Positioning and clamping device for CNC equipment

Abstract

The invention discloses a positioning and clamping device for CNC equipment, and belongs to the field of machining clamps. The device comprises a fixed base, a pin base, a plurality of pin assemblies arranged in a matrix, a self-locking assembly, a constraint frame, a thermoplastic elastomer working layer, an elastic film, a heating unit and a cooling unit. The core method comprises the following steps: softening a working layer by heating, and pressing a special-shaped curved surface workpiece into the working layer so that a pin assembly passively fits the curved surface of the workpiece; and then the pin assembly is locked through the self-locking assembly, the working layer is cooled and solidified, and a continuous rigid supporting face completely attached to the workpiece is formed. A vacuum adsorption function in the pin assembly is also integrated, so that the clamping force is enhanced. According to the device, self-adaptive, gapless and low-stress clamping of any special-shaped curved surface workpiece is achieved, the problems that due to the fact that traditional pin array supporting is discontinuous, the workpiece is prone to deformation, and a magnetorheological fluid scheme is high in energy consumption and unstable in material are solved, and the device has the advantages of being high in flexibility, low in energy consumption and stable and reliable in clamping.

Description

Technical Field

[0001] This invention relates to the field of clamping technology, and more specifically to a positioning and clamping device for CNC equipment. Background Technology

[0002] In CNC (Computer Numerical Control) machining, fixtures are used to fix workpieces to ensure machining accuracy. Traditional rigid fixtures (such as vises, clamping plates, and special pneumatic fixtures) work well for rigid workpieces with regular shapes, but for workpieces with irregular curved surfaces, it is generally necessary to customize expensive contouring fixtures, and changing fixtures during production changes is time-consuming. Later, some flexible clamps emerged. One type utilizes a positionable pin array to adapt to the clamping requirements of irregularly shaped curved workpieces. However, its problem is that only the part in contact with the pins provides support, while the non-contact parts are difficult to support, easily leading to workpiece deformation during processing. The other type utilizes deformation generated by magnetorheological fluids to adapt to the curvature of irregularly shaped curved workpieces. However, this method requires continuous supply of magnetism to the magnetorheological fluid during processing, which requires electromagnetic coils to provide the magnetic core, resulting in high power consumption. At the same time, the density of magnetic particles in the magnetorheological fluid is generally 5-8 times higher than that of the carrier fluid, and sedimentation under gravity is inevitable. In addition, magnetic particles are prone to agglomeration, which occurs throughout the entire sedimentation process. Even after short-term static storage, sedimentation will still occur. Summary of the Invention

[0003] The purpose of this invention is to provide a positioning and clamping device for CNC equipment, which solves the above-mentioned problems existing in the current CNC machining of irregular curved parts.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A positioning and clamping device for CNC equipment includes: a fixed base, a pin base, a plurality of pin assemblies, a self-locking assembly, a constraint frame, a working layer, an elastic membrane, a heating unit, and a cooling unit.

[0005] The fixed base is used to securely connect the positioning and clamping device to the worktable of the CNC equipment. The pin base is positioned above the fixed base. The pin base has multiple pin assemblies arranged in a matrix of M rows by N columns. Each pin assembly can independently move along its own axis between an extended position and a retracted position. A self-locking component is located inside the pin base, its function being to selectively lock each pin assembly in its current extended or retracted position. The constraint frame is a hollow frame structure located at the upper end of the pin base, with the upper regions of the multiple pin assemblies situated within the internal space enclosed by the constraint frame. The working layer, made of thermoplastic elastomer material, fills and is disposed within the constraint frame. The working layer has a softening temperature and a curing temperature. When heated above the softening temperature, the working layer transforms into a viscoelastic state with flowability or compressibility; when cooled below the curing temperature, the working layer reverts to a high-hardness solid state and can generate a continuous clamping force. The elastic membrane covers the upper surface of the constraint frame. Multiple clearance holes are formed in the elastic membrane, each corresponding to a pin assembly, allowing the top of each pin assembly to pass through the clearance hole and be positioned above the elastic membrane. The heating unit includes multiple heating elements disposed within the pin assemblies to generate heat to heat the working layer. The cooling unit includes cooling elements disposed inside the constraint frame to absorb heat and cool the working layer.

[0006] As a further technical solution, the specific structure of the pin base includes an upper support plate, a lower support plate, and a valve body. Both the upper and lower support plates are machined with multiple sliding holes corresponding to multiple pin assemblies. Each pin assembly is slidably fitted into its corresponding sliding hole. The valve body internally comprises a sleeve mounting groove, a high-pressure medium flow groove, and a pin assembly mounting groove. One end of the sleeve mounting groove opens onto the surface of the valve body, and the other end communicates with the pin assembly mounting groove. A sleeve is disposed within the sleeve mounting groove, tightly fitted onto the outer circumference of the pin assembly. The high-pressure medium flow groove is arranged approximately perpendicular to the sleeve mounting groove and communicates with the central region of the sleeve mounting groove. The pin assembly mounting groove is coaxially arranged with the sleeve mounting groove and extends through the upper and lower surfaces of the valve body. The high-pressure medium flow channel is used to introduce a high-pressure medium (such as high-pressure oil or high-pressure gas), which can cause the expansion sleeve to produce radial elastic deformation, thereby gripping the pin assembly inserted therein and locking the position of the pin assembly.

[0007] As a further technical solution, a circumferential positioning protrusion is provided on the outer circumferential wall of each pin assembly. This positioning protrusion is located within the pin assembly mounting groove of the valve body. Inside the valve body, a spring is also provided in the pin assembly mounting groove. One end of the spring abuts against the lower end face of the positioning protrusion, and the other end abuts against the upper end face of the lower support plate. A positioning step is provided in the upper region of the pin assembly mounting groove. The upper end face of the positioning protrusion cooperates with the positioning step to limit the highest upward movement position of the pin assembly (i.e., the upper limit of the retracted position). The pin assembly can move axially within the space defined by the pin assembly mounting groove and the corresponding sliding hole, and can be reset to the retracted position under the elastic restoring force of the spring.

[0008] As a further technical solution, the lower end of each pin assembly passes through the lower support plate and extends below it. The fixing base has an inverted U-shaped structure with an internal clearance portion for accommodating and accommodating the lower ends of the multiple downwardly extending pin assemblies. A sealing ring is provided at one end of the expansion sleeve mounting groove near the pin assembly mounting groove to prevent leakage of high-pressure media. On the valve body, an oil seal mounting groove is provided at the outer opening of the expansion sleeve mounting groove, and an oil seal is installed in the oil seal mounting groove to prevent external contaminants from entering the working area of ​​the expansion sleeve.

[0009] As a further technical solution, each pin assembly includes a cylinder and a negative pressure tube. The cylinder is hollow, with one end (lower end) open. A connecting seat is located at one end of the negative pressure tube, and the cylinder has external threads on its open end. The connecting seat achieves a sealed connection with the external threads of the cylinder through internal threads. A threaded seat is located at the other end (upper end) of the negative pressure tube, and internal threads are located at a corresponding position inside the cylinder. The upper end of the negative pressure tube is fixedly connected to the internal threads of the cylinder through the threaded seat. A negative pressure channel is axially arranged at the center of the negative pressure tube. This negative pressure channel is used to adsorb the workpiece by drawing a vacuum when the top of the cylinder abuts against the workpiece surface, providing auxiliary fixing force. A vacuum connection valve is provided on the connecting seat for connecting to an external vacuum source pipeline.

[0010] As a further technical solution, a universal adsorption assembly is provided at the upper end of the cylinder (i.e., the end closest to the workpiece). This universal adsorption assembly includes a hollow ball head, a universal ball seat, a cap, and an adsorption plate. The universal ball seat is fixed to the top of the cylinder via a threaded connection. A spherical groove is formed in the center of the universal ball seat. The hollow ball head is rotatably disposed within this spherical groove. The cap is screwed onto the top of the universal ball seat via a thread or other means to confine the hollow ball head within the spherical groove, preventing it from detaching. The adsorption plate is fixedly connected to the top of the hollow ball head and rotates with it. A negative pressure adsorption hole is formed on the adsorption plate, communicating with the internal cavity of the hollow ball head. A vent hole is provided at the center of the bottom surface of the hollow ball head, which is used to seal and connect with the negative pressure channel inside the negative pressure tube, thereby transmitting negative pressure to the adsorption plate.

[0011] As a further technical solution, a heating element is provided within the annular space formed between the inner wall of the cylinder and the outer wall of the negative pressure pipe. The heating element is preferably a heating wire. The two polar wires of the heating wire pass through the connector and extend outwards for connection to an external power source. When energized, the heating wire generates heat, which is conducted through the cylinder to the working layer of the constraint frame, thus heating it.

[0012] As a further technical solution, the cooling component includes multiple cooling medium channels disposed inside the housing of the constraint frame. An inlet and an outlet are provided on the outer wall of the constraint frame. Preferably, the inlet is located at the lower part of the outer wall of the constraint frame, and the outlet is located at the upper part of the outer wall of the constraint frame, to facilitate the circulation and heat exchange of the cooling medium. The inlet is used to input a low-temperature cooling medium (such as cooling water or cooling oil), and the outlet is used to discharge the cooling medium that has absorbed heat. Through the circulating flow of the cooling medium, the heat of the working layer is carried away, achieving rapid cooling of the working layer.

[0013] As a further technical solution, one or more temperature sensors are provided on the bottom surface of the constraint frame (i.e., the surface in contact with the working layer). The temperature sensor is used to detect the temperature of the working layer inside the constraint frame in real time and feed the temperature signal back to the CNC system or a dedicated temperature controller to achieve precise closed-loop control of the heating and cooling process.

[0014] As a further technical solution, a flow sensor is installed on the vacuum connection valve. This flow sensor detects the gas flow rate in the negative pressure channel. When the adsorption plate forms an effective seal with the workpiece surface and establishes a negative pressure, the flow rate in the negative pressure channel will significantly decrease; conversely, if no seal is formed or leakage exists, there will be a continuous flow. The signal from the flow sensor can be used to determine whether the workpiece has been successfully adsorbed.

[0015] The beneficial effects of this invention are: This invention utilizes the phase change properties of thermoplastic elastomers and an independently movable pin array to achieve perfect fit for workpieces with arbitrarily complex curved surfaces. The cured working layer not only forms a rigid support with the pin assembly but also fills the gaps between the pins, providing a continuous support surface for the workpiece. This completely avoids the localized deformation problems caused by point contact in traditional pin arrays. Heating and cooling are only required during workpiece installation and removal, eliminating the need for continuous power supply during processing sessions lasting several hours. Compared to magnetorheological fluid solutions that require continuous power to maintain the magnetic field, energy consumption is significantly reduced. Furthermore, the working layer uses a thermoplastic elastomer, eliminating issues such as magnetic particle sedimentation or agglomeration that lead to uneven performance, resulting in extremely high long-term stability.

[0016] The pin assembly achieves mechanical locking through a self-locking unit, eliminating the need for complex electronic feedback and drive systems. This results in a reliable structure and controllable costs. A single unit can be applied to countless workpieces of different shapes, significantly reducing changeover time and making it particularly suitable for multi-variety, small-batch production. The overall enveloping clamping after the working layer has cured, combined with the optional vacuum adsorption function, provides uniformly distributed and controllable clamping force, preventing damage to the workpiece surface due to excessive localized clamping force. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the positioning and clamping device for CNC equipment according to the present invention; Figure 2 This is a schematic diagram of the positioning and clamping device for CNC equipment of the present invention after removing the pin base; Figure 3 This is a side view of the positioning and clamping device for CNC equipment according to the present invention; Figure 4 yes Figure 3 AA view; Figure 5 This is a top view of the positioning and clamping device for CNC equipment of the present invention after removing the air-filled pin base; Figure 6 yes Figure 5 BB view; Figure 7 This is a cross-sectional view of the valve body in the positioning and clamping device for CNC equipment according to the present invention; Figure 8 This is a schematic diagram of the pin assembly in the positioning and clamping device for CNC equipment according to the present invention; Figure 9 yes Figure 8 CC view; Figure 10 This is a schematic diagram (three-dimensional view) of the universal adsorption component in the positioning and clamping device for CNC equipment of the present invention. Figure 11 This is an exploded view (structural diagram) of the universal adsorption component in the positioning and clamping device for CNC equipment of the present invention.

[0018] The names corresponding to each mark in the diagram: 1-Fixed base; 101-Allowing part; 2-Pin base; 201-Upper support plate; 202-Lower support plate; 203-Valve body; 2031-Expansion sleeve mounting groove; 2032-High pressure medium flow groove; 2033-Pin assembly mounting groove; 2034-Positioning step; 204-Expansion sleeve; 3-Pin assembly; 301-Cylinder; 302-Negative pressure pipe; 3021-Connecting seat; 3022-Threaded seat; 3023-Negative pressure channel; 303-Positioning protrusion; 304-Spring; 305-Vacuum connection valve; 306-Universal adsorption assembly; 3061-Hollow ball head; 3062-Universal ball seat; 3063-Cap; 3064-Adsorption sheet; 3065-Ventilation hole; 4-Constraint frame; 401-Cooling medium flow channel; 402-Inlet; 403-Outlet; 5-Working layer; 7-Heating element; 8-Temperature sensor. Detailed Implementation

[0019] 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0020] This detailed description of the embodiments will provide a specific example of a positioning and clamping device for CNC equipment provided by the present invention. The core concept of this invention lies in utilizing the properties of thermoplastic elastomers—softening upon heating and hardening upon cooling—in conjunction with an array of numerous independently extendable and lockable pins. When installing a workpiece, the thermoplastic elastomer is first heated to soften it, and then the workpiece is pressed in, causing the pin array to passively adapt to the complex curved surface of the workpiece's bottom. Subsequently, the positions of all pins are locked, and the thermoplastic elastomer is cooled and solidified. The solidified elastomer not only forms a robust support layer itself but also firmly binds all the pins together, providing a continuous, highly rigid, and perfectly fitting support and clamping surface for the workpiece. Furthermore, the pin assembly can integrate a vacuum adsorption function to further enhance the workpiece's fixation capability.

[0021] Please see Figures 1-11This invention demonstrates the overall assembly structure of a positioning and clamping device according to a specific embodiment. The device mainly includes a fixed base 1, a pin base 2, multiple pin assemblies 3, a self-locking assembly (in this embodiment, it mainly consists of a valve body 203, an expansion sleeve 204, a high-pressure medium flow channel 2032, etc.), a constraint frame 4, a working layer 5, an elastic membrane, a heating unit (including multiple heating elements 7), and a cooling unit (including a cooling medium flow channel 401, an inlet 402, and an outlet 403).

[0022] The fixed base 1 serves as the mounting foundation for the entire device. Its bottom has a suitable connection structure (e.g., T-slot bolt holes) for securely fixing the entire positioning and clamping device to the CNC machine's worktable (not shown). In this embodiment, the fixed base 1 is designed as an inverted U-shape. This shape allows for the formation of a spacious clearance 101 within it. The primary function of this clearance 101 is to provide ample movement space for the lower end of the downwardly extending pin assembly 3, preventing interference. Simultaneously, this hollow structure helps reduce the overall weight of the device and provides space for the arrangement of possible auxiliary pipelines (such as vacuum lines and hydraulic lines).

[0023] Figure 2 As shown, the pin base 2 is fixedly installed above the fixed base 1. The pin base 2 is a composite structure that supports and guides multiple pin assemblies 3 and houses the main components of the self-locking assembly. Specifically, the pin base 2 includes an upper support plate 201, a lower support plate 202, and a valve body 203. The upper support plate 201 and the lower support plate 202 are typically made of high-strength, wear-resistant steel (such as bearing steel or mold steel), and are arranged in parallel and fixedly connected to the valve body 203 as a whole by multiple bolts. Both the upper support plate 201 and the lower support plate 202 are machined with M rows × N columns of precision sliding holes. The positions of these sliding holes correspond one-to-one, forming the sliding guide rails for the multiple pin assemblies 3. The inner surfaces of the sliding holes are precision ground and may undergo surface hardening treatment (such as carburizing or hard chrome plating) to ensure that the pin assemblies 3 can slide smoothly and accurately axially for a long time.

[0024] Figure 3 and Figure 4 As shown, the constraint frame 4 is a rectangular hollow frame, whose bottom is fixed to the upper surface of the pin base 2 by bolts or locating pins. The interior of the constraint frame 4 forms a cavity for filling the working layer 5. The material of the constraint frame 4 needs to have good thermal conductivity and sufficient structural strength; aluminum alloy, copper alloy, or stainless steel with high thermal conductivity are typically selected. Its inner wall should be smooth to reduce the flow resistance of the working layer 5 in a softened state and to facilitate cleaning after processing.

[0025] The working layer 5 fills the entire internal cavity of the constraint frame 4. The working layer 5 is made of a thermoplastic elastomer. The choice of the specific thermoplastic elastomer is crucial to the effectiveness of the invention. Ideally, the material should possess the following characteristics: high hardness and modulus of elasticity (e.g., Shore hardness D greater than 50) at room temperature (i.e., below the curing temperature, e.g., below 40°C), providing sufficient support and resistance to cutting vibrations; a significant decrease in viscosity upon heating to a relatively low softening temperature (e.g., between 80°C and 150°C), exhibiting flowability and compressibility similar to a high-viscosity fluid; and stable physical and chemical properties after multiple heat-cooling cycles, without decomposition, precipitation, or permanent deformation. Materials meeting these conditions include, but are not limited to, polyurethane (TPU), polyamide (TPAE), copolyester (TPC-ET), etc. In particular, certain low-melting-point copolyamides (CoPA) or polyester elastomers specifically designed for hot embossing or thermoforming are also preferred materials. The working layer 5 is initially solid, and its top surface may be slightly lower than the upper edge of the constraint frame 4 or in contact with the lower surface of the elastic membrane.

[0026] The elastic membrane is a thin film with good elasticity and toughness, which is tightly covered and fixed to the upper surface of the constraint frame 4 (not shown in the figure). The function of the elastic membrane is to prevent the softened working layer 5 from overflowing from the top of the constraint frame 4 when under pressure, while uniformly transmitting the pressure of the workpiece to the pin assembly 3 and the working layer 5 below. The elastic membrane can be made of silicone rubber, fluororubber, or a highly elastic polyurethane film. A clearance hole is pre-drilled on the elastic membrane corresponding to the position of each pin assembly 3. The tip of the pin assembly 3 passes through this clearance hole and is slightly higher than the upper surface of the elastic membrane. In this way, when the workpiece is placed down, it first contacts the tip of the pin assembly 3, while the elastic membrane acts as a seal and uniformly transmits pressure.

[0027] There are numerous pin assemblies 3 arranged in a dense matrix. Each pin assembly 3 is an independent, axially movable unit. Its specific structure will be described in detail later. In this overall structure, the main body of each pin assembly 3 passes sequentially through the sliding hole of the upper support plate 201, the pin assembly mounting groove 2033 of the valve body 203, and the sliding hole of the lower support plate 202. Its top passes through the clearance hole of the elastic membrane, and its bottom extends into the clearance part 101 of the fixed base 1.

[0028] This embodiment employs a hydraulically or pneumatically driven expansion sleeve locking mechanism. Please refer to the following for details. Figure 5 , Figure 6 and Figure 7Inside the valve body 203, each pin assembly 3 is individually equipped with a sleeve mounting groove 2031 and a high-pressure medium flow groove 2032 perpendicularly connected to the groove. An elastic sleeve 204 is installed in the sleeve mounting groove 2031 and tightly fitted onto the outer circumference of the pin assembly 3. The sleeve 204 is typically made of a rubber sleeve and a metal retaining ring, with the metal retaining ring located at both ends of the rubber sleeve. When high-pressure oil or high-pressure gas is introduced into the sleeve mounting groove 2031 through the high-pressure medium flow groove 2032, the sleeve 204 is subjected to external pressure and undergoes radial contraction, thereby gripping the pin assembly 3 and generating a large static friction force, locking the pin assembly 3 in its current position. When the high-pressure medium is depressurized, the sleeve 204 returns to its original shape due to its elasticity, releasing the lock on the pin assembly 3.

[0029] Figure 7 As shown, the heating unit includes multiple heating elements 7. Figure 2 and Figure 3 As shown, each heating element 7 is integrated inside the corresponding pin assembly 3. The heating element 7 is preferably a high-performance heating wire (e.g., nichrome wire) or a ceramic heating rod. When current passes through the heating element 7, Joule heating is generated. The heat is first transferred to the cylinder 301 of the pin assembly 3, and then, primarily through thermal conduction, to the surrounding working layer 5 via the outer wall of the cylinder 301 and the upper surface in contact with the working layer 5. Because the pin assemblies 3 are densely distributed within the constraint frame 4, each pin assembly 3 becomes a heat source, enabling rapid and uniform heating of the working layer 5.

[0030] The cooling unit is integrated into the structure of constraint box 4. Please refer to [link / reference]. Figure 4 and Figure 6 Inside the housing of the constraint frame 4, a series of labyrinthine or spiral cooling medium channels 401 are formed by casting or machining. On the outer wall of the constraint frame 4, inlets 402 and outlets 403 communicating with these channels are provided. To achieve better heat exchange efficiency, inlets 402 are typically located at the bottom, and outlets 403 at the top. When the working layer 5 needs to be cured, a low-temperature cooling medium (e.g., cooling water or cooling oil at 0°C to 10°C) is pumped into the inlet 402 via an external pump station. The cooling medium circulates within the cooling medium channels 401, absorbing heat from the working layer 5, and then flows out from the outlet 403. By controlling the flow rate and temperature of the cooling medium, precise control of the cooling rate of the working layer 5 can be achieved, thereby optimizing its cured crystal structure and mechanical properties.

[0031] Please combine further Figure 4 and Figure 6 To ensure reliable and independent locking of each pin assembly 3, this embodiment optimizes the design details of the pin base 2 and the self-locking assembly.

[0032] Inside the valve body 203, an annular positioning step 2034 is machined at the upper part of each pin assembly mounting groove 2033, i.e., at the end near the upper support plate 201. Simultaneously, an annular positioning protrusion 303 is integrally machined or fixedly installed on the outer wall of the cylinder 301 of each pin assembly 3. The outer diameter of the positioning protrusion 303 is larger than the inner diameter of the positioning step 2034. When the pin assembly 3 is subjected to an upward force (e.g., the elastic force from the lower spring 304), the upper end face of the positioning protrusion 303 contacts the lower end face of the positioning step 2034, thereby limiting the highest position of upward movement of the pin assembly 3. This position is defined as the "extended" position of the pin assembly 3. In the extended position, the top of the pin assembly 3 is typically flush with or slightly lower than the upper surface of the elastic diaphragm.

[0033] Spring 304 is sleeved on the cylinder 301 of pin assembly 3, located within the pin assembly mounting groove 2033. The lower end of spring 304 abuts against the upper surface of the lower support plate 202, and the upper end abuts against the lower end face of the positioning protrusion 303. Spring 304 is always in a compressed state, thus applying an upward thrust to pin assembly 3. The function of this thrust is: when the self-locking component is unlocked and the working layer 5 is in a softened state, spring 304 can automatically push pin assembly 3 upward to the retracted position. When the workpiece presses down on pin assembly 3, it needs to overcome the elastic force of spring 304. By selecting and designing springs 304 with different stiffness coefficients, the initial force required for the workpiece to press down on pin assembly 3 can be adjusted to accommodate workpieces of different weights and stiffnesses.

[0034] To prevent high-pressure media (especially hydraulic oil) from leaking from the end of the expansion sleeve mounting groove 2031 or along the axial direction of the pin assembly 3, this embodiment also incorporates a multi-layer sealing structure. First, a sealing ring (e.g., an O-ring or Glyd ring) is installed at the bottom of the expansion sleeve mounting groove 2031 near the bottom of the pin assembly mounting groove 2033. This sealing ring fits onto the pin assembly 3, tightly against the end face of the expansion sleeve 204, preventing high-pressure oil from leaking into the pin assembly mounting groove 2033. Second, an oil seal mounting groove is machined on the outer side of the valve body 203, corresponding to the open end of the expansion sleeve mounting groove 2031, where an oil seal (e.g., a skeleton oil seal) is installed. The oil seal fits onto the pin assembly 3, its lip tightly against the outer circumferential surface of the pin assembly 3, preventing high-pressure oil from leaking outwards, and also preventing external dust, chips, and other contaminants from entering the working area of ​​the expansion sleeve 204, ensuring the long-term cleanliness and reliability of the locking system.

[0035] The inlet end of the high-pressure medium flow channel 2032 is machined with a standard pipe thread for connecting to an external high-pressure pipeline. A proportional valve or on / off valve can be installed on the pipeline, controlled by a CNC system to precisely control the on / off state and pressure of the high-pressure medium. For example, when locking is required, high-pressure oil at a preset pressure (e.g., 5-10 MPa) is introduced; when unlocking is required, the high-pressure oil circuit is connected back to the oil tank via a reversing valve to achieve pressure relief.

[0036] Please see Figure 8 and Figure 9 To further improve the clamping stability of the workpiece, especially for large thin-walled parts or applications requiring large cutting forces, this embodiment integrates a vacuum adsorption function in each pin assembly 3.

[0037] Each pin assembly 3 mainly includes a cylinder 301 and a negative pressure tube 302. The cylinder 301 is a cylindrical part that is open at the bottom, closed at the top, and has a central hole. The negative pressure tube 302 is a slender tubular part whose outer diameter is much smaller than the inner diameter of the cylinder 301, thus forming an annular space between them, which is just large enough to accommodate the heating element 7. The lower end of the negative pressure tube 302 is fixedly connected to a connecting seat 3021. The connecting seat 3021 is also a sealing joint, with threads on its outer circumference that engage with the internal threads of the lower opening of the cylinder 301. By tightening the connecting seat 3021, the negative pressure tube 302 can be fixed to the cylinder 301, and the annular space between them can be sealed. The upper end of the negative pressure pipe 302 is provided with a threaded seat 3022, which engages with the internal thread at the upper end of the cylinder 301, thereby fixing the upper end of the negative pressure pipe 302 inside the cylinder 301 and ensuring its axial position. The center of the negative pressure pipe 302 is a through negative pressure channel 3023. The lower center of the connecting seat 3021 is provided with a vacuum connection valve 305 (e.g., a one-way valve or quick connector) for connecting the hose of an external vacuum pump.

[0038] At the top of the cylinder 301, a universal adsorption assembly 306 is provided. This assembly allows the adsorption sheet 3064 to tilt freely within a certain angle range, thereby better conforming to the locally tilted surface of the irregular curved workpiece and improving the sealing effect and adsorption force of vacuum adsorption.

[0039] Figure 10 and Figure 11As shown, the specific structure of the universal adsorption assembly 306 is as follows: A universal ball seat 3062 has an external thread at its lower part, which is screwed and fixed in the internal threaded hole at the top of the cylinder 301. A hemispherical spherical groove is machined at the center of the upper end face of the universal ball seat 3062. A hollow ball head 3061 is placed in this spherical groove, and the spherical outer surface of the hollow ball head 3061 is precisely fitted with the inner surface of the spherical groove to achieve low-friction universal rotation. A cover 3063 is fixed above the universal ball seat 3062 by threads or snaps. The center of the cover 3063 has a circular hole with a diameter slightly smaller than the maximum diameter of the hollow ball head 3061, which is used to constrain the hollow ball head 3061 in the spherical groove to prevent it from falling out, while allowing the upper end of its ball head portion to be exposed. A disc-shaped adsorption plate 3064 is fixedly connected to the top of the hollow ball head 3061. The upper surface of the adsorption plate 3064 can be a flat surface or a flexible lip with concentric annular grooves to enhance the seal with the workpiece surface. The adsorption plate 3064 has negative pressure adsorption holes. The hollow ball head 3061 has an internal cavity with a vent 3065 at its center. This vent 3065 is sealed to the outlet of the negative pressure channel 3023 at the top of the negative pressure pipe 302. Thus, negative pressure is transmitted from an external vacuum source through the vacuum connection valve 305, the negative pressure channel 3023, and the internal cavity of the hollow ball head 3061, ultimately reaching the vent 3065 on the adsorption plate 3064. When the adsorption plate 3064 is in close contact with the workpiece surface, the vent 3065 is blocked, forming a vacuum cavity, thereby generating adsorption force.

[0040] To achieve precise automated control, this embodiment also integrates a variety of sensors and feedback elements.

[0041] Temperature sensor 8: such as Figure 1 As shown, multiple temperature sensors 8 are installed on the bottom inner surface of the constraint frame 4, or embedded inside the working layer 5. The temperature sensors 8 can be thermocouples or thermistors (RTDs). The temperature sensors 8 detect the temperature of the working layer 5 in real time and feed back electrical signals to a temperature controller (usually integrated into a CNC system). Based on preset heating and cooling curves, the temperature controller controls the operation of the heating unit (i.e., the energizing time and power of the heating element 7) and the cooling unit (e.g., controlling the valve opening of the cooling medium or the pump speed), ensuring that the working layer 5 is precisely heated above the softening temperature without overheating and decomposing, or precisely cooled below the curing temperature.

[0042] Flow sensor: A miniature flow sensor (not shown in the figure) can be installed on the pipeline of vacuum connection valve 305 or inside connection seat 3021. This flow sensor is used to monitor the gas flow rate in negative pressure channel 3023. When the adsorption plate 3064 has not yet made contact with the workpiece surface or the seal is poor, external air will be continuously drawn in, and the flow sensor will detect a continuous and large flow rate value. When the adsorption plate 3064 forms a good seal with the workpiece surface and establishes negative pressure, the drawn-in air flow rate will drop sharply, even approaching zero. By reading the signal from this flow sensor, the CNC system can accurately determine whether each pin assembly 3 has successfully adsorbed the workpiece surface or whether there is a leak. This is crucial for multiple pins to work together and ensure that each contact point provides effective adsorption force. If the flow sensor of a certain pin assembly 3 shows a continuous high flow rate, the system can issue an alarm to prompt the operator to check the contact condition or seal at that point.

[0043] Pressure sensor: Similarly, a pressure sensor (not shown in the figure) can also be installed on the pipeline supplying the high-pressure medium to the self-locking assembly. This pressure sensor is used to monitor the locking pressure. The CNC system only allows the machining program to begin when the pressure reaches a preset safety threshold (e.g., ensuring that the static friction provided by the expansion sleeve 204 is sufficient to resist the maximum axial force during machining). If the pressure unexpectedly drops during machining, the system can immediately trigger an emergency stop to prevent safety accidents and workpiece scrap caused by workpiece loosening.

[0044] The following is combined Figure 6 This document describes in detail the complete operation process of using the positioning and clamping device of the above embodiment to fix an irregularly shaped curved workpiece. This process can be automatically controlled and executed by a CNC system.

[0045] Step S1: Initialization and Reset. Activate the positioning and clamping device. First, control the self-locking component to unlock, that is, release the pressure in the high-pressure medium flow channel 2032, causing the expansion sleeve 204 to loosen its lock on the pin assembly 3. Under the thrust of the spring 304, all pin assemblies 3 move upward until their positioning protrusions 303 contact the positioning steps 2034 of the valve body 203, meaning all pin assemblies 3 are in the fully retracted position. At this time, the top of the pin assembly 3 is basically flush with the upper surface of the elastic diaphragm. The working layer 5 is in a solid state at room temperature.

[0046] Step S2: Heating and softening the working layer. The CNC system activates the heating unit via a temperature controller. Current flows through the heating element 7 (heating wire) inside each pin assembly 3, generating heat. The heat is conducted to the working layer 5, causing its temperature to rise rapidly. The temperature sensor 8 monitors the temperature in real time. When the temperature of the working layer 5 reaches and stabilizes above the preset softening temperature (e.g., 120°C for TPU material), the working layer 5 transforms into a viscous fluid or gel, becoming flowable. At this point, heating is stopped or switched to low-power heat preservation.

[0047] Step S3: Placement and Fitting of the Workpiece. The irregularly shaped curved workpiece to be processed is placed onto the elastic membrane using a robotic arm or manually. Under the weight of the workpiece itself and / or externally applied auxiliary pressure, the workpiece moves downwards. The lower surface of the workpiece first contacts the tops of each pin assembly 3 (more specifically, the suction plates 3064 of the universal suction assembly 306). As the workpiece continues to press down, the pin assemblies 3 in contact with the protruding parts of the lower surface of the workpiece are pushed downwards against the elastic force of the spring 304. Simultaneously, the working layer 5, in a viscous flow state, is squeezed and flows from the gaps between the pin assemblies 3 to accommodate the height changes of the pin assemblies 3. The pin assemblies 3 corresponding to the concave parts of the lower surface of the workpiece maintain a higher protrusion height. This process continues until the workpiece completely stops moving. At this point, the top of each pin assembly 3 is tightly fitted to the lower surface of the workpiece under the reaction force of the spring 304, forming a precise replication of the curvature of the lower surface of the workpiece. The working layer 5 is also uniformly squeezed, filling all gaps.

[0048] Step S4: Locking the Pin Assembly. After confirming that the workpiece is fully fitted, the CNC system controls the self-locking assembly to operate. High-pressure oil at a preset pressure (e.g., 8 MPa) is introduced into each high-pressure medium flow channel 2032. The high-pressure oil enters the expansion sleeve mounting groove 2031, compressing the expansion sleeve 204 to produce radial contraction. The expansion sleeve 204 locks onto the outer wall of the cylinder 301 of the pin assembly 3, relying on the huge static friction force to firmly lock each pin assembly 3 in its current position. At this time, even if the external pressure is removed, the workpiece can no longer push the pin assembly 3.

[0049] Step S5: Cooling and solidifying the working layer. The cooling unit is activated. The external cooling water circulation system begins operation, pumping 5°C cooling water from the inlet 402 into the cooling medium channel 401 inside the constraint frame 4. The cooling water flows within the cooling medium channel 401, absorbing a large amount of heat from the working layer 5, and then flows out from the outlet 403. The temperature of the working layer 5 drops rapidly. The temperature sensor 8 monitors this in real time. When the temperature of the working layer 5 drops below its curing temperature (e.g., 40°C), the working layer 5 re-solidifies into a high-hardness, high-rigidity solid. At this point, the solidified working layer 5 not only becomes a sturdy support block itself, but also, like potting compound, firmly bonds the cylindrical sections 301 of the numerous pin assemblies 3 at different heights together. The bottom of the workpiece receives a completely fitted, gapless, continuous rigid support surface.

[0050] Step S6: Apply vacuum adsorption. Depending on process requirements, the vacuum adsorption function can be activated. The CNC system controls the vacuum pump to start, establishing negative pressure at the adsorption plate 3064 of each pin assembly 3 in contact with the workpiece surface via vacuum connection valve 305 and negative pressure channel 3023. Since the adsorption plate 3064 has achieved surface contact with the workpiece surface through the hollow ball head 3061, a good seal is formed, generating a strong adsorption force that firmly pulls the workpiece downwards, further enhancing the reliability of clamping. A flow sensor is used to monitor the sealing status of each adsorption point to ensure effective adsorption.

[0051] Step S7: Perform CNC machining. After completing all the above steps, the workpiece has been reliably positioned and clamped. The CNC system confirms that all sensor (pressure, temperature, flow) signals are normal, and then begins to execute the preset machining program to perform milling, drilling, grinding and other machining operations on the workpiece.

[0052] Step S8: Workpiece Disassembly and Device Reset. After machining is completed, the CNC program ends. First, shut down the vacuum adsorption system to release the negative pressure. Then, restart the heating unit to heat the working layer 5 above its softening temperature, making it flowable again. Simultaneously, unlock the self-locking assembly, release the high-pressure oil, and loosen the expansion sleeve 204. At this point, under the elastic force of the spring 304, all pin assemblies 3 automatically move upward, returning to their initial retracted positions. The flow of the working layer 5 also adapts to the reset of the pin assemblies 3. Finally, easily remove the machined workpiece using a robotic arm or manually. The device returns to its initial state, ready to clamp the next workpiece.

[0053] It is worth noting that although the above embodiments describe locking achieved by hydraulically driven expansion sleeves, those skilled in the art will appreciate that the self-locking assembly can also take other forms, such as electromagnetic brakes, pneumatic grippers, or locking mechanisms driven by shape memory alloys. Similarly, the heating element is not limited to integration within the pin assembly; it can also be a separate heating plate located on the side wall or bottom of the constraint frame. The cooling unit is not limited to liquid cooling; it can also employ semiconductor cooling chips or forced air cooling. These variations, as long as they do not depart from the core concept defined in the claims of this invention, should be considered within the scope of protection of this invention.

[0054] In summary, the positioning and clamping device for CNC equipment provided by this invention creatively combines an independently lockable pin array with the phase change characteristics of thermoplastic elastomers, successfully solving the problem of flexible clamping of irregularly shaped curved workpieces in CNC machining. This device not only achieves complete fit and continuous support of the workpiece surface, effectively avoiding machining deformation, but also has outstanding advantages such as low energy consumption, good material stability, and ease of automation control, making it extremely valuable for industrial applications.

Claims

1. A positioning and clamping device for CNC equipment, characterized in that, include: Fixed base, used to securely connect the worktable to the CNC equipment; A pin base is disposed above the fixed base. The pin base is provided with pin assemblies arranged in a matrix of M rows × N columns. Each pin assembly can move independently along its axis between an extended position and a retracted position. A self-locking component is disposed in the pin base for locking in the extended or retracted position of the pin; A constraint frame is disposed on the upper end of the pin base, and the pin assembly portion is located within the constraint frame; The working layer, made of thermoplastic elastomer material, is disposed in the constraint frame. The working layer has a flowable or compressible viscoelasticity when heated to above the softening temperature, and recovers high hardness and generates clamping force when cooled to below the curing temperature. An elastic membrane covers the upper end of the constraint frame, and clearance holes are provided on the elastic membrane. The top of the pin assembly is located above the elastic membrane. The heating unit includes multiple heating elements disposed in the pin assembly; The cooling unit includes a cooling component disposed within the constraint frame.

2. The positioning and clamping device for CNC equipment according to claim 1, characterized in that, The pin base includes an upper support plate, a lower support plate, and a valve body. Both the upper and lower support plates have sliding holes corresponding to the pin assemblies. Each pin assembly is fitted into a sliding hole. The valve body has an expansion sleeve mounting groove, a high-pressure medium flow groove, and a pin assembly mounting groove. One end of the expansion sleeve mounting groove is located on the surface of the valve body, and the other end communicates with the pin assembly mounting groove. An expansion sleeve is provided in the expansion sleeve mounting groove and is fitted onto the pin assembly. The high-pressure medium flow groove is perpendicular to and communicates with the expansion sleeve mounting groove. The pin assembly mounting groove is coaxial with the expansion sleeve mounting groove and communicates with the valve body. A high-pressure medium is introduced into the high-pressure medium flow groove to deform the expansion sleeve and position the pin assembly.

3. The positioning and clamping device for CNC equipment according to claim 2, characterized in that, The outer wall of the pin assembly is provided with a positioning protrusion in the circumferential direction. The positioning protrusion is located in the pin assembly mounting groove. A spring is provided in the valve body in the pin assembly mounting groove. One end of the spring abuts against the positioning protrusion and the other end abuts against the lower support plate. A positioning step is provided at the upper part of the pin assembly mounting groove. The positioning protrusion is used to cooperate with the positioning step to position the pin assembly. The pin assembly can move axially in the pin assembly mounting groove and can be reset by the elastic force of the spring.

4. The positioning and clamping device for CNC equipment according to claim 3, characterized in that, The lower end of the pin assembly is located below the lower support plate. The fixing base is arranged in an inverted U-shape and has a clearance part for avoiding the pin assembly. A sealing ring is provided at one end of the expansion sleeve mounting groove near the pin assembly mounting groove. An oil seal mounting groove is provided on the outside of the expansion sleeve mounting groove on the valve body, and an oil seal is provided in the oil seal mounting groove.

5. The positioning and clamping device for CNC equipment according to claim 1, characterized in that, The pin assembly includes a cylinder and a negative pressure tube. The cylinder is hollow and open at one end. A connecting seat is provided at one end of the negative pressure tube. Threads are provided on the outer wall of the open end of the cylinder, and the connecting seat is threadedly connected to the cylinder. A threaded seat is provided at the other end of the negative pressure tube, and corresponding threads are provided on the cylinder. The other end of the negative pressure tube is threadedly connected to the cylinder. A negative pressure channel is provided in the negative pressure tube, which is used to adsorb the workpiece when the cylinder comes into contact with it. A vacuum connection valve is provided on the connecting seat.

6. The positioning and clamping device for CNC equipment according to claim 5, characterized in that, A universal adsorption assembly is provided on the cylindrical body at one end near the workpiece. The universal adsorption assembly includes a hollow ball head, a universal ball seat, a cover, and an adsorption plate. The universal ball seat is threaded to the top of the cylindrical body. A spherical groove is formed on the universal ball seat. The hollow ball head is disposed in the spherical groove. The cover is placed on the universal ball seat to position the hollow ball head. The adsorption plate is connected to the top of the hollow ball head. A negative pressure adsorption hole is formed on the adsorption plate and communicates with the hollow ball head. A vent hole is provided on the bottom surface of the hollow ball head and is used to connect with the negative pressure channel.

7. The positioning and clamping device for CNC equipment according to claim 6, characterized in that, The heating element is provided between the inner wall of the cylinder and the negative pressure pipe. The heating element includes a heating wire, the two poles of which pass through the connecting seat. The heating wire is used to conduct electricity to heat the working layer in the constraint frame.

8. The positioning and clamping device for CNC equipment according to claim 1, characterized in that, The cooling component includes a cooling medium flow channel disposed inside the constraint frame. The outer wall of the constraint frame is provided with a liquid inlet and a liquid outlet. The liquid inlet is disposed at the lower part of the outer wall of the constraint frame, and the liquid outlet is disposed at the lower part of the outer wall of the constraint frame. The liquid inlet is used to input the cooling medium, and the liquid outlet is used to input the cooling medium. The cooling medium is used to cool the working layer located in the constraint frame.

9. The positioning and clamping device for CNC equipment according to claim 1, characterized in that, A temperature sensor is provided on the bottom surface of the constraint frame, and the temperature sensor is used to detect the temperature of the working layer in the constraint frame.

10. The positioning and clamping device for CNC equipment according to claim 5, characterized in that, The vacuum connection valve is equipped with a flow sensor, which is used to detect whether there is negative pressure in the negative pressure channel.

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