3D printer powder bed density calibration and measurement device

Abstract

The invention relates to the technical field of powder characteristic measurement, in particular to a 3D printer powder bed density calibration and measurement device which comprises a rack, a mounting plate is fixedly connected to the inner wall of a mounting sleeve, and a first laser distance measuring sensor and a second laser distance measuring sensor which are located at the same height are fixedly connected to the bottom of the mounting plate; the first laser distance measuring sensor transmitting point is located on the axis of the mounting sleeve, the horizontal distance between the second laser distance measuring sensor transmitting point and the first laser distance measuring sensor transmitting point is L. The first laser distance measuring sensor and the second laser distance measuring sensor are used for compensating the steel ball offset error by measuring the height of two points on the spherical surface of the steel ball. The first laser distance measuring sensor and the second laser distance measuring sensor are used for measuring the heights of two points on the spherical surface of the steel ball respectively, the actual circle center height is calculated through the horizontal distance L between the two points and the diameter D of the steel ball, errors caused by steel ball offset are offset, rapid and accurate measurement is achieved, and depth measurement errors are avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of powder property measurement, and more particularly to a 3D printer powder bed density calibration and measurement device. BACKGROUND

[0002] In powder type 3D printing technology, the powder bed density is a key parameter affecting the accuracy and mechanical properties of the printed part, and its accurate measurement and calibration directly determines the stability of the printing quality.

[0003] In the prior art, a single laser ranging sensor is used to measure the depth of the steel ball falling into the powder bed, and the density is calculated through the correlation between the steel ball falling depth and the powder bed density, but the device has limitations. Among them, the 3D printing powder in the powder box has uneven particle size and uneven surface. The steel ball is easily affected by the resistance of the powder bed during free falling. The steel ball is subjected to lateral force when it contacts the powder, resulting in a certain degree of deviation between the actual landing point and the theoretical axis. Even by reciprocating the powder box between the steel ball release device and the laser sensor through the sliding block and adjusting the position of the sliding block and the angle of the laser sensor, it is difficult to quickly and accurately find the highest point of the steel ball, causing depth measurement error. SUMMARY

[0004] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a 3D printer powder bed density calibration and measurement device, which measures the height of two points on the steel ball surface through a first laser ranging sensor and a second laser ranging sensor, calculates the actual center height using the horizontal distance L between the two points and the diameter D of the steel ball, offsets the error caused by the deviation of the steel ball, and avoids causing depth measurement error.

[0005] The present application provides a 3D printer powder bed density calibration and measurement device, which includes a rack, a bracket fixed in the rack, and a positioning groove formed in the inner wall of the bracket to clamp a powder box,

[0006] The top of the rack is fixedly connected with a mounting sleeve, and the axis of the mounting sleeve is opposite to the center of the powder box;

[0007] The inner wall of the mounting sleeve is fixedly connected with a mounting plate, and the bottom of the mounting plate is fixedly connected with a first laser ranging sensor and a second laser ranging sensor at the same height;

[0008] The emission point of the first laser ranging sensor is located on the axis of the mounting sleeve, and the horizontal distance between the emission point of the second laser ranging sensor and the emission point of the first laser ranging sensor is L;

[0009] The first laser ranging sensor and the second laser ranging sensor are used to compensate the deviation error of the steel ball by measuring the height of two points on the steel ball surface.

[0010] The steel ball is provided in the mounting sleeve, and the diameter D of the steel ball is greater than L.

[0011] Further, the release mechanism comprises symmetrically arranged clamping arms and a driving assembly, the clamping arms are provided in the side wall of the mounting sleeve and are slidingly connected, and a holding groove is formed in the inner end of the clamping arm to hold the steel ball.

[0012] The driving assembly comprises a gear, two ball screws are fixedly connected to the gear, and the ball screws are connected to the clamping arms through ball nuts.

[0013] Further, the driving assembly further comprises a bracket and a second air cylinder.

[0014] The bracket is fixedly connected to the outer wall of the mounting sleeve, and a second air cylinder is fixedly connected to the top of the bracket.

[0015] A sliding rod is fixedly connected to the inner wall of the bracket.

[0016] A tooth plate is mounted on the output end of the second air cylinder, the tooth plate is slidingly connected to the sliding rod, and the tooth plate is engaged with the gear.

[0017] Further, a guide rod is fixedly connected to the inner wall of the bracket, a pressing plate is slidingly connected to the outer wall of the guide rod, a first air cylinder is fixedly connected to the top of the bracket, and the output end of the first air cylinder is fixedly connected to the pressing plate to press the powder box.

[0018] Further, the horizontal distance L satisfies: 0.2D≤L≤0.8D.

[0019] Further, a fixed rod is fixedly connected to the outer wall of the tooth plate, and the fixed rod is fixedly connected to the output end of the second air cylinder.

[0020] Further, the first laser ranging sensor and the second laser ranging sensor are configured to measure the height values HA and HB of points A and B on the spherical surface of the steel ball, and to calculate the actual center height of the steel ball based on HA, HB and the horizontal distance L to compensate for the offset error.

[0021] Further, the formula for calculating the actual center height of the steel ball is:

[0022] , = , where D is the diameter of the steel ball.

[0023] Further, the emission points of the first laser ranging sensor and the second laser ranging sensor are parallel to the axis of the mounting sleeve.

[0024] Further, before the steel ball is released, the center of the steel ball is located on the axis of the mounting sleeve.

[0025] By the above technical solution, the application has the following beneficial effects:

[0026] In the application, the device measures the height of two points on the spherical surface of the steel ball by the first and second laser ranging sensors, calculates the actual center height by the horizontal distance L and the diameter D of the steel ball, and realizes fast and accurate measurement without manually searching for the highest point of the steel ball, thereby avoiding depth measurement error. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0028] Figure 1 It is a schematic diagram of the overall structure of the application;

[0029] Figure 2 It is a schematic diagram of the mounting structure of the extrusion plate of the application;

[0030] Figure 3 It is a schematic diagram of the mounting structure of the laser ranging sensor of the application;

[0031] Figure 4 It is a schematic diagram of the mounting structure of the second cylinder of the application;

[0032] Figure 5 It is a schematic diagram of the mounting structure of the tooth plate of the application.

[0033] In the figure: 1, frame; 2, bracket; 3, positioning groove; 4, guide rod; 5, extrusion plate; 6, first cylinder; 7, powder box; 8, mounting sleeve; 9, mounting plate; 10, first laser ranging sensor; 11, second laser ranging sensor; 12, support; 13, second cylinder; 14, slide rod; 15, fixed rod; 16, tooth plate; 17, clamping arm; 18, bracket; 19, ball nut; 20, ball screw; 21, gear. DETAILED DESCRIPTION

[0034] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application. The specific embodiments of the present application will be described in detail below with reference to the drawings in the specification.

[0035] As shown in Figure 1 and Figure 2 , a 3D printer powder bed density calibration and measurement device, comprising a rack 1, the rack 1 is fixedly connected with a bracket 2, a positioning groove 3 is formed in the inner wall of the bracket 2, a powder box 7 is horizontally placed on the top of the bracket 2, and the positioning groove 3 is used for clamping and positioning the powder box 7.

[0036] As shown in Figure 2 , two guide rods 4 are fixedly connected to the inner wall of the bracket 2, and an extrusion plate 5 is slidably connected to the outer wall of the guide rod 4, and the extrusion plate 5 is used for extruding the powder box 7 so as to be fixedly installed in the positioning groove 3.

[0037] As shown in Figure 2 , a first air cylinder 6 is fixedly connected to the top of the bracket 2, the output end of the first air cylinder 6 is fixedly connected with the extrusion plate 5, and the first air cylinder 6 drives the extrusion plate 5 to slide along the outer wall of the guide rod 4.

[0038] As shown in Figure 3 , a mounting sleeve 8 is fixedly connected to the top of the rack 1, a mounting plate 9 is fixedly connected to the inner wall of the mounting sleeve 8, and a first laser ranging sensor 10 and a second laser ranging sensor 11 are fixedly connected to the bottom of the mounting plate 9 and are located on the same horizontal plane.

[0039] The axis of the mounting sleeve 8 is opposite to the center of the powder box 7.

[0040] The emitting points of the first laser ranging sensor 10 and the second laser ranging sensor 11 are parallel to the axis of the mounting sleeve 8, the emitting point of the first laser ranging sensor 10 is located on the axis of the mounting sleeve 8, and the horizontal distance between the emitting point of the second laser ranging sensor 11 and the emitting point of the first laser ranging sensor 10 is L, L is a fixed value, and the diameter D of the steel ball is greater than L; it can ensure that the two laser points fall on the spherical surface, ensure the effectiveness of the compensation calculation, overcome the measurement defects caused by the deviation of the single laser sensor, and improve the precision of the powder bed density calibration and measurement.

[0041] The two-point height of the spherical surface of the steel ball is measured by the double laser ranging sensor, and the actual center height is calculated combined with the horizontal distance L, which effectively compensates for the offset error of the steel ball, solves the problem of low measurement accuracy caused by the offset of the steel ball in the traditional single laser sensor, and ensures the accurate initial falling position of the steel ball due to the coaxial design of the mounting sleeve 8 and the powder box 7.

[0042] As shown in Figure 1 、 Figure 3 、 Figure 4 and Figure 5 , the mounting sleeve 8 is provided with a steel ball 22, and the center of the steel ball 22 is located on the axis of the mounting sleeve 8;

[0043] The release mechanism is installed on the mounting sleeve 8, and the release mechanism includes two clamping arms 17 and two ball screws 20. The clamping arms 17 pass through the mounting sleeve 8 and are in sliding connection with the mounting sleeve 8. The outer wall of the ball screw 20 is sleeved with a ball nut 19 matched with it. The ball nut 19 is fixedly connected with the end of the corresponding clamping arm 17. The ends of the two ball nuts 19 are fixedly connected with each other. The connecting part of the two ball screws 20 is fixedly connected with a gear 21;

[0044] The end of the clamping arm 17 close to each other is provided with a supporting groove 18. The two clamping arms 17 respectively support the steel ball 22 through the supporting groove 18;

[0045] The supporting groove 18 of the clamping arm 17 stably supports the steel ball 22. The transmission of the gear 21 and the ball screw 20 makes the clamping arm 17 move synchronously and reversely, so as to realize the stable release of the steel ball 22 and avoid the offset of the steel ball 22 caused by the lateral force during the release process.

[0046] The outer wall of the mounting sleeve 8 is fixedly connected with a support 12. The top of the support 12 is fixedly connected with a second air cylinder 13. The output end of the second air cylinder 13 penetrates through the support 12 and extends below the support 12. The output end of the second air cylinder 13 is fixedly connected with a fixed rod 15. The outer wall of the fixed rod is fixedly connected with a toothed plate 16. The toothed plate 16 is engaged with the gear 21;

[0047] The inner wall of the support 12 is fixedly connected with a sliding rod 14. The end of the sliding rod 14 penetrates through the toothed plate 16 and is in sliding connection with the toothed plate 16.

[0048] The lead hammer method is used to measure the density of the powder bed. The depth of the steel ball 22 falling into the powder bed is used to measure the density of the powder bed. First, the device is used to calibrate the powder bed with different densities manufactured by humans. The relationship between the density of the powder bed and the depth of the steel ball 22 falling into the powder bed is fitted, and the relationship curve is fitted.

[0049] When the lead hammer method is used to measure the density of the powder bed, the steel ball 22 may be offset due to the resistance of the powder after falling freely into the powder bed. In order to accurately measure the center height of the steel ball, the device adopts a double laser ranging sensor to compensate for the offset error.

[0050] The powder box 7 is placed in the positioning groove 3, the extrusion plate 5 is pushed to slide along the guide rod 4 by the first cylinder 6, and then the powder box 7 is extruded, so that the powder box 7 is stably installed below the steel ball 22;

[0051] The second cylinder 13 drives the fixed rod 15 to move, the fixed rod 15 drives the tooth plate 16 to move, the tooth plate 16 slides downward along the slide rod 14, the tooth plate 16 drives the gear 21 to rotate, the gear 21 drives the two ball screws 20 to rotate respectively, the ball nut 19 drives the clamping arm 17 to move, and then the steel ball 22 is quickly released, so that the steel ball 22 is free falling and falls into the powder box 7 filled with the prefabricated density powder;

[0052] The first laser ranging sensor 10 and the second laser ranging sensor 11 emit laser beam points with the same height and a horizontal distance L, and the diameter of the steel ball 22 is D;

[0053] After the steel ball is stationary, the first laser ranging sensor 10 detects a measurement point A on the spherical surface of the steel ball 22, and the second laser ranging sensor 11 detects a measurement point B on the spherical surface of the steel ball 22, the height of the measurement point A is HA, and the height of the measurement point B is HB;

[0054] The actual center height of the steel ball is calculated :

[0055] The horizontal distance between the measurement points A and B is L, and the diameter D of the steel ball is greater than L;

[0056] The center offset angle ;

[0057] The actual center height = .

[0058] The horizontal distance L satisfies 0.2D≤L≤0.8D; the horizontal distance L is limited in the range of 0.2D-0.8D, which ensures that both laser points fall on the spherical surface of the steel ball and the distance is reasonable, which avoids both points being too close to increase the calculation error and prevents one point from being out of the spherical surface due to the steel ball 22 offset, thereby ensuring the applicability of the offset compensation formula.

[0059] When L<0.2D, the distance between the two points is too small, and the calculation error of θ increases; when L>0.8D, one point may be out of the spherical surface due to the steel ball 22 offset, so the range can ensure that both points are on the spherical surface and the calculation accuracy is reliable.

[0060] Calibration: standard powder bed samples with different densities are prepared, the actual center height of the steel ball 22 after falling is recorded, the corresponding relationship with the powder bed density is calculated by the double sensors, and the relationship curve and mathematical expression of the center height-powder bed density are fitted.

[0061] In the design of the release height of the steel ball 22, it is necessary to avoid the offset of the steel ball 22 too large, so that the laser beams emitted by the first laser ranging sensor 10 and the second laser ranging sensor 11 cannot fall on the surface of the steel ball 22.

[0062] The formula derivation is as follows: let the center of the steel ball be O, points A and B be on the spherical surface, OA=OB=D / 2. Draw a horizontal line through O and intersect the perpendiculars of A and B at point C to form a right triangle OAC, where , OC=L, so . The center height is the lowest point plus (the vertical distance from the center to the lowest point).

[0063] Working principle: when the 3D printer powder bed density calibration and measurement device works, first, the powder box 7 filled with 3D printing powder is clamped into the positioning groove 3 of the bracket 2, the first cylinder 6 pushes the extrusion plate 5 to move downward along the guide rod 4, and the powder box 7 is pressed to prevent it from moving.

[0064] When the release mechanism acts, the second cylinder 13 drives the toothed plate 16 to move along the slide rod 14, and through the meshing with the gear 21, the two ball screws 20 are driven to rotate, so that the ball nut 19 drives the clamping arm 17 to slide to both sides, the supporting groove 18 releases the steel ball 22, and the steel ball 22 freely falls from the installation sleeve 8 to the powder bed of the powder box 7.

[0065] After the steel ball 22 is stationary, the first laser ranging sensor 10 and the second laser ranging sensor 11 measure the heights of two points A and B on the spherical surface of the steel ball respectively. Based on the horizontal distance L between the two points and the diameter D of the steel ball, the actual center height of the steel ball is calculated, the offset error of the steel ball caused by the resistance of the powder bed is compensated, and finally the depth of the steel ball falling into the powder bed is obtained through the difference in the center height, and the accurate measurement of the powder bed density is realized by combining the pre-calibrated density-depth relationship.

[0066] The basic principles, main features and advantages of the present application are shown and described above. Those skilled in the art should understand that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only preferred examples of the present application and are not intended to limit the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A 3D printer powder bed density calibration and measurement device, comprising a frame (1) and a bracket (2) fixed inside the frame (1), wherein a positioning groove (3) is formed on the inner wall of the bracket (2) to engage a powder box (7), characterized in that: The top of the frame (1) is fixedly connected to an installation sleeve (8), and the axis of the installation sleeve (8) is directly opposite the center of the powder box (7); The mounting sleeve (8) is fixedly connected to the inner wall of the mounting plate (9), and the bottom of the mounting plate (9) is fixedly connected to the first laser range sensor (10) and the second laser range sensor (11) at the same height. The first laser rangefinder (10) emits at a point on the axis of the mounting sleeve (8), and the horizontal distance between the second laser rangefinder (11) emits at a point on the axis of the first laser rangefinder (10) is L. The first laser rangefinder (10) and the second laser rangefinder (11) are used to compensate for the offset error of the steel ball by measuring the height of two points on the spherical surface of the steel ball (22); The mounting sleeve (8) contains a steel ball (22) and a release mechanism, with the steel ball diameter D > L.

2. The 3D printer powder bed density calibration and measurement device according to claim 1, characterized in that: The release mechanism includes: Symmetrically arranged clamping arms (17) are inserted through the side wall of the mounting sleeve (8) and slidably connected. The inner end of the clamping arm (17) is provided with a support groove (18) to support the steel ball (22). The drive assembly includes a gear (21) which is fixedly connected to two ball screws (20), which are connected to a clamping arm (17) via ball nuts (19).

3. The 3D printer powder bed density calibration and measurement device according to claim 2, characterized in that: The driving component also includes: The bracket (12) is fixedly connected to the outer wall of the mounting sleeve (8), and a second cylinder (13) is fixedly connected to the top of the bracket (12). The slide bar (14) is fixedly connected to the inner wall of the bracket (12); The second cylinder (13) has a toothed plate (16) installed at its output end. The toothed plate (16) is slidably connected to the slide rod (14), and the toothed plate (16) meshes with the gear (21).

4. The 3D printer powder bed density calibration and measurement device according to claim 1, characterized in that: The inner wall of the bracket (2) is fixedly connected to a guide rod (4), and the outer wall of the guide rod (4) is slidably connected to an extrusion plate (5). The top of the bracket (2) is fixedly connected to a first cylinder (6), and the output end of the first cylinder (6) is fixedly connected to an extrusion plate (5) to press the powder box (7).

5. The 3D printer powder bed density calibration and measurement device according to claim 1, characterized in that: The horizontal distance L satisfies: 0.2D≤L≤0.8D.

6. The 3D printer powder bed density calibration and measurement device according to claim 3, characterized in that: The toothed plate (16) is fixedly connected to the outer wall of the fixing rod (15), and the fixing rod (15) is fixedly connected to the output end of the second cylinder (13).

7. The 3D printer powder bed density calibration and measurement device according to claim 1, characterized in that: The first laser rangefinder (10) and the second laser rangefinder (11) are configured to measure the height values ​​HA and HB of points A and B on the spherical surface of the steel ball (22), and calculate the actual center height of the steel ball based on HA, HB and horizontal distance L to compensate for offset error.

8. The 3D printer powder bed density calibration and measurement device according to claim 7, characterized in that: The calculation of the actual center height of the steel ball The formula is: , = , where D is the diameter of the steel ball.

9. The 3D printer powder bed density calibration and measurement device according to claim 1, characterized in that: The emission points of the first laser rangefinder (10) and the second laser rangefinder (11) are parallel to the axis of the mounting sleeve (8).

10. The 3D printer powder bed density calibration and measurement device according to claim 1, characterized in that: Before the steel ball (22) is released, its center is located on the axis of the mounting sleeve (8).

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