Method for preheating a circuit board, method for additive manufacturing a workpiece, machine tool, and control device.

Abstract

The present invention provides a method for preheating a substrate body 200, particularly a metallic substrate body, in preparation for an additive manufacturing process by irradiation with a laser beam L, comprising the steps of: detecting the actual temperature of the substrate body 200, particularly by a thermal imaging camera 50; determining a movement parameter representing the relative movement between the laser beam L and the substrate body 200 based on at least the detected actual temperature; and moving the laser beam L and the substrate body 200 relatively according to at least the determined movement parameter, wherein the incident point A of the laser beam L moves along the surface 201 of the substrate body 200 to be irradiated.

Description

[Technical Field]

[0001] The present invention relates to a method for preheating a substrate body, a method for additive manufacturing a workpiece, a machine tool, and a control device for use in a machine tool. [Background technology]

[0002] Additive manufacturing methods have become increasingly important in recent years for the industrial production of workpieces because they offer particularly flexible and rapid possibilities for the primary shaping of workpieces.

[0003] Additive manufacturing methods, in particular, include cladding methods, also known as DED (Directed Energy Deposition), in which an energy beam (laser, electron beam, or plasma arc) is used to coat the surface of a work blank (generally the substrate body) with build-up material in a material bonding manner, thereby forming a portion of the workpiece.

[0004] To ensure the highest possible workpiece quality, the workpiece blank is optionally preheated before cladding, thereby reducing the risk of material defects, particularly at the interface between the workpiece blank and the applied build-up material. Preheating is performed under non-melting heating conditions so that the workpiece blank maintains its solid aggregate state and microstructure.

[0005] For preheating, the use of a heating furnace is known, particularly from the prior art, in which the work blank is preheated before undergoing cladding. This requires several time-consuming work steps, during which the work blank is transported from the heating furnace to a machine tool used for additive manufacturing, where it is clamped, and then the work blank needs to be measured before the actual manufacturing begins.

[0006] Furthermore, WO2021099459A1 discloses a method for performing additive manufacturing of a workpiece via cladding, in which the workpiece is pre-deformed by thermal energy input from stationary irradiation of a laser beam in order to compensate for deformation during subsequent cladding.

[0007] Heating by laser beam represents an alternative to heating furnaces with fewer work steps; however, thermal stress due to uneven heating of the workpiece blank is acceptable, which, in the case of WO2021099459A1, is intentionally utilized for deformation. [Overview of the project] [Problems that the invention aims to solve]

[0008] The object of the present invention is to provide a more efficient possibility for additive manufacturing by cladding (DED method), and in particular to provide a method characterized by fewer work steps and high manufacturing quality. [Means for solving the problem]

[0009] To achieve this objective, the method for preheating described in claim 1, the method for additive manufacturing described in claim 14, the machine tool described in claim 16, and the control device described in claim 22 are proposed.

[0010] The remaining dependent claims relate to preferred embodiments of methods or machine tools, which may be provided individually or in combination.

[0011] According to a first aspect of the present invention, a method is provided for preheating a substrate body, particularly a metallic substrate body, by irradiation with a laser beam in preparation for an additive manufacturing method, the method comprising: detecting the actual temperature of the substrate body, particularly by a thermal imaging camera; determining a movement parameter representing the relative movement between the laser beam and the substrate body, based at least on the detected actual temperature; and moving the laser beam and the substrate body relatively according to at least the determined movement parameter, wherein the point of incidence of the laser beam onto the substrate body moves along the surface of the substrate body to be irradiated.

[0012] In other words, during irradiation of the substrate, the laser beam is moved relative to the substrate based on the detected actual temperature, and when the laser beam is switched on, the point of incidence moves across the surface of the substrate being irradiated, thereby achieving a locally dispersed energy input to the substrate, and this energy input is controlled in a desired manner by relative kinematics.

[0013] Thus, despite the use of a point-like energy source, the energy input by the laser beam is dispersed over most of the substrate body by its movement, allowing the entire substrate body to be preheated particularly quickly and uniformly. Furthermore, by taking into account the detected actual temperature, localized overheating that would, in extreme cases, lead to undesirable melting of the substrate body material is prevented.

[0014] Essentially, the energy input is controlled via relative kinematics (and therefore via the transport parameter). For example, the transport parameter is determined such that as the actual temperature approaches the melting temperature of the substrate body, the relative velocity increases to reduce the energy input per unit area and thereby avoid the localized overheating.

[0015] Therefore, this method enables high energy input to the substrate body for uniform heating of the substrate body without creating the risk of localized overheating, and as a result, the substrate body can be preheated quickly and uniformly without melting, which cannot be achieved by simply point-like stationary irradiation, as in the case of WO2021099459A1, for example.

[0016] The uniform and rapid preheating of the substrate body performed in this manner provides an optimal starting point for subsequent additive manufacturing involving the bonding and coating of build-up materials. This reduces the risk of material defects and weak points that may arise, particularly from uneven or insufficient preheating before additive manufacturing, such as defects in the form of internal stress, cracks resulting from uneven cooling of the substrate body that has not been uniformly heated, and defects in the form of pores or gas entrapment.

[0017] Such material defects can be reliably avoided by the method according to the first embodiment without increasing the process time (compared to the use of a heating furnace). Furthermore, the energy input by the laser is more localized than, for example, that of a heating furnace, which has a favorable effect on energy costs.

[0018] The laser beam is preferably operated at a constant output, particularly within the nominal output range or at maximum output, so as to maximize the energy input per unit time to the substrate body, thereby reducing the preheating time.

[0019] The substrate body should be understood as a solid, unified entity (i.e., not a powder), and preheating should be understood as non-melting heating, during which the melting temperature of the substrate body material must not be exceeded. In other words, the substrate body being preheated remains a solid aggregate.

[0020] The point of incidence of the laser beam is not a point in a mathematical sense, but rather a region on the surface of the substrate that receives energy input from the laser beam.

[0021] The surface of the irradiation object is normally continuous, in particular a continuously distinguishable surface that can be defined by the edge of the substrate body, and the area thereof is at least 5 times, preferably at least 10 times, particularly preferably at least 50 times the focal area of the laser beam used in particular.

[0022] Since the temperature of the substrate body is normally non-uniform, the detected actual temperature is preferably the maximum value among a plurality of actual temperatures detected at different positions of the substrate body. In particular, these are derived from measurements by a thermal imaging camera or an infrared camera.

[0023] Movement parameters within the meaning of the present method should be understood as any movement parameter suitable for describing the relative movement between the substrate body and the laser beam, where the incident point of the laser beam moves over the surface of the substrate body. For example, this may in particular be the relative displacement, velocity or acceleration of the incident point on the surface to be irradiated, or may be a control parameter of a drive unit that implements the relative movement of the NC axis of a machine tool, for example. The relative displacement, velocity or acceleration may also be, for example, an average value, and the relative movement only needs to satisfy the movement parameter on average.

[0024] Preferably, at least the detection of the actual temperature, the determination of the movement parameter, and the relative movement between the laser beam and the substrate body are repeatedly performed, and the sequence of these steps is understood as a heating cycle.

[0025] In other words, in the course of the present method, the laser beam is normally guided multiple times across the surface of the irradiation object, and in each case, the current actual temperature is detected in advance, and the respective movement parameter is determined based thereon.

[0026] Preferably, the relative movement is performed such that the incident point of the laser beam moves over at least 60%, preferably at least 80% or 90%, particularly preferably at least 95% of the surface of the irradiation object, particularly in the course of a single heating cycle.

[0027] As a result, for example, during a single heating cycle, the energy input to the surface of the irradiated object can be increased and distributed as evenly as possible across the substrate.

[0028] The relative movement of the laser beam during irradiation may be a continuous movement with a relative velocity of non-zero, or it may be a segmented movement in which the incident point moves between predetermined points and stops for a predetermined period of time at each point.

[0029] This method is specifically designed for use in machine tools, and the irradiation of the substrate body is performed using a laser device of the machine tool that supplies the laser beam. The machine tool includes at least one drive unit capable of performing relative motion between the laser beam and the substrate body.

[0030] Here, the step of moving the laser beam and the substrate body relative to each other includes controlling at least one drive unit according to the determined movement parameters, in this case particularly the feed parameters.

[0031] Preferably, preheating is performed with the substrate body, which can also be considered a work blank, already clamped, so that additional manufacturing can be started immediately after preheating without the need to reclamp the substrate body.

[0032] As an alternative embodiment of the method according to the first embodiment, a method is provided that is particularly usable for very small workpieces, which includes the steps of detecting the actual temperature of the substrate body by a thermal imaging camera, irradiating the substrate body with a laser beam, and controlling the laser beam according to the detected actual temperature, and in particular including terminating the irradiation when the detected actual temperature reaches a predetermined limit temperature. This procedure is particularly suitable when the workpiece is very small and it is not possible to perform scanning motion of the laser on the surface to be irradiated. Furthermore, this procedure may include the step of detecting the area of ​​the surface to be irradiated in the method according to the first embodiment, and the movement parameters may be set such that the relative velocity between the laser and the substrate body becomes zero when the detected surface area is smaller than a predetermined minimum size.

[0033] In a preferred embodiment, the method further includes the step of providing a limit temperature for preheating, which in particular depends on one or more material parameters of the substrate body, and the determination of the transfer parameters is based on at least the detected actual temperature and the provided limit temperature. The limit temperature preferably depends on the melting temperature of the substrate body and should not be exceeded during preheating.

[0034] In this way, both the current temperature of the substrate body and the maximum allowable temperature are taken into consideration in controlling the relative movement of the laser beam, and as a result, the desired energy input to the substrate body during relative movement, particularly during heating cycles, can be determined, for example, based on the difference between the two values. Therefore, the determination of the movement parameters can be carried out under the condition that, when the output of the laser beam is constant, the relative velocity between the laser beam and the substrate body increases as the difference between the two values ​​decreases, thereby reducing the energy input during relative movement.

[0035] In a preferred embodiment, the determination of the movement parameters is further based on the output parameters of the laser beam and / or the area of ​​the laser beam incident point and / or the absorptivity of the substrate body.

[0036] In this way, the energy input to the substrate can be estimated more accurately, and the movement parameters can be set to achieve maximum energy input without causing localized overheating.

[0037] In a preferred embodiment, the movement parameter is a velocity parameter representing the relative velocity of the laser beam with respect to the substrate body, particularly the relative velocity at the point of incidence.

[0038] In this way, the energy input to the substrate body is essentially determined by the relative velocity. The velocity parameter may be a constant or averaged relative velocity, and in particular may be the feed rate of the laser device supplying the laser beam.

[0039] In a preferred embodiment, the method further includes the step of providing a preheating path that passes over the surface of the substrate body to be irradiated, and the relative movement of the laser beam and the substrate body is further carried out in accordance with the provided preheating path, and the incident point moves along the provided preheating path on the surface of the substrate body to be irradiated.

[0040] The preheating path described here refers to the path on the surface of the object being irradiated, and can be described as a set of points or a line, for example, although this is not limited to such paths.

[0041] The movement parameter can be understood here as being designed for the preheating path, and therefore, the movement parameter specifies, for example, the speed when scanning the preheating path, as a velocity parameter.

[0042] In a preferred embodiment, the preheating path extends spirally from the outer region of the surface to be irradiated to the central region of the surface to be irradiated.

[0043] The inventors have found that as motion progresses, energy input concentrates toward the center and is then conducted through the substrate itself to its outer regions, resulting in a particularly uniform heat distribution. Furthermore, the helical shape makes it possible to keep the time between heating cycles when the substrate is not irradiated short, especially in the case of multiple heating cycles.

[0044] In a preferred embodiment, providing a preheating path includes a substep of determining a preheating path that passes over the surface of the substrate body to be irradiated, based at least on the shape and / or dimensions of the surface to be irradiated and / or the diameter of the incident point of the laser beam.

[0045] This allows for the determination of the optimal preheating path for each individual substrate, and during scanning, the laser beam preferably strikes every point on the surface.

[0046] Preferably, the distance between adjacent subsegments of the preheating path is selected so that they correspond to the diameter of the incident point, thereby ensuring that the entire surface of the object being irradiated is covered as much as possible by the laser beam when scanning the preheating path.

[0047] In a preferred embodiment, the method includes multiple executions of the heating cycle described above, and each step of the heating cycle may be designed in the sense of the preferred embodiment described above.

[0048] In a preferred embodiment, the determination of the transport parameters in the nth heating cycle is further based on the transport parameters determined from the (n-1)th heating cycle.

[0049] In this way, the transfer parameters are recursively determined, and the transfer parameters from the previous heating cycle can be adjusted by a correction factor.

[0050] In a preferred embodiment, the determination of the movement parameter in the n-th heating cycle is performed based on the movement parameter determined from the (n-1)-th heating cycle, and the difference between the provided limit temperature and the actual temperature detected in the n-th heating cycle.

[0051] This particular form of recursive adaptation makes it possible to simply and reliably implement the approach of the present invention of achieving maximum energy input without causing local overheating.

[0052] When the movement parameter is a speed parameter that describes a relative speed, such recursive assignment can be expressed, for example without limitation, as follows:

[0053]

Mathematical Expression

[0054] In order to take into account technical limitations, such as the maximum speed of the drive for implementing relative movement, especially when T G approaches T Ist,n , it is suitable to incorporate Equation 1 into the recursive assignment rule with case division according to Equation 2 below:

[0055]

Mathematical Expression

[0056] wherein v max represents the achievable maximum relative speed. When the recursively determined relative speed v n reaches the value v max , it is fixed at this value and does not increase further.

[0057] In a preferred embodiment, the method further includes the steps of providing a target temperature and terminating preheating if an actual temperature higher than the provided target temperature is detected.

[0058] In this way, the target criteria for completing preheating are defined.

[0059] In the case of multiple heating cycles, the actual temperature refers to the actual temperature in each heating cycle.

[0060] When recursive assignment is used, the transfer parameters for the first heating cycle may be estimated or specified by the operator.

[0061] In exemplary embodiments, during the relative movement between the laser beam and the substrate body, and especially when an inverse expander (a reducer that reduces the raw beam in front of the focusing lens) is used in the laser device used for this purpose, the point of incidence of the laser beam coincides with the focal point of the laser beam.

[0062] In a preferred embodiment, the method is carried out on a machine tool for additive manufacturing, in which the laser beam is provided by the machine tool's laser device, in particular a DED laser device.

[0063] As a result, additional manufacturing can be performed immediately after preheating without having to reclamp the substrate body, which serves as the work blank.

[0064] In a preferred embodiment, the method includes the steps of fixing the substrate body to a holding device of a machine tool, or clamping the substrate body to a work carrier and fixing the work carrier to a holding device of a machine tool.

[0065] Preferably, the method further includes the steps of adjusting the output parameters of the laser beam in accordance with at least the detected actual temperature, and / or adjusting the distance between the incident point and the focal point of the laser beam.

[0066] This allows process control during preheating to be extended with additional adjustment variables that can prevent overheating, particularly in the case of relatively small workpieces, where the maximum output of the laser beam could lead to direct melting of the substrate itself.

[0067] According to a second embodiment, a method for additively manufacturing a workpiece is provided, the method comprising the steps of preheating a workpiece blank by a method according to the first embodiment or one of its preferred embodiments, and forming at least a portion of the workpiece to be manufactured by additional material bonding application of a build-up material onto the preheated workpiece blank.

[0068] Therefore, an additive manufacturing method is provided for uniformly, quickly, and reliably preheating the work blank for additional build-up.

[0069] In a preferred embodiment, material bonding and coating are performed by a DED laser method, and the laser beam for preheating and the laser beam for the DED laser method are provided by the same laser device.

[0070] As a result, additional laser equipment can be omitted in additive manufacturing, making the entire process feasible, for example, on a machine tool equipped with only one laser device, thereby reducing manufacturing time and costs in particular.

[0071] According to a third embodiment, a machine tool is provided, which comprises a laser device, a workspace, a holding device disposed within the workspace and configured to fixedly receive a work blank or a work carrier carrying a work blank, and one or more drive units, in particular numerically controlled drive units, the drive units enabling the laser device and the holding device to move relative to each other, and further comprising a temperature measuring device configured to detect the temperature of a work blank located in the workspace, in particular the temperature measuring device being a thermal imaging camera, and further comprising a control device for controlling the machine tool, wherein the machine tool is configured to preheat a work blank received in the holding device and / or a work blank carried by a work carrier received in the holding device, in particular metal work blanks are preheated by irradiation with a laser beam from the laser device, and for this purpose the control device is configured to determine a movement parameter representing the relative motion between the laser beam and the work blank, at least based on the actual temperature of the work blank detected by the temperature measuring device, and further controls one or more drive units of the machine tool according to the movement parameter determined during irradiation of the work blank with the laser beam, so that the incident point of the laser beam moves along the surface of the work blank to be irradiated.

[0072] Therefore, since the machine tool according to the present invention is configured to implement the preheating method described above, there is no need to repeat the relevant advantages at this point.

[0073] In a preferred embodiment, a path dataset describing a preheating path across the surface of a workpiece blank to be irradiated is provided to the control device, and the control device is configured to control one or more drive units so that the incident point moves along the preheating path described by the path dataset during irradiation of the workpiece blank.

[0074] In a preferred embodiment, the control device is configured to predetermine path data in accordance with at least data provided to the control device regarding the shape and / or dimensions of the surface to be irradiated and / or the diameter of the laser beam incident point, in particular, the preheating path described by the path data set is configured to extend spirally from the outer region of the surface to be irradiated to the central region of the surface to be irradiated.

[0075] In a preferred embodiment, the control device is configured to determine the movement parameters based on the detected actual temperature and the limit temperature of the work blank provided to the control device.

[0076] In a preferred embodiment, the movement parameter is a velocity parameter representing the relative velocity of the laser beam with respect to the substrate body, particularly the relative velocity of the laser beam at the point of incidence.

[0077] In a preferred embodiment, the machine tool is further configured to additively manufacture the workpiece, and for that purpose, a laser device is configured for the additive material bonding coating of the build-up material, and in particular, the laser device is a DED laser device.

[0078] In a preferred embodiment, the control device is configured to determine the movement parameters based at least on the detected actual temperature and a provided limit temperature that depends in particular on one or more material parameters of the work blank.

[0079] In a preferred embodiment, the control device is configured to determine the movement parameters based on the power parameters of the laser device and / or the area of ​​the laser beam incidence point and / or the absorption rate of the workpiece blank.

[0080] In a preferred embodiment, the control device is configured to perform preheating in the form of several heating cycles.

[0081] In a preferred embodiment, the control device is configured to determine the movement parameters in the nth heating cycle based on the actual temperature detected for the nth heating cycle, and further based on the movement parameters previously determined from the (n-1)th heating cycle.

[0082] A fourth aspect provides a control device for a machine tool according to the third aspect or a preferred embodiment relating to this point, the control device being configured to control at least a machine tool and to preheat a work blank, particularly a metal work blank, received in a holding device of the machine tool and / or supported by a work carrier received in a holding device, by irradiation with a laser beam of the laser device of the machine tool, for this purpose the control device being configured to determine a movement parameter describing the relative motion between the laser beam and the substrate body based at least on the actual temperature detected by a temperature measuring device, and further controlling one or more drive units of the machine tool in accordance with the determined movement parameter during irradiation of the work blank with the laser beam, so that the incident point of the laser beam moves along the surface of the work blank to be irradiated.

[0083] In this way, an existing machine tool that already has all the components according to the third aspect of the present invention, separate from the control device, can be applied to such a machine tool.

[0084] Further embodiments and their advantages, as well as more specific exemplary embodiments of the above-described embodiments and embodiments, are described below with reference to the drawings shown in the accompanying drawings. [Brief explanation of the drawing]

[0085] [Figure 1] A schematic flowchart of an exemplary embodiment of the preheating method according to the present invention is shown. [Figure 2] A schematic flowchart of an exemplary embodiment of a method for additionally manufacturing a workpiece according to the present invention is shown. [Figure 3] This shows an exemplary movement path of the laser beam incidence point in an exemplary embodiment of the preheating method according to the present invention. [Figure 4] The following shows an exemplary distribution of several process parameters in an exemplary embodiment of the preheating method according to the present invention. [Figure 5] A schematic diagram of an exemplary embodiment of the machine tool according to the present invention is shown. [Modes for carrying out the invention]

[0086] It is emphasized that the present invention is not limited to the exemplary embodiments and their implemented features described below. The present invention further includes, within the scope of protection of the independent claims, modifications of the exemplary embodiments mentioned, in particular, those arising from modifications and / or combinations of individual or some features of the described exemplary embodiments.

[0087] Figure 1 shows a schematic flowchart of an exemplary embodiment of the method according to the present invention for preheating a substrate body by irradiation with a laser beam.

[0088] In step S1, a limit temperature and a target temperature are provided for the method, the target temperature representing the temperature to be reached during the preheating process, and the limit temperature representing the temperature of the substrate body that must not be exceeded, for example, the temperature at which the substrate body material begins to melt.

[0089] In step S2, a preheating path is provided through which the incident point of the laser beam moves on the surface of the substrate body to be irradiated.

[0090] Steps S3 to S6 are repeated, and the sequence of these steps can be combined into a heating cycle Hi that is performed multiple times.

[0091] In step S3, the actual temperature of the preheated substrate is detected, in particular, by a thermal imaging camera.

[0092] In step S4, the detected actual temperature is compared with the target temperature provided in step S1. If the substrate body has reached this temperature, the process proceeds to step S7, and preheating is completed.

[0093] Otherwise, step S5 proceeds, in which a movement parameter representing the relative movement between the laser beam and the substrate body is determined based on the actual temperature detected in step S3 and the limit temperature provided in step S1. In particular, this is a velocity parameter representing the relative velocity between the laser beam and the substrate body.

[0094] In step S6, the relative movement between the laser beam and the substrate body is performed according to the preheating path provided in step S2 and according to the movement parameters determined in step S5, and the incident point of the laser beam moves along the preheating path on the surface of the substrate body to be irradiated at a relative velocity specified in particular by the velocity parameter.

[0095] Once the provided preheating path has been scanned, step S6 ends and a new heating cycle is initiated by a new step S3.

[0096] According to the procedure described above, the energy input to the substrate body is controlled in each heating cycle at least in accordance with the detected actual temperature, which affects the relative motion between the laser beam and the substrate body via the movement parameters determined based on that temperature.

[0097] In this way, the substrate can be preheated quickly and uniformly to the desired target temperature without the risk of localized overheating, and the energy input can be controlled particularly advantageously through relative motion. Furthermore, since the energy input by the laser can be performed more locally, the energy cost is significantly reduced compared to preheating by a heating furnace.

[0098] Particularly advantageous is that the above method is carried out using a machine tool, in which case step S6 preferably includes a substep of controlling at least one drive unit of the machine tool, thereby performing relative movement between the laser beam and the substrate body according to the movement parameters determined in step S5.

[0099] Figure 2 shows a schematic flowchart of an exemplary embodiment of the method according to the present invention for additive manufacturing of workpieces.

[0100] In this example, the method includes steps S1 to S7 for preheating the substrate body shown in Figure 1, which corresponds to the work blank. The explanation of steps S1 to S7 is omitted here.

[0101] Step S8, following the completion of preheating in step S7, includes forming (building up) at least a portion of the workpiece to be manufactured by additional material bonding application of build-up material onto the preheated workpiece blank.

[0102] This provides an additive manufacturing method that uniformly, quickly, and reliably preheats the workpiece blank for additional build-up, reducing the risk of internal stress or cracks, as well as pores or gas inclusions within the workpiece.

[0103] Figure 3 shows an exemplary movement process of the incident point A in an embodiment of the method according to the present invention for preheating the substrate body 200.

[0104] During the process of this method, as the laser beam moves relative to the substrate body 200, the incident point A of the laser beam moves relative to the substrate body 200 along the surface 201 of the object to be irradiated.

[0105] Therefore, the energy input is provided through the surface 201, which is limited by the outer edge 202.

[0106] The incident point A has a diameter dA and moves along the preheating path P, which passes over the surface 201 of the object being irradiated, from the starting point P0 to the ending point Pend. As an example, the positions A0 and A1 of the incident point A at the start of the relative movement and at subsequent points are shown.

[0107] According to the present invention, the relative movement of the incident point A on the surface 201 of the irradiated object is performed according to a predetermined movement parameter, which depends on the detected actual temperature. For example, this could be a velocity parameter representing the relative velocity of the incident point A as it moves along the preheating path P.

[0108] The preheating path P extends spirally from the outer region 201a of the surface 201 of the irradiated object to the central region 201b of the surface 201 of the irradiated object, thereby achieving particularly good energy input.

[0109] Preferably, the preheating path P is scanned multiple times by the laser beam during the process of this method as part of each heating cycle, and the relative motion during the heating cycle is determined via a movement parameter according to the actual temperature of the substrate body 200 detected at the start of the heating cycle.

[0110] The preheating path P is selected such that the distance between adjacent subsegments in the preheating path substantially corresponds to the diameter dA of the incident point A, thereby ensuring that the entire surface 201 of the target is covered as much as possible by the laser beam when scanning the preheating path P.

[0111] Figure 4 shows an exemplary distribution of several process parameters in an exemplary embodiment of the preheating method according to the present invention.

[0112] Here, the substrate itself is heated and must not exceed the specified limit temperature TG.

[0113] As described in the general description section of this specification, the relative movement between the laser beam and the substrate body is controlled according to a movement parameter based on the detected actual temperature TIst, in this example being a velocity parameter representing the relative velocity between the laser beam or its incident point and the substrate body, and in particular a feed parameter.

[0114] The figure is a bar graph displaying time t, showing multiple heating cycles (each bar corresponding to one heating cycle) and the corresponding relative speed or feed rate between the laser beam and the substrate body.

[0115] The maximum relative velocity is limited by the respective drive units used to perform the relative motion.

[0116] As can be seen from the diagram, the relative velocity is initially set relatively low, resulting in a high energy input to the main body of the substrate.

[0117] As the actual temperature TIst rises, the actual temperature TIst of the substrate itself approaches the critical temperature TG. Therefore, in order to achieve uniform heating while avoiding undesirable overheating, the energy input per heating cycle is reduced, and as a result, the relative speed also increases.

[0118] Figure 5 shows a schematic diagram of an exemplary embodiment of the machine tool 100 according to the present invention.

[0119] The machine tool 100 comprises a laser device 10, a work space 20, a holding device 30 positioned in the work space 20 and configured to fix and receive a work blank 200 or a work carrier (not shown) that carries a work blank, and a plurality of numerically controlled drive units 41, 42 that enable the laser device 10 to move relative to the holding device 30. In this example, movement is performed in the horizontal planes in the X and Y directions.

[0120] Furthermore, the machine tool 100 includes a thermal imaging camera 50 as a temperature measuring device for detecting the temperature of the work blank 200 located within the work space 20, and a control device 60 for controlling the machine tool 100.

[0121] The machine tool 100 is configured to perform a work blank preheating method according to at least the first embodiment, in which the work blank 200 received in the holding device 30 is preheated by irradiation with the laser beam L of the laser device 10, and for this purpose the control device 60 is configured to determine a movement parameter representing the relative motion between the laser beam and the work blank 200, based at least on the actual temperature of the work blank 200 detected by the thermal imaging camera 50, and further, while the laser beam is irradiated onto the work blank 200, the drive units 41 and 42 of the machine tool 100 are controlled according to the determined movement parameter so that the incident point of the laser beam moves along the surface of the work blank 200 to be irradiated (see Figure 3).

[0122] Therefore, the machine tool 100 is configured to implement the above-described preheating method, which enables the work blank 200 to be preheated quickly and uniformly without creating a risk of localized overheating.

[0123] Preferably, since the laser device 10 is a DED laser device, additional material bonding and coating of build-up material onto the work blank can be performed immediately after preheating without releasing the clamp by the holding device 30 beforehand.

[0124] Although preferred embodiments of the present invention have been described in detail above with reference to the attached drawings, the present invention is not limited to these examples.

[0125] It is again emphasized that the present invention is not limited to the exemplary embodiments and their implemented features described above. The present invention further includes, within the scope of protection of the independent claims, modifications of the exemplary embodiments mentioned, in particular modifications and / or combinations of individual or several features of the described exemplary embodiments. [Explanation of Symbols]

[0126] 10 Laser devices 20 workspace 30 Holding device 41 Numerical control drive unit X direction 42 Numerical control drive unit Y direction 50 Thermal imaging cameras 60 Control device 100 Machine tools 200 Work Blanks 201 Surface of the target to be irradiated 201a Outer region of the surface of the irradiated object 201b Central region of the surface to be irradiated 202 Edges of the surface to be irradiated A. Point of incidence of the laser beam L laser beam P Preheating path

Claims

1. A method for preheating a substrate body (200), particularly a metal substrate body (200), by irradiation with a laser beam (L) in preparation for an additional manufacturing method, a) A step of detecting the actual temperature of the substrate body (200) in particular by a thermal imaging camera (50), b) A step of determining a movement parameter representing the relative movement between the laser beam (L) and the substrate body (200) based at least on the detected actual temperature, wherein the movement parameter is preferably a velocity parameter representing the relative velocity of the laser beam (L) with respect to the substrate body (200), particularly the relative velocity of the incident point (A) of the laser beam (L), c) A step of moving the laser beam (L) and the substrate body (200) relative to each other according to at least the determined movement parameters, wherein the incident point (A) of the laser beam (L) is moved along the surface (201) of the substrate body (200) to be irradiated, Methods that include...

2. The further step includes providing a limit temperature for preheating that depends in particular on one or more material parameters of the substrate body (200), The determination of the movement parameters is made based on at least the detected actual temperature and the provided limit temperature. The method according to claim 1.

3. The determination of the movement parameters is further based on the output parameters of the laser beam (L), and / or the area of ​​the incident point (A) of the laser beam (L), and / or the absorptivity of the substrate body (200). The method according to claim 1 or 2.

4. In particular, the step further includes providing a preheating path (P) that extends spirally from the outer region (201a) of the surface (201) to be irradiated to the central region (201b) of the surface (201) to be irradiated, on the surface (201) of the substrate body (200) to be irradiated, The relative movement between the laser beam (L) and the substrate body (200) is further carried out according to the provided preheating path (P), and the incident point (A) moves along the provided preheating path (P) on the surface (201) of the substrate body (200) to be irradiated. The provision of the preheating path (P) preferably includes a substep of determining the preheating path (P) extending on the surface (201) of the substrate body (200) to be irradiated, according to at least the shape and / or dimensions of the surface (201) to be irradiated and / or the diameter of the incident point (A) of the laser beam (L). The method according to at least one of claims 1 to 3.

5. Includes several heating cycles, Each heating cycle includes at least steps a), b), and c), The method according to at least one of claims 1 to 4.

6. The determination of the transfer parameter in the nth heating cycle is further based on the transfer parameter determined from the (n-1)th heating cycle. The method according to claim 5.

7. The determination of the transfer parameter in the nth heating cycle is based on the transfer parameter determined from the (n-1)th heating cycle and the difference between the provided limit temperature and the actual temperature detected from the nth heating cycle. The method according to at least claims 2 and 5.

8. A step of providing the target temperature, If an actual temperature higher than the provided target temperature is detected, the preheating is terminated. Further including, The method according to at least one of claims 1 to 7.

9. The method is carried out in a machine tool (100) for additive manufacturing, in which the laser beam (L) is provided by a laser device (10) of the machine tool (100), in particular a DED laser device. The step of moving the laser beam (L) and the substrate body (200) relative to each other further includes the step of controlling at least one drive unit of the machine tool (100) according to the determined movement parameter, The above method is preferably, The steps of fixing the substrate body (200) to the holding device (30) of the machine tool (100), or The steps include clamping the substrate body (200) onto the work carrier and fixing the work carrier to the holding device (30) of the machine tool (100), Further including, The method according to at least one of claims 1 to 8.

10. A method for additively manufacturing a workpiece, A step of preheating a work blank (200) by the method described in one of claims 1 to 9, A step of building up at least a portion of the workpiece, which is manufactured by additional material bonding coating of build-up material onto the preheated workpiece blank, preferably by a DED laser method, wherein the laser beam (L) for preheating and the laser beam (L) for the DED laser method are preferably supplied by the same laser device (10), Methods that include...

11. A machine tool (100), Laser device (10), The workspace (20) and A holding device (30) is positioned within the aforementioned workspace (20) and is configured for the fixed reception of a work blank (200) or a work carrier that holds the work blank, One or more drive units (41, 42), particularly numerically controlled drive units (41, 42), wherein the laser device (10) and the holding device (30) are movable relative to each other via the one or more drive units (41, 42), A temperature measuring device (50) configured to detect the temperature of a work blank (200) located within the aforementioned workspace (20), wherein the temperature measuring device is a thermal imaging camera (50), A control device (60) for controlling the machine tool (100), Equipped with, The machine tool (100) is configured to preheat the work blank received in the holding device (30) and / or the work blank held by the work carrier received in the holding device (30), particularly metal work blanks, by irradiation with the laser beam (L) of the laser device (10). For this purpose, the control device (60) is configured to determine a movement parameter representing the relative movement between the laser beam (L) and the work blank (200) based on the actual temperature of the work blank (200) detected by at least the temperature measuring device (50), and to control one or more drive units (41, 42) of the machine tool (100) in accordance with the determined movement parameter while the work blank (200) is irradiated by the laser beam (L). The incident point (A) of the laser beam (L) moves along the surface (201) of the work blank (200) to be irradiated. The aforementioned movement parameter is preferably a velocity parameter representing the relative velocity of the laser beam (L) with respect to the substrate body (200), particularly the relative velocity of the incident point (A). Machine tools (100).

12. A path data set representing the preheating path (P) extending on the surface (201) of the work blank (200) to be irradiated is provided to the control device (60). The control device (60) is configured to control one or more drive units such that the incident point (A) moves along the preheating path (P) represented by the path data set during irradiation of the work blank (200), The control device (60) is preferably configured to predetermine the path data set in accordance with data provided to the control device (60) regarding the shape and / or dimensions of the surface (201) to be irradiated and / or the diameter of the incident point (A) of the laser beam (L), wherein, in particular, the preheating path (P) represented by the path data set extends spirally from the outer region (201a) of the surface (201) to the central region (201b) of the surface (201) to be irradiated. The machine tool (100) according to claim 11.

13. The control device (60) is The system is configured to determine the movement parameters based on the detected actual temperature and the limit temperature of the work blank (200) provided to the control device (60). A machine tool (100) according to at least one of claim 11 or 12.

14. The machine tool (100) is further configured to additively manufacture workpieces, and for this purpose, the laser device (10) is configured for the additional material bonding coating of build-up material, and in particular the laser device (10) is a DED laser device. A machine tool (100) according to at least one of claims 11 to 13.

15. A control device (60) for the machine tool (100) according to one of claims 11 to 14.

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