Closed-loop feedback adjustable diamond cutting tool

Abstract

The invention provides a closed-loop feedback adjustable diamond cutting tool which comprises a first adjusting unit capable of deflecting and adjusting in an X-Y plane around a Z axis, a second adjusting unit capable of sliding and adjusting is connected above the first adjusting unit, and a sliding surface of the second adjusting unit is parallel to the X-Y plane. The second adjusting unit is connected with a fourth adjusting unit through a third adjusting unit used for Z-direction leveling, the fourth adjusting unit drives the diamond to rotate along the Y axis, and the top face of the fourth adjusting unit is provided with a visual calibration plate for a camera to shoot. The shot visual calibration board judges whether the first adjusting unit and / or the third adjusting unit are / is parallel to the camera or not through the visual analysis system, and if the first adjusting unit and / or the third adjusting unit are / is not parallel, the first adjusting unit and / or the third adjusting unit are / is adjusted. According to the tool, four stages of adjusting mechanisms are integrated, the application range is greatly widened, the machining universality is greatly improved, the positioning precision after diamond clamping is effectively improved, and the section cutting accuracy is improved.

Description

A closed-loop feedback adjustable diamond faceting tool Technical Field

[0001] This invention belongs to the technical field of diamond processing, specifically a closed-loop feedback adjustable diamond cutting tool. Background Technology

[0002] With the continuous iteration of superhard material processing technology, diamond, as a material with extreme physical properties, has expanded its application scenarios from traditional cutting tools to high-end fields such as semiconductor chips, optical components, and precision aerospace parts. This has placed unprecedentedly stringent requirements on the cutting accuracy, edge quality, and processing consistency of diamond products. In the diamond laser cutting process, the tooling, as the core component for workpiece positioning and fixation, directly determines the cutting accuracy, workpiece yield, and processing efficiency through its structural design.

[0003] Existing diamond laser cutting fixtures mostly follow the design concept of traditional superhard material cutting fixtures, failing to fully consider the material characteristics of diamond, such as high hardness, brittleness, and special thermal stability, resulting in several technical shortcomings: First, the positioning reference of diamond laser cutting fixtures is singular, often using single-sided positioning, which cannot achieve multi-dimensional precise positioning of diamond workpieces, easily leading to problems such as cutting size deviation, kerf tilt, and low fixture utilization; Second, cutting fixtures cannot simultaneously take into account positioning accuracy, adaptability, and automation adaptability.

[0004] Therefore, how to effectively solve the problem of diamond laser cutting tooling having a single positioning reference and being unable to simultaneously take into account positioning accuracy, adaptability and automation adaptability is an urgent technical problem to be solved.

[0005] It should be noted that the above technical information is intended only to enhance the understanding of the overall background technology of the present invention, and should not be regarded as an admission or in any way implying that the above technical information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] To address the shortcomings of the aforementioned background technology, this invention proposes a closed-loop feedback adjustable diamond cutting fixture, which solves the problems of diamond laser cutting fixtures having a single positioning reference and being unable to simultaneously consider positioning accuracy, workpiece protection, adaptability, and automation adaptability.

[0007] The technical solution of this application is: a closed-loop feedback adjustable diamond cutting fixture, including a first adjustment unit that can be adjusted to deflect around the Z-axis in the XY plane, a second adjustment unit that can be slidably adjusted connected above the first adjustment unit, the sliding surface of the second adjustment unit being parallel to the XY plane, the second adjustment unit being connected to a fourth adjustment unit through a third adjustment unit for Z-axis leveling, the fourth adjustment unit driving the diamond to rotate along the Y-axis, and a visual calibration plate for camera shooting provided on the top surface of the fourth adjustment unit, the visual calibration plate being photographed determining whether the first adjustment unit and / or the third adjustment unit are parallel to the camera through a visual analysis system, if it is determined that they are not parallel, then the first adjustment unit and / or the third adjustment unit are adjusted.

[0008] Furthermore, the first adjustment unit includes a base with a rotating shaft, and the base plate is provided with mounting holes for rotating with the rotating shaft. The base is adjustable by deflection in the XY plane via a drive component.

[0009] Furthermore, the drive assembly includes a fixture adjustment block fixedly connected to the base plate. The side of the fixture adjustment block is provided with at least two bolt holes, and the adjustment screw is threadedly engaged with the bolt holes. The end of the adjustment screw abuts against the side of the base.

[0010] Furthermore, the second adjustment unit includes a limiting strip disposed on the upper surface of the base. Two limiting strips are symmetrically arranged, and a sliding strip is slidably engaged between the two limiting strips. The sliding strip drives the third adjustment unit to translate in the XY plane.

[0011] Furthermore, the limiting strip is in the shape of an inverted trapezoid, the sliding strip is in the shape of a trapezoid, and the outer wall of the sliding strip is in contact with the inner wall of the limiting strip.

[0012] Furthermore, the outer wall of the sliding bar is provided with a friction-reducing groove to reduce the contact area.

[0013] Furthermore, the third adjustment unit includes a leveling base plate connected to the sliding bar, and a leveling top plate is provided parallel to and spaced apart from the leveling base plate. At least four leveling screws are provided between the leveling base plate and the leveling top plate.

[0014] Furthermore, the fourth adjustment unit includes a core-taking height block connected to the leveling top plate, and an angle adjustment plate is hinged to the top of the core-taking height block. The angle adjustment plate is rotated along the Y-axis by the second drive assembly, and an adhesive groove for attaching diamonds is provided on the angle adjustment plate.

[0015] Furthermore, the core extraction height block is provided with a clearance groove for accommodating the second drive assembly. The second drive assembly includes a servo motor connected to the leveling top plate. The servo motor drives the lead screw to rotate, and two nuts with opposite threads move relative to the lead screw. Each nut is hinged to a connecting rod, and the other end of the connecting rod is hinged to the angle adjustment plate.

[0016] Furthermore, a visual calibration plate with a checkerboard pattern is provided on the top surface of the core extraction height block. A camera is positioned parallel to the top of the visual calibration plate and connected to a visual analysis system. The camera captures images of the visual calibration plate, whose surface has multiple square calibration grids with a standard size of 1mm × 1mm. The visual analysis system analyzes the acquired images, identifying the actual display size of the square calibration grids and the angle formed with the camera's reference crosshair. Whether the dimensions in both the X-axis and Y-axis directions are 1mm and whether the angle formed with the camera's reference crosshair is 0° are used as the criteria for determining whether the camera is parallel to the visual calibration plate. By adjusting the leveling screws and adjustment screws, the size of the square calibration grids in the image is made to be 1mm × 1mm and the angle formed with the camera's reference crosshair is 0°, thus achieving parallelism between the core extraction height block and the camera. Image recognition and attitude feedback through an external visual analysis system replace traditional manual visual adjustment, significantly improving the adjustment accuracy and efficiency of the tooling.

[0017] The specific beneficial effects of this invention include: 1. The tooling of this invention integrates a four-level adjustment mechanism, which can achieve precise positioning of diamonds in multiple degrees of freedom, such as horizontal rotation, horizontal translation, horizontal leveling, and tilt angle, meeting the high-precision cutting requirements of diamonds with different crystal faces and different cutting angles, and greatly improving the applicability and processing versatility; 2. Each adjustment unit is arranged sequentially from bottom to top, with a clear layered structure and reasonable force distribution. They can be adjusted independently without interference, enabling both rapid coarse adjustment and fine adjustment, effectively improving the positioning accuracy of the diamond after clamping and enhancing the accuracy of the cut surface; 3. Both angle adjustment plates can be bonded to products, enabling simultaneous processing on both sides, effectively increasing processing capacity and significantly improving production efficiency; 4. Image recognition and posture feedback are performed through an external vision analysis system, replacing traditional manual visual adjustment, greatly improving the adjustment accuracy and efficiency of the tooling; 5. The angle adjustment plate is driven by a servo motor for angle adjustment, replacing manual adjustment. While improving adjustment efficiency, it can achieve high-precision angle control, with an adjustment accuracy of ±0.1°. Attached Figure Description

[0018] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 is a three-dimensional schematic diagram of the present invention; Figure 2 is a three-dimensional schematic diagram of the present invention; Figure 3 is a side view of the present invention; Figure 4 is a schematic diagram of the second driving component in the present invention; Figure 5 is a cross-sectional view of the vertical angle adjustment unit in the present invention.

[0020] Explanation of the reference numerals: 1. Base plate; 2. Base; 3. Limiting strip; 4. Fixture adjusting block; 5. Adjusting screw; 6. Sliding strip; 7. Leveling base plate; 8. Leveling top plate; 9. Leveling screw; 10. Core taking height block; 11. Angle adjusting plate; 12. Servo motor; 13. Nut; 14. Slide rail; 15. Vision calibration plate; 16. Lead screw; 17. Connecting rod; 18. Pin one; 19. Anti-friction groove; 20. Adhesive groove; 21. Pin two. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the core concept of the present invention and the following embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] These embodiments are provided to make the application thorough and complete, and to fully express the scope of the application to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​illustrated in these embodiments should be interpreted as merely exemplary and not as limiting.

[0023] It should be noted that, in the description of this application, unless otherwise stated, "several" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "axial," "radial," etc., indicating orientation or positional relationships are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0024] Furthermore, the terms "first," "second," and similar terms used in this application do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. "Vertical" is not strictly vertical, but within the permissible margin of error. "Parallel" is not strictly parallel, but within the permissible margin of error. Terms such as "including" or "contains" mean that the element preceding the word encompasses the element listed after it, and do not exclude the possibility of encompassing other elements as well.

[0025] It should also be noted that, in the description of this application, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application depending on the specific circumstances. When a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device.

[0026] All terms used in this application have the same meaning as understood by one of ordinary skill in the art to which this application pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0027] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0028] A closed-loop feedback adjustable diamond faceting fixture, as shown in Figures 1-3, includes a first adjustment unit that can be adjusted to deflect around the Z-axis in the XY plane. A second adjustment unit that can be slidably adjusted is connected above the first adjustment unit. The sliding surface of the second adjustment unit is parallel to the XY plane. The second adjustment unit is connected to a fourth adjustment unit through a third adjustment unit for Z-axis leveling. The fourth adjustment unit drives the diamond to rotate along the Y-axis. A visual calibration plate 15 for camera shooting is provided on the top surface of the fourth adjustment unit. The visual calibration plate 15 being photographed determines whether the first adjustment unit and / or the third adjustment unit are parallel to the camera through a visual analysis system. If it is determined that they are not parallel, the first adjustment unit and / or the third adjustment unit are adjusted. The tooling of this invention integrates a four-level adjustment mechanism, which can achieve precise positioning of diamonds in multiple degrees of freedom, such as horizontal rotation, horizontal translation, horizontal leveling, and tilt angle. This meets the high-precision cutting requirements of diamonds with different crystal faces and different cutting angles, greatly improving the applicability and processing versatility. Each adjustment unit is arranged sequentially from bottom to top, with a clear layered structure and reasonable force distribution. They can be adjusted independently without interference, enabling both rapid coarse adjustment and fine adjustment, effectively improving the positioning accuracy of the diamond after clamping and enhancing the accuracy of the cut surface.

[0029] Specifically, as shown in Figure 1, the X-axis and Y-axis are perpendicular to each other in the horizontal plane, and the Z-axis is set vertically and perpendicular to the X-axis and Y-axis respectively.

[0030] Based on the above embodiments, as a preferred embodiment, the first adjustment unit includes a base 2 with a rotating shaft. The base plate 1 is provided with an assembly hole for rotating with the rotating shaft. The base 2 is adjustable by deflection in the XY plane via a drive component. The base plate 1 is square, and the base 2 is rectangular. The base 2 and the base plate 1 have the same length. This fixture can rotate circumferentially in the horizontal direction on the base plate 1. The assembly hole adopts a rotating shaft, and the rotating shaft and the rotating shaft hole form a precise guiding fit. The rotation process has high coaxiality and small wobbling.

[0031] Based on the above embodiments, as a preferred embodiment, the drive assembly includes a fixture adjustment block 4 bolted to the base plate 1. The fixture adjustment block 4 has at least two bolt holes on its side. An adjustment screw 5 is threaded into the bolt holes. The end of the adjustment screw 5 abuts against the side of the base 2. One adjustment screw 5 is threaded with the right thread and the other adjustment screw 5 is threaded with the left thread. That is, one adjustment screw 5 pushes the base 2 forward to deflect it around the Z-axis by a certain angle, and the other adjustment screw 5 retracts and limits the position of the base 2. The adjustment screw 5 translates in the XY plane. The screw abuts and drives the movement. The structure is simple, the operation is convenient, and the self-locking performance after adjustment is good. It is not easy to loosen and can ensure the stability of the angle position during processing.

[0032] Based on the above embodiments, as a preferred embodiment, the second adjustment unit includes a limiting strip 3 disposed on the upper surface of the base 2. Two limiting strips 3 are symmetrically arranged, and a sliding strip 6 is slidably engaged between the two limiting strips 3. The third adjustment unit is connected to the sliding strip 6, and the sliding strip 6 drives the diamond and the third adjustment unit to translate in the XY plane.

[0033] Based on the above embodiments, as a preferred embodiment, the limiting strip 3 is inverted trapezoidal, the sliding strip 6 is trapezoidal, and the outer wall of the sliding strip 6 is fitted with the inner wall of the limiting strip 3. The two limiting strips 3 and the base 2 form a trapezoidal cross-section. The trapezoidal mating surface can effectively restrict vertical and lateral movement, and the sliding strip 6 will not come out of the limiting strip 3, effectively improving stability during processing.

[0034] Based on the above embodiments, as a preferred embodiment, the outer wall of the sliding strip 6 is provided with a friction-reducing groove 19 for reducing the contact area and friction.

[0035] Based on the above embodiments, as a preferred embodiment, the third adjustment unit includes a leveling base plate 7 connected to the sliding bar 6, a leveling top plate 8 is provided parallel to and spaced apart from the leveling base plate 7, and at least four leveling screws 9 are provided between the leveling base plate 7 and the leveling top plate 8.

[0036] Specifically, the leveling base plate 7 and the leveling top plate 8 are the same size and are arranged in parallel. Four leveling screws 9 are respectively set at the four corners. By loosening or tightening the leveling nuts, the third adjustment unit can be adjusted to be parallel to the camera. The camera is set directly above the entire fixture.

[0037] Based on the above embodiments, as a preferred embodiment, the fourth adjustment unit includes a core-taking height block 10 connected to the leveling top plate 8. The top of the core-taking height block 10 is hinged to an angle adjustment plate 11. The angle adjustment plate 11 is rotated along the Y-axis by a driving assembly. The angle adjustment plate 11 is provided with an adhesive groove 20 for attaching diamonds.

[0038] Specifically, both sides of the core height block 10 are hinged with angle adjustment plates 11, and each angle adjustment plate 11 is provided with several diamond bonding grooves 20. Diamond slices / cubes / irregular shapes can be bonded to the bonding grooves 20 with adhesive, allowing cutting to be carried out on both sides at the same time, thus improving work efficiency.

[0039] Based on the above embodiments, as a preferred embodiment, as shown in Figures 4-5, the core extraction height block 10 is provided with a clearance groove for accommodating the second drive assembly. The second drive assembly includes a servo motor 12 connected to the leveling top plate 8. The servo motor 12 drives the lead screw 16 to rotate. Two nuts 13 with opposite threads move relative to the lead screw 16. Each nut 13 is hinged to a connecting rod 17, and the other end of the connecting rod 17 is hinged to the angle adjustment plate 11.

[0040] Specifically, the leveling top plate 8 is also connected to a square-shaped slide rail 14. The lead screw 16 passes through the central axis of the slide rail 14. The servo motor 12 drives the lead screw 16 to rotate. The lead screw 16 drives the positive and negative nuts 13 to move along the slide rail 14 in opposite directions or in opposite directions. The positive and negative nuts 13 respectively drive their respective hinged connecting rods 17 to rotate. The connecting rods 17 are hinged to the angle adjustment plate 11 through a first pin 18. The angle adjustment plate 11 is hinged to the core extraction height block 10 through a second pin 21. The rotation of the connecting rods 17 pushes the angle adjustment plate 11 to rotate around the second pin 21 to adjust the vertical angle.

[0041] Based on the above embodiments, as a preferred embodiment, the top surface of the core sampling height block 10 is provided with a visual calibration plate 15 with a checkerboard pattern, and a camera is arranged parallel above the visual calibration plate 15, the camera being connected to the visual analysis system.

[0042] Specifically, a camera is used to photograph a visual calibration plate 15, whose surface has multiple square calibration grids with a standard size of 1mm × 1mm. The visual analysis system analyzes the acquired image, identifying the actual display size of the square calibration grids and the angle formed with the camera's reference crosshair. Whether the dimensions in both the X and Y axes are 1mm and whether the angle with the camera's reference crosshair is 0° are used as criteria to determine whether the camera is parallel to the visual calibration plate 15. By adjusting the leveling screw 9 and the adjusting screw 5, the size of the square calibration grids in the image is made to be 1mm × 1mm and the angle formed with the camera's reference crosshair is 0°, thus achieving parallelism between the core extraction height block 10 and the camera. Image recognition and attitude feedback through an external visual analysis system replace traditional manual visual adjustment, significantly improving the accuracy and efficiency of tooling adjustment.

[0043] Specifically, the visual analysis system utilizes the VisionMaster vision platform developed by Hikvision Robotics. Its built-in distortion correction module can correct lens distortion and more accurately handle scenarios where the camera's focal plane is not parallel to the calibration block being measured. When the two are not parallel, perspective distortion occurs, leading to problems such as scale distortion and edge tilting in the system-acquired calibration block image. In this case, the visual analysis system provides real-time feedback on non-compliance signals such as dimensional deviation and morphological distortion of the calibration block, prompting the operator to adjust the calibration block's posture. Based on the system feedback, the operator gradually adjusts the position and angle of the calibration block until the visual analysis system reports that the calibration block image has no perspective distortion, is dimensionally regular, and meets the standards. This indicates that the two are parallel, effectively improving the calibration and adjustment accuracy of the entire system. The VisionMaster vision platform is a mature, existing technology.

[0044] The workflow of this invention is as follows: 1. During operation, the product is glued to the adhesive grooves 20 of the angle adjustment plates 11 on both sides; 2. By using an external vision system to identify the visual calibration plate 15, it is determined whether the core extraction height block 10 is perpendicular to the camera. By loosening or tightening the leveling nut, the core extraction height block 10 can be made perpendicular to the camera; 3. By loosening or tightening the adjusting screw 5, the angle of the base 2 can be adjusted; 4. By setting the stroke of the servo motor 12, the lead screw 16 can be driven to rotate, causing the positive and negative nuts 13 to move in opposite directions along the slide rail 14. The positive and negative nuts 13 push the connecting rod 17 to move, and the connecting rod 17 pushes the angle adjustment plate 11 to move, so that the angle adjustment plate 11 can be quickly adjusted to the target angle.

[0045] All aspects not detailed in this invention are conventional technical means known to those skilled in the art.

[0046] The above content shows and describes the basic principles, main features, and beneficial effects of the present invention. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A closed-loop feedback adjustable diamond cutting fixture, characterized in that: The system includes a first adjustment unit that can be adjusted to deflect around the Z-axis in the XY plane. A second adjustment unit that can be slidably adjusted is connected above the first adjustment unit. The sliding surface of the second adjustment unit is parallel to the XY plane. The second adjustment unit is connected to a fourth adjustment unit through a third adjustment unit for Z-axis leveling. The fourth adjustment unit drives the diamond to rotate along the Y-axis. A visual calibration plate (15) for camera shooting is provided on the top surface of the fourth adjustment unit. The visual calibration plate (15) being shot determines whether the first adjustment unit and / or the third adjustment unit are parallel to the camera through a visual analysis system. If it is determined that they are not parallel, the first adjustment unit and / or the third adjustment unit are adjusted.

2. The closed-loop feedback adjustable diamond facet tooling according to claim 1, characterized in that: The first adjustment unit includes a base (2) with a rotating shaft. The base plate (1) is provided with an assembly hole for rotating with the rotating shaft. The base (2) can be adjusted by deflection in the XY plane through a drive component.

3. The closed-loop feedback adjustable diamond facet tooling according to claim 2, characterized in that: The drive assembly includes a fixture adjustment block (4) fixedly connected to the base plate (1). The side of the fixture adjustment block (4) is provided with at least two bolt holes. The adjustment screw (5) is threadedly engaged with the bolt holes. The end of the adjustment screw (5) abuts against the side of the base (2).

4. The closed-loop feedback adjustable diamond faceting fixture according to any one of claims 1-3, characterized in that: The second adjustment unit includes a limiting strip (3) disposed on the upper surface of the base (2). Two limiting strips (3) are symmetrically arranged, and a sliding strip (6) is slidably engaged between the two limiting strips (3). The sliding strip (6) drives the third adjustment unit to translate in the XY plane.

5. The closed-loop feedback adjustable diamond facet tooling according to claim 4, characterized in that: The limiting strip (3) is in the shape of an inverted trapezoid, the sliding strip (6) is in the shape of a trapezoid, and the outer wall of the sliding strip (6) is in contact with the inner wall of the limiting strip (3).

6. The closed-loop feedback adjustable diamond facet tooling according to claim 5, characterized in that: The outer wall of the sliding bar (6) is provided with a friction-reducing groove (19) to reduce the contact area.

7. The closed-loop feedback adjustable diamond facet tooling according to claim 6, characterized in that: The third adjustment unit includes a leveling base plate (7) connected to the sliding bar (6), and a leveling top plate (8) is provided parallel to the leveling base plate (7). At least four leveling screws (9) are provided between the leveling base plate (7) and the leveling top plate (8).

8. The closed-loop feedback adjustable diamond facet tooling according to claim 7, characterized in that: The fourth adjustment unit includes a core-taking height block (10) connected to the leveling top plate (8). An angle adjustment plate (11) is hinged to the top of the core-taking height block (10). The angle adjustment plate (11) rotates along the Y-axis via the second drive assembly. The angle adjustment plate (11) is provided with a bonding groove (20) for bonding diamonds.

9. The closed-loop feedback adjustable diamond facet tooling according to claim 8, characterized in that: The core extraction height block (10) is provided with a clearance groove for accommodating the second drive assembly. The second drive assembly includes a servo motor (12) connected to the leveling top plate (8). The servo motor (12) drives the lead screw (16) to rotate. Two nuts (13) with opposite threads move relative to the lead screw (16). Each nut (13) is hinged to a connecting rod (17). The other end of the connecting rod (17) is hinged to the angle adjustment plate (11).

10. The closed-loop feedback adjustable diamond faceting fixture according to any one of claims 8-9, characterized in that: The top surface of the core sampling height block (10) is provided with a visual calibration plate (15) with a checkerboard pattern. A camera is arranged parallel above the visual calibration plate (15) and the camera is connected to the visual analysis system.

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