Substrate preheating method, workpiece additive manufacturing method, machine tool and control equipment

Abstract

A method of preheating a substrate (200), in particular a metal substrate (200), by irradiation with a laser beam (L) for an additive manufacturing process is provided. The method comprises: detecting an actual temperature of the substrate (200), in particular by means of a thermal imaging camera (50); determining a motion parameter describing a relative motion between the laser beam (L) and the substrate (200) based at least on the detected actual temperature; and moving the laser beam (L) and the substrate (200) relative to each other at least as a function of the determined motion parameter, the incidence point (A) of the laser beam (L) being moved along the surface (201) of the substrate (200) to be irradiated.

Description

TECHNICAL FIELD

[0001] The present invention relates to a substrate preheating method, a workpiece additive manufacturing method, a machine tool and a control device for the machine tool. BACKGROUND

[0003] In recent years, additive manufacturing processes are increasingly important in the industrial production of workpieces, as they provide a particularly flexible and fast method for the initial shaping of workpieces.

[0004] The additive manufacturing processes in particular include cladding methods, also known as directed energy deposition (DED) methods. In this method, a build material is applied in a material-bonding manner to the surface of a workpiece blank, usually a substrate, using an energy beam (laser, electron beam or plasma arc), thereby forming a workpiece section.

[0005] In order to ensure that the workpiece quality is at the highest level, the workpiece blank can be preheated before cladding, thereby reducing the risk of material defects at the interface between the workpiece blank and the deposited material. The preheating is carried out under the premise of non-melting heating, so that the workpiece blank maintains its solid aggregate state and microstructure.

[0006] One of the preheating methods known from the prior art is the use of a heating furnace, in which the workpiece blank is preheated before the build-up welding. This requires a number of, in particular very time-consuming, steps in which the workpiece blank has to be transported from the heating furnace to the additive manufacturing machine tool and clamped, and then measured before the actual manufacturing begins.

[0007] Furthermore, WO2021099459A1 discloses a method for additive manufacturing of a workpiece by cladding, in which the workpiece is pre-deformed by a fixed irradiation of a laser beam to input thermal energy, in order to compensate for deformations in the subsequent cladding process.

[0008] Laser beam heating is a method that replaces the heating furnace and has fewer process steps. However, this method inevitably generates thermal stresses due to uneven heating of the workpiece blank; in WO2021099459A1, these thermal stresses are intentionally used to induce deformations. SUMMARY

[0009] It is an object of the present invention to provide a more efficient cladding additive manufacturing (DED method) which is characterized by fewer process steps and a higher manufacturing quality.

[0010] To achieve this object, the present invention proposes a preheating method according to claim 1, an additive manufacturing method according to claim 14, a machine tool according to claim 16 and a control device according to claim 22.

[0011] The remaining dependent claims relate to preferred embodiments of the method or machine tool, which can be provided individually or in combination.

[0012] According to a first aspect of the present application, a method for preheating a substrate, in particular a metal substrate, by irradiation with a laser beam for an additive manufacturing process is provided, comprising the steps of: detecting an actual temperature of the substrate, in particular by means of a thermal imaging camera; determining movement parameters describing a relative movement between the laser beam and the substrate based on at least the detected actual temperature; moving the laser beam and the substrate relative to each other in accordance with at least the determined movement parameters, wherein an impingement point of the laser beam moves along a surface of the substrate to be irradiated.

[0013] In other words, during irradiation of the substrate, the laser beam is moved relative to the substrate in accordance with the detected actual temperature, such that the impingement point is movable upon switching on of the laser beam, thereby enabling a locally distributed energy input into the substrate and precise control by relative kinematics.

[0014] In this way, the entire substrate can be preheated quickly and uniformly, despite the use of a point energy source, since the energy input of the laser beam is distributed to a large area of the substrate due to the movement of the laser beam. At the same time, the consideration of the detected actual temperature ensures that no local overheating occurs, thus avoiding unnecessary melting of the substrate material in extreme cases.

[0015] Essentially, the energy input is controlled by relative kinematics, i.e. by means of the movement parameters. For example, by setting the movement parameters, the relative speed is increased to reduce the energy input per area when the actual temperature approaches the melting point of the substrate, thus avoiding local overheating.

[0016] The method thus allows for a high energy input into the substrate, enabling uniform heating without local overheating. In this way, the substrate can be preheated quickly and uniformly without melting, which is not possible with punctual and stationary irradiation as shown in WO2021099459A1.

[0017] The uniform and rapid preheating of the substrate achieved in this way provides optimal initial conditions for the subsequent additive application of the build material in a material-bonding manner in the additive manufacturing. This reduces the risk of material defects or weak points, such as internal stresses, cracks due to non-uniform cooling as a result of non-uniform heating of the substrate, and porosities or gas inclusions, due to non-uniform preheating before the additive manufacturing.

[0018] As mentioned above, the method reliably avoids such material defects without increasing the process time (compared to the use of a heating furnace). Furthermore, the energy input of the laser is more precise than, for example, a heating furnace, thus helping to reduce energy costs.

[0019] The laser beam is preferably operated at a constant power, especially at the rated power range or at the maximum power, so as to maximize the energy input to the substrate per unit time and thus shorten the preheating time.

[0020] The substrate should be understood as a solid and complete entity (i.e., not in powder form), and the preheating should be understood as non-melting heating, during which the melting temperature of the substrate material should not be exceeded. In other words, the substrate to be preheated will always maintain its solid aggregated state.

[0021] The incident point of the laser beam is not a point in the mathematical sense, but refers to the area on the substrate surface that receives the energy input of the laser beam.

[0022] The surface to be irradiated is typically continuous, particularly a continuously differentiable surface, which may be defined by the edge of the substrate, and its area is particularly at least 5 times the focal area of ​​the laser beam used, preferably at least 10 times, and more preferably at least 50 times.

[0023] The temperature of the substrate is typically non-uniform; therefore, the detected actual temperature is preferably the maximum value of multiple detected actual temperatures at different locations on the substrate. Specifically, these temperature values ​​are obtained through measurements using a thermal imaging camera or an infrared thermal imager.

[0024] For the purposes of this method, motion parameters should be understood as any motion parameters suitable for describing the relative motion between the substrate and the laser beam, wherein the incident point of the laser beam moves on the surface of the substrate. For example, this can be relative displacement, velocity, or acceleration, particularly the relative displacement, velocity, or acceleration of the incident point on the irradiated surface, or it can be control parameters of the drive mechanism that realizes the relative motion, such as the control parameters of a CNC axis on a machine tool. The relative displacement, velocity, or acceleration can also be the average value of the relative motion, such that the relative motion is only intended to satisfy predetermined motion parameters on average.

[0025] Preferably, the actual temperature detection, determination of motion parameters, and relative motion between the laser beam and the substrate are repeated at least once, wherein the sequence of these steps can be understood as a heating cycle.

[0026] In other words, in this method, the laser beam is usually irradiated onto the surface to be irradiated multiple times. Before each irradiation, the current actual temperature is detected in advance, and the corresponding motion parameters are determined accordingly.

[0027] Preferably, the relative movement causes the incident point of the laser beam to move to cover at least 60% of the surface to be irradiated, preferably at least 80% or 90%, more preferably at least 95%, especially during a single heating cycle.

[0028] Therefore, for example, during a single heating cycle, the energy input to the surface to be irradiated can be increased and distributed as evenly as possible on the substrate.

[0029] During irradiation, the relative movement of the laser beam can be a continuous movement with a non-zero relative velocity, or it can be a segmented movement, wherein the incident point moves between predetermined points and stays at each predetermined point for a predetermined time.

[0030] This method is particularly suitable for machine tools, wherein the irradiation of the substrate is performed by a laser device within the machine tool that provides the laser beam. The machine tool includes at least one drive mechanism that enables relative movement between the laser beam and the substrate.

[0031] Here, the step of realizing the relative motion between the laser beam and the substrate includes controlling the at least one driving device according to determined motion parameters (in this example, the motion parameters are specifically feed parameters).

[0032] Preferably, preheating is performed while the substrate is already clamped, and the substrate can also be regarded as a workpiece blank. This allows additive manufacturing to begin directly after preheating without having to re-clamp the substrate.

[0033] In an alternative embodiment of the method according to the first aspect (particularly suitable for very small workpieces), the method includes: detecting the actual temperature of the substrate (particularly by means of a thermal imaging camera); fixing the substrate with a laser beam for irradiation; and controlling the laser beam according to the detected actual temperature, particularly including terminating irradiation when the detected actual temperature reaches a predetermined limit temperature. This method is particularly suitable if the workpiece is so small that movement of the laser on the surface to be irradiated is impossible. Furthermore, the method can also be implemented in the method described in the first aspect, which includes detecting the surface dimensions of the surface to be irradiated, and if the detected surface dimensions are smaller than a predetermined minimum dimension, setting the relative velocity between the laser and the substrate to zero.

[0034] In a preferred embodiment, the method further includes providing a limiting temperature for the preheating, the limiting temperature being particularly dependent on one or more material parameters of the substrate; wherein the determination of the motion parameters is based at least on the detected actual temperature and the provided limiting temperature. This limiting temperature preferably depends on the melting point of the substrate and should not be exceeded during preheating.

[0035] In this way, by simultaneously considering the current temperature and maximum permissible temperature of the substrate when controlling the relative motion of the laser beam, the required energy input to the substrate during relative motion (especially during heating cycles) can be determined, for example, based on the difference between these two values. Therefore, with a constant laser beam power, as the difference between the two values ​​decreases, the relative velocity between the laser beam and the substrate increases, thereby reducing the energy input during relative motion, and thus the motion parameters can be determined.

[0036] In a preferred embodiment, the calculation is also based on the power parameters of the laser beam and / or the area of ​​the incident point of the laser beam and / or the absorptivity of the substrate.

[0037] In this way, the energy input to the substrate can be estimated more accurately, and motion parameters can be set to achieve maximum energy input without local overheating.

[0038] In a preferred embodiment, the motion parameter is a velocity parameter describing the relative velocity of the laser beam relative to the substrate, particularly the relative velocity of the incident point.

[0039] Thus, the energy input to the substrate is essentially determined by this relative velocity. This velocity parameter can be a constant or average relative velocity, particularly the feed rate of the laser device providing the laser beam.

[0040] In a preferred embodiment, the method further includes: providing a preheating path extending on the surface of the substrate to be irradiated; wherein the relative movement of the laser beam and the substrate also depends on the provided preheating path, such that the incident point moves along the provided preheating path on the surface of the substrate to be irradiated.

[0041] The preheating path here describes the path on the surface to be irradiated, which can be described as a set of points or a line, for example (but not limited to).

[0042] The motion parameters here can be understood as being designed for the preheating path; therefore, as a speed parameter, it specifies, for example, the speed at which the object moves along the preheating path.

[0043] 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.

[0044] The inventors discovered that this design enables a particularly uniform heat distribution because, as motion continues, energy input concentrates at the center and is conducted from the center through the substrate to the outer regions. Furthermore, the spiral shape allows the time between heating cycles in which the substrate is not irradiated (especially in the case of multiple heating cycles) to remain at a low level.

[0045] In a preferred embodiment, providing a preheating path includes the following sub-steps: determining the preheating path extending on the surface of the substrate to be irradiated, the preheating path depending at least on the shape and / or size of the surface to be irradiated and / or the diameter of the incident point of the laser beam.

[0046] Therefore, an optimal preheating path can be determined for a specific substrate, preferably in which each surface point is irradiated by the laser beam as it passes through the path.

[0047] Preferably, the distance between adjacent segments of the preheating path is selected to correspond to the diameter of the incident point, so that the entire surface to be irradiated is covered by the laser beam as much as possible when the laser beam passes through the preheating path.

[0048] In a preferred embodiment, the method includes multiple heating cycles as described above. Each step of the heating cycle can be designed according to each of the preferred embodiments described above.

[0049] In a preferred embodiment, the determination of the motion parameters in the nth heating cycle is also based on the motion parameters determined in the (n-1)th heating cycle.

[0050] In this way, the motion parameters are recursively determined, where the motion parameters of the previous heating cycle can be adjusted by a correction factor.

[0051] In a preferred embodiment, the determination of the motion parameters in the nth heating cycle is based on the motion parameters determined in the (n-1)th heating cycle and the difference between the provided limit temperature and the actual temperature detected from the nth heating cycle.

[0052] This special recursive adaptive form can simply and reliably implement the maximum energy input strategy described in this invention without causing local overheating.

[0053] If the motion parameter is a velocity parameter describing relative velocity, then this recursive assignment can be expressed as (for example, but not limited to) the following: [Formula 1]

[0054] Among them, v n and v n 1. Describe the relative velocities in the nth and (n-1th)th heating cycles, respectively, where α is an arbitrary adaptive factor, and T... G Corresponding to the set limit temperature, T Ist This corresponds to the actual temperature detected at the start of the nth heating cycle.

[0055] To account for technological limitations, such as the maximum speed of the drive mechanism used to achieve relative motion, especially when T G Approaching T Ist,n In this case, it is appropriate to integrate Formula 1 into the recursive assignment rule that distinguishes cases based on Formula 2: [Formula 2]

[0056] v here max This describes the maximum achievable or attainable relative velocity. If the relative velocity v is recursively determined... n Reaching v max If the value is fixed, it will be fixed at that value and will not be higher than that value.

[0057] In a preferred embodiment, the method further includes providing a target temperature and terminating preheating when the actual temperature is detected to be higher than the set target temperature.

[0058] Therefore, a target standard can be defined, and the preheating is completed.

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

[0060] If recursive assignment is used, the operator can estimate or specify the motion parameters for the first heating cycle.

[0061] In one exemplary embodiment, during the relative motion between the laser beam and the substrate, the incident point of the laser beam coincides with the focal point of the laser beam, particularly in cases where a backward beam expander (i.e., a beam reducer, used to reduce the original beam before the focusing lens) is used in a laser device for this purpose.

[0062] In a preferred embodiment, the method is performed on an additive manufacturing machine tool, wherein the laser beam is provided by the machine tool's laser equipment (particularly a DED laser equipment).

[0063] Therefore, additive manufacturing can be performed directly after preheating without re-clamping the substrate used as the workpiece blank.

[0064] In a preferred embodiment, the method includes fixing the substrate in the clamping device of a machine tool, or clamping the substrate onto a workpiece carrier and fixing the workpiece carrier in the clamping device of the machine tool.

[0065] Preferably, the method further includes the following steps: adjusting the power parameters of the laser beam at least according to the detected actual temperature, and / or adjusting the distance between the incident point and the focal point of the laser beam.

[0066] By further adjusting variables that can prevent overheating, process control during preheating can be expanded, especially when the workpiece size is small, as the maximum power of the laser beam may cause the substrate to melt directly.

[0067] According to a second aspect, a method for additive manufacturing of a workpiece is provided, the method comprising: preheating a workpiece blank using the method of the first aspect or one of its preferred embodiments, and depositing at least one portion of the workpiece to be manufactured by additively applying deposited material to the preheated workpiece blank in a material bonding manner.

[0068] Therefore, the present invention provides an additive manufacturing method in which a workpiece blank is uniformly, rapidly and reliably preheated for additive manufacturing.

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

[0070] Therefore, additive manufacturing can eliminate the need for other laser equipment. For example, the entire process can be completed on a machine tool equipped with only one laser device, which can reduce manufacturing time and production costs.

[0071] According to a third aspect, a machine tool is provided, comprising: a laser device; a workspace; a clamping device disposed within the workspace for clamping a workpiece blank or a workpiece holder carrying the workpiece blank; one or more drive devices (particularly CNC drive devices) by which the laser device and the clamping device are movable relative to each other; a temperature measuring device (particularly a thermal imaging camera) for detecting the temperature of the workpiece blank located within the workspace; and a control device for controlling the machine tool. The machine tool is configured to preheat the workpiece blank received within the clamping device and / or the workpiece blank carried by the workpiece holder received within the clamping device (particularly a metal workpiece blank) by irradiation with a laser beam from the laser device. For this purpose, the control device is configured to determine motion parameters describing the relative motion between the laser beam and the workpiece blank, at least based on the actual temperature of the workpiece blank detected by the temperature measuring device, and to control one or more drive devices of the machine tool according to the determined motion parameters during the irradiation of the workpiece blank by the laser beam. The motion parameters are determined when the laser beam irradiates the workpiece blank, wherein the incident point of the laser beam moves along the surface of the workpiece blank to be irradiated.

[0072] Therefore, the machine tool configuration according to the present invention is used to implement the above-described preheating method, and its related advantages will not be repeated here.

[0073] In a preferred embodiment, a path dataset is provided to a control device, which describes a preheating path extending across the surface of a workpiece blank to be irradiated. The control device is configured to control one or more drive mechanisms such that, during workpiece irradiation, the incident point moves along the preheating path described by the path dataset.

[0074] In a preferred embodiment, the control device is configured to predetermine the path dataset based at least on data provided to the control device regarding the shape and / or size of the surface to be irradiated and / or the diameter of the incident point of the laser beam, particularly such that the preheating path described by the path dataset extends 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 motion parameters based on the detected actual temperature and the limit temperature of the workpiece blank provided to the control device.

[0076] In a preferred embodiment, the motion parameter is a velocity parameter used to describe the relative velocity of the laser beam with respect to the substrate, particularly the relative velocity of the laser beam incident point.

[0077] In a preferred embodiment, the machine tool is also configured for additive manufacturing of workpieces, and for this purpose, the laser device is configured to additively apply deposited material in a material bonding manner, and in particular, the laser device is a DED laser device.

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

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

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

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

[0082] According to a fourth aspect, a control device for a machine tool according to a third aspect or preferred embodiment is provided. This control device is configured at least to: control the machine tool and preheat a workpiece blank received within a clamping device and / or a workpiece blank carried by a workpiece carrier received within the clamping device, particularly a metal workpiece blank, by irradiation with a laser beam from the laser device. To this end, the control device is configured to determine motion parameters describing the relative motion between the laser beam and the workpiece blank, at least based on the actual temperature of the workpiece blank detected by the temperature measuring device, and to control one or more drive mechanisms of the machine tool according to the determined motion parameters during the irradiation of the workpiece blank by the laser beam. The incident point of the laser beam moves along the surface of the workpiece blank to be irradiated.

[0083] Thus, existing machine tools (which, except for the control equipment, already contain all the components according to the third aspect of the present invention) can be improved into the machine tools described in the present invention.

[0084] Other aspects and advantages of the above-described aspects and embodiments, as well as more specific exemplary embodiments, will be described below with the aid of the accompanying drawings.

[0085] Figure 1 A flowchart illustrating an exemplary embodiment of the preheating method according to the present invention is shown.

[0086] Figure 2 A flowchart illustrating an exemplary embodiment of the additive manufacturing method according to the present invention is shown.

[0087] Figure 3 The trajectory of the incident point is shown in an exemplary embodiment of the preheating method according to the present invention.

[0088] Figure 4 A schematic diagram showing the distribution of several process parameters according to an exemplary embodiment of the preheating method of the present invention is shown.

[0089] Figure 5 A schematic diagram of an exemplary embodiment of a machine tool according to the present invention is shown.

[0090] It should be emphasized that the present invention is not limited to the exemplary embodiments and features described below. The present invention also includes modifications to the exemplary embodiments, particularly modifications made by modifying and / or combining one or more features of the exemplary embodiments within the scope of the independent claims.

[0091] Detailed description of the attached figures Figure 1 A flowchart of an exemplary method for preheating a substrate by laser beam irradiation according to the present invention is shown.

[0092] In step S1, a limit temperature and a target temperature are set for the method. The target temperature is the temperature to be reached during the preheating process, and the limit temperature is the temperature that must not be exceeded when the substrate material begins to melt.

[0093] In step S2, a preheating path is provided on the surface of the substrate to be irradiated, and the incident point of the laser beam will move along this path.

[0094] Repeat steps S3 to S6. The sequence of these steps can be summarized as a heating cycle Hi, which is repeated multiple times.

[0095] In step S3, the actual temperature of the substrate to be preheated is detected, particularly by using a thermal imaging camera.

[0096] In step S4, the detected actual temperature is compared with the target temperature set in step S1. If the substrate reaches the target temperature, step S7 is executed directly, and the preheating process terminates.

[0097] Otherwise, proceed to step S5, whereby motion parameters describing the relative motion between the laser beam and the substrate are determined based on the actual temperature detected in step S3 and the limit temperature set in step S1. Specifically, these motion parameters are velocity parameters describing the relative speed between the laser beam and the substrate.

[0098] In step S6, the laser beam is moved relative to the substrate according to the preheating path provided in step S2 and the motion parameters determined in step S5. During this process, the incident point of the laser beam moves along the preheating path on the surface of the substrate to be irradiated at a relative velocity (specifically specified by the velocity parameters).

[0099] If the preheating path has been traversed, step S6 ends and a new heating cycle begins from step S3.

[0100] Through the above procedure, in each heating cycle, the energy input to the substrate is controlled at least according to the detected actual temperature, which affects the relative motion of the laser beam and the substrate through motion parameters determined based on this temperature.

[0101] In this way, the substrate can be rapidly and uniformly preheated to the desired target temperature without the risk of localized overheating, where energy input can be precisely controlled, particularly through relative kinematics. Furthermore, energy costs are significantly reduced compared to preheating using a furnace, because the laser energy input can be much more precise.

[0102] It is particularly advantageous that the above method is implemented on a machine tool, wherein step S6 preferably includes the following sub-step: controlling at least one drive device of the machine tool according to the motion parameters determined in step S3, thereby realizing the relative motion between the laser beam and the substrate.

[0103] Figure 2 A flowchart illustrating an exemplary embodiment of the additive manufacturing method for a workpiece according to the present invention is shown.

[0104] The method includes steps S1 to S7, for determining according to Figure 1 The substrate is preheated; in this example, the substrate corresponds to the workpiece blank. Steps S1 to S7 will not be described in detail here.

[0105] After preheating is completed in step S7, step S8 involves additively applying material to the preheated workpiece blank in a material bonding manner to deposit at least one part of the workpiece to be manufactured.

[0106] Therefore, the present invention provides an additive manufacturing method in which a workpiece blank is uniformly, rapidly and reliably preheated for additive manufacturing, thereby particularly reducing the risk of internal stress or cracks, as well as pores or gas inclusions in the workpiece.

[0107] Figure 3 An exemplary motion trajectory of the incident point A is shown in an exemplary embodiment of the method of preheating substrate 200 according to the present invention.

[0108] In this method, the laser beam moves relative to the substrate 200 such that the incident point A of the laser beam moves relative to the substrate 200 along the surface 201 to be irradiated.

[0109] Energy is thus input through the surface 201, which is defined by the outer edge 202.

[0110] The diameter of the incident point A is d A It moves along the preheating path P, which is located on the surface 201 to be irradiated, from the starting point P0 to the ending point P0. end For example, the figure shows the positions A0 and A1 of the incident point A at the initial moment and at subsequent moments during the relative movement.

[0111] According to the present invention, the relative movement of the incident point A on the irradiated surface 201 depends on predetermined motion parameters, which are themselves determined by the detected actual temperature. For example, this parameter can be a velocity parameter, used to specify the relative velocity of the incident point A as it moves along the preheating path P.

[0112] The preheating path P extends in a spiral shape from the outer region 201a of the surface to be irradiated 201 to the central region 201b of the surface to be irradiated 201, thereby achieving particularly efficient energy input.

[0113] Preferably, in this method, the laser beam passes through the preheating path P multiple times in each heating cycle, wherein the relative kinematics during the heating cycle, by means of motion parameters, depends on the actual temperature of the substrate 200 detected at the start of the heating cycle.

[0114] When selecting the preheating path P, the distance between adjacent segments of the preheating path should approximately correspond to the diameter d of the incident point A. A This ensures that the entire surface 201 to be irradiated is covered by the laser beam as much as possible while passing through the preheating path P.

[0115] Figure 4 An example distribution of several process parameters according to an exemplary embodiment of the preheating method of the present invention is shown.

[0116] The substrate needs to be heated here, but the specified limit temperature T should not be exceeded. G .

[0117] As described in the summary section of the specification, the relative motion between the laser beam and the substrate is based on the detected actual temperature T. Ist The motion parameters are controlled, and in this example, these motion parameters correspond to the velocity parameters of the relative velocity between the specified laser beam or its incident point and the substrate, particularly the feed parameters.

[0118] This figure shows the changes of multiple heating cycles (one bar for each heating cycle) over time t, as well as the relative velocity or feed rate between the laser beam and the substrate, in the form of a bar chart.

[0119] The maximum relative speed is limited by the drive mechanism used to achieve the relative motion.

[0120] As shown in the figure, the initial stage has a relatively low velocity in order to input higher energy to the substrate.

[0121] With the actual temperature T Ist As the temperature increases, the relative velocity also increases, because the actual temperature T of the substrate increases. Ist Approaching the limit temperature T G To avoid overheating and achieve uniform heating, the energy input for each heating cycle is reduced.

[0122] Figure 5 This is a schematic diagram of an exemplary embodiment of a machine tool 100 according to an embodiment of the present invention.

[0123] The machine tool 100 includes: a laser device 10, a workspace 20, a clamping device 30 located within the workspace 20 for clamping a workpiece blank 200 or a workpiece bracket (not shown in the figure) that carries the workpiece blank, and a plurality of CNC drive devices 41, 42. The laser device 10 can be moved relative to the clamping device 30 by these drive devices. In this example, the laser device 10 can be moved in the X and Y directions on a horizontal plane.

[0124] In addition, the machine tool 100 includes a thermal imaging camera 50 used as a temperature measuring device, and a control device 60 for controlling the machine tool 100. The thermal imaging camera 50 is used to detect the temperature of the workpiece blank 200 located in the workspace 20.

[0125] Machine tool 100 is at least configured to perform the workpiece blank preheating method described in the first aspect. This method aims to preheat a workpiece blank 200 held in device 30 by irradiation with a laser beam L from laser device 10. To achieve this, control device 60 is configured to perform the following operations: determine motion parameters describing the relative motion between the laser beam and the workpiece blank 200, based at least on the actual temperature of the workpiece blank 200 detected by thermal imaging camera 50; and, during the irradiation of the workpiece blank 200 with the laser beam, control the drive devices 41, 42 of machine tool 200 according to the determined motion parameters, thereby moving the incident point of the laser beam along the surface of the workpiece blank 200 to be irradiated (see also...). Figure 3 ).

[0126] Therefore, the machine tool 100 is configured to implement the above-mentioned preheating method, which can quickly and uniformly preheat the workpiece blank 200 without the risk of local overheating.

[0127] Preferably, the laser device 10 is a DED laser device so that after preheating, the workpiece blank does not need to be released from the clamping device 30 beforehand, that is, the accumulated material is additively applied to the workpiece blank in a material bonding manner.

[0128] Exemplary embodiments of the present invention and their advantages have been described in detail above with reference to the accompanying drawings.

[0129] To reiterate, this invention is not limited to the exemplary embodiments and their implementations described above. This invention also includes modifications to the exemplary embodiments, particularly modifications resulting from changes and / or combinations of one or more features of the exemplary embodiments within the scope of the independent claims.

[0130] Reference tag list 10. Laser equipment 20 Workspaces 30 Clamping devices 41. CNC X-axis drive device 42 CNC Y-axis drive device 50 thermal imaging cameras 60 Control equipment 100 machine tools 200 workpiece blanks 201 Surface to be irradiated 201a Outer region of the surface to be irradiated 201b Central region of the surface to be irradiated 202 Edge of the surface to be irradiated A. Incident point of the laser beam L laser beam P Preheating Path

Claims

1. A method for preheating a substrate (200), particularly a metal substrate (200), by laser beam (L) irradiation for use in an additive manufacturing process, comprising the following steps: a) Detect the actual temperature of the substrate (200), particularly by means of a thermal imaging camera (50); b) Determine the motion parameters describing the relative motion between the laser beam (L) and the substrate (200) based at least on the actual temperature detected; The motion parameters are preferably velocity parameters describing the relative velocity of the laser beam (L) relative to the substrate (200), particularly the relative velocity of the incident point (A) of the laser beam (L); and c) Move the laser beam (L) and the substrate (200) relative to each other at least according to the determined motion parameters, wherein the incident point (A) of the laser beam (L) moves along the surface (201) of the substrate (200) to be irradiated.

2. The method according to claim 1, wherein, The method also includes: The preheating limit temperature is provided, which in particular depends on one or more material parameters of the substrate (200); wherein, The determination of the motion parameters is based at least on the detected actual temperature and the provided limit temperature.

3. The method according to claim 1 or 2, wherein, The determination of the motion parameters is also based on the power 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 (200).

4. The method according to at least one of claims 1 to 3, wherein, The method also includes: A preheating path (P) is provided, the preheating path (P) extending on the surface (201) of the substrate (200) to be irradiated, particularly spirally extending from the outer region (201a) of the surface (201) to the central region (201b) of the surface (201); wherein, The relative movement of the laser beam (L) and the substrate (200) also depends on the provided preheating path (P), such that the incident point (A) moves along the provided preheating path (P) on the surface (201) of the substrate (200) to be irradiated, and wherein, Providing the preheating path (P) preferably includes the following sub-steps: Determine the preheating path (P) extending on the surface (201) of the substrate (200) to be irradiated, the preheating path depending at least on the shape and / or size of the surface (201) to be irradiated and / or the diameter of the incident point (A) of the laser beam (L).

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

6. The method of claim 5, wherein, The determination of motion parameters in the nth heating cycle is also based on the motion parameters determined in the (n-1)th heating cycle.

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

8. The method according to at least one of claims 1 to 7, wherein, The method further includes: Provide the target temperature; If the actual temperature is detected to be higher than the provided target temperature, preheating is terminated.

9. The method according to at least one of claims 1 to 8, wherein: The method is performed on a machine tool (100) for additive manufacturing, wherein the laser beam (L) is provided by a laser device (10) of the machine tool (100), particularly a DED laser device; and wherein: The step of moving the laser beam (L) and the substrate (200) relative to each other further includes: controlling at least one drive device of the machine tool (100) according to the determined motion parameters; and wherein: The method preferably includes: The substrate (200) is fixed in the clamping device (30) of the machine tool (100); or The substrate (200) is clamped onto the workpiece holder, and the workpiece holder is fixed in the clamping device (30) of the machine tool (100).

10. A method for additive manufacturing a workpiece, comprising: The workpiece blank (200) is preheated using the method according to at least one of claims 1 to 9. as well as At least one portion of the workpiece to be manufactured is deposited by additively applying material in a material-bonding manner onto a preheated workpiece blank, preferably using a DED laser method. The laser beam (L) used for the preheating and the laser beam (L) used for the DED laser method are preferably provided by the same laser device (10).

11. A machine tool (100), comprising: Laser equipment (10); Workspace (20); A clamping device (30) is provided in the workspace (20) and is used to clamp a workpiece blank (200) or a workpiece bracket that carries the workpiece blank; One or more drive devices (41, 42), particularly CNC drive devices (41, 42), through which the laser device (10) and the clamping device (30) are movable relative to each other; A temperature measuring device (50) for detecting the temperature of a workpiece blank (200) located within a workspace (20), and in particular, said temperature measuring device is a thermal imaging camera (50); and Control device (60) for controlling the machine tool (100); wherein, The machine tool (100) is configured to preheat the workpiece blank received in the clamping device (30) and / or the workpiece blank carried by the workpiece carrier received in the clamping device (30), particularly the metal workpiece blank, by irradiation of the laser beam (L) of the laser device (10). For this purpose, the control device (60) is configured to determine motion parameters describing the relative motion between the laser beam (L) and the workpiece blank (200) based at least on the actual temperature of the workpiece blank (200) detected by the temperature measuring device (50), and to control one or more drive devices (41, 42) of the machine tool (100) according to the determined motion parameters during the period when the laser beam (L) irradiates the workpiece blank (200). The incident point (A) of the laser beam (L) moves along the surface (201) of the workpiece blank (200) to be irradiated; The motion parameters are preferably velocity parameters that describe the relative velocity of the laser beam (L) relative to the substrate (200), and in particular the relative velocity of the incident point (A).

12. The machine tool (100) according to claim 11, wherein, A path dataset is provided to the control device (60), the path dataset describing a preheating path (P) extending on the surface (201) of the workpiece blank (200) to be irradiated; wherein, The control device (60) is configured to control one or more drive devices such that, during irradiation of the workpiece blank (200), the incident point (A) moves along the preheating path (P) described by the path dataset; wherein, The control device (60) is preferably configured to predetermine the path dataset based at least on data provided to the control device (60) regarding the shape and / or size of the surface (201) to be irradiated and / or the diameter of the incident point (A) of the laser beam (L), in particular such that the preheating path (P) described by the path dataset 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.

13. The machine tool (100) according to at least one of claims 11 or 12, wherein: The control device (60) is configured to determine motion parameters based on the detected actual temperature and the limit temperature of the workpiece blank (200) provided to the control device (60).

14. The machine tool (100) according to at least one of claims 11 to 13, wherein: The machine tool (100) is also configured to manufacture workpieces by additive manufacturing, for which the laser device (10) is configured to apply stacked material additively in a material bonding manner, and in particular, the laser device (10) is a DED laser device.

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

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