Measurement of molten pool position in additive manufacturing

Abstract

To provide an additive manufacturing device.SOLUTION: An additive manufacturing device comprises a light source, a material supply device, a first photodetection device for detecting radiation from the molten pool, and a detector for measuring an output related to the temperature of the molten pool, and detects information related to the height of the molten pool based on the output of the first photodetection device and the output of the detector. A plurality of detectors is positioned along a tilted optical axis to detect optical radiation from a work surface. Variations in the detected optical power is used to estimate the work surface position along the work surface axis. The detected optical power can be radiated from the work surface, and the estimated temperature of the work surface is used to adjust the detected optical power. One or two single element detectors or linear detectors may be used. A position of a focused spot produced from the optical power detected at the linear detector can be used to assess the axial position of the work surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to evaluating material deposition in additive manufacturing. [Background technology]

[0002] Some additive manufacturing systems use a laser processing beam to create a molten pool into which additional material is directed. This material is incorporated into the molten pool, increasing the height of the part being built. It is desirable to have a measurement of the part height. Therefore, an improved approach is needed. Summary of the Invention

[0003] A representative apparatus includes tracking optics positioned along a tracking axis, the tracking optics including at least one focusing element and at least one photodetector. The at least one focusing element is positioned to receive optical radiation from the weld pool and direct the received optical radiation to the photodetector. The tracking axis is tilted relative to the processing axis, and the photodetector includes at least one single-pixel or linear photodetector. The photodetector is connected to the photodetector and is operable to generate a tracking signal related to the position of the weld pool along the processing axis based on the received optical radiation directed to the photodetector. In some examples, the tracking axis is tilted at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, or 90 degrees relative to the processing axis. In a typical example, the optics further includes an aperture plate positioned to attenuate the received optical radiation toward the photodetector, and the at least one optical element is a lens positioned to focus the optical radiation received from the weld pool proximate the aperture plate. In some representative examples, the aperture plate defines a circular aperture, a rectangular aperture, a slit, or two or more aperture edges. In some cases, the aperture plate is positioned to block 20% to 80% of the received optical radiation from the focusing element, such that beam displacements in opposite directions produce opposite changes in received optical power at the photodetector. In some examples, the processing beam source is operable to generate the processing beam, and the positioning element is responsive to a tracking signal to adjust the relative position of the weld pool and the tracking axis. In some examples, the positioning element is a stage operable to adjust the position of the weld pool along the processing axis.

[0004] According to additional examples, the at least one detector of the tracking optics includes a first detector and a second detector, and the receiver is operatively positioned to generate corresponding first and second tracking signals related to the position of the weld pool along the processing axis based on the portion of the received optical radiation. The first and second tracking signals are configured to have opposite slopes relative to changes in the position of the weld pool along the processing axis. In a convenient example, the optics further includes first and second aperture plates positioned to attenuate the received optical radiation toward the first and second optical detectors, respectively. In some examples, the at least one optical detector is a linear array, and the receiver is coupled to the optical detector and operative to generate a tracking signal related to the position of the weld pool along the processing axis based on the position at which the received optical radiation is incident on the optical detector. In some embodiments, the position of the weld pool along the processing axis is based on the centroid of the intensity pattern of the radiation incident on the optical detector.

[0005] In some examples, the processing beam source is operable to generate the processing beam, and the positioning element is responsive to the tracking signal to adjust the relative position of the weld pool and the tracking axis. In a representative example, the beam splitter is positioned to direct first and second portions of the received radiation to corresponding first and second ranges of the linear detector array. According to some embodiments, the first and second portions of the received radiation are different spectral portions, and the beam splitter is a dichroic beam splitter that selectively directs the different spectral portions to the corresponding first and second ranges of the linear detector array. In further examples, the beam splitter is positioned to direct the first and second portions of the received radiation to corresponding first and second ranges of the linear detector array that are spaced apart as the distance to the weld pool increases.

[0006] A typical system includes a processing beam source positioned to direct a processing beam along a processing axis toward a working area of ​​the substrate, thereby focusing the processing beam at the working area. An optical focus sensor positioned to receive optical radiation from the working area in response to the processing beam along an axis tilted relative to the processing axis and to establish a position of the processing beam focus relative to the working area. The optical focus sensor includes at least one of a single pixel detector and a linear detector positioned to receive the optical radiation.

[0007] The method includes receiving optical radiation from a working area of ​​a substrate along a tracking axis that is tilted relative to a substrate axis perpendicular to the working area. The power of the optical radiation received from the working area and transmitted by an aperture positioned along the tracking axis is measured. A displacement of the working area along the substrate axis is estimated based on the measured power. In some cases, the displacement of the working area is adjusted or one or more processing conditions are modified based on the displacement. In a typical example, the optical radiation from the working area is generated by irradiating the working area with a processing beam or is a portion of a tracer beam directed toward the working area. In a further example, the displacement of the working area is adjusted by moving the working area along the substrate axis or by adjusting a processing beam directed toward the working area. In some examples, the optical radiation is associated with a melt pool generated by the processing beam, such as blackbody radiation or other radiation generated based on the temperature of the melt pool. In an additional example, the temperature of the melt pool is estimated and the measured power is adjusted based on the estimated temperature, wherein the displacement of the working area along the substrate axis is determined based on the adjusted measured power. In another exemplary embodiment, measuring the power includes measuring first and second powers of optical radiation received from the working region and transmitted by first and second apertures positioned along the tracking axis, wherein a displacement of the working region along the substrate axis is determined based on the first and second powers.

[0008] An additional exemplary method includes receiving optical radiation from a working area of ​​a substrate along a tracking axis that is tilted relative to a substrate axis that is normal to the working area, and directing the received optical radiation to a linear detector, wherein a displacement of the working area along the substrate axis is determined based on the location at which the received optical radiation is incident on the linear detector, and a displacement of the working area or a processing condition is adjusted.

[0009] The detection device for detecting the molten pool generated by the processing beam includes a first light-receiving device that receives first radiation emitted from the molten pool along a first axis and a second light-receiving device that receives second radiation emitted from the molten pool along a second axis tilted relative to the first axis. The first light-receiving device may include a first focusing optical system that focuses the first radiation and a first photodetector that photoelectrically converts the focused first radiation. The first light-receiving device may include an aperture member defining an aperture positioned at a position where the first radiation is focused by the first focusing optical system, and the first photodetector receives the first radiation that passes through the aperture of the aperture member. The first photodetector may include a linear detector positioned at a position where the first radiation is focused by the first focusing optical system and may include photoelectric conversion elements arranged in a one-dimensional direction. In some examples, a first angle formed by the propagation axis of the processing beam and the first axis is greater than a second angle formed between the propagation axis of the processing beam and the second axis. In a further example, the second angle formed between the processing beam's propagation axis and the second axis is different from a third angle formed between the processing beam's propagation axis and the axis of specular reflection from the molten pool. In an additional example, the second angle formed between the processing beam's propagation axis and the second axis is smaller than the third angle formed between the processing beam's propagation axis and the axis of specular reflection from the molten pool. According to this disclosure, the second angle formed between the processing beam's propagation axis and the second axis is larger than the third angle formed between the processing beam's propagation axis and the axis of specular reflection from the molten pool. In a typical example, the second axis is slightly tilted from the processing beam's propagation axis. The second axis may be substantially parallel to the processing beam's propagation axis. In an example, a folding element is disposed in the processing beam's optical path to bend the second axis. The second radiation may be received by a second light receiving device via the folding element.

[0010] In a further example, the detection device of claim 29 includes a controller, a first light-receiving device including a first photodetector that photoelectrically converts the first radiation, and a second light-receiving device including a second photodetector that photoelectrically converts the second radiation, and the controller calculates a first output from the first photodetector and a second output from the second photodetector. In some examples, the controller obtains dimensions of the weld pool based on the first output and the second output. The dimensions of the weld pool include at least one of a height of the weld pool and a size perpendicular to the height direction of the weld pool. In a further example, a processing device that processes a workpiece by forming a weld pool on the workpiece with a processing beam includes the detection device. In some examples, the characteristic-altering device is positioned to alter a characteristic of the processing beam, such as beam shape, size, power, polarization state, propagation direction, or other characteristic, based on an output from the characteristic-altering device. The material supplying device is positioned to supply one or more materials to the weld pool. The processing device may build an object on the workpiece by supplying material to the weld pool.

[0011] The foregoing and other features and advantages of the present disclosure will become more apparent from the following detailed description which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 shows a typical additive manufacturing system (AMS) including an optical height sensor. [Figure 2A] FIG. 2A shows a portion of an AMS including an optical height sensor and an optical weld pool temperature sensor. [Figure 2B] FIG. 2B shows a typical beam splitter used in the optical height sensor of FIG. 2A. [Figure 2C] FIG. 2C is a graph showing detected optical power as a function of aperture position for the exemplary optical height sensor of FIG. 2A. [Figure 2D]FIG. 2D shows a typical arrangement of the processing beam axis and the temperature sensor axis. [Figure 2E] FIG. 2E shows a typical arrangement of the processing beam axis and the temperature sensor axis. [Figure 2F] FIG. 2F shows a typical arrangement of the processing beam axis and the temperature sensor axis. [Figure 2G] FIG. 2G shows a typical arrangement of the processing beam axis and the temperature sensor axis. [Figure 2H] FIG. 2H shows a typical arrangement of the processing beam axis and the temperature sensor axis. [Figure 3A] FIG. 3A is a diagram illustrating a portion of an AMS that includes an optical height sensor that includes dual photodetectors and respective apertures. [Figure 3B] FIG. 3B is a graph showing detected optical power as a function of aperture position for each of the dual detectors of the exemplary optical height sensor of FIG. 3A. [Figure 3C] FIG. 3C is a graph showing detected optical power as a function of aperture position for each of the dual detectors of the exemplary optical height sensor of FIG. 3A. [Figure 4A] FIG. 4A illustrates a portion of an AMS that includes an optical height sensor that includes a linear detector array. [Figure 4B] FIG. 4B is a diagram illustrating the transmission of the beam on the linear detector array of FIG. 4A as a function of height variation. [Figure 4C] FIG. 4C shows a linear detector array and a cylindrical lens that increases the optical power for the linear detector array. [Figure 5A] FIG. 5A illustrates a portion of an AMS that includes an optical height sensor that includes a linear detector array positioned to receive dual detection beams. [Figure 5B] FIG. 5B shows the focused spot position on the linear detector array of FIG. 5A for two different heights. [Figure 5C] FIG. 5C is a diagram illustrating the optical power at the linear detector array of FIG. 5A. [Figure 5D]FIG. 5D is a diagram illustrating the optical power at the linear detector array of FIG. 5A. [Figure 6A] FIG. 6A shows a portion of an AMS that includes an optical height sensor with a linear detector array positioned to receive dual detection beams with crossed optical paths. [Figure 6B] FIG. 6B is a diagram illustrating the focused spot positions on the linear detector array of FIG. 6A for different heights. [Figure 6C] FIG. 6C is a diagram illustrating the focused spot position on the linear detector array of FIG. 6A for different heights. [Figure 6D] FIG. 6D is a diagram illustrating the optical power at the linear detector array of FIG. 6A for the focused spot shown in FIG. 6C. [Figure 7] FIG. 7 illustrates an exemplary build method including the optical height sensor disclosed herein. [Figure 8] FIG. 8 illustrates a calibration method for using on-axis and off-axis signal pixel photodetectors to make height measurements on the weld pool. [Figure 8A] FIG. 8A illustrates a calibration method for using on-axis and off-axis signal pixel photodetectors to measure height for the weld pool. [Figure 8B] FIG. 8B illustrates a calibration method for using on-axis and off-axis signal pixel photodetectors to measure height for the weld pool. [Figure 8C] FIG. 8C illustrates a calibration method for using on-axis and off-axis signal pixel photodetectors to make height measurements on the weld pool. [Figure 9] FIG. 9 illustrates an additive manufacturing method using the disclosed methods and apparatus for height sensing. DETAILED DESCRIPTION OF THE INVENTION

[0013] As used in this application and in the claims, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise. Additionally, the term "includes" means "comprises." Furthermore, the term "coupled" does not exclude the presence of intermediate elements between the coupled items.

[0014] The systems, devices, and methods described herein should not be construed as limiting in any way. Instead, this disclosure is directed to all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and subcombinations with one another. The disclosed systems, methods, and devices are not limited to any particular aspect or feature or combination thereof, nor are the disclosed systems, methods, and devices required for any one or more particular benefits to exist or problems to be solved. While a theory of operation is provided for ease of explanation, the disclosed systems, methods, and devices are not limited to such a theory of operation.

[0015] Although some actions of the disclosed methods are described in a particular order for convenience, it should be understood that the methods of this description encompass reordering, unless the specific order is required by specific language defined below. For example, actions described sequentially may, in some cases, be reordered or performed simultaneously. Moreover, for simplicity, the accompanying figures may not show the various ways in which the disclosed systems, methods, and apparatuses can be used in conjunction with other systems, methods, and apparatuses. In addition, the description sometimes uses terms such as "produce" and "provide" to describe the disclosed methods. These terms are high-level abstractions of actual actions that are performed. The actual actions corresponding to these terms may vary depending on the particular implementation and are readily discernible by those skilled in the art.

[0016] For convenience in the following description, the terms "light" and "optical radiation" refer to propagating electromagnetic waves in the wavelength range of 300 nm to 10 μm, although other wavelengths may be used. This radiation is referred to herein as propagating in one or more "beams," typically based on optical radiation generated by a laser, such as a laser diode or other light source, or emitted from a molten pool or other heat source. The beams may have a spatial extent associated with one or more laser transverse modes and may be substantially collimated.

[0017] For convenience, beams are described as propagating along one or more axes. Such axes are generally based on one or more line segments, whereby the axes may include several non-collinear portions as axes are bent, folded, or otherwise responsive to mirrors, prisms, lenses, and other optical elements. The term "lens" is used herein to refer to a single refractive optical element (singlet) or a compound lens including one or more singlets, doublets, or other compound lenses. In some examples, beams are shaped or directed by refractive optical elements, while in other examples, reflective optical elements such as mirrors are used, or a combination of refractive and reflective elements is used. Such optical systems may be referred to as refractive, reflective, and catadioptric, respectively. Other types of refractive, reflective, diffractive, holographic, and other optical elements may be used as well. In some examples, a beam splitter, such as a cube beam splitter, is used to separate an input beam into transmitted and reflected beams, although plate or other beam splitters may also be used. As used herein, angles of less than 0.5, 1, 2, 5, 10, or 20 degrees are referred to as nominal angles, and axes at angles of less than 0.5, 1, 2, 5, 10, or 20 degrees are referred to as substantially parallel.

[0018] Examples are described using an XYZ coordinate system, generally describing methods and apparatus for height adjustment or the Z axis. In most examples, thermally induced radiation (such as blackbody radiation) is used to estimate height changes, although dedicated optical or processing beam portions may also be used. Single-element photodetectors (also called single-pixel photodetectors) or linear detectors are convenient; however, imaging array detectors may also be used, although these may be unnecessarily complex and expensive compared to single-element or linear detectors. An axis tilted relative to the work surface normal is sometimes referred to as the tracking axis or simply the tilted axis. The processing beam also propagates along an axis with a slight tilt, but it will be clear in the description which axis is intended. The work surface position may be measured relative to the surface normal or the processing beam axis; it is generally preferred that height be measured relative to the surface normal; in either case, such position measurements are referred to as height measurements. The work surface or weld pool axis is the axis perpendicular to the work surface or weld pool and is typically slightly different from the processing axis. "Photoreceiver" refers to an electronic system operable to generate an output, either digital or analog, in response to optical power detected by one or more photodetectors, and may include processing to compensate for substrate temperature or other processes. Such processing may also be performed by additional processing hardware or processor-executable instructions.

[0019] Representative additive manufacturing systems Referring to FIG. 1 , a typical additive manufacturing system 100 includes laser optics 102 with a processing beam aligned along axis 104 at angle α relative to axis 106 normal to a target region 107 on a substrate 108. For convenience, a typical XYZ coordinate system 101 is shown. An xyz stage 105 is coupled to laser optics 102 to adjust the processing beam focus size or focus position. The processing beam is generally directed toward a target region 107 to be melted, which is therefore referred to herein as a melt pool. In a typical AMS application, the processing beam provides sufficient power to generate a melt pool. The substrate 108 is held by an XYZ stage 109. During processing, the motion of the stages 105, 109 may be coordinated so that both move simultaneously or sequentially. In other examples, the stage 105 or the XYZ stage 109 may be a five-axis or six-axis stage system. The part of the manufacturing process may be moved relative to the processing head, or the processing head may be moved relative to the part, or both may be moved relative to each other. In the following, a Z sensor is used to determine the position of the processing beam.

[0020] The nozzles 110, 112 are connected by supply lines 111, 113, respectively, to a material supply 114, which can supply material to the molten pool 107 to produce the intended part. The nozzles 110, 112 and substrate substrate 108 are located within a chamber 134 which is connected to a reservoir 136 containing an inert gas, such as nitrogen, so that processing can occur in a suitable atmosphere.

[0021] During machining, material from nozzles 110, 112 is added to the weld pool 107, causing the Z position of the weld pool 107 to change. This height change can be measured by a Z sensor 122 positioned to receive optical radiation (and typically blackbody radiation or other thermal radiation emitted in response to the machining beam) along an axis 120 tilted at an angle Θ relative to axis 106, where Θ is generally greater than 5, 10, 15, 20, 25, 30, 40, 45, or 50 degrees. In other examples, an additional optical source may be provided that directs a beam at the weld pool 107, with a portion of this beam being used by the Z sensor 122. The optical radiation received by the Z sensor 122 may be visible or infrared radiation, or radiation in another spectral range. Visible and infrared radiation are advantageous due to the availability of inexpensive detectors in these spectral ranges. Alternatively, a reflected or scattered portion of the machining beam may be used by the Z sensor 122. In some cases, a portion of the machining beam may be used. The optical power emitted from the weld pool 107 depends on the temperature of the weld pool, and typically, the measurement of the optical radiation received by the Z sensor 122 is adjusted based on the temperature of the weld pool when determining the height of the weld pool. The Z sensor 122 may be fixed to an x-y-z stage 123 to allow positioning along and around the axis 120. Alternatively, the laser optics 102 and the Z sensor may be coupled to a common x-y-z stage. The Z sensor 122 is coupled to a controller 130, which may adjust processing conditions such as processing beam focus, substrate position, or material flow rate or processing beam power. The controller 130 is coupled to a database 132 containing part specifications to be used in the build and to valves 111A, 113A that can control material flow into the weld pool 107.

[0022] The processing beam is transmitted to the melt pool 107 via a beam splitter 121 positioned to receive optical radiation from the melt pool 107 and direct the optical radiation to a temperature sensor (T sensor) 126. Typically, the T sensor 126, Z sensor 122, and laser optics 102 are positionable on a common x-y-z stage. The beam splitter 121 typically includes an aperture that transmits the processing beam and a portion about the aperture that reflects the optical radiation from the melt pool 107. Other beam splitters, such as neutral or dichroic beam splitters, may be used; in other examples, the processing beam is reflected by the beam splitter to the substrate 108, and the temperature sensor 126 receives the optical radiation transmitted by the beam splitter. In yet other examples, a beam splitter is not used, and the optical paths to the laser optics 102 and the temperature sensor 126 do not overlap. The optical radiation emitted from the weld pool 107 is based on the weld pool temperature, so the received optical power can be used to estimate the weld pool temperature. The temperature output of the temperature sensor 126 can be used in conjunction with the Z sensor 122 to compensate for the dependence of the optical power at the Z sensor 122 on the weld pool temperature. In alternative embodiments, the Z sensor 122 can be rotated to measure the position of the weld pool 107 along the X, Y, or other axis, or one or more additional sensors providing multiple sensors can be positioned in different configurations and can provide different position information, allowing compensation for position or other dependencies. For example, the Z sensor 122 can be positioned to measure the position of the weld pool 107 along the X and Y axes.

[0023] Typical single-detector Z sensor Figure 2A shows AMS 200 and representative Z sensor 203 and T sensor 201. An XYZ coordinate system 291 is used for convenience. Referring to Figure 2A, processing beam 202 is directed along tilt axis 204 to lens 206 and through beam splitter 208 to surface 211 of a melt pool on substrate 210. As shown in Figure 2B, beam splitter 208 is oriented along axis 209 tilted relative to the X and Y axes of coordinate system 291 and includes aperture 208A that transmits processing beam 202. Beam splitter 208 is tilted so that aperture 208A is elongated to provide a substantially circular effective aperture in a plane perpendicular to axis 204 for transmission of processing beam 202. Emitted radiation from the weld pool is directed along axis 240 to beam splitter 208 and T-sensor 201, which includes a lens 242 that focuses the emitted radiation through an aperture defined in aperture plate 244 onto detector 246. Detector 246 generates an output signal related to the weld pool temperature.

[0024] Z sensor 203 includes a lens 220 positioned along tilt axis 216 that directs radiation 214 emitted from surface 211 toward an aperture 222 defined in aperture plate 224. Radiation emitted from surface 211 is focused at a first location 217. Detector 230 is positioned optically behind aperture plate 224 and generates a Z signal that can be used to determine the Z-axis position of surface 211. During processing, surface 211 is constructed to become surface 211', which has a displacement Δz relative to surface 211. Radiation emitted from surface 211' then propagates along axis 232 to a second focal point 233 that is displaced from first focal point 217. Because first focal point 217 and second focal point 233 are displaced, the received radiation may be attenuated differently at aperture plate 224, causing detector 230 to generate a different output signal that may be related to the Z-axis displacement, such as ΔZ.

[0025] The position of aperture 222 along axis 236 may be selected to produce the appropriate Z-dependent attenuation. As shown in FIG. 2C, the aperture may be centered at 250 relative to the beam focus of the melt pool radiation. With additional Z displacement in either direction, the received optical power decreases. However, if the aperture is positioned to block a portion of the focused beam, such as at 252, such that +Z axis displacement increases the received beam power and −z displacement decreases the received power, the processing beam or substrate stage control can be adjusted in the appropriate direction.

[0026] In the exemplary configuration of FIG. 2A , processing beam 202 is directed at surface 211 at a slight angle of incidence to generate specularly reflected beam 203 propagating along axis 205 that is between axis 204 and axis 240 associated with T-sensor 201. Other configurations may be used, and axis 240 need not be perpendicular to surfaces 211, 211′. For example, with reference to FIG. 2D , processing beam 202A may be directed at surface 211 along axis 204A to generate specularly reflected beam 203A propagating along axis 205A, which is at an angle greater than the angle of axis 240. In another example, shown in FIG. 2E , processing beam 202B may be directed at surface 211 along axis 204B to generate specularly reflected beam 202B propagating along axis 205B, whose angle is directed away from axis 240.

[0027] Axial arrangements like those in FIGS. 2A and 2E-2F are shown in FIGS. 2F-2H, with optical elements omitted for convenience. In FIG. 2F, processing beam 272 is incident along axis 274, and the reflected portion of processing beam 273 is reflected along axis 275, which is shown relative to normal 270 to surface 271. The temperature sensor is positioned to receive radiation along axis 277, which is at an angle relative to normal 270 that is greater than the angle of axis 275. In FIG. 2G, processing beam 282 is incident along axis 284, and the reflected portion of processing beam 283 is reflected along axis 285, which is shown relative to normal 280 to surface 271. The temperature sensor is positioned to receive radiation along axis 287, which is at an angle relative to normal 280 that is less than the angle of axis 285 and is therefore located between normal 280 and axis 285. 2H, processing beam 292 is incident along axis 294, and the reflected portion of processing beam 293 is reflected along axis 295, which is shown relative to normal 290 to surface 271. The temperature sensor is positioned to receive radiation along axis 297, which is at an angle relative to normal 290 that is less than the angle of axis 294 and is therefore located between normal 290 and axis 294. None of these axes need be perpendicular to surface 271.

[0028] Typical dual target Z sensor Referring to FIG. 3A, a typical dual-detector Z sensor 300 includes a lens 302 positioned to direct radiation emitted from a region 304 of a substrate 306 toward a tilt plate 308. An XYZ coordinate system 301 is used for convenience. A beam splitter 310 directs portions of the focused emitted radiation toward apertures 312, 313 defined in aperture plates 316, 317 and detectors 320, 321. The beam splitter 310 may be a neutral beam splitter or a dichroic beam splitter. A dichroic beam splitter may produce different spectral portions that can be measured and compared to assess the substrate temperature. As shown in FIGS. 3B-3C, the apertures 312, 313 may be positioned to be associated with different signs of tilt with respect to Z-axis displacement. The tilt plate 308 may be adjusted to properly align or "bias" the beam to each aperture. 3A, radiation emitted from region 304 is incident near the edges of aperture plates 316 and 317 in a direction along axis 340, causing the emitted radiation to be attenuated corresponding to bias positions such as 350 and 351 in FIGS. 3B-3C. As region 304 is displaced as region 304', the emitted radiation is focused along axis 342 more toward the center of aperture 312 and more toward the edges of aperture 313, causing an increase in detected power associated with aperture 312 and a decrease in detected power associated with aperture 313, as shown in FIGS. 3B-3C, respectively. Rotation of tilt plate 308 displaces axes 340 and 342, which may adjust the attenuation of beams propagating along these axes to apertures 312 and 313. For example, rotation may be applied to attenuate by 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or other numerical value in the range of 0-100%. When a beam is incident on an aperture and initially centered on the aperture, subsequent changes in Z position will reduce the beam power received at the associated detector, but generally no indication of the direction of the Z change is provided.For example, with appropriate rotation of the tilt plate 308, a position change in the +Z direction may be associated with an increase in the received beam power at the detector 320, and a position change in the −Z direction may be associated with a decrease in the beam power at the detector 320. Thus, a change in the received beam power may be associated with both the magnitude and direction of the Z-axis position change of the region 304 of the substrate 306.

[0029] In this example, the optical power received from the weld pool depends on the weld pool temperature, but the optical power at each of the detectors 320, 321 is proportional, so that a ratio or other combination can be used to reduce or eliminate the temperature dependence in the Z sensor optical power, and a separate temperature sensor is not required. In this and other examples, the Z sensor includes a circular or elliptical aperture, although a slit, opaque or reflective spot, rectangle, other curved or polygonal shape, or the detector size itself may be used instead. The dimensions of the apertures 312, 313 along axes 315, 319, respectively, are selected based on the beam size to provide a selected beam attenuation as a function of Z-axis displacement of region 304.

[0030] Typical linear detector Z sensor Referring to FIG. 4A , a representative Z sensor 400 includes a linear detector 402 positioned to receive optical radiation from a weld pool surface 404 on a substrate 405 along a tilt axis 414. The linear detector 402 is typically a unitary linear photodiode array, such as a self-scanning diode array including photodiodes arranged along axis 403, although other linear arrangements, such as two or more discrete photodiodes, may be used. As shown, as the weld pool surface 404 grows along axis 405 by an amount ΔZ to become a displaced surface 404′, the beam from the weld pool surface initially propagating along tilt axis 414 (i.e., 404 or 404′ formed by lens 411) propagates along tilt axis 416. However, depending on the configuration of lens 411 and any associated optics, the displaced axis may be either above or below the initial axis at linear detector 402. The linear detector 402 is connected to a processor 410 operable to determine the weld pool temperature and Z-axis displacement. A Z-axis controller 412 is connected to the processor 402 and is further connected to the substrate stage, the processing beam optics, or both, for adjusting the Z-axis position as needed. In Figure 4A, emitted radiation from surface 404 is directed and focused along tilt axis 414 to focus spot 450, while emitted radiation from displaced surface 404' is directed along axis 416 to focus spot 452, producing a displaced focus spot on linear detector 402. As shown, a +Z displacement of the weld pool surface produces a downward shift of focus spot 450, although in other examples it may produce an upward shift.

[0031] For example, referring to FIG. 4B, along axis 414, a focus spot 450 generated on linear detector 402 is located within active area 451 of linear detector 402. Along axis 416, a focus spot 452 generated on linear detector 402 is located within active area 451 and displaces along linear detector axis 454. Thus, displacement of the weld pool results in displacement of focus spots 450, 452, and the position of the focus spot indicates Z position. A linear sensor does not require precise measurement of power, allowing detector elements to be saturated. The beam center on a linear detector can be found by identifying the edge position of a detector element with linear or other response, or the center of the saturated spot.

[0032] FIG. 4C shows an exemplary linear sensor assembly 460 that includes a linear sensor 462 and a cylindrical lens 464 positioned to increase the optical power sent to the linear sensor 462 .

[0033] Typical dual beam linear detector Z sensor Referring to FIG. 5A, a representative dual-beam linear detector Z sensor 500 is similar to the Z sensor of FIG. 4A but includes a beam splitter 550 and a tilting plate 552. The beam splitter 550 directs first and second beam portions from a work surface 506 along respective axis portions 502, 503 toward mirrors, prisms, or other reflectors 560, 562, causing the first and second beam portions to impinge on different regions of a linear detector 556. The beam portions are generally focused to produce first and second beam spots at the linear detector 556. When the work surface 506 is displaced by ΔZ, shown as work surface 506′, the beam portions are directed along axis portions 512, 513 and focused as respective first and second spots displaced relative to the beam spot associated with the previous position of the work surface. The tilting plate 552 may be rotated to select the appropriate location of the beam spots.

[0034] Figure 5B shows the active area 570 of linear detector 556, showing first and second beam spots 572, 573 associated with work surface 506, and first and second beam spots 574, 575 associated with work surface 506'. Figures 5C-5D show beam spot intensity as a function of position on active area 570. Figure 5C corresponds to work surface 506, and Figure 5D corresponds to work surface 506'. As shown, in the configuration of Figure 5A, the beam spots move apart as the work surface is raised.

[0035] Beam splitter 550 may be a dichroic beam splitter, whereby beam spots such as beam spots 572, 573 are associated with different spectral portions of the beam from work surface 506. Differences in power or spot shape with the spectral portions allow for estimation of the work surface temperature.

[0036] Typical dual beam linear detector Z sensor with crossed beams Referring to FIG. 6A, a representative dual-beam linear detector Z sensor 600 is similar to the Z sensor of FIG. 5A and includes a beam splitter 650 and a tilting plate 652. The beam splitter 650 directs first and second beam portions from a work surface 606 along respective axis portions 602, 603 toward mirrors, prisms, or other reflectors 660, 662, causing the first and second beam portions to impinge on different regions of a linear detector 656. The beam portions are generally focused to produce first and second beam spots at the linear detector 656. When the work surface 606 is displaced by ΔZ, shown as work surface 606′, the beam portions are directed along axis portions 612, 613 and focused as respective first and second spots displaced relative to the beam spot associated with the previous position of the work surface. The tilting plate 652 may be rotated to select the appropriate location of the beam spots. In contrast to FIG. 5A, the propagation axes associated with the beam sub-sections and the beam spot at the line detector approach as the work surface height increases, as shown in FIGS. 6B-6C.

[0037] Figure 6B shows the active area 670 of linear detector 656, showing first and second beam spots 672, 673 associated with work surface 606, and first and second beam spots 674, 675 associated with work surface 606'. In a further example shown in Figure 6C, active area 670 receives first and second beam spots 672, 673 associated with work surface 606, and first and second beam spots 678, 679 associated with work surface 606'. In this example, first and second beam spots 678, 679 are touching and beginning to overlap. A typical power distribution at linear detector 656 is shown in Figure 6D.

[0038] Typical Z sensing methods Referring to FIG. 7 , an exemplary method 700 includes receiving optical radiation from a work surface along a tilt axis at 702. The optical radiation may be radiation emitted from the weld pool, a portion of a processing beam, or a dedicated Z-sensing beam. For example, thermal radiation emitted by the weld pool, a scattered or reflected portion of a processing beam, or a scattered or reflected portion of a Z-axis analysis beam from a dedicated Z-axis source may be used. To accommodate different sensing configurations, a detector or sensor type is selected at 704. If a single-element optical detector is used, the optical power transmitted by an aperture located about the tilt axis is measured at 706, and the measured power is corrected for the weld pool temperature, if necessary, at 708. The Z position is determined at 710, and the Z position of the substrate or processing beam focus may be adjusted at 712, or other processing conditions may be applied based on the determined Z position.

[0039] If dual single element detectors are used, the optical power transmitted by each aperture located about the tilt axis is measured at 714 and a power ratio is obtained at 716. The Z position is determined at 710 and a Z axis or processing adjustment is made at 712; if a linear detector is used, the beam position on the linear detector is measured at 720 and the Z position is determined at 710 and adjusted at 712. In some cases, the measured Z position is used to interrupt or accelerate material deposition at one or more locations by controlling the processing beam diameter, the optical power of the processing beam, or material flow, and the Z position need not be adjusted.

[0040] Typical Z calibration The signals from the on-axis and off-axis detectors may be used to determine height using a lookup table or other approach. Referring to FIGS. 8-8C, an exemplary method 800 includes a calibration method 801A and a height measurement method 801B. At 802, the signals at the on-axis and off-axis detectors (VON and VOFF, respectively) are measured as a function of weld pool temperature for multiple heights Z. The resulting data appears similar to curves 851-853 shown in FIG. 8A for three heights Z1-Z3. For the data at each height Z, the slope (C1) and intercept (C2) of a linear fit to VOFF as a function of VON are calculated at 804. The slope and intercept are different for each height Z, so that C1 = C1(Z) and C2 = C2(Z). At 806, a linear fit of C2(Z) as a function of C1(Z) is performed with a slope C3 and an intercept C4. FIG. 8B shows a representative graph of C2(Z) as a function of C1(Z) as measured 861 along a linear fit 862. At 808, C1(Z) is fit to a Gaussian distribution, shown as curve 871 in FIG. 8C. Similarly, C2(Z) is fit to a Gaussian distribution, shown as curve 872 in FIG. 8C, but only one of C1(Z) and C2(Z) is needed. At 808, this fit is inverted to find Z = F(C1), where F is the inverse of the Gaussian distribution. That is, C1(Z) is fit to a Gaussian distribution as C1(Z) = Aexp[-aZ2], where A and a are fitting constants and Z = [In(A / Cl) / a]1 / 2. C3, C4, and F (the fitting constants A and a) are stored for use in the measurement. Representative measurement data is shown graphically in FIGS. 8A-8C; the graphs are for convenience only and do not require any necessary calibration steps to be performed.

[0041] Once calibration method 801A is complete, height measurements can be performed as shown in method 801B. At 820, off-axis and on-axis signals are measured at each detector, and at 822, Cl is calculated as Cl=(VOFF-C4) / (VON+C3), where C3 and C4 were previously determined in calibration. For Cl, at 824, height can be found as Z=F(C1), where F was previously determined in calibration.

[0042] Typical modeling methods Referring to FIG. 9 , an exemplary method 900 includes selecting or generating a suitable part design at 901 and preparing a substrate at 902. At 903, additive manufacturing is used to build the part according to the design, measuring height using one or more optical beams propagating along one or more axes tilted relative to the substrate surface, or a working area such as a molten pool on the substrate. Based on the measured height, height or processing parameters may be adjusted. At 904, the built part is post-processed as needed, for example, to polish or smooth the surface or to remove excess material added by the building process. At 906, the part is inspected before delivery.

[0043] The processing beam from the AMS may include a beam such as a laser beam, synchrotron radiation, x-ray beam, electron beam, ion beam, or other beam. The operator may use only one of the dual detectors as needed. For example, the user may switch between the two detectors to observe the weld pool using only one of the on-axis and off-axis detectors.

[0044] In view of the many possible embodiments to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated embodiments are merely preferred examples of the invention and should not be construed as limiting the scope of this disclosure. I claim as my invention all that comes within the scope and spirit of the appended claims, all novel and non-obvious features and combinations of the features disclosed.

[0045] Innovative Features The innovative features described herein include, but are not limited to: [A1] a tracking optical system located along a tracking axis and having at least one focusing element and at least one photodetector, wherein the at least one focusing element is positioned to receive optical radiation from the molten pool and direct the received optical radiation to the photodetector, the tracking axis being tilted with respect to the machining axis, and the photodetector includes at least one single pixel photodetector or a linear detector; an optical receiver connected to the optical detector and operable to generate a tracking signal associated with a position of the weld pool along the processing axis or a weld pool axis perpendicular to the weld pool based on the received optical radiation directed to the optical detector; An apparatus comprising: [A2] The tracking axis is inclined at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, or 90 degrees relative to the processing axis or the weld pool axis. The device described in A1. [A3] The optical system further includes an aperture plate positioned to attenuate the received optical radiation directed to the photodetector. The device according to any one of A1 and A2. [A4] The at least one optical element is a lens positioned to focus the received optical radiation from the molten pool adjacent the aperture plate. An apparatus according to any one of A1 to A3. [A5] The aperture plate defines a circular aperture, a rectangular aperture, a slit, or two or more aperture edges. An apparatus according to any one of A1 to A4. [A6] The aperture plate is a slit or is defined by two or more aperture edges. A device according to any one of A1 to A5. [A7] An aperture plate is positioned to block 20% to 80% of the received optical radiation from the focusing element, such that beam displacements in opposite directions produce opposite changes in received optical power. The device according to any one of A1 to A6. [A8] a processing beam source operable to generate the processing beam; and a positioning element responsive to the tracking signal to adjust the relative position of the weld pool and the tracking axis. An apparatus according to any one of A1 to A7. [A9] The positioning element is a stage operable to adjust the position of the weld pool along the processing axis or the weld pool axis. An apparatus according to any one of A1 to A8. [A10] At least one detector of the tracking optics includes a first detector and a second detector, and the receiver is operatively positioned to generate corresponding first and second tracking signals related to the position of the weld pool along the processing axis based on the portion so of the received optical radiation, wherein the first and second tracking signals have opposite slopes relative to changes in the position of the weld pool along the processing axis or the weld pool axis. The device according to any one of A1 to A9. [A11] The optical system further includes a first aperture plate and a second aperture plate positioned to attenuate the received optical radiation toward the first detector and the second detector, respectively. The device according to any one of A1 to A10. [A12] The at least one photodetector is a linear detector array. An apparatus according to any one of A1 to A11. [A13] The optical receiver is coupled to the optical detector and is operable to generate the tracking signal associated with the position of the weld pool along the processing axis based on the position at which the received optical radiation is incident on the optical detector. The device according to any one of A1 to A12. [A14] The position of the weld pool along the processing axis or the weld pool axis is based on the centroid of an intensity pattern of the radiation intensity relative to the photodetector. The device according to any one of A1 to A13. [A15] a processing beam source operable to generate the processing beam; and a positioning element responsive to the tracking signal to adjust the relative position of the weld pool and the tracking axis. An apparatus according to any one of A1 to A14. [A16] a beam splitter positioned to direct the first and second portions of the received optical radiation onto corresponding first and second regions of the linear detector array. A device according to any one of A1 to A15. [A17] The first and second portions of the received optical radiation are different spectral portions, and the beam splitter is a dichroic beam splitter that selectively directs the different spectral portions to the corresponding first and second regions of the linear detector array. The device according to any one of A1 to A16. [A18] The beam splitter is positioned so that the first and second portions of the received optical radiation are directed to corresponding first and second regions of the linear detector array having a separation that increases with increasing distance to the weld pool. An apparatus according to any one of A1 to A17. [A19] The optical radiation received from the weld pool is one or more of thermal radiation emitted from the weld pool in response to a processing beam, a portion of the processing beam, or a portion of an analysis beam from an analysis beam source. An apparatus according to any one of A1 to A18. [B1] a processing beam source positioned to direct a processing beam along a processing axis toward a working area of ​​the substrate, whereby said processing beam is focused at said working area; an optical focus sensor positioned to receive optical radiation from the working area in response to the machining beam along an axis tilted relative to the machining axis; Equipped with The optical focus sensor includes at least one of a single pixel detector and a linear detector positioned to receive the optical radiation. system. [C1] receiving optical radiation from a working area of ​​the substrate along a tracking axis that is tilted relative to a substrate axis that is perpendicular to the working area; measuring the power of the optical radiation received from the working area and transmitted by an aperture positioned along the tracking axis; determining a displacement of the working region along the substrate axis based on the measured power; adjusting at least one processing parameter based on the determined displacement; A method comprising: [C2] The processing parameter is the position of the working area. The method described in C1. [C3] The optical radiation from the working area is generated by irradiation of the working area with a processing beam or is part of a tracer beam directed to the working area. The method according to any one of C1 and C2. [C4] The displacement of the working area is adjusted by moving the working area along the substrate axis or by adjusting the direction of the processing beam toward the working area. A method according to any one of C1 to C3. [C5] The optical radiation is associated with a molten pool produced by a processing beam. A method according to any one of C1 to C4. [C6] The optical radiation is thermal radiation associated with the molten pool. A method according to any one of C1 to C5. [C7] estimating the temperature of the molten pool; adjusting the measured power based on the estimated temperature; and Further comprising: A displacement of the working region along the substrate axis is determined based on the adjusted measured power. A method according to any one of C1 to C6. [C8] Measuring the power includes measuring first and second powers of the optical radiation received from the working area and transmitted by first and second apertures, and the displacement of the working area along the substrate axis is determined based on the first and second powers. A method according to any one of C1 to C7. [D1] receiving optical radiation from a working area of ​​the substrate along a tracking axis that is tilted relative to a substrate axis that is normal to the working area; directing the received optical radiation to a linear detector; determining a displacement of the working area along the substrate axis based on a position at which the received optical radiation is incident on the linear detector; adjusting at least one processing parameter based on the determined displacement; A method comprising: [D2] The processing parameter is the displacement of the working area. The method described in D1. [D3] The received optical radiation from the working region is one or more of thermal radiation emitted from the substrate, a portion of a processing beam directed toward the substrate, or a portion of an analysis beam directed toward the substrate from an analysis beam source. The method according to any one of D1 and D2. [E1] a detection device for detecting a molten pool produced by the processing beam, a first light receiving device configured to receive first radiation emitted from the molten pool along a first axis; a second light receiving device for receiving second radiation emitted from the molten pool along a second axis tilted relative to the first axis; A detection device comprising: [E2] The first light receiving device includes a first focusing optical system that focuses the first radiation, and a first photodetector that photoelectrically converts the focused first radiation. The detection device described in E1. [E3] The first light receiving device includes an aperture member defining an aperture disposed at a position where the first radiation is collected by the first collecting optical system, and the first photodetector receives the first radiation passing through the aperture member. A detection device according to any one of E1 and E2. [E4] The first photodetector includes a linear detector arranged at a position where the first radiation is focused by the first focusing optical system, and includes photoelectric conversion elements arranged in a one-dimensional direction. A detection device according to any one of E1 to E3. [E5] A first angle formed by the propagation axis of the processing beam and the first axis is greater than a second angle formed between the propagation axis of the processing beam and the second axis. A detection device according to any one of E1 to E4. [E6] A second angle formed between the axis of propagation of the processing beam and the second axis is different from a third angle formed between the axis of propagation of the processing beam and an axis of specular reflection of the processing beam from the molten pool. A detection device according to any one of E1 to E5. [E7] A second angle formed between the axis of propagation of the processing beam and the second axis is smaller than a third angle formed between the axis of propagation of the processing beam and an axis of specular reflection of the processing beam from the molten pool. A detection device according to any one of E1 to E6. [E8] A second angle formed between the axis of propagation of the processing beam and the second axis is greater than a third angle formed between the axis of propagation of the processing beam and an axis of specular reflection of the processing beam from the molten pool. A detection device according to any one of E1 to E7. [E9] The second axis is slightly tilted from the propagation axis of the processing beam. A detection device according to any one of E1 to E8. [E10] The second axis is substantially parallel to the propagation axis of the processing beam. A detection device according to any one of E1 to E9. [E11] a folding member disposed in the optical path of the processing beam and bending the second axis; A detection device according to any one of E1 to E10. [E12] The second radiation is received by the second light receiving device through the folding member. A detection device according to any one of E1 to E11. [E13] Further comprising a controller, The first light receiving device includes a first photodetector that photoelectrically converts the first radiation, the second light receiving device includes a second photodetector that photoelectrically converts the second radiation, and the controller calculates a first output from the first photodetector and a second output from the second photodetector. A detection device according to any one of E1 to E12. [E14] The controller obtains a dimension of the molten pool based on the first output and the second output. A detection device according to any one of E1 to E13. [E15] The dimensions of the weld pool include at least one of a height of the weld pool and a size of the weld pool. A detection device according to any one of E1 to E14. [E16] The dimensions of the weld pool include at least one transverse dimension of the weld pool. A detection device according to any one of E1 to E15. [F1] 1. A processing device for processing a workpiece by forming a molten pool on the workpiece with a processing beam, comprising: The detection device according to any one of E1 to E16 Processing device. [F2] a characteristic-altering device for altering a characteristic of the processing beam based on an output from the characteristic-altering device; A processing device as described in F1. [F3] a material supply device for supplying material to the molten pool; A processing device according to any one of F1 and F2. [F4] The processing device builds an object on the workpiece by supplying the material to the molten pool. A processing device according to any one of F1 to F3.

Claims

1. a light source that irradiates a processing beam and forms a molten pool on the workpiece with the processing beam; a material supply device that supplies a modeling material to the molten pool and deposits it on the workpiece; In addition, a light receiving device for receiving radiation emitted from the molten pool and having a temperature-dependent optical power; a detector for measuring an output related to the temperature of the molten pool; Equipped with Based on the output of the light receiving device and the output of the detector, information regarding the height of the molten pool is detected. Additive manufacturing equipment.

2. The light receiving device includes a focusing optical system that focuses the radiation, and a photodetector that photoelectrically converts the focused radiation. The additive manufacturing apparatus of claim 1 .

3. The light receiving device includes an aperture member defining an aperture disposed at a position where the radiation is collected by the collecting optical system, and the photodetector receives the radiation passing through the aperture member. The additive manufacturing apparatus of claim 2.

4. The photodetector includes a linear detector arranged at a position where the radiation is focused by the focusing optical system, and includes photoelectric conversion elements arranged in a one-dimensional direction. The additive manufacturing apparatus of claim 2.

5. Further comprising a controller, the light-receiving device includes a photodetector that photoelectrically converts the radiation; The controller compensates for the dependency of the output detected by the photodetector on the temperature of the molten pool based on the output of the detector, and calculates information about the height of the molten pool. Additive manufacturing apparatus according to any one of claims 1 to 4.

6. The detector measures an output related to the temperature of the molten pool based on radiation from the molten pool. Additive manufacturing apparatus according to any one of claims 1 to 5.

7. 1. A processing device for processing a workpiece by forming a molten pool on the workpiece with a processing beam, comprising: The additive manufacturing apparatus according to any one of claims 1 to 6 is provided. Processing device.

8. The processing device builds an object on the workpiece by supplying the build material to the molten pool. The processing device according to claim 7 .

9. A processing beam is irradiated to form a molten pool on the workpiece, a material supply device that supplies a modeling material to the molten pool and deposits it on the workpiece; In addition, a light receiving device for receiving radiation emitted from the molten pool and having a temperature-dependent optical power; a detector for measuring an output related to the temperature of the molten pool; Equipped with Based on the output of the light receiving device and the output of the detector, information regarding the height of the molten pool is detected. Additive manufacturing equipment.

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