A device for safe polishing of products

Abstract

The utility model discloses a device for product safety polishing, including casing and setting in the polishing and grinding module of casing, the polishing and grinding module includes polishing head and the polishing feed adjusting module of drive polishing head movement, the polishing feed adjusting module includes the polishing D axle for controlling the feed of polishing head, still include: positioning and correction module, including the product positioning fixture for fixing product and the correction component for calibrating the position of polishing head, the correction component includes correction module and displacement sensor, the correction module sets up on product positioning fixture, the displacement sensor is used for detecting the position when polishing head and correction module contact, and based on this detection position control the feed of polishing D axle.

Description

Technical Field

[0001] This utility model relates to the field of polishing technology, specifically to a device for safe polishing of products. Background Technology

[0002] In the manufacturing process of high-end consumer electronics products (such as smartphones, tablets, and smart wearable devices), high-precision polishing of the product's surface is a key process for enhancing the product's aesthetics, feel, and overall value. This process places extremely high demands on the uniformity, consistency, and surface smoothness of the polishing quality.

[0003] Currently, the traditional polishing and grinding equipment commonly used in the industry operates on the principle of fixed feed rate grinding. This type of equipment typically includes a machine base, a grinding head assembly controlled by the Z-axis, and a polishing wheel (grinding disc) mounted on the grinding head. During operation, a fixed feed rate is set on the D-axis (the axis controlling the grinding head's feed), driving the grinding head to press the grinding disc against the product surface, completing the grinding operation through rotational friction.

[0004] However, this traditional fixed-feed grinding method has inherent and insurmountable technical defects, mainly in the following aspects: The inherent tolerances and installation errors of the hardware cannot be eliminated: the grinding disc itself has manufacturing tolerances (typically up to ±0.5mm), and at the same time, multiple independent grinding axes (such as the D-axis and Z-axis) inevitably have micron-level errors in the height direction during installation. Traditional devices lack effective error detection and compensation mechanisms, and these initial errors are directly transmitted to the grinding process.

[0005] Poor grinding quality stability and inability to guarantee product consistency: Due to the aforementioned errors and the fixed feed rate, the device cannot dynamically adjust based on the actual thickness of each grinding disc and the real-time position of each axis. This results in variations in grinding depth and polishing intensity between different products, and even between different areas of the same product, even within the same batch. This manifests as uneven surface gloss and large fluctuations in roughness, severely impacting product appearance consistency and yield.

[0006] Low product qualification rate and high production cost: In mass production environments, traditional equipment cannot guarantee the uniformity of product polishing and grinding effects, resulting in a product qualification rate that is usually below 85%. A large number of defective products require manual screening and rework repair, which not only significantly increases labor and time costs, but also restricts the improvement of production efficiency and automation level.

[0007] In summary, existing fixed-feed grinding devices, due to their inherent open-loop control and rigid execution, can no longer meet the growing demands of high-end manufacturing industries for product surface treatment precision and batch production consistency. Utility Model Content

[0008] In view of this, the purpose of this utility model is to provide a device for safe grinding of products, which aims to overcome at least one related technical problem existing in the background art.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A device for safe product polishing includes a housing and a polishing module disposed within the housing. The polishing module includes a polishing head and a polishing feed adjustment module for driving the movement of the polishing head. The polishing feed adjustment module includes a polishing D-axis for controlling the feed amount of the polishing head. The device also includes: The positioning and calibration module includes a product positioning fixture for fixing the product and a calibration component for calibrating the position of the grinding head. The calibration component includes a calibration module and a displacement sensor. The calibration module is mounted on the product positioning fixture, and the displacement sensor is used to detect the position of the grinding head when it contacts the calibration module, and to control the feed amount of the grinding D-axis based on the detected position.

[0010] To address the issue of potential displacement or vibration during product polishing, which could affect polishing consistency, in some embodiments, the product positioning fixture includes a positioning plate and a positioning pad. The positioning plate is mounted on the positioning pad and is equipped with a pneumatic suction structure for fixing the product.

[0011] In order to provide strong suction while avoiding scratching the back of the product with a rigid positioning plate and to accommodate minor unevenness on the bottom of the product, in some embodiments, the pneumatic suction structure includes negative pressure holes formed on the positioning plate and air-sealing cotton strips arranged around the negative pressure holes.

[0012] In order to achieve grinding of complex contour surfaces and separate control of macro positioning and micro feed, in some embodiments, the grinding feed adjustment module further includes the X-axis, Y-axis and Z-axis of the machine tool. The X-axis and Y-axis are used to realize the overall displacement adjustment of the product positioning fixture; the Z-axis is used to realize the overall displacement adjustment of the grinding D-axis.

[0013] To facilitate the rapid replacement of worn parts and provide stable and reliable grinding power, in some embodiments, the grinding head is detachably equipped with a grinding disc, and the grinding head has a built-in rotary power component for driving the grinding disc to rotate.

[0014] To address the issue of inaccurate positioning caused by direct rigid contact between the grinding head and the precision displacement sensor, in some embodiments, the calibration module includes a sensor fixing block fixed to one side of the positioning pad. The displacement sensor is mounted on the sensor fixing block, with its detection end facing a sensing plate. The sensing plate is slidably mounted on the sensor fixing block via an elastic support structure, allowing the grinding head to press down the sensing plate and trigger the displacement sensor. To obtain a stable, linear reset force and precise guidance, in some embodiments, the elastic support structure is a spring-loaded support pin.

[0015] To prevent the sensing element from tilting or getting stuck when under pressure, and to ensure that it always slides down smoothly and vertically, in some embodiments, the elastic support structure is provided in three parts, arranged in a triangular pattern.

[0016] In some embodiments, the spring support pin includes a guide shaft and a spring. One end of the guide shaft slides through the sensor mounting block and connects to a sensing element disposed on the upper part of the sensor mounting block. The spring is sleeved on the guide shaft and located between the sensing element and the sensor mounting block, with its two ends abutting against the lower surface of the sensing element and the upper surface of the sensor mounting block, respectively. The guide shaft provides precise linear guidance to prevent the sensing element from wobbling. The spring provides a restoring force. When the sensing element is compressed, the guide shaft slides downward, and the spring is compressed; after the pressure is released, the spring pushes the sensing element and the guide shaft back to their original positions.

[0017] In order to capture minute positional changes caused by grinding disc tolerances and installation errors, and to provide a high-resolution, high-reliability data foundation for subsequent feed compensation, in some embodiments, the displacement sensor is a precision displacement sensor. Precision displacement sensors (such as high-resolution inductive displacement sensors) can detect displacement changes at the micrometer level or even smaller and convert them into high-precision electrical signal outputs.

[0018] The beneficial effects that the device for safe polishing of products disclosed in this application may bring include, but are not limited to: 1. Improved the consistency of grinding precision and quality: Through real-time online detection using a "precision displacement sensor + buffer correction module" and dynamic compensation of the grinding D-axis, the influence of grinding disc thickness tolerance (0.5mm) and installation error on the final grinding effect is completely eliminated.

[0019] The pass rate of product polishing and grinding has been significantly improved from ≤85% in the traditional method and stabilized at ≥99%. The surface gloss, roughness and other quality indicators of products in the same batch are highly consistent, perfectly meeting the ultimate requirements of high-end consumer electronics products for appearance.

[0020] 2. Significantly improved the level of automation and intelligence in production: The entire process, including error self-correction, feed self-adaptation, and multi-axis linkage grinding, is completed automatically without the need for manual intervention or parameter adjustment based on experience.

[0021] It eliminates the reliance on skilled workers, reduces the time and cost of manual screening and rework, and in mass production, the daily grinding efficiency of a single machine is increased by more than 30% compared with traditional equipment, realizing truly "unmanned" intelligent production.

[0022] 3. Greatly enhances the versatility of the equipment and the flexibility of the production line: The product positioning fixture features a modular, detachable design, allowing for quick replacement to accommodate products of different sizes and shapes. The stable design of the calibration module ensures reliable calibration accuracy even after line changes.

[0023] Enterprises can use the same equipment to quickly respond to production tasks of multiple varieties and small batches, which significantly reduces the investment cost of special equipment and shortens the new product launch cycle.

[0024] 4. Ensures the reliability, safety, and ease of maintenance of the equipment: Reliability: The "sensor plate + elastic support structure" design in the calibration module avoids direct impact of the grinding head on the precision sensor, protecting the safety and lifespan of the core measuring components. It also increases the contact probability between the grinding head and the displacement sensor, and the three-point support structure ensures the repeatability and long-term reliability of the calibration operation.

[0025] Safety: The equipment operates within a sealed casing, effectively isolating high-speed moving parts and grinding dust.

[0026] Ease of maintenance: Grinding heads, grinding discs, positioning plates, etc., are all standardized and modular in design, making disassembly and assembly simple and greatly reducing the difficulty and time required for daily maintenance and replacement of vulnerable parts. This improves overall equipment reliability and service life, extends maintenance cycles, and reduces overall operation and maintenance costs. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the device for safe grinding of products according to this utility model.

[0028] Figure 2 This is a schematic diagram of the polishing and grinding module of this utility model.

[0029] Figure 3 This is a schematic diagram of the grinding disc of this utility model.

[0030] Figure 4 This is a schematic diagram of the positioning and correction module of this utility model.

[0031] Figure 5 This is a schematic diagram of the positioning fixture for the product of this utility model.

[0032] Figure 6 This is a schematic diagram of the correction module of this utility model.

[0033] The numbers in the diagram are as follows: 1-Main housing, 2-Polishing and grinding module, 3-Z-axis, 4-Grinding head, 5-Y-axis, 6-X-axis, 7-Product positioning fixture, 8-D-axis, 9-Grinding disc, 11-Positioning pad, 12-Correction module, 13-Displacement sensor, 14-Positioning plate, 15-Air barrier strip, 16-Negative pressure hole, 17-Sensing plate, 18-Spring, 19-Guide shaft, 20-Sensor fixing block. Detailed Implementation

[0034] Various exemplary embodiments, features, and aspects of this application will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0035] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, an indirect connection through an intermediate medium, or the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0036] like Figure 1-6 As shown, this application provides a device for safe product polishing, including a housing 1 and a polishing module 2 disposed within the housing 1. The polishing module 2 includes a polishing head 4 and a polishing feed adjustment module for driving the movement of the polishing head 4. The polishing feed adjustment module includes a polishing D-axis 8 for controlling the feed amount of the polishing head 4; it also includes: The positioning and calibration module 12 includes a product positioning fixture 7 for fixing the product and a calibration component for calibrating the position of the grinding head 4. The calibration component includes the calibration module 12 and a displacement sensor 13. The calibration module 12 is mounted on the product positioning fixture 7. The displacement sensor 13 is used to detect the position of the grinding head 4 when it contacts the calibration module 12, and to control the feed amount of the grinding D-axis 8 based on the detected position.

[0037] The technical solution of this application constitutes the core architecture of this utility model. The positioning and correction module 12 works in conjunction with the polishing and grinding module 2. Before operation, the grinding head 4 moves above and contacts the correction module 12. The displacement sensor 13 detects this contact position in real time. This position data is directly used to calculate and control the actual feed amount of the grinding D-axis 8, forming a direct detection-control closed loop.

[0038] The calibration module 12 is directly or indirectly installed on or near the product positioning fixture 7 to ensure that the calibration reference is consistent with the product positioning reference. The displacement sensor 13 is installed in conjunction with the calibration module 12, and its detection signal is output to the control system, which is then electrically connected to the driver of the grinding D-axis 8.

[0039] For example, the control system may include an industrial computer and a CNC controller; the displacement sensor 13 is electrically connected to the industrial computer and is used to send position detection data; the industrial computer is electrically connected to the CNC controller and is used to send the processed data to the CNC controller; the CNC controller is electrically connected to the grinding D-axis 8 and is used to control the feed amount of the grinding D-axis 8 according to the data.

[0040] This invention innovatively integrates a positioning and calibration module 12, mounted on the product positioning fixture 7, into the traditional grinding module. This module detects the relative position of the grinding head 4 and the calibration module 12 via a displacement sensor 13, and directly controls the feed amount of the grinding D-axis 8 based on this detected position. This achieves a shift from fixed-value feed to adaptive feed based on the actual zero point, ensuring grinding accuracy. It fundamentally solves the problem of uncontrollable grinding depth caused by tolerances and installation errors in the grinding disc 9.

[0041] To address the issue of potential displacement or vibration during product polishing, which could affect polishing consistency, in some embodiments, the product positioning fixture 7 includes a positioning plate 14 and a positioning pad 11. The positioning plate 14 is mounted on the positioning pad 11 and is equipped with a pneumatic suction structure for fixing the product. This design provides non-contact, uniformly distributed suction force, enabling quick and non-destructive product fixation, and is particularly suitable for high-end electronic products requiring high surface finish.

[0042] The positioning pad 11 serves as the basic support and mounting base, while the positioning plate 14 directly supports the product. When the pneumatic suction structure is in operation, it generates negative pressure to firmly adhere the product to the surface of the positioning plate 14.

[0043] Specifically, the positioning plate 14 is mounted on the upper surface of the positioning pad 11 using bolts, pins, and other connecting components. The positioning pad 11 is then fixed to the moving parts of the machine tool (such as the Y-axis 5 slide). The air passage is connected from the inside or side of the positioning pad 11 and communicates with the air passage on the positioning plate 14.

[0044] To provide strong suction while preventing the rigid positioning plate 14 from scratching the back of the product and accommodating minor unevenness on the bottom of the product, in some embodiments, the pneumatic suction structure includes a negative pressure hole 16 formed on the positioning plate 14 and an air-sealing strip 15 disposed around the negative pressure hole 16. When the product is placed on the air-sealing strip 15, a vacuum generator draws air through the negative pressure hole 16, creating a negative pressure zone between the product and the surface of the positioning plate 14. The air-sealing strip 15 acts as a sealant, filling the microscopic gap between the product and the positioning plate 14 to prevent air leakage and ensure sufficient suction force.

[0045] The pneumatic suction structure is specifically optimized to have a negative pressure hole 16 combined with an air-sealing cotton strip 15. The flexible nature of the air-sealing cotton strip 15 ensures both a sealing effect and provides cushioning and protection.

[0046] Of course, the air-sealing strip 15 can be replaced by other flexible sealing materials, such as silicone sealing rings, foam tape, etc.

[0047] In order to achieve grinding of complex contour surfaces and separate control of macro positioning and micro feed, in some embodiments, the grinding feed adjustment module further includes the X-axis 6, Y-axis 5 and Z-axis 3 of the machine tool. The X-axis 6 and Y-axis 5 are used to realize the overall displacement adjustment of the product positioning fixture 7; the Z-axis 3 is used to realize the overall displacement adjustment of the grinding D-axis 8.

[0048] In the product stage movement scheme, the product positioning fixture 7 is mounted on the Y-axis slide 5, which in turn is mounted on the X-axis slide 6. The grinding head unit 4 (including the D-axis 8) is mounted on the Z-axis slide 3. Each axis is driven by an independent servo motor. The X-axis 6 and Y-axis 5 form a horizontal motion system, driving the fixed product to perform precise two-dimensional movement to cover the entire area to be ground. The Z-axis 3 is responsible for driving the entire grinding head unit 4 (including the D-axis 8) to perform a large-range lifting and lowering positioning. The D-axis 8, based on the positioning of the Z-axis 3, performs fine feed motion.

[0049] This architecture allows the D-axis (8) to focus on high-precision pressure / depth control, while the X, Y, and Z axes (3) are responsible for trajectory motion. This clear division of labor results in higher system control precision.

[0050] To facilitate rapid replacement of worn parts and provide stable and reliable grinding power, in some embodiments, the grinding head 4 is detachably equipped with a grinding disc 9. The grinding head 4 has a built-in rotary power assembly for driving the grinding disc 9 to rotate. The output end of the grinding head 4 is provided with a standard interface (such as a thread or snap-fit), through which the grinding disc 9 is quickly installed. The grinding disc 9 is directly installed at the end of the output shaft of the grinding head 4. The rotary power assembly (motor) is encapsulated inside the housing of the grinding head 4, forming an integrated power unit. The motor inside the housing of the grinding head 4 transmits power to the output shaft through a transmission mechanism, driving the grinding disc 9 to rotate at high speed.

[0051] It should be noted that the grinding head 4 is a mature product in the existing technology, so it will not be discussed in detail here.

[0052] To address the issue of inaccurate positioning caused by direct rigid contact between the grinding head 4 and the precision displacement sensor 13, in some embodiments, the calibration module 12 includes a sensor fixing block 20 fixed to one side of the positioning pad 11. The displacement sensor 13 is mounted on the sensor fixing block 20, with its detection end facing a sensing plate 17. The sensing plate 17 is slidably mounted on the sensor fixing block 20 via an elastic support structure, allowing the grinding head 4 to press down the sensing plate 17 and trigger the displacement sensor 13. This is a key structure for achieving high-precision calibration. During calibration, the grinding head 4 descends, contacts the sensing plate 17, and applies pressure. The sensing plate 17 compresses the elastic support structure and generates a precise downward displacement. The displacement sensor 13 detects the displacement of the sensing plate 17. When the displacement reaches a preset trigger threshold, the system records this position as the "actual zero point."

[0053] With the above structure, the grinding head 4 is equivalent to contacting the displacement sensor 13 as long as it contacts the sensing plate 17, which is equivalent to expanding the structure of the displacement sensor 13 and improving the accuracy of contact.

[0054] In order to obtain a stable, linear restoring force and precise guidance, in some embodiments, the elastic support structure is a spring 18 supporting pin.

[0055] To prevent the sensing element 17 from tilting or getting stuck under pressure and to ensure its smooth and vertical sliding, in some embodiments, three elastic support structures are provided, arranged in a triangular pattern. The three elastic support points, distributed in a triangle, jointly support and guide the sensing element 17. Preferably, the three elastic support structures are evenly distributed below the sensing element 17, forming a stable triangular support. This three-point support principle constitutes a stable kinematic constraint, eliminating the uncertainty caused by over-positioning and ensuring the repeatability and reliability of the calibration process.

[0056] In some embodiments, the spring 18 support pin includes a guide shaft 19 and a spring 18. One end of the guide shaft 19 slides through the sensor fixing block 20 and is connected to the sensing plate 17 disposed on the upper part of the sensor fixing block 20. The spring 18 is sleeved on the guide shaft 19 and located between the sensing plate 17 and the sensor fixing block 20, with its two ends abutting against the lower surface of the sensing plate 17 and the upper surface of the sensor fixing block 20, respectively. The guide shaft 19 provides precise linear guidance to prevent the sensing plate 17 from wobbling. The spring 18 provides a restoring force. When the sensing plate 17 is compressed, the guide shaft 19 slides downward, and the spring 18 is compressed; after the pressure is released, the spring 18 pushes the sensing plate 17 and the guide shaft 19 to return to their original positions.

[0057] In order to capture minute positional changes caused by the tolerance and installation error of the grinding disc 9, and to provide a high-resolution, high-reliability data basis for subsequent feed compensation, in some embodiments, the displacement sensor 13 is a precision displacement sensor 13. The precision displacement sensor 13 (such as a high-resolution inductive displacement sensor 13) can detect displacement changes at the micrometer level or even smaller and convert them into high-precision electrical signal outputs.

[0058] The core working principle of this invention lies in constructing an intelligent closed-loop control system of "real-time detection-feedback-compensation" to replace the traditional open-loop mode of "fixed input-rigid execution," thereby achieving quantitative control over grinding quality. Its specific workflow is as follows: Initialization and zero-point calibration phase: The system executes an automatic calibration procedure each time the equipment is started or the grinding disc 9 is replaced.

[0059] The CNC controller commands the D-axis 8 to drive the grinding head 4 downwards, so that it slowly contacts and gently presses against the sensing plate 17 of the calibration module 12.

[0060] The sensing plate 17 generates a precise micro-displacement under pressure, which is immediately captured by the precision displacement sensor 13 and converted into an electrical signal. The position corresponding to this signal is the "actual mechanical zero point" that includes all comprehensive errors such as the actual thickness of the current grinding plate 9 and the installation height of the D-axis 8.

[0061] The "zero point" data is sent to the control system.

[0062] Data processing and compensation calculation stage: The control system (such as an industrial computer or CNC) compares the received "actual mechanical zero point" with the preset "theoretical standard zero point" in the system and calculates the precise position deviation value (i.e., compensation amount).

[0063] This compensation amount is integrated into the subsequent polishing process.

[0064] Adaptive precision polishing execution phase: The operator places the product on the product positioning fixture 7 and activates the pneumatic suction structure, which secures the product firmly.

[0065] According to the preset program, the system coordinates and controls the movement of the X-axis 6, Y-axis 5 (which moves the product) and Z-axis 3 (which drives the grinding head 4 for coarse positioning), so that the area to be ground is moved directly below the grinding head 4.

[0066] The D-axis 8 begins feeding during grinding. At this point, the feed rate is no longer a fixed theoretical value, but rather a combination of "theoretical value + compensation value". This ensures that the contact depth between the grinding disc 9 and the product surface is always precisely controlled within the preset ideal range, completely eliminating the influence of hardware tolerances and errors.

[0067] Throughout the polishing process, the polishing head 4 rotates at high speed to achieve high consistency and high precision polishing of the product surface.

[0068] This device acquires real-time errors through the calibration module 12 and displacement sensor 13, processes and transforms the errors through the control system, and finally performs dynamic compensation through the grinding D-axis 8, transforming a passive and rigid open-loop system into an active and intelligent closed-loop system, fundamentally solving the problem of grinding quality fluctuations caused by inherent hardware deviations.

[0069] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A device for safe polishing of products, comprising a housing (1) and a polishing module (2) disposed within the housing (1), the polishing module (2) comprising a polishing head (4) and a polishing feed adjustment module for driving the movement of the polishing head (4), the polishing feed adjustment module comprising a polishing D-axis (8) for controlling the feed amount of the polishing head (4); characterized in that, Also includes: The positioning and calibration module (12) includes a product positioning fixture (7) for fixing the product and a calibration component for calibrating the position of the grinding head (4). The calibration component includes a calibration module (12) and a displacement sensor (13). The calibration module (12) is set on the product positioning fixture (7). The displacement sensor (13) is used to detect the position of the grinding head (4) when it contacts the calibration module (12) and to control the feed amount of the grinding D-axis (8) based on the detected position.

2. The apparatus according to claim 1, characterized in that: The product positioning fixture (7) includes a positioning plate (14) and a positioning pad (11). The positioning plate (14) is set on the positioning pad (11), and the positioning plate (14) is provided with a pneumatic suction structure for fixing the product.

3. The apparatus according to claim 2, characterized in that: The pneumatic suction structure includes a negative pressure hole (16) opened on the positioning plate (14) and an air-sealing cotton strip (15) arranged around the negative pressure hole (16).

4. The apparatus according to claim 1, characterized in that: The grinding feed adjustment module also includes the X-axis (6), Y-axis (5) and Z-axis (3) of the machine. The X-axis (6) and Y-axis (5) are used to realize the overall displacement adjustment of the product positioning fixture (7); the Z-axis (3) is used to realize the overall displacement adjustment of the grinding D-axis (8).

5. The apparatus according to claim 1, characterized in that: The grinding head (4) is detachably equipped with a grinding disc (9), and the grinding head (4) has a built-in rotary power component for driving the grinding disc (9) to rotate.

6. The apparatus according to claim 2, characterized in that: The calibration module (12) includes a sensor fixing block (20), which is fixed on one side of the positioning pad block (11). The displacement sensor (13) is set on the sensor fixing block (20), and the detection end of the displacement sensor (13) is opposite to a sensing plate (17). The sensing plate (17) is slidably set on the sensor fixing block (20) through an elastic support structure, so that the grinding head (4) can press down the sensing plate (17) and trigger the displacement sensor (13).

7. The apparatus according to claim 6, characterized in that: The elastic support structure is a spring (18) support pin.

8. The apparatus according to claim 6, characterized in that: The elastic support structure consists of three parts, arranged in a triangular pattern.

9. The apparatus according to claim 7, characterized in that: The spring (18) support pin includes a guide shaft (19) and a spring (18). One end of the guide shaft (19) slides through the sensor fixing block (20) and is connected to the sensing plate (17) located on the upper part of the sensor fixing block (20). The spring (18) is sleeved on the guide shaft (19) and is located between the sensing plate (17) and the sensor fixing block (20).

10. The apparatus according to claim 6, characterized in that: The displacement sensor (13) is a precision displacement sensor (13).

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