is possible to average the temperature across all voxels that can be assigned to a specific component region or component. This provides a more coherent picture of the Meissner Bolte 8 M / EOSG-061-PC.

[0053] the process conditions in this region, which are not distorted by partially differing individual values.

[0054] In other examples, averaging can be done over a longer period, for example to determine the temperature trend or an average temperature.

[0055] Furthermore preferably, the at least one state value in step a) is derived from a relationship of a plurality of individual measurements, preferably the slope of a graph of the individual measurements.

[0056] The relationships between individual measurements can be more complex than simply average values. In particular, individual measurements can be plotted to determine derived state values. For example, the temperature at a specific voxel or in a particular component region can be measured over an extended period and plotted against time. The resulting temperature curve can then be used to determine the slope, which represents the heat input or output as a derived state value.

[0057] This allows for the representation of more complex relationships than is possible by considering direct measurement results.

[0058] The task is also solved by a system for the additive manufacturing of objects, in particular a laser sintering or laser melting system, comprising a control unit and an adjustment and / or setting unit, wherein the control unit is configured to carry out the process according to the method described above.

[0059] The described system offers the same advantages as those already explained in relation to the procedure.

[0060] The task is also solved by a computer-readable storage medium containing instructions that cause at least one processor to execute the described procedure when the instructions are carried out by the at least one processor.

[0061] The invention is described below with regard to further details, features, and advantages, which are explained in more detail with reference to the figures. The described features and combinations of features, as shown below in the figures and described with reference to the drawing, are not only present in the respective Meissner Bolte 9 M / EOSG-061-PC.

[0062] The specified combination is not only applicable, but also in other combinations or on its own, without leaving the scope of the invention.

[0063] This shows:

[0064] Figure 1: a schematic summary of the procedure; and

[0065] Figure 2: a representation of a measured temperature profile with derived state values.

[0066] Figure 3: a representation of a measured spatial temperature profile with derived state values.

[0067] Figure 1 shows a schematic representation of the method according to the invention. In a first step 101, the manufacturing of the component is started according to the preset process parameters, preferably by irradiating the component. The process parameters include, for example, the path of motion and the intensity of a laser beam used to melt the build material.

[0068] Subsequently, preferably during the construction process, a status value is measured in a further step 102. The status value can be, for example, a surface temperature of the component or, preferably, a region of the component.

[0069] Based on the measured state value, a process status is then determined in a further step 103 to ascertain whether the conditions reflected by the state value have led to the actual realization of all or at least some target variables.

[0070] The measured state value is then compared with reference data in a further step 104. For example, the measured surface temperature is compared with other surface temperatures from previous construction processes. Preferably, further comparisons are also made, such as the respective process status or the respective target variables resulting from the construction process.

[0071] In a further step 106, at least one process parameter is then adjusted based on the comparison 104. For example, the comparison of surface temperatures might have shown that the surface temperature in Meissner Bolte 10 M / EOSG-061-PC

[0072] The temperature in previous build processes was lower than the temperature measured in the current build process, resulting in a distortion of the component's wall thickness. Accordingly, in a further step, the laser power can be reduced as a process parameter. Alternatively, exposure times can be adjusted to incorporate exposure breaks into the build process, thereby lowering the overall temperature.

[0073] In a preferred embodiment, the process can be iterative, wherein in a further step 105 the process is repeated with the new process parameters until an optimal realization of the target dimensions of the component is achieved.

[0074] Figure 2 shows an example of various derived state values, which are composed of a large number of individual measurements 201. It depicts a temperature profile of a region of the component, with the multiple individual measurements 201 being performed sequentially. From this, an approximate temperature profile can be derived, which is given by the dashed curve 204.

[0075] Based on the temperature profile 204, or directly on the individual measurements 201, an average temperature 202 for the component region can be derived, which can then be recorded as a status value. Alternatively, a slope can be determined from the temperature profile 204, representing the temperature change 203 at a given time. Furthermore, it is possible to determine a mean or mode value based on the individual measurements.

[0076] While Figure 2 shows a time course on the horizontal axis, the same method can also be applied to spatially separated individual measurements.

[0077] This is illustrated in Figure 3. For example, the horizontal axis can be divided into voxels in the longitudinal or vertical direction of the component to capture spatial temperature gradients. It is particularly preferred to capture the temperature increase or decrease in the vertical direction (Z), as shown in Figure 3, where the multitude of individual measurements 201 each correspond to a layer of applied building material, which are superimposed. In this case, the locations of the individual measurements 201 are at least substantially vertically aligned.

[0078] It should be noted here that all parts described above, considered individually and in any combination, and in particular the details shown in the drawings, are claimed as essential to the invention. Modifications to this are familiar to those skilled in the art. Meissner Bolte 11 M / EOSG-061-PC

[0079] Furthermore, it is noted that the broadest possible scope of protection is sought. Therefore, the disclosure contained in the claims can also be specified by features that are described by further features (even if these further features are not necessarily included). It is explicitly pointed out that parentheses and the term "in particular" are intended to emphasize the optionality of features in the respective context (which does not imply that a feature is mandatory in the corresponding context without such indication). The term "element" can denote a coherent structure, which in turn may be connected to at least one other structure (to form a potentially monolithic and / or internally immobile overall structure) (or may be distinct from all other structures).

[0080] Reference symbol list

[0081] 101 Start of radiation therapy

[0082] 102 Measurement of the state value

[0083] 103 Determination of the process status

[0084] 104 Comparison with comparative values

[0085] 105 Iterative continuation of new construction process

[0086] 106 Adjustment

[0087] 201 individual measurements

[0088] 202 Average or mean value as a state value

[0089] 203 Gradient as a state value

[0090] 204 Temperature profile

Claims

Meissner Bolte 12 M / EOSG-061-PC Claims 1. A method for the additive manufacturing of a three-dimensional component by layer-by-layer application of a build material and locally selective solidification of the build material by means of at least one beam impacting the build material, wherein the guidance of the beam is carried out on the basis of a plurality of process parameter values, comprising the following steps: a) Measuring at least one state value relating to a construction process, in particular within a process chamber, further preferably of state values ​​of the component, preferably the temperature, further preferably the surface temperature, by means of at least one measuring device, further preferably during the construction process; b) Determining a process status based on at least one state value measured in step a); c) Comparing the at least one measured state value with reference data, the reference data preferably being stored in a database; d) Adjusting at least one process parameter based on the comparison in step c), preferably to achieve at least one target variable.

2. Method according to claim 2, further comprising a step of updating the comparison data based on the state values ​​measured in step a).

3. Method according to one of the preceding claims, comprising determining a correlation between at least one target variable and at least one process parameter, preferably based on the measured state values.

4. Method according to one of the preceding claims, wherein the adjustment of at least one process parameter is carried out by selecting a new process parameter from the comparison data.

5. A method according to any one of the preceding claims, wherein the at least one state value comprises at least one gray value, and / or the at least one measuring device comprises an optical tomography camera. Meissner Bolte 13 M / EOSG-061-PC 6. Method according to one of the preceding claims, in particular according to claim 5, wherein the adjustment of the at least one process parameter is based on a correlation between a gray value and a target quantity, preferably an electrical conductivity.

7. Method according to one of the preceding claims, wherein the adjustment of the at least one process parameter leads to a, preferably temporary, shutdown of the beam.

8. Method according to one of the preceding claims, wherein the adjustment of the at least one process parameter comprises an adjustment of the laser power, preferably by implementing a waiting time.

9. Method according to one of the preceding claims, wherein the at least one state value in step a) is an average value formed from a plurality of individual measurements, preferably averaged over time and / or location.

10. Method according to one of the preceding claims, wherein the at least one state value in step a) is derived from a relationship of a plurality of individual measurements, preferably the slope of a graph of the individual measurements.

11. System for the additive manufacturing of objects, in particular a laser sintering or laser melting system, comprising a control unit and an adjustment and / or setting unit, wherein the control unit is configured to control the adjustment and / or setting unit to carry out the method according to any one of claims 1 to 10.

12. Computer-readable storage medium containing instructions that cause at least one processor to control a method according to any one of the preceding claims 1 to 10 when the instructions are executed by the at least one processor.

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