Laser light absorption rate measuring device and method for 3D modeling

Abstract

To provide a three-dimensional molding-purpose laser light absorptivity measurement device that can measure temperature dependency of absorptivity of a powder and the like with respect to laser light used in a device capable of laminate molding.SOLUTION: A method, which is configured to install a metal plate 63 having a dent 63a formed in an existing laminate molding device, laminate a sample 62 serving as a measurement object in the dent, and measure laser light absorptivity of the sample, using a laser device 20 scanning and irradiating laser light with respect to an irradiation surface of the sample 62, and a thermocouple thermometer 42 measuring a sample temperature of an irradiation spot portion of the irradiation surface to be irradiated with the laser light by a thermocouple terminal 30 attached to a rear surface of the metal plate having the dent formed is irradiated, comprises an actual absorptivity calculation step of calculating an actual laser light absorptivity of the sample 62 or the metal plate 63, using an irradiation condition of the laser device, a rising temperature in the irradiation spot portion and a theoretical relation of a heat loss.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for measuring laser light absorption rate for 3D modeling, which is suitable for use in powder bed fusion and the like. [Background technology]

[0002] The light absorption rate of a material has been calculated for ideal surface conditions for some typical materials, but there are not many types of materials, and the surface condition of the material in the actual usage environment may differ from the ideal, so the light absorption rate may change. Furthermore, the temperature dependence of the material's absorption rate has hardly been calculated at present.

[0003] In Non-Patent Documents 1 and 2, a dedicated measurement system was constructed in an external environment without using an additive manufacturing device, and the temperature dependence of the metal plate and metal powder on the laser wavelength used there was measured. In Non-Patent Document 3, a specially created additive manufacturing device was used to measure the absorption rate of laser light during the manufacturing process. Patent Document 1 proposes a method for measuring the laser light absorption rate of a sample by measuring the temperature rise process of the laser light irradiated area using an infrared camera. Patent Document 2 proposes a method for measuring the absorption rate of optical components that make up a laser processing machine or the like, in which the temperature is automatically measured multiple times in a short period of time and a temperature rise curve is determined by statistical processing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-207344 [Patent Document 2] Japanese Patent Application Publication No. 62-297745 [Non-patent literature]

[0005] [Non-Patent Document 1] A. Rubenchik, et al., “Direct measurements of temperature-dependent laser absorptivity of metal powders,” Appl. Opt. 54, 7230-7233 (2015). [Non-patent document 2] AM Rubenchik, et al., “Temperature-dependent 780-nm laser absorption by engineering grade aluminum, titanium, and steel alloy surfaces,” Opt. Eng. 53, 122506 (2014) [Non-patent document 3] J. Trapp, et al., “In situ absorptivity measurements of metallic powders during laser powder-bed fusion additive manufacturing,” Appl. Mater. Today 9, 341-349 (2017). Summary of the Invention [Problem to be solved by the invention]

[0006] However, in Non-Patent Documents 1 and 2, the temperature dependence of the absorptance is obtained not in the environment in which additive manufacturing is performed, but in the environment of a dedicated measuring device prepared separately outside, which poses the problem that the wavelength of the laser used and the measurement environment are different from those used in actual additive manufacturing. Furthermore, in Non-Patent Document 3, the absorptance of laser light during the modeling process in the environment of a specially created additive manufacturing device is obtained, but this is the overall absorptance when the powder is melted and keyholes are generated, and the temperature dependence of the absorptance is not measured. Even when the powder is not melted, there is a problem in that the absorptance is the overall absorptance under those measurement conditions, and the temperature dependence is not measured.

[0007] Patent Document 1 proposes non-contact measurement of sample temperature using an infrared camera device, but when attempting to attach an external infrared camera device to a metal powder 3D printer, the printer does not necessarily have an observation window, limiting the types of metal powder 3D printers that can be used. Patent Document 2 is intended to measure the optical properties of infrared-transparent materials, and therefore has the problem that it cannot be directly applied to measuring the absorption rate of laser light in a sample in a situation where the laser light is focused into a narrow beam diameter and scanned back and forth at high speed, such as in a metal powder 3D printer, which is the intended use of the present invention.

[0008] The present invention aims to solve the above-mentioned problems by providing a laser light absorptance measurement device and method for 3D printing that can measure the temperature dependence of the absorptance of a material such as powder for laser light used in an apparatus capable of additive manufacturing, in order to clarify the absorptance of laser light for materials and environments actually used in the apparatus. [Means for solving the problem]

[0009] Therefore, the inventors thought that it might be possible to utilize laser additive manufacturing devices, which have recently become increasingly popular, to measure the temperature dependence of the material's absorption rate for the laser light used in the device in an environment that can be set by the additive manufacturing device, and came up with the idea of ​​the laser light absorption rate measurement device and method for 3D modeling of the present invention.

[0010] [1] The laser light absorptance measurement method for 3D printing of the present invention is a method for measuring the laser light absorptance of a sample by using, for example, a laser device 20 that scans and irradiates a laser beam onto an irradiation surface of the sample 62, as shown in FIG. 1, a metal plate 63 with a depression 63a in it, and deposits a sample 62 to be measured in the depression, and a thermocouple temperature measurement unit 42 that measures the actual temperature of an irradiation spot portion of the irradiation surface irradiated with the laser beam by a thermocouple terminal 30 attached to the back surface of the metal plate with the depression, a sample temperature measuring step of measuring the actual temperature of the irradiation spot portion before, during, and after the irradiation of the laser light by the thermocouple temperature measuring unit; The method further includes an actual absorption rate calculation step of calculating an actual laser light absorption rate of at least one of the sample 62 and the metal plate 63 using the irradiation conditions of the laser device, the temperature rise measured by the thermocouple temperature measurement unit due to irradiation of the laser light to the irradiation spot portion, and a theoretical relationship of heat loss due to the temperature rise measured by the thermocouple temperature measurement unit.

[0011] [2] In the laser light absorptance measurement method for 3D printing according to the present invention [1], preferably, when the metal plate is heated by the laser device, A time corresponding to a response time of at least one of heating and cooling of the metal plate by the laser device is obtained by numerical calculation; Calculating a theoretical relationship of heat loss due to temperature rise in the irradiation spot portion by excluding the temperature history over time, including transient phenomena, from the analysis; The method may further comprise an actual absorption rate calculation step of calculating the actual laser light absorption rate of the sample while suppressing measurement errors resulting from non-uniform heating of the metal plate by the laser device. [3] In the laser beam absorptance measurement method for 3D printing [1] or [2] of the present invention, the actual laser beam absorptance of the sample in the actual absorptance calculation step is preferably calculated using the following formula:

number

number

number

number

[0012] [7] In the laser light absorptance measurement method for 3D printing of the present invention [1] to [6], it is preferable to measure the laser light absorptance of the sample in the additive manufacturing environment together with its temperature dependency by scanning the laser light at high speed while defocusing the laser light. Here, defocusing refers to enlarging the area of ​​the irradiated light compared to when the laser light is focused and irradiated onto the irradiated surface of the sample. When the laser light is focused and irradiated onto the irradiated surface of the sample, the sample temperature at the irradiation spot on the irradiated surface exceeds the melting temperature of the sample. However, by defocusing the laser light, the energy irradiated onto the sample at the irradiation spot on the irradiated surface is reduced, making it possible to suppress the temperature rise to a level that does not melt the sample. Furthermore, high-speed scanning refers to scanning the laser light at a higher speed than when scanning at a normal speed, thereby reducing the energy irradiated onto the sample at the irradiation spot on the irradiated surface and suppressing the temperature rise to a level that does not melt the sample. When scanning the laser light at a normal speed, the sample temperature at the irradiation spot on the irradiated surface exceeds the melting temperature of the sample. [8] In the laser light absorptance measurement method for 3D printing according to the present invention [1] to [7], it is preferable that the laser light is scanned at high speed while being defocused, so that the temperature of the irradiation spot on the irradiation surface where the laser light is irradiated rises within a range where the sample does not melt. [9] In the laser light absorptance measurement method for 3D printing [7] or [8] of the present invention, preferably, the laser light is scanned at high speed while being defocused, and the spacing and length of the stripes of the laser light on the irradiation surface, as well as the power and scanning speed of the laser light, are determined so that the temperature rise of the irradiation spot on the irradiation surface where the laser light is irradiated is kept within an allowable limit for the uniformity of heating of the sample and the metal plate by the laser device.

[10] In the laser light absorptance measurement method for 3D printing [1] to [9] of the present invention, it is preferable to further include a laser light irradiation control unit that changes the heating pattern by changing the interval between each scanning line, the number of times the entire scanning line pattern is irradiated, or the time interval between irradiation of the entire scanning line pattern.

[11] In the laser light absorptance measurement method for 3D printing of the present invention [1] to

[10] , the sample is preferably a metal powder, a ceramic powder, or a plastic powder.

[0013]

[12] The laser light absorptance measurement method for 3D printing of the present invention is a method for measuring the laser light absorptance of a metal plate by using, for example, a metal plate 63 placed in an existing additive manufacturing apparatus as shown in FIG. 1, a laser device 20 that scans and irradiates the irradiation surface of the metal plate 63 with laser light, and a thermocouple temperature measurement unit 42 that measures the actual temperature of the irradiation spot portion of the irradiation surface irradiated with the laser light by a thermocouple terminal 30 attached to the back surface of the metal plate 63, a temperature measuring step of measuring the actual temperature of the irradiation spot portion before, during, and after the irradiation of the laser light by the thermocouple temperature measuring unit; The method further includes an actual absorption rate calculation step of calculating an actual laser light absorption rate of the metal plate 63 using the irradiation conditions of the laser device, the temperature rise measured by the thermocouple temperature measurement unit due to irradiation of the laser light to the irradiation spot portion, and a theoretical relationship of heat loss due to the temperature rise measured by the thermocouple temperature measurement unit.

[0014]

[13] The laser light absorptance measuring device for 3D printing of the present invention, for example, as shown in FIG. 1, is configured by placing a metal plate 63 with a depression 63a in an existing additive manufacturing device, depositing a sample 62 to be measured in the depression, and using a laser device 20 that scans and irradiates the irradiation surface of the sample 62 with a laser beam, and a thermocouple temperature measuring unit 42 that measures the actual temperature of the irradiation spot on the irradiation surface irradiated with the laser beam by a thermocouple terminal 30 attached to the back surface of the metal plate with the depression, to measure the laser light absorptance of the sample. The apparatus includes a thermocouple temperature measuring unit 42 that measures the actual temperature of the irradiation spot portion before, during, and after irradiation of the laser light using a thermocouple terminal 30, and an actual absorption rate calculating unit 45 that calculates the actual laser light absorption rate of at least one of a sample 62 and a metal plate 63 using the irradiation conditions of the laser device, the temperature rise measured by the thermocouple temperature measuring unit 42 that occurs when the laser light is irradiated onto the irradiation spot portion, and a theoretical relationship of heat loss due to the temperature rise measured by the thermocouple temperature measuring unit 42.

[14] In the laser light absorptance measuring device for 3D printing of the present invention

[13] , the sample is preferably a metal powder, a ceramic powder, or a plastic powder.

[15] The laser light absorptance measuring device for 3D printing of the present invention is a device that measures the laser light absorptance of a metal plate by installing a metal plate 63 with a depression 63a in an existing additive manufacturing device, and using a laser device 20 that scans and irradiates the irradiation surface of the metal plate 63 with laser light, and a thermocouple temperature measuring unit 42 that measures the actual temperature of the irradiation spot portion of the irradiation surface irradiated with the laser light by a thermocouple terminal 30 attached to the back surface of the metal plate 63, The thermocouple temperature measuring unit 42 measures the actual temperature of the irradiation spot portion before, during, and after the irradiation of the laser light by the thermocouple terminal 30, and The apparatus further includes an actual absorption rate calculation unit 45 that calculates the actual laser light absorption rate of the metal plate 63 using the irradiation conditions of the laser device, the temperature rise measured by the thermocouple temperature measurement unit 42 that occurs when the laser light is irradiated onto the irradiation spot portion, and a theoretical relationship of the heat loss due to the temperature rise measured by the thermocouple temperature measurement unit 42. [Effects of the Invention]

[0015] The laser light absorptance measuring device for 3D printing of the present invention can measure the temperature dependence of the laser light absorptance of powders actually used in additive manufacturing using various powders in the environment in which the additive manufacturing device is used. The measured values ​​can be used in numerical calculations to determine optimal parameters when manufacturing an additively manufactured object, to narrow down the additive manufacturing conditions for creating the object, and to improve the additive manufacturing efficiency and various properties of the object. By utilizing the laser light and laser light scanning system used in existing additive manufacturing devices and scanning the laser at high speed while defocusing it, it is possible to measure the laser absorption rate of materials such as powder in the additive manufacturing environment, along with its temperature dependence, and a laser light absorption rate measurement device for 3D manufacturing can be constructed with minimal additional cost.

[0016] The laser beam absorptance measurement method for 3D printing of the present invention as set forth in claim 12 and the laser beam absorptance measurement device for 3D printing as set forth in claim 15 can measure the temperature dependence of the absorptance of a metal plate alone, without loading it with a metal powder sample. These measured values ​​can then be used for numerical calculations and narrowing down processing conditions for laser welding or laser surface modification of materials made of the same material as the metal plate. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a functional block diagram of a laser light absorptance measuring device for 3D printing used in implementing the present invention. [Figure 2] FIG. 1 is an overall functional block diagram showing one embodiment of a metal powder 3D printer used for powder bed fusion. [Figure 3] 10 is a flowchart illustrating an example of the operation of a metal powder 3D printer. [Figure 4] 1A and 1B are diagrams showing the configuration of a main part of an embodiment of a laser beam irradiation range of a metal powder sample, in which (A) is a perspective view and (B) is a cross-sectional view of the main part. [Figure 5] FIG. 10 is a diagram for explaining a formula for calculating laser light absorption rate, and is a diagram for explaining a formula for calculating light absorption rate from a stepwise heating process. [Figure 6] FIG. 1 is a diagram illustrating the temperature dependence of the specific heat of a titanium alloy (Ti-6Al-4V) according to an embodiment of the present invention. [Figure 7A] This figure explains the maximum temperature achieved when one stepwise heating process is repeated 10 times under each stepwise heating process condition, which is one embodiment of the present invention, and shows the case of a single titanium alloy (Ti-6Al-4V) tray. [Figure 7B] FIG. 1 is a diagram illustrating temperature changes when one step heating process is repeated 10 times, in accordance with one embodiment of the present invention, for a single titanium alloy (Ti-6Al-4V) tray. [Figure 7C]This figure explains the maximum temperature achieved by a titanium alloy (Ti-6Al-4V) powder sample when one stepwise heating process is repeated 10 times under each stepwise heating process condition, which is one embodiment of the present invention, and shows the case where the powder is loaded on a tray. [Figure 7D] This figure explains the temperature change due to heat radiation in a titanium alloy (Ti-6Al-4V) powder sample when one step heating process is repeated 10 times, which is one example of the present invention. It shows the case of a tray alone and the case of powder loaded on a tray. [Figure 8A] This is an explanatory diagram (an example of a cooling curve) for determining the parameter L(T), which represents the temperature dependence of heat loss, from the temperature drop curve during the cooling process under certain step-wise heating conditions. [Figure 8B] This is an explanatory diagram for determining the parameter L(T), which represents the temperature dependence of heat loss, from the temperature drop curve during the cooling process under certain step-wise heating conditions (first derivative of the cooling curve dT / dt [K / s]). [Figure 8C] This is an explanatory diagram for determining the parameter L(T), which represents the temperature dependence of heat loss, from the temperature drop curve during cooling under certain step heating conditions (m·c(T)·dT / dt[W] related to the heat loss parameter L(T) determined from the cooling curve). [Figure 9A] This is a graph showing the absorption rate A(T) under each stepwise heating process condition (for a single tray). [Figure 9B] A graph showing the absorption rate A(T) under each stepwise heating process condition (when powder is loaded on a tray). [Figure 10] This is an explanatory diagram of the temperature distribution during the first step heating process based on numerical calculations simulating a single tray. (A) shows the temperature distribution in the direction perpendicular to the stripes on the tray surface and bottom, (B) shows the intensity distribution of the irradiated laser light, (C) shows the overall temperature distribution for a single tray, and (D) shows the temperature scale of the overall temperature distribution diagram (C). [Figure 11A] An explanatory diagram of the temperature change curve during the first step heating process based on numerical calculations simulating a single tray (temperature change at the center of the tray surface). [Figure 11B]An explanatory diagram of the temperature change curve during the first step heating process based on numerical calculations simulating a single tray (temperature change near the position where thermocouple terminal 30 is attached on the bottom of the tray). [Figure 12] This is an explanatory diagram of the temperature change curve when the first step heating process is repeated 10 times using numerical calculations simulating a single tray. (A) shows the temperature change at the center of the tray surface, and (B) shows the temperature change near the position of the thermocouple terminal 30 on the bottom of the tray. [Figure 13] Figure 12(B) is an explanatory diagram of the change in temperature difference ΔT over time between each irradiation in the case of no cooling (w / o Cooling) calculated by numerical calculation, and shows the values ​​obtained from the local maximum and minimum values. [Figure 14] This figure shows the absorption rate A(T) calculated by extracting the section where the influence of the transient phenomenon at the beginning of heating disappears under each stepwise heating process condition. (A) shows the case of a tray alone, and (B) shows the case where powder is loaded on the tray. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described below with reference to the drawings. 1 is a functional block diagram of a laser beam absorptance measuring device for 3D printing used in the practice of the present invention. The laser beam absorptance measuring device for 3D printing of the present invention is a method for measuring the temperature dependence of the absorptance of a material such as powder using a metal powder additive manufacturing device. The laser beam absorptance measuring device 10 shown in FIG. 1 is a device that measures the laser beam absorptance (actual laser beam absorptance A(T)) of a metal powder sample 62 by irradiating the metal powder sample 62 with a laser beam L1. In this case, the metal powder sample 62 preferably has the same material, shape, and specifications as a metal component to be 3D-printed by laser irradiation. In this embodiment, the metal tray 63 and the metal powder sample 62 may be made of any material that can be laser-machined, such as titanium alloy (Ti-6Al-4V), nickel-based superalloy such as Hastelloy (registered trademark), or stainless steel such as SUS316. The metal tray 63 has a tray recess 63a in the center, and the metal powder sample 62 is dispersed in this tray recess 63a.

[0019] Furthermore, the irradiation surface 62a of the metal powder sample 62 is assumed to be in a powder state before being irradiated with the laser beam L1. Therefore, the irradiation surface 62a is more likely to absorb the laser beam L1 than when the tray 63 is in a polished mirror state. This makes it easier to obtain accurate results for the present invention, which determines the actual laser beam absorptance A(T) of the metal powder sample 62 by absorbing the irradiated laser beam L1 into the irradiation surface 62a and raising the temperature. Details of the actual laser beam absorptance A(T) will be described later.

[0020] 1, the laser light absorptance measuring device 10 includes a laser device 20, a thermocouple terminal 30, and a control unit 40. The laser device 20 includes a laser oscillator 21, a laser head 22, and a housing 23. The laser head 22 is disposed within the housing 23.

[0021] In this embodiment, the laser oscillator 21 is a fiber laser oscillator. The wavelength of the laser light L1 oscillated by the laser oscillator 21 is approximately 1070 nm (1.07 μm). The output of the laser oscillator 21 can be changed under the control of the control unit 40.

[0022] The laser oscillator 21 is not limited to a fiber laser oscillator, but may also be a semiconductor laser, YAG laser, or CO2 laser oscillator. Blue laser beams have also been used for metals in 3D modeling (ultraviolet laser beams for resins), and it is preferable that the wavelength of each laser beam be in the range of 0.4 μm to 1.2 μm. The laser oscillator 21 includes a mechanism 25 that transmits the laser beam L1 emitted from the laser oscillator 21 to the laser head 22.

[0023] As shown in FIG. 2, laser head 22 disposed in housing 23 is disposed at a distance X from irradiation surface 62a of metal powder sample 62 and faces irradiation surface 62a of metal powder sample 62. The laser head 22 has a Z-axis lens 24, a deflection mirror 26, and a deflection control device 28. The deflection mirror 26 changes the traveling direction of the collimated laser beam L1. In this embodiment, the deflection mirror 26 irradiates the laser beam L1 at a desired position on the irradiation surface 62a of the metal powder sample 62 in response to a deflection control signal from the deflection control device 28, and scans the laser beam L1 at a predetermined period and spatial interval, for example. The laser beam L1 is deflected by the deflection mirror 26 onto the plane of the metal powder sample 62 as a deflected beam and is focused by the Z-axis lens 24. The Z-axis lens 24 is composed of two lenses that change the focusing distance, and is composed of, for example, two lenses (one plano-concave and one biconvex).

[0024] Next, we will explain the thermocouple terminal 30. The thermocouple terminal 30 is attached to the bottom surface of the tray 63, and generates an electromotive force corresponding to the temperature of the location on the bottom surface of the tray 63 where the thermocouple terminal is attached. The thermocouple terminal 30 is a temperature sensor made up of two different metal conductors, and generates a voltage due to the Seebeck effect, which is the temperature difference T between the temperature at the junction of the two metals (temperature measurement junction) and the junction on the measuring instrument side (reference junction). When measuring temperature using a thermocouple, this voltage is measured with a measuring instrument, and there are two measurement methods as follows: The first method is to set the reference junction to 0°C (cold junction compensation) and read the temperature directly. The second method is to measure the temperature of the reference junction (reference junction compensation) and add it to the temperature difference. For example, the positive electrode may be a platinum-rhodium alloy and the negative electrode may be platinum, allowing for measurements in the range of 0 to +1100°C. Alternatively, the positive electrode may be an alloy primarily made of nickel and chromium, and the negative electrode may be an alloy primarily made of nickel and aluminum, allowing for measurements in the range of -200 to +1200°C.

[0025] The control unit 40 includes a laser light irradiation control unit 41 , a thermocouple temperature measurement unit 42 , a tray position control unit 43 , a metal powder supply control unit 44 , and an actual absorption rate calculation unit 45 . The laser light irradiation control unit 41 is electrically connected to the laser oscillator 21 of the laser device 20, and controls the irradiation time by turning the irradiation of the laser light L1 on and off, controls the irradiation output P of the laser light L1, and also sends a signal related to focusing to the Z-axis lens 24 and a scan control signal to the deflection control device 28. The laser light irradiation control unit 41 also outputs a control signal for scanning the laser light L1 at high speed while defocusing it, and controls the spacing and length of the stripes on the surface irradiated with the laser light L1, as well as the power and scanning speed of the laser light L1, so that the temperature rise of the irradiation spot on the surface irradiated with the laser light L1 is kept within allowable limits, and the uniformity of heating of the metal powder sample 62 and the tray 63 by the laser device 20 is kept within allowable limits. The thermocouple temperature measuring unit 42 is electrically connected to the thermocouple terminal 30 and converts the voltage generated by the two different metal conductors of the thermocouple terminal 30 into temperature (actual temperature) data of the thermocouple terminal 30 .

[0026] The tray position control section 43 controls the three-dimensional position of the tray 63 as a metal plate in the front-rear direction, width direction, and height direction. The metal powder supply control unit 44 controls the supply of metal powder stored in a hopper (not shown) to a tray recess 63 a, which is a recess provided in the tray 63 . The actual absorption rate calculation unit 45 calculates the actual absorption rate of the laser beam in the metal powder sample 62 according to the temperature at the location where the thermocouple terminal 30 is attached to the bottom surface of the tray 63 .

[0027] The metal powder additive manufacturing apparatus used in the laser light absorptance measuring device for 3D modeling of the present invention can be, for example, the SLM280 manufactured by SLM Solutions GmbH, located in Lübeck, Federal Republic of Germany. [Outline of the laser metal powder additive manufacturing device] 2 is an overall functional block diagram showing an embodiment of a metal powder 3D printer used in powder bed fusion. Referring to FIG. 2, the additive manufacturing apparatus 100 is, for example, a laser additive manufacturing apparatus. The additive manufacturing apparatus 100 includes a laser device 110, a galvanometer mirror 120, a control device 130, and a chamber 200.

[0028] The laser device 110 emits laser light. The laser device 110 is, for example, a fiber laser or a CO2 laser. The laser device 110 may be provided with a lens system (not shown). The lens system receives the laser light from the laser device 110 and focuses the laser light to form a laser 112. The galvanometer mirror 120 controls the irradiation of the laser 112. In other words, the galvanometer mirror 120 adjusts the position where the laser 112 is irradiated.

[0029] The chamber 200 includes a layer formation chamber 210, a modeling table 230, a powder supply chamber 220, and a recoater 250. To prevent oxidation of the metal powder particles 140 during irradiation with the laser 112, the chamber 200 is filled with an inert gas (argon, nitrogen, etc.) or maintained in a vacuum state.

[0030] The layer formation chamber 210 is a housing-like structure with an opening at the top. The modeling table 230 is housed in the layer formation chamber 210 and supported so as to be movable up and down. The modeling table 230 is raised and lowered by a motor (not shown).

[0031] The powder supply chamber 220 is located next to the layer formation chamber 210. The powder supply chamber 220 is shaped like a housing and includes a piston 240 that can move up and down. Metal powder particles 140 are stacked on the piston 240. The metal powder particles 140 serve as the raw material for the molded object. As the piston 240 rises, a layer of the metal powder particles 140 is discharged from the top opening of the layer formation chamber 210. The metal powder particles 140 are, for example, metal powders of highly heat-resistant nickel-based superalloys, cobalt-based superalloys, or iron-based superalloys, and examples of such metal powder particles include Hastelloy. Note that instead of the metal powder particles 140, ceramics such as Al2O3 may be used together with the metal powder particles 140, or inorganic powder particles such as ceramic particles may be used alone.

[0032] The recoater 250 is disposed near the upper opening of the powder supply chamber 220. The recoater 250 is moved in a specific direction (horizontal direction) by a motor (not shown), and reciprocates between the powder supply chamber 220 and the layer formation chamber 210. In Figure 2, the recoater 250 reciprocates in the X direction. The recoater 250 moves in the X direction, thereby moving the layer of metal powder particles 140 discharged from the powder supply chamber 220 in the horizontal direction and supplying it to the layer formation chamber 210. The metal powder particles 140 deposited on the modeling table 230 in the layer formation chamber 210 form a metal powder layer 260 made of the metal powder particles 140 on the modeling table 230. As the recoater 250 moves in the X direction, the metal powder particles 140 move in the horizontal direction, smoothing the surface of the metal powder layer 260.

[0033] The control device 130 includes a central processing unit (CPU), a memory, and a storage device such as a hard disk drive (HDD), which are not shown. The storage device stores well-known CAD (Computer Aided Design) applications and CAM (Computer Aided Manufacturing) applications. The control device 130 uses the CAD application to create three-dimensional shape data of the object to be manufactured.

[0034] The control device 130 further uses a CAM application to create processing condition data based on the three-dimensional data. In the additive manufacturing method, a model is formed by stacking multiple model portions formed by the laser 112. The processing condition data includes the processing conditions when each model portion is formed. In other words, processing condition data is created for each model portion. The control device 130 controls the laser device 110, the lens system, and the galvanometer mirror 120 based on the processing condition data to adjust the output, scanning speed, scanning interval, and irradiation position of the laser 112.

[0035] [Manufacturing process details] 3 is a flowchart illustrating an example of the operation of a metal powder 3D printer. In the metal powder additive manufacturing apparatus, an object to be molded is manufactured in the following steps according to the flowchart shown in FIG. As a preliminary preparation step for the metal powder additive manufacturing apparatus, a vacuum pump is used to evacuate the chamber 200. After the chamber 200 is evacuated, an inert gas (argon, nitrogen, etc.) is supplied into the chamber 200. Note that the atmosphere in the chamber 200 may be replaced by flowing an inert gas without evacuating it, and the modeling table 230 in the layer formation chamber 210 may be preheated.

[0036] Next, a metal powder layer 260, which is a thin layer of powder material containing metal particles, is formed (S100). Next, a laser beam is selectively irradiated onto the thin layer to form a model layer in which the metal particles contained in the powder material are sintered or melt-bonded (S110). The steps of forming the thin layer and forming the model layer are repeated in this order multiple times to stack the model layers (S120). In this way, the desired shape of the three-dimensional object is obtained (S140). [Example]

[0037] FIG. 4 is a diagram showing the essential configuration of one embodiment of the laser light irradiation range of a metal powder sample, where (A) is a perspective view and (B) is a cross-sectional view of the essential part. The metal powder sample 62 is scattered in a tray recess 63a provided in a horizontal tray 63. The tray 63 is provided in a metal powder additive manufacturing apparatus. The tray 63 has external dimensions of 10 mm x 10 mm x 1 mm, and the tray recess 63a has external dimensions of 9 mm x 9 mm x 0.1 mm. The metal powder sample 62 is filled in the tray recess 63a, and the external dimensions of the area irradiated with laser light are 8 mm x 8 mm. The laser light L1 is defocused, and the diameter of the irradiation area on the surface of the metal powder sample 62 is, for example, approximately 0.44 mm. When the stripe spacing is 0.02 mm, the number of stripes is 401, and when the stripe spacing is 0.05 mm, the number of stripes is 161. The length of each stripe irradiated with laser light is 8 mm.

[0038] The tray 63 and the metal powder sample 62 were made of titanium alloy (Ti-6Al-4V). The mass of the tray 63 alone was 0.4083 g, and the total mass of the tray 63 and the metal powder sample 62 was 0.4242 g. The power of the laser light irradiation was 50 W to 70 W, the irradiation interval of the stripe-shaped irradiation pattern was about 1 second, the number of irradiations was 10, and the irradiation speed was 20 m / second.

[0039] Assuming one-dimensional heat conduction, the temperature rise rate calculated for the tray 63 and the metal powder sample 62 as a unit is expressed by the following equation:

number

[0040] Figure 5 explains the formula for calculating the laser light absorption rate from the stepwise heating process. The laser light irradiation by the metal powder additive manufacturing device is performed using a scanning line scanning method similar to the raster scanning method, and the laser light irradiation is turned on during the forward and backward scanning passes and turned off when changing direction between them. If the temperature rise in one step heating process is ΔT and the time interval between steps is Δt, the above equation (1) can be expressed as follows using the difference:

number

number

[0041] By modifying the above equation (3), the parameter A(T) that represents the temperature dependence of the absorptance is expressed by the following equation: Note that the parameter L(T) that represents the temperature dependence of the heat loss takes into account the temperature dependence, and shows the case where the mass of the metal powder sample and the tray are clearly distinguished.

number

number

number

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[0042] Figure 6 is a diagram illustrating the temperature dependence of the specific heat of a titanium alloy (Ti-6Al-4V) according to one embodiment of the present invention. The specific heat of the titanium alloy is approximately 0.55 [J / (g K)] at 25°C, and increases linearly to approximately 0.73 [J / (g K)] at 900°C.

[0043] FIG. 7A is a diagram illustrating the maximum temperature achieved when one stepwise heating process is repeated 10 times under each stepwise heating process condition, which is one embodiment of the present invention, and shows the case of a single titanium alloy (Ti-6Al-4V) tray. The conditions for each stepwise heating process are a laser beam irradiation power of 50 W to 70 W, stripe spacing of 0.05 mm and 0.02 mm, number of stripes of 161 and 401, and a single tray 63. The maximum temperature achieved by a single titanium alloy (Ti-6Al-4V) tray was approximately 85°C when the laser irradiation power was 50 W, the stripe spacing was 0.05 mm, and the number of stripes was 161. It was approximately 190°C when the laser irradiation power was 70 W, the stripe spacing was 0.02 mm, and the number of stripes was 401. Under other step-wise heating process conditions, the maximum temperature achieved was somewhere in between and depended on the total irradiation power of the laser irradiation.

[0044] Figure 7B shows the temperature change of a single titanium alloy (Ti-6Al-4V) tray when a single step heating process is repeated 10 times, as an example of the present invention. This figure shows the temperature history for a single tray, where the laser beam power is 70 W, the stripe spacing is 0.05 mm, and the number of stripes is 161. By repeating the step-wise heating process 10 times, the temperature rises from 38°C before heating to approximately 105°C after 10 repetitions. Although one step-wise heating raises the temperature by about 8°C, cooling reduces the temperature by about 2 to 4°C.

[0045] FIG. 7C is a diagram illustrating the maximum temperature achieved by a titanium alloy (Ti-6Al-4V) powder sample when one stepwise heating process is repeated 10 times under each stepwise heating process condition, which is an embodiment of the present invention, and shows the case where the powder is loaded on a tray. The conditions for each stepwise heating process are: laser light irradiation power of 50W to 70W, stripe spacing of 0.05mm and 0.02mm, number of stripes of 161 and 401, and heating of tray 63 alone and tray 63 and metal powder sample 62 simultaneously. The maximum temperature of a titanium alloy (Ti-6Al-4V) powder sample was approximately 115°C when the laser irradiation power was 50 W, the stripe spacing was 0.05 mm, and the number of stripes was 161. It was approximately 270°C when the laser irradiation power was 70 W, the stripe spacing was 0.02 mm, and the number of stripes was 401. Under other stepwise heating process conditions, the maximum temperature was intermediate and depended on the total irradiation power of the laser irradiation.

[0046] Figure 7D illustrates the temperature drop due to heat loss in a titanium alloy (Ti-6Al-4V) powder sample when a single step-wise heating process is repeated 10 times, as in one embodiment of the present invention, with both a tray and a tray loaded with powder. Under each step-wise heating process, deviations from the overall trend in the temperature drop rate are apparent in the high-temperature region at the start of cooling. This is presumably due to a transient phenomenon that accompanies the uniformity of the temperature distribution caused by the non-uniform heating of the tray 63.

[0047] Figure 8 is an explanatory diagram for determining the parameter L(T), which represents the temperature dependence of heat loss, from the temperature drop curve during the cooling process under certain step-wise heating conditions. (A) shows an example of a cooling curve, (B) shows the first derivative dT / dt [K / s] of the cooling curve, and (C) shows m·c(T)·dT / dt [W], which is related to the heat loss parameter L(T) determined from the cooling curve. This shows the temperature history when the laser light irradiation power is 70 W, the stripe spacing is 0.05 mm, and there are 161 stripes. The cooling curve shows a concave curve that drops from 90°C after the transient phenomenon associated with the uniform temperature distribution to the ambient temperature of 38°C, with a time constant of approximately 24 seconds as approximated by a broken line. The first derivative of the cooling curve is approximately 2.3 [K / s] near 90°C. The heat loss parameter L(T) is approximately 0.5 [W].

[0048] Figure 9 is an explanatory diagram of the absorption rate A(T) calculated from the above equation 5 under each stepwise heating process condition, where (A) shows the case of a tray alone and (B) shows the case of a tray loaded with powder. The absorption coefficient A(T) is 0.35 to 0.45 for the tray alone, and 0.6 to 0.8 when powder is loaded on the tray, but the results fluctuate greatly at relatively low temperatures below about 80°C.

[0049] Figure 10 is an explanatory diagram of the temperature distribution during the first step heating process based on numerical calculations simulating a single tray. (A) shows the temperature distribution in the direction perpendicular to the stripes on the tray surface and bottom, (B) shows the intensity distribution of the irradiated laser light, (C) shows the overall temperature distribution diagram simulating the tray, and (D) shows the temperature scale of the overall temperature distribution diagram (C). Since the temperature distribution is non-uniform mainly in the direction perpendicular to the stripe, there is a discrepancy between the location where the irradiated laser light is absorbed and the measurement by the thermocouple.

[0050] Figure 11 is an explanatory diagram of the temperature change curve during the first step heating process based on a numerical calculation simulating a single tray, where (A) shows the temperature change at the center of the tray surface and (B) shows the temperature change near the location of the thermocouple terminal 30 on the bottom of the tray. Here, "w / o Cooling" indicates that neither thermal radiation nor heat transfer is performed (no cooling) in the heat balance calculation, while "w / Radiation & Transfer" indicates the case where both thermal radiation and heat transfer are taken into account. The estimated heat transfer coefficient from the experiment is 98 W / (m 2 ·K). At the center of the tray surface, the irradiation time of the irradiated laser beam, for example, assuming a defocused laser beam diameter of 0.44 mm and a scanning speed of 20 m / s, takes approximately 22 μs to pass through an area approximately the diameter of the irradiated laser beam. Therefore, when neither thermal radiation nor heat transfer is considered in the heat balance calculation, the maximum temperature at the center of the tray surface reaches approximately 89°C. However, once the irradiated laser beam passes, the temperature begins to drop, dropping to approximately 50°C within one second. In contrast, the maximum temperature at the bottom of the tray near the thermocouple terminal 30 reaches approximately 49°C. Although the temperature begins to drop once the irradiated laser beam passes, it remains above 48°C even after one second. In both cases, the temperature changes over time for approximately three seconds after the laser beam passes. Approximately three seconds after the laser beam stops passing, the temperatures at the center of the tray surface and the bottom of the tray drop to the same approximately 47.5°C and then become almost flat. Furthermore, when both thermal radiation and heat transfer are considered in the heat balance calculation, the temperature drops more rapidly than when they are not considered.

[0051] Figure 12 is an explanatory diagram of the temperature change curves when the first step heating process is repeated 10 times using numerical calculations simulating a single tray, with (A) showing the temperature change at the center of the tray surface and (B) showing the temperature change near the location of the thermocouple terminal 30 on the bottom of the tray. Here, "without cooling" means that there is no heat radiation or heat transfer (no cooling) in the heat balance calculations. "with radiation & transfer" takes both heat radiation and heat transfer into account.

[0052] Figure 13 is an explanatory diagram of the change over time in the temperature difference ΔT between each irradiation in the case of no cooling (w / o Cooling) calculated by numerical calculation in Figure 12(B), and shows the values ​​obtained from the local maximum and minimum values. In the 3-second period from the start of laser light irradiation, the temperature difference ΔT between each irradiation changes suddenly, and is not flat like the value in the period 3 seconds after the start of laser light irradiation. Therefore, we thought it would be best to extract a period where the influence of the transient phenomenon at the beginning of heating disappears, so we removed this 3-second period from the start of laser light irradiation and recalculated.

[0053] Figure 14 shows the absorption rate A(T) calculated by extracting the section where the influence of the transient phenomenon at the beginning of heating disappears under each stepwise heating process condition. (A) shows the case of a tray alone, and (B) shows the case where powder is loaded on the tray. The absorption coefficient A(T) is 0.35 to 0.40 for the tray alone, and 0.61 to 0.66 when powder is loaded on the tray, but even at relatively low temperatures below 80°C, the results are similar to those at relatively high temperatures above 80°C, eliminating fluctuations.

[0054] In the above embodiment, the tray recess 63a is provided in the center of the metal tray 63, and the metal powder sample 62 is deposited in this tray recess 63a. However, the present invention is not limited to this, and the laser light absorption rate of the tray material may be measured using only the tray. In this case, there is no need to use the metal powder sample. Furthermore, in the above embodiment, the laser light absorption rate of a metal powder sample is measured, but the present invention is not limited to this, and the powder material used as the sample may be a material such as ceramics or plastic used in 3D modeling. [Industrial Applicability]

[0055] The laser light absorptance measurement device and method for 3D printing of the present invention utilizes laser additive manufacturing devices, which have become increasingly popular recently, and can measure the laser light absorptance of materials for 3D printing in an environment where the temperature dependence of the absorptance of the 3D printing material for the laser light used can be set using the additive manufacturing device. [Explanation of symbols]

[0056] 10. Laser light absorption rate measuring device, 20...Laser device, 30...thermocouple terminal, 40... control unit, 41...Laser light irradiation control unit, 42 Thermocouple temperature measurement section, 43 Tray position control unit 44···Metal powder supply control unit, 45... Actual absorption rate calculation section, 62···Metal powder sample (sample), 62a···Irradiation surface, 63···Tray (metal plate), 63a···Tray recess (depression), c(T)...Specific heat, m...mass, A(T) is a parameter that describes the temperature dependence of the absorptance. L(T) Parameter that represents the temperature dependence of heat loss L1: Laser light, P: Laser light irradiation power, E: Irradiation energy within the irradiation interval (step interval), T...Temperature, w / o Cooling: No heat radiation or heat transfer (no cooling) w / Radiation & Transfer...Consideration of both heat radiation and heat transfer Δt Time interval between irradiations

Claims

1. A metal plate with a depression is placed in an existing additive manufacturing device, and a sample to be measured is deposited in the depression. a laser device that scans and irradiates a laser beam onto the irradiation surface of the sample; a thermocouple thermometer that measures the actual temperature of an irradiation spot portion of the irradiation surface irradiated with the laser light by a thermocouple attached to a rear surface of the metal plate having the depression; A method for measuring the laser light absorption rate of a sample using a sample temperature measuring step of measuring the actual temperature of the irradiation spot portion before, during, and after the irradiation of the laser light by the thermocouple thermometer; an actual absorption rate calculation step of calculating an actual laser light absorption rate of at least one of the sample and the metal plate using the irradiation conditions of the laser device, the temperature rise measured by the thermocouple thermometer due to irradiation of the laser light onto the irradiation spot portion, and a theoretical relationship of heat loss due to the temperature rise measured by the thermocouple thermometer; Along with providing an actual absorption rate calculation step of calculating an actual laser light absorption rate of the sample by calculating, through numerical calculation, a time corresponding to a response time of at least one of heating and cooling of the metal plate by the laser device when the metal plate is heated by the laser device, excluding from the analysis a temperature history over time including a transient phenomenon, calculating a theoretical relationship of heat loss due to a temperature rise in the irradiation spot portion, and suppressing measurement errors resulting from non-uniform heating of the metal plate by the laser device; A laser light absorption rate measuring method comprising:

2. 2. The laser light absorptance measuring method according to claim 1, wherein the actual laser light absorptance of the sample is calculated in the actual absorptance calculation step using the following equation: [Equation 1] Here, the subscript 1 represents the sample, the subscript 2 represents the metal plate, m represents the mass, c represents the specific heat, T represents the temperature, A(T) is a parameter representing the temperature dependence of the absorptance, L(T) is a parameter representing the temperature dependence of the heat loss, E is the irradiation energy within the irradiation interval (step interval), and Δt is the temporal irradiation interval.

3. 2. The laser light absorptance measuring method according to claim 1, wherein the actual laser light absorptance of the sample is calculated in the actual absorptance calculation step using the following equation: [Equation 2] Here, the subscript 1 represents the sample, and the subscript 2 represents the metal plate. m is mass, c is specific heat, T is temperature, A(T) is a parameter representing the temperature dependence of absorptance, L(T) is a parameter representing the temperature dependence of heat loss, E is the irradiation energy within the irradiation interval (step interval), and Δt is the time interval between irradiations. The specific heats of the sample and the metal plate are assumed to be the same within the tolerance range.

4. 2. The laser light absorptance measuring method according to claim 1, wherein the actual laser light absorptance of the sample is calculated in the actual absorptance calculation step using the following equation: [Equation 3] Here, the subscript 1 represents the sample, and the subscript 2 represents the metal plate. m is the mass, c is the specific heat, T is the temperature, A(T) is a parameter representing the temperature dependence of the absorptance, L(T) is a parameter representing the temperature dependence of the heat loss, E is the irradiation energy within the irradiation interval (step interval), and Δt is the time interval between irradiations. The specific heat of the sample is assumed to be a constant value within the allowable error range.

5. 2. The laser light absorptance measuring method according to claim 1, wherein the actual laser light absorptance of the sample is calculated in the actual absorptance calculation step using the following equation: [Equation 4] Here, the subscript 2 represents the metal plate, m is mass, c is specific heat, T is temperature, A(T) is a parameter representing the temperature dependence of absorptivity, L(T) is a parameter representing the temperature dependence of heat loss, E is the irradiation energy within the irradiation interval (step interval), Δt is the time interval between irradiations, and the heat capacity of the sample is assumed to be negligible within the allowable error range compared to the heat capacity of the metal plate material.

6. 6. The laser light absorptance measuring method according to claim 1, wherein the laser light is scanned at high speed while being defocused, to measure the laser light absorptance of the sample in the additive manufacturing environment together with its temperature dependency.

7. 7. The laser light absorption rate measuring method according to claim 1, wherein the laser light is scanned at high speed while being defocused, so that the temperature of the irradiation spot portion of the irradiation surface irradiated with the laser light rises within a range that does not melt the sample.

8. 8. The laser light absorptance measuring method according to claim 6 or 7, wherein the laser light is scanned at high speed while being defocused, and the interval and length of stripes of the laser light on the irradiation surface, as well as the power and scanning speed of the laser light, are determined so that a temperature rise in an irradiation spot portion of the irradiation surface irradiated with the laser light is suppressed within an allowable limit for uniform heating of the sample and the metal plate by the laser device.

9. The laser light absorption rate measuring method according to any one of claims 1 to 8, further comprising a laser light irradiation control unit that changes the heating pattern by changing the interval between each scanning line, the number of times the entire scanning line pattern is irradiated, or the time interval between irradiation of the entire scanning line pattern.

10. 10. The laser light absorption rate measuring method according to claim 1, wherein the sample is a metal powder, a ceramic powder, or a plastic powder.

11. a laser device that places a metal plate in an existing additive manufacturing device and scans and irradiates an irradiation surface of the metal plate with laser light; a thermocouple thermometer that measures the actual temperature of an irradiation spot portion of the irradiation surface irradiated with the laser light by a thermocouple attached to a back surface of a metal plate having a depression; A method for measuring the laser light absorption rate of the metal plate using a temperature measuring step of measuring the actual temperature of the irradiation spot portion before, during, and after the irradiation of the laser light by the thermocouple thermometer; an actual absorption rate calculation step of calculating an actual laser light absorption rate of the metal plate using the irradiation conditions of the laser device, the temperature rise measured by the thermocouple thermometer due to irradiation of the laser light onto the irradiation spot portion, and a theoretical relationship of heat loss due to the temperature rise measured by the thermocouple thermometer; In addition to providing an actual absorption rate calculation step of calculating an actual laser light absorption rate of the sample by calculating, through numerical calculation, a time corresponding to a response time of at least one of heating and cooling of the metal plate by the laser device when the metal plate is heated by the laser device, excluding from the analysis a temperature history over time including a transient phenomenon, calculating a theoretical relationship of heat loss due to a temperature rise in the irradiation spot portion, and suppressing measurement errors resulting from non-uniform heating of the metal plate by the laser device; A laser light absorption rate measuring method comprising:

12. A metal plate with a depression is placed in an existing additive manufacturing device, and a sample to be measured is deposited in the depression. a laser device that scans and irradiates a laser beam onto the irradiation surface of the sample; a thermocouple temperature measuring unit that measures the actual temperature of an irradiation spot portion of the irradiation surface that is irradiated with the laser light by a thermocouple attached to a back surface of a metal plate having a depression; An apparatus for measuring the laser light absorption rate of a sample using the thermocouple temperature measurement unit measures the actual temperature of the irradiation spot portion before, during, and after the irradiation of the laser light by the thermocouple; an actual absorption rate calculation unit that calculates an actual laser light absorption rate of at least one of the sample and the metal plate using the irradiation conditions of the laser device, the temperature rise measured by the thermocouple temperature measurement unit due to irradiation of the laser light onto the irradiation spot portion, and a theoretical relationship of heat loss due to the temperature rise measured by the thermocouple temperature measurement unit; Along with providing an actual absorption rate calculation unit that, when heating the metal plate with the laser device, obtains by numerical calculation a time corresponding to a response time of at least one of heating and cooling of the metal plate with the laser device, calculates a theoretical relationship of heat loss due to a temperature rise in the irradiation spot portion by excluding from the analysis a temperature history including a transient phenomenon, and calculates an actual laser light absorption rate of the sample while suppressing measurement errors resulting from non-uniform heating of the metal plate with the laser device; A laser light absorption rate measuring device comprising:

13. 13. The laser light absorptance measuring device according to claim 12, wherein the sample is a metal powder, a ceramic powder, or a plastic powder.

14. a laser device that places a metal plate in an existing additive manufacturing device and scans and irradiates an irradiation surface of the metal plate with laser light; a thermocouple temperature measuring unit that measures the actual temperature of an irradiation spot portion of the irradiation surface that is irradiated with the laser light by a thermocouple attached to a back surface of a metal plate having a depression; An apparatus for measuring the laser light absorption rate of the metal plate using the thermocouple temperature measurement unit measures the actual temperature of the irradiation spot portion before, during, and after the irradiation of the laser light by the thermocouple; an actual absorption rate calculation unit that calculates an actual laser light absorption rate of the metal plate using the irradiation conditions of the laser device, the temperature rise measured by the thermocouple temperature measurement unit due to irradiation of the laser light onto the irradiation spot portion, and a theoretical relationship of heat loss due to the temperature rise measured by the thermocouple temperature measurement unit; Along with providing an actual absorption rate calculation unit that, when heating the metal plate with the laser device, obtains by numerical calculation a time corresponding to a response time of at least one of heating and cooling of the metal plate with the laser device, calculates a theoretical relationship of heat loss due to a temperature rise in the irradiation spot portion by excluding from the analysis a temperature history including a transient phenomenon, and calculates an actual laser light absorption rate of the sample while suppressing measurement errors resulting from non-uniform heating of the metal plate with the laser device; A laser light absorption rate measuring device comprising:

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