Device and method for determining the coefficient of friction of a powder for additive manufacturing

Abstract

The application relates to a device and a method for measuring the friction coefficient of powder for additive manufacturing, in particular to the measurement of the powder-powder substrate friction coefficient and the measurement of the powder-substrate friction coefficient, which comprises a shell, a hopper, an electric control valve, a laser emitting device, a laser receiving device, a powder scraping device, a powder laying device, a mechanical claw, a telescopic arm, a tensile tester, an electric control translation stage, a measuring platform and a powder collecting barrel. The application adopts the electric control valve, the laser emitting and receiving device, the powder scraping device and other components to measure the repose angle of the powder to be measured, realizes the automatic measurement of the powder-powder friction coefficient, places the substrate through the control of the mechanical claw, lays the powder bed through the powder laying device, measures the friction force through the tensile tester, realizes the automatic measurement of the powder-substrate friction coefficient, reduces the manual intervention, improves the measurement precision, integrates the two measuring devices into one through the hydraulic device, and simplifies the device.

Description

Technical Field

[0001] The present application relates to the technical field of powder friction coefficient measurement, and specifically to a device and method for measuring the friction coefficient of powder for additive manufacturing. Background Art

[0002] Existing methods for determining the powder-powder friction coefficient mainly include the shear method and the angle of repose method. The shear method is quite different from the actual additive manufacturing process because the pre-compression and consolidation processes change the initial state of the powder, resulting in significant deviations in the measurement results. Although the angle of repose method is easy to operate, existing patent documents, such as the patent document with publication number CN108240949A, require reliance on complex image processing systems, which are costly and complex to operate; the patent document with publication number CN102445403A relies on manual visual judgment and has low accuracy; and the patent document with announcement number CN217359491U has problems such as many manual operations and easy introduction of errors, and it is difficult to meet the needs of the additive manufacturing field for high-precision and automated measurement.

[0003] Existing methods for measuring the powder-substrate friction coefficient mainly include the inclined plane method and the flat plate method. For the inclined plane method, existing technologies such as the patent document with publication number CN210626293U rely on manual judgment of the material sliding moment, which has the defects of strong subjectivity and low precision. Although the patent document with publication number CN114965257A uses a displacement detection sensor to monitor the material sliding, it has the advantages of faster response and lower error probability compared to manual observation, and the sliding friction coefficient obtained is more accurate. However, due to the monitoring principle of the displacement detection sensor, the device can only measure some larger bulk materials. Although the flat plate method can be automated, the existing technology is difficult to apply to small powders, and the powder-substrate interaction mechanism is quite different from that in the actual additive manufacturing process. In addition, although the existing friction coefficient measuring instrument can measure the friction coefficient of a variety of materials, its principle and test method are not applicable to small powders, and it is impossible to measure the powder-powder and powder-substrate friction coefficients simultaneously. Summary of the Invention

[0004] The purpose of the present invention is to provide a device and method for measuring the friction coefficient of powder for additive manufacturing, which can overcome the defects of the existing technology such as many manual operations, easy introduction of errors, difficulty in meeting the needs of high-precision and automated measurement in the field of additive manufacturing, reliance on manual judgment of the material sliding moment, strong subjectivity, low accuracy and limited measurement range, and inability to meet the requirements of additive manufacturing processes. The device and method can also simultaneously measure the powder-powder friction coefficient and the powder-substrate friction coefficient.

[0005] The first technical solution adopted by the present invention is: a device for measuring the friction coefficient of powder for additive manufacturing, comprising a shell, a funnel, an electric-controlled valve, a laser emitting device, a laser receiving device, a powder scraping device, a powder spreading device, a mechanical claw, a telescopic arm, a dynamometer, an electric-controlled translation stage, a measuring platform and a powder collecting bucket; a transparent observation window is provided on the panel of the shell, a display screen and buttons are provided under the panel, and a single-chip microcomputer is built into the display screen; the funnel is provided on the top of the shell, and the electric-controlled valve is provided at the discharge port of the funnel; the laser emitting device and the laser receiving device are relatively provided on both sides of the inner wall of the shell, and the powder scraping device is provided on the laser beam. between the light emitting device and the laser receiving device, and the bottom of the powder scraping device is at the same height as the lower vertex of the laser; the powder spreading device is arranged directly below the powder scraping device, the measuring platform is arranged directly below the powder spreading device, and the powder collecting bucket is arranged at the bottom of the shell and is located directly below the measuring platform; the telescopic arm and the electric-controlled translation platform are arranged on the side wall of the shell, one end of the telescopic arm is provided with the mechanical claw, the dynamometer is arranged on the electric-controlled translation platform, one end of the dynamometer is provided with a wire, and the other end of the wire is provided with a tooling fixture; the electric-controlled valve, laser emitting device, laser receiving device, telescopic arm, electric-controlled translation platform and button are all connected to the single-chip microcomputer.

[0006] Furthermore, the powder scraping device includes a scraper and a first swinging device, the first swinging device is fixed on the housing and connected to the scraper, the first swinging device is connected to the single chip microcomputer, and the single chip microcomputer controls the first swinging device to swing left and right.

[0007] Furthermore, the powder spreading device includes a scraper knife, a powder spreading knife, a motor and a second swinging device. The second swinging device is fixed on the shell and connected to the motor. The motor is also connected to the scraper knife and the powder spreading knife. The scraper knife and the powder spreading knife are arranged back to back. The blade surface of the scraper knife coincides with the upper plane of the measuring platform, and there is a gap between the blade surface of the powder spreading knife and the upper plane of the measuring platform; the motor and the second swinging device are connected to the single-chip microcomputer, and the single-chip microcomputer controls the rotation of the motor and the left and right swing of the second swinging device.

[0008] Furthermore, the measuring platform includes a powder-powder friction coefficient measuring platform, a powder-substrate friction coefficient measuring platform, a hydraulic rod and a powder collection funnel. One end of the hydraulic rod is connected to the bottom of the shell, and the other end is connected to the powder-powder friction coefficient measuring platform. The powder-substrate friction coefficient measuring platform is connected to the outer shell of the hydraulic rod through a support rod and is sleeved on the outside of the powder-powder friction coefficient measuring platform. The powder collection funnel is sleeved on the outside of the hydraulic rod, and the outlet of the powder collection funnel is aligned with the powder collection barrel; the hydraulic rod is also connected to the single-chip microcomputer.

[0009] Furthermore, a base is provided at the bottom of the shell, and the base is provided at the four corners of the bottom of the shell, and a rubber pad is provided at the bottom of the base.

[0010] The second technical solution adopted by the present invention is: a method for measuring the friction coefficient of powder for additive manufacturing, using the device described in the first technical solution for measurement, comprising the following steps:

[0011] S1: Add the powder to be tested into the funnel, fix the substrate to be tested on the fixture, place the substrate to be tested on the mechanical gripper, and close the transparent observation window;

[0012] S2: Use the button to input the number of times the powder-powder friction coefficient is measured to start measuring the powder-powder friction coefficient. The specific steps are as follows:

[0013] S201: The single chip microcomputer controls the extension of the hydraulic rod to raise the powder-powder friction coefficient measurement platform until the upper plane coincides with the blade surface of the scraper;

[0014] S202: The single chip microcomputer controls the electronically controlled valve to open, and the powder to be tested begins to flow out of the discharge port of the funnel, falls onto the powder-powder friction coefficient measurement platform, and accumulates into a cone shape;

[0015] S203: The single-chip microcomputer controls the electric control valve to close and controls the laser emitting device to emit a horizontal linear laser with a width of L0. Part of the laser light is blocked by the accumulated powder to be tested, and the other part of the laser light is received by the laser receiving device. The laser receiving device transmits the received laser light width L to the single-chip microcomputer and calculates the powder-powder friction coefficient.

[0016] S204: After the data is transmitted and the calculation is completed, the single chip microcomputer controls the laser emitting device and the laser receiving device to stop working, and controls the powder scraping device to scrape off the powder to be measured on the powder-powder friction coefficient measurement platform, completing a powder-powder friction coefficient measurement.

[0017] S205: Repeat steps S202 to S204 according to the number of measurements input, and take the average value of the powder-powder friction coefficient calculated each time as the final measurement result;

[0018] S3: Use the button to input the number of times the friction coefficient between the powder and the substrate is measured to start measuring the friction coefficient between the powder and the substrate. The specific steps are as follows:

[0019] S301: The single chip computer first controls the hydraulic rod to retract, so that the upper surface of the powder-powder friction coefficient measurement platform drops to coincide with the upper plane of the powder-substrate friction coefficient measurement platform;

[0020] S302: The single chip microcomputer controls the electronically controlled valve to open, and the powder to be tested begins to flow out of the discharge port of the funnel, falls onto the powder-substrate friction coefficient measurement platform, and accumulates into a cone shape. At this time, the single chip microcomputer controls the electronically controlled valve to close;

[0021] S303: The single chip microcomputer controls the powder spreading device to spread the powder to be tested. The fallen powder to be tested falls into the powder collecting funnel and finally flows into the powder collecting bucket for collection.

[0022] S304: Repeat steps S302 to S303 at least three times to ensure that the powder to be tested is evenly spread on the powder-substrate friction coefficient measurement platform;

[0023] S305: After the powder is applied, the single-chip microcomputer controls the mechanical claw to clamp the substrate to be tested, then flips the substrate to be tested counterclockwise so that the upper surface of the substrate to be tested is initially facing downward and parallel to the horizontal plane. The telescopic arm and the mechanical claw are then controlled to move the substrate to be tested to a position where the lower surface is 1 mm away from the upper surface of the powder to be tested on the powder-substrate friction coefficient measurement platform. The mechanical claw is then controlled to open so that the substrate to be tested is placed on the upper surface of the powder to be tested. The single-chip microcomputer then controls the mechanical claw and the telescopic arm to return to their initial positions.

[0024] S306: The single-chip microcomputer controls the electric translation stage to drive the dynamometer to move rightward at a uniform speed. The dynamometer pulls the substrate to be tested on the powder to be tested to move rightward at a uniform speed via the wire. The dynamometer measures the friction force F at the moment of pulling and transmits the data in real time to the single-chip microcomputer to calculate the powder-substrate friction coefficient.

[0025] S307: The single-chip microcomputer controls the mechanical claw to flip counterclockwise and control the telescopic arm to extend to the specified position. The mechanical claw controls the mechanical claw to clamp the substrate to be measured and move to the specified position, then flips 90 degrees clockwise. Then, the telescopic arm and the electronically controlled translation stage return to their initial positions, completing a powder-substrate friction coefficient measurement.

[0026] S308: After data transmission and calculation are completed, the single chip microcomputer controls the powder spreading device to clean the powder to be tested on the powder-substrate friction coefficient measurement platform. The scraped powder to be tested falls into the powder collection funnel and flows into the powder collection bucket for collection;

[0027] S309: Repeat steps S302 to S308 according to the input number of measurements, and take the average value of the powder-substrate friction coefficient calculated each time as the final measurement result.

[0028] Furthermore, the specific formula for calculating the powder-powder friction coefficient is:

[0029] μ1= tanθ = h / r;

[0030] h = L0– L;

[0031] Wherein, μ1 represents the powder-powder friction coefficient, θ represents the angle of repose, h represents the height of the piled powder to be tested, and r represents the radius of the powder-powder friction coefficient measurement platform.

[0032] Furthermore, the specific formula for calculating the powder-substrate friction coefficient is:

[0033] μ2= F / N;

[0034] Where μ2 represents the powder-substrate friction coefficient, and N represents the normal pressure of the substrate.

[0035] The beneficial effects of the present invention are: the present invention can measure both the powder-powder friction coefficient and the powder-substrate friction coefficient, thereby saving equipment costs; the present invention has a simple structure, is easy to operate, can perform repeated experiments, and has a high degree of automation. No excessive manual intervention is required during the measurement process, effectively preventing operational errors introduced by manual operation, improving measurement accuracy while saving the labor of researchers; the present invention adopts a closed design, which is conducive to reducing external interference and improving the accuracy of the results, while also avoiding the risk of fine powder flying into the air being inhaled by the human body, thereby protecting the health of personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 A front view of an embodiment of the present invention;

[0038] Figure 2 Schematic diagram of the structure of the wire and fixture in an embodiment of the present invention;

[0039] Figure 3 Schematic diagram of the structure of the powder spreading device in an embodiment of the present invention;

[0040] Figure 4 Schematic diagram of the structure of the measurement platform in an embodiment of the present invention;

[0041] Figure 5 Schematic diagram of the working state when measuring the powder-powder friction coefficient according to the embodiment of the present invention Figure 1 ;

[0042] Figure 6 Schematic diagram of the working state when measuring the powder-powder friction coefficient according to the embodiment of the present invention Figure 2 ;

[0043] Figure 7 Schematic diagram of the working state when measuring the powder-substrate friction coefficient according to an embodiment of the present invention.

[0044] Explanation of the accompanying drawings: 1-shell, 2-funnel, 3-electrically controlled valve, 4-laser emitting device, 5-laser receiving device, 6-mechanical claw, 7-telescopic arm, 8-tensile force gauge, 9-electrically controlled translation stage, 10-powder collecting bucket, 11-transparent observation window, 12-display screen, 13-button, 14-wire, 15-tooling fixture, 16-scraper, 17-first swinging device, 18-powder scraping knife, 19-powder spreading knife, 20-motor, 21-second swinging device, 22-powder-powder friction coefficient measuring platform, 23-powder-substrate friction coefficient measuring platform, 24-hydraulic rod, 25-powder collecting funnel, 26-base, 27-powder to be measured, 28-substrate to be measured. DETAILED DESCRIPTION

[0045] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0046] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by persons of ordinary skill in the field described in this application. "First", "second" and similar words used in this patent application specification and claims do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, "one" or "an" and similar words do not indicate a quantity limitation, but rather indicate the existence of at least one. "Connected" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship also changes accordingly.

[0047] like Figures 1 to 4As shown, a device for measuring the friction coefficient of powder used in additive manufacturing comprises a housing 1, a hopper 2, an electrically controlled valve 3, a laser emitting device 4, a laser receiving device 5, a powder scraping device, a powder spreading device, a mechanical gripper 6, a telescopic arm 7, a dynamometer 8, an electrically controlled translation stage 9, a measurement platform, and a powder collection bucket 10. A transparent observation window 11 is provided on the panel of the housing 1, and a display screen 12 and buttons 13 are provided below the panel. The display screen 12 houses a built-in single-chip microcomputer (not shown). The transparent observation window 11 provides an operator with a visual field. The operator can interact with the device through the display screen 12, read measurement results, and issue operational instructions through the buttons 13.

[0048] The funnel 2 is arranged at the top of the shell 1, and the electric control valve 3 is arranged at the discharge port of the funnel 2. The discharge of the funnel 2 can be controlled by the electric control valve 3. The laser emitting device 4 and the laser receiving device 5 are arranged on both sides of the inner wall of the shell 1. The laser emitting device 4 and the laser receiving device 5 are both rectangular structures and can emit a linear laser beam of a certain width. The powder scraping device is arranged between the laser emitting device 4 and the laser receiving device 5, and the bottom of the powder scraping device is at the same height as the lower vertex of the laser; the powder spreading device is arranged directly below the powder scraping device, the measuring platform is arranged directly below the powder spreading device, and the powder collecting bucket 10 is arranged at the bottom of the shell 1 and is located directly below the measuring platform. The telescopic arm 7 and the electrically controlled translation platform 9 are arranged on the side wall of the shell 1, the mechanical claw 6 is provided at one end of the telescopic arm 7, the dynamometer 8 is provided on the electrically controlled translation platform 9, a wire 14 is provided at one end of the dynamometer 8, and a fixture 15 is provided at the other end of the wire 14. The substrate 28 to be tested is clamped by the fixture 15 for measurement; the electrically controlled valve 3, laser emitting device 4, laser receiving device 5, telescopic arm 7, electrically controlled translation platform 9 and button 13 are all connected to the single chip microcomputer, and automatic control is achieved by the single chip microcomputer.

[0049] In an embodiment of the present invention, the powder scraping device includes a scraper 16 and a first swinging device 17. The first swinging device 17 is fixed on the housing 1 and connected to the scraper 16. The first swinging device 17 is connected to the single-chip microcomputer, and the single-chip microcomputer controls the first swinging device 17 to swing left and right, thereby driving the scraper 16 to swing to perform powder scraping operations. The powder spreading device includes a scraper 18, a powder spreading knife 19, a motor 20 and a second swinging device 21. The second swinging device 21 is fixed on the shell 1 and connected to the motor 20. The motor 20 is also connected to the scraper 18 and the powder spreading knife 19. The scraper 18 and the powder spreading knife 19 are arranged back to back. The blade surface of the scraper 18 coincides with the upper plane of the measuring platform to ensure that the scraper 18 can fully scrape off the powder 27 to be tested on the surface of the measuring platform, and there is a gap between the blade surface of the powder spreading knife 19 and the upper plane of the measuring platform. In the embodiment of the present invention, the width of the gap is 5 mm, that is, the powder 27 to be tested can be spread 5 mm thick on the surface of the measuring platform using the powder spreading knife 19. The motor 20 and the second swing device 21 are connected to the single chip microcomputer, and the single chip microcomputer controls the rotation of the motor 20 and the left and right swing of the second swing device 21, thereby driving the scraping knife 18 and the powder spreading knife 19 to swing, and perform the scraping operation or the powder spreading operation; the rotation of the motor 20 can adjust the position of the scraping knife 18 and the powder spreading knife 19, and adjust the tool to be used to the position below for operation.

[0050] The measuring platform includes a powder-powder friction coefficient measuring platform 22, a powder-substrate friction coefficient measuring platform 23, a hydraulic rod 24, and a powder collection funnel 25. One end of the hydraulic rod 24 is connected to the bottom of the housing 1, and the other end is connected to the powder-powder friction coefficient measuring platform 22. The powder-substrate friction coefficient measuring platform 23 is connected to the outer shell of the hydraulic rod 24 via a support rod and is sleeved on the outside of the powder-powder friction coefficient measuring platform 22. The powder collection funnel 25 is sleeved on the outside of the hydraulic rod 24, and the outlet of the powder collection funnel 25 is aligned with the powder collection bucket 10. The hydraulic rod 24 is also connected to the single-chip microcomputer, which controls the hydraulic rod 24 to rise and fall, thereby adjusting whether the embodiment of the present invention enters the powder-powder friction coefficient measuring mode or the powder-substrate friction coefficient measuring mode. The powder collection funnel 25 can collect the fallen powder 27 to be measured in the powder collection bucket 10 for easy recovery. In order to keep the device stable, the embodiment of the present invention further provides a base 26 at the bottom of the shell 1. The base 26 is provided at the four corners of the bottom of the shell. The bottom of the base 26 is provided with a rubber pad to alleviate vibration and reduce interference with the experiment.

[0051] The method for measuring the friction coefficient of powder for additive manufacturing according to an embodiment of the present invention specifically comprises the following steps:

[0052] S1: Add test powder 27 to funnel 2, fix the test substrate 28 to the fixture 15, place the test substrate 28 on the mechanical gripper 6, and close the transparent observation window 11. The test substrate 28 used in the measurement process has a size of 150 mm long, 50 mm wide, and 5 mm high.

[0053] S2: Press button 13 to input the number of times the powder-powder friction coefficient is measured to start measuring the powder-powder friction coefficient. The specific steps are as follows:

[0054] S201: If Figure 5 As shown, the single chip microcomputer controls the hydraulic rod 24 to extend, so that the powder-powder friction coefficient measuring platform 22 rises until the upper plane of the powder-powder friction coefficient measuring platform 22 coincides with the blade surface of the scraper 16 .

[0055] S202: The single chip microcomputer controls the electronically controlled valve 3 to open, and the powder 27 to be tested begins to flow out from the discharge port of the funnel 2, falls onto the powder-powder friction coefficient measuring platform 22, and accumulates into a cone shape.

[0056] S203: If Figure 6 As shown, when the powder 27 to be tested forms a conical powder pile on the surface of the powder-powder friction coefficient measurement platform 22, the single-chip microcomputer controls the electric control valve 3 to close, and the powder 27 to be tested stops falling. The single-chip microcomputer controls the laser emitting device 4 to emit a horizontal linear laser with a width of L0. Part of the laser is blocked by the accumulated powder 27 to be tested, and the other part is received by the laser receiving device 5. The laser receiving device 5 transmits the received laser width L to the single-chip microcomputer and calculates the powder-powder friction coefficient. The specific formula for calculating the powder-powder friction coefficient is:

[0057] μ1= tanθ = h / r;

[0058] h = L0– L;

[0059] Here, μ1 represents the powder-powder friction coefficient, θ represents the angle of repose, h represents the height of the accumulated powder 27 to be measured, and r represents the radius of the powder-powder friction coefficient measurement platform 22 .

[0060] S204: After the data is transmitted and the calculation is completed, the single-chip microcomputer controls the laser emitting device 4 and the laser receiving device 5 to stop working, and then controls the powder scraping device to swing back and forth to scrape the powder 27 to be tested from the powder-powder friction coefficient measurement platform 22. In the embodiment of the present invention, the swing angle of the first swinging device 17 is between -60° and 60°. The scraped powder 27 to be tested falls onto the upper surface of the powder-substrate friction coefficient measurement platform 23. When the powder scraping device has completely scraped off the powder 27 to be tested from the upper surface of the powder-powder friction coefficient measurement platform 22, the single-chip microcomputer controls the powder scraping device to stop working. At this point, a powder-powder friction coefficient measurement is completed.

[0061] S205: Repeat steps S202 to S204 according to the input number of measurements, and take the average value of the powder-powder friction coefficient calculated each time as the final measurement result.

[0062] S3: Press button 13 to input the number of times the friction coefficient between the powder and the substrate is measured, and start measuring the friction coefficient between the powder and the substrate. The specific steps are as follows:

[0063] S301 : The single chip microcomputer first controls the hydraulic rod 24 to retract, so that the upper surface of the powder-powder friction coefficient measuring platform 22 drops to coincide with the upper plane of the powder-substrate friction coefficient measuring platform 23 .

[0064] S302: The single chip microcomputer controls the electronically controlled valve 3 to open, and the powder 27 to be tested begins to flow out from the discharge port of the funnel 2, falls to the powder-substrate friction coefficient measurement platform 23, and accumulates into a cone. At this time, the single chip microcomputer controls the electronically controlled valve 3 to close.

[0065] S303: The microcontroller controls the oscillating mechanism of the powder spreading device to start operating, driving the powder spreading blade 19 to swing back and forth, spreading the test powder 27 flat. In this embodiment, the swing angle of the second oscillating mechanism 21 is also -60° to 60°. The falling test powder 27 falls into the powder collection hopper 25 and ultimately flows into the powder collection bucket 10 for collection.

[0066] S304 : Repeat steps S302 to S303 at least three times to ensure that the powder 27 to be tested is evenly spread on the powder-substrate friction coefficient measuring platform 23 .

[0067] S305: If Figure 7As shown, after the powder spreading is completed, the single chip microcomputer controls the mechanical claw 6 to clamp the substrate to be tested 28, and then flips the substrate to be tested 28 counterclockwise so that the upper surface of the substrate to be tested 28 is initially facing downward and parallel to the horizontal plane, and then controls the telescopic arm 7 and the mechanical claw 6 to move the substrate to be tested 28 to a position where the lower surface is 1 mm away from the upper surface of the powder to be tested 27 on the powder-substrate friction coefficient measuring platform 23, and controls the mechanical claw 6 to open so that the substrate to be tested 28 is placed on the upper surface of the powder to be tested 27; then the single chip microcomputer controls the mechanical claw 6 and the telescopic arm 7 to return to the initial position.

[0068] S306: The single-chip microcomputer controls the electric translation stage 9 to drive the dynamometer 8 to move rightward at a uniform speed. The dynamometer 8 pulls the substrate 28 to be tested on the powder 27 to move rightward at a uniform speed via the wire 14. The dynamometer 8 measures the friction force F at the moment of pulling and transmits the data in real time to the single-chip microcomputer to calculate the powder-substrate friction coefficient. The specific formula for calculating the powder-substrate friction coefficient is:

[0069] μ2= F / N;

[0070] Where μ2 represents the powder-substrate friction coefficient, and N represents the normal pressure of the substrate.

[0071] S307: The single-chip microcomputer controls the mechanical claw 6 to flip counterclockwise and controls the telescopic arm 7 to extend to the specified position. The mechanical claw 6 controls the mechanical claw 6 to clamp the substrate 28 to be tested and move to the specified position, then flips 90 degrees clockwise. Then, the telescopic arm 7 and the electrically controlled translation stage 9 are controlled to return to their initial positions, completing a measurement of the powder-substrate friction coefficient.

[0072] S308: After the data is transmitted and the calculation is completed, the single-chip microcomputer controls the motor 20 of the powder spreading device to operate so that the blade surface of the powder scraper 18 coincides with the plane on the powder-substrate friction coefficient measurement platform 23. The single-chip microcomputer then controls the swing device to drive the powder scraper 18 to swing back and forth, cleaning the powder 27 to be tested on the powder-substrate friction coefficient measurement platform 23. The scraped powder 27 to be tested falls into the powder collection funnel 25 and flows into the powder collection bucket 10 for collection.

[0073] S309: Repeat steps S302 to S308 according to the input number of measurements, and take the average value of the powder-substrate friction coefficient calculated each time as the final measurement result.

[0074] This embodiment of the present invention utilizes a high-precision laser emitting device 4 and a laser receiving device 5 to measure the height of the powder being measured. These devices can emit and receive linear laser beams with a width accuracy of 4 to 132 microns. This accuracy surpasses the 1mm accuracy achieved by conventional length measuring rulers and the 0.1-degree accuracy achieved by conventional angle measuring rulers. By employing this high-precision laser measurement system, the embodiment of the present invention significantly improves the accuracy of measurement results. During the powder-substrate friction coefficient measurement process, the tensile gauge employed in this embodiment of the present invention achieved a full-scale accuracy of ±0.5%, further ensuring the accuracy and stability of tensile force measurements.

[0075] In the embodiment of the present invention, 316L stainless steel powder was used as the test object. In the process of measuring the powder-powder friction coefficient, the width of the laser emitted by the laser emitting device 4 was about 30 mm, and the width of the laser received by the laser receiving device 5 was about 22 to 23 mm. The stacking height of the powder to be tested on the platform was 7 to 8 mm, and the radius was 25 mm. According to the formula, the powder-powder friction coefficient was calculated to be 0.28 to 0.32. In the process of measuring the powder-substrate friction coefficient, for a 316L stainless steel substrate with a size of 150 mm long, 50 mm wide and 5 mm high, its density was 7.98 g / cm 3 , the normal pressure N of the substrate is calculated to be 2.93265N; the friction force F measured by the dynamometer 8 ranges from 0.58653N to 1.466325N. According to the formula, the powder-substrate friction coefficient ranges from 0.2 to 0.5.

[0076] After the measurement is completed, the operator can read the measurement results from the display screen 12. The embodiment of the present invention can measure both the powder-powder friction coefficient and the powder-substrate friction coefficient, thereby saving equipment costs. The present invention has a simple structure, is easy to operate, can perform repeated experiments, and has a high degree of automation. During the measurement process, no excessive manual intervention is required, effectively preventing operational errors introduced by manual operation, improving measurement accuracy, and saving researchers' labor. The present invention adopts a closed design, which is conducive to reducing external interference and improving the accuracy of the results. It also avoids the risk of fine powder flying into the air being inhaled by the human body, thereby protecting the health of personnel.

[0077] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A device for measuring the friction coefficient of powder for additive manufacturing, characterized in that: It includes a shell, a funnel, an electric-controlled valve, a laser emitting device, a laser receiving device, a powder scraping device, a powder spreading device, a mechanical claw, a telescopic arm, a dynamometer, an electric-controlled translation platform, a measuring platform and a powder collecting bucket; a transparent observation window is provided on the panel of the shell, a display screen and buttons are provided under the panel, and a single-chip microcomputer is built in the display screen; the funnel is provided on the top of the shell, and the electric-controlled valve is provided at the discharge port of the funnel; the laser emitting device and the laser receiving device are relatively provided on both sides of the inner wall of the shell, and the powder scraping device is provided between the laser emitting device and the laser receiving device, and The bottom of the powder scraping device is at the same height as the lower vertex of the laser; the powder spreading device is arranged directly below the powder scraping device, the measuring platform is arranged directly below the powder spreading device, and the powder collecting bucket is arranged at the bottom of the shell and is located directly below the measuring platform; the telescopic arm and the electric-controlled translation platform are arranged on the side wall of the shell, one end of the telescopic arm is provided with the mechanical claw, the dynamometer is arranged on the electric-controlled translation platform, one end of the dynamometer is provided with a wire, and the other end of the wire is provided with a fixture; the electric-controlled valve, laser emitting device, laser receiving device, telescopic arm, electric-controlled translation platform and button are all connected to the single-chip microcomputer; The measuring platform includes a powder-powder friction coefficient measuring platform, a powder-substrate friction coefficient measuring platform, a hydraulic rod, and a powder collection funnel. One end of the hydraulic rod is connected to the bottom of the housing, and the other end is connected to the powder-powder friction coefficient measuring platform. The powder-substrate friction coefficient measuring platform is connected to the housing of the hydraulic rod via a support rod and is sleeved on the outside of the powder-powder friction coefficient measuring platform. The powder collection funnel is sleeved on the outside of the hydraulic rod, and the powder collection funnel outlet is aligned with the powder collection bucket. The hydraulic rod is also connected to the single-chip microcomputer. The bottom of the shell is also provided with a base, which is arranged at the four corners of the bottom of the shell, and the bottom of the base is provided with a rubber pad; The laser emitting device and the laser receiving device can emit and receive horizontal linear lasers with a width accuracy of 4-132 microns.

2. The device for measuring the friction coefficient of powder for additive manufacturing according to claim 1, characterized in that: The powder scraping device includes a scraper and a first swinging device, the first swinging device is fixed on the housing and connected to the scraper, the first swinging device is connected to the single chip microcomputer, and the single chip microcomputer controls the first swinging device to swing left and right.

3. The device for measuring the friction coefficient of powder for additive manufacturing according to claim 1, characterized in that: The powder spreading device includes a powder scraper, a powder spreading knife, a motor and a second swinging device. The second swinging device is fixed on the shell and connected to the motor. The motor is also connected to the powder scraper and the powder spreading knife. The powder scraper and the powder spreading knife are arranged back to back. The blade surface of the powder scraper coincides with the upper plane of the measuring platform, and there is a gap between the blade surface of the powder spreading knife and the upper plane of the measuring platform; the motor and the second swinging device are connected to the single-chip microcomputer, and the single-chip microcomputer controls the rotation of the motor and the left and right swing of the second swinging device.

4. A method for measuring the friction coefficient of powder for additive manufacturing, using the device according to claim 1, characterized in that: The process includes the following steps: S1: Add the powder to be tested into the funnel, fix the substrate to be tested on the fixture, place the substrate to be tested on the mechanical claw, and close the transparent observation window; S2: Operate the button to input the number of times the powder-powder friction coefficient is measured to start measuring the powder-powder friction coefficient. The specific steps are as follows: S201: The single chip microcomputer controls the extension of the hydraulic rod to raise the powder-powder friction coefficient measurement platform until the upper plane coincides with the blade surface of the scraper; S202: The microcontroller controls the electronically controlled valve to open, and the powder to be tested begins to flow out of the discharge port of the funnel, falls onto the powder-powder friction coefficient measurement platform, and accumulates into a cone shape; S203: The single chip microcomputer controls the electric control valve to close, and controls the laser emitting device to emit a horizontal linear laser with a width of L0. Part of the laser light is blocked by the accumulated powder to be tested, while the other part is received by the laser receiving device. The laser receiving device transmits the received laser width L to the single chip microcomputer and calculates the powder-powder friction coefficient. S204: After the data is transmitted and the calculation is completed, the microcontroller controls the laser emitting device and the laser receiving device to stop working, and controls the powder scraping device to scrape off the powder-powder friction coefficient measurement platform to be tested, completing a powder-powder friction coefficient; S205: Repeat steps S202 to S204 according to the number of measurements entered, taking the average value of the powder-powder friction coefficient calculated each time as the final measurement result; S3: Use the button to input the number of times the powder-substrate friction coefficient is measured to start measuring the powder-substrate friction coefficient. The specific steps are as follows: S301: The microcontroller first controls the hydraulic rod to retract, so that the upper surface of the powder-powder friction coefficient measurement platform drops to coincide with the upper plane of the powder-substrate friction coefficient measurement platform; S302: The microcontroller controls the electronically controlled valve to open, and the powder to be tested begins to flow out of the discharge port of the funnel, falls onto the powder-substrate friction coefficient measurement platform, and accumulates into a cone. At this time, the microcontroller controls the electronically controlled valve to close; S303: MCU control the powder shop device to work, the powder to be tested flattened, the powder to be tested falls into the powder collection funnel, and eventually flows into the powder collection bucket for collection; S304: Repeat steps S302 to S303 at least three times to ensure that the powder to be tested is evenly spread on the powder-substrate friction coefficient measurement platform; S305: After the powder is applied, the microcontroller controls the mechanical claw to clamp the substrate to be tested, then flips the substrate counterclockwise so that its upper surface is initially facing downward and parallel to the horizontal plane. The telescopic arm and mechanical claw are then controlled to move the substrate to a position where its lower surface is 1 mm from the upper surface of the powder to be tested on the powder-substrate friction coefficient measurement platform. The mechanical claw is then controlled to open, placing the substrate to be tested on the upper surface of the powder to be tested. The microcontroller then controls the mechanical claw and telescopic arm to return to their initial positions. S306: The microcontroller controls the electronically controlled translation stage to drive the dynamometer to move in a uniform linear motion to the right. The dynamometer pulls the substrate to be tested on the powder to be tested in a uniform linear motion to the right through the wire. The dynamometer measures the friction force F at the moment of pulling and transmits the data in real time to the microcontroller to calculate the powder-substrate friction coefficient. S307: The microcontroller controls the mechanical claw to flip counterclockwise and extend the telescopic arm to the specified position. The mechanical claw then clamps the substrate to be tested and moves to the specified position before flipping 90 degrees clockwise. The telescopic arm and the electronically controlled translation stage then return to their initial positions, completing a powder-substrate friction coefficient measurement. S308: After the data is transmitted and the calculation is completed, the microcontroller controls the powder spreading device to clean the powder to be tested on the powder-substrate friction coefficient measurement platform. The scraped powder to be tested falls into the powder collection funnel and flows into the powder collection bucket for collection; S309: Repeat steps S302 to S308 according to the number of measurements input, and take the average value of the powder-substrate friction coefficient calculated each time as the final measurement result; The specific formula for calculating the powder-powder friction coefficient is: μ1=tanθ=h / r; h=L0–L; where μ1 represents the powder-powder friction coefficient, θ represents the angle of repose, h represents the height of the piled powder to be tested, and r represents the radius of the powder-powder friction coefficient measurement platform; The specific formula for calculating the powder-substrate friction coefficient is: μ2=F / N; Where μ2 represents the powder-substrate friction coefficient and N represents the normal pressure of the substrate.

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