Anodic oxidation or platinum electroplating tool clamp suitable for complex inner cavity

Abstract

The invention provides an anodic oxidation or platinum electroplating tool clamp suitable for a complex inner cavity, and belongs to the technical field of metal surface treatment equipment. Comprising a clamp main body, an inner cavity adaptive assembly, a conductive connecting mechanism and a sealing positioning unit, the clamp body is of a frame type structure and used for bearing a to-be-treated workpiece. The inner cavity adaptive assembly is detachably connected to the clamp body and can stretch into a complex inner cavity of a workpiece to be treated and be attached to the wall of the inner cavity. One end of the conductive connecting mechanism is conducted with an external power supply, and the other end is electrically connected with the clamp body and the inner cavity adaptive assembly. Through the detachable inner cavity adaptive assembly with the self-adaptive adjusting capacity, the problem that a traditional device is difficult to adapt to a workpiece with a complex inner cavity is effectively solved, the elastic supporting framework is combined with the inflatable adjusting structure, the shape can be flexibly adjusted according to the shape of the inner cavity, stable attachment is kept, and the platinum alloy conductive contact layer with conductive protruding points on the surface is matched; and the electric conduction uniformity and reliability of the inner cavity wall are ensured.

Description

Technical Field

[0001] This invention belongs to the technical field of metal surface treatment equipment, specifically relating to a fixture for anodizing or electroplating platinum in complex cavities. Background Technology

[0002] In high-end manufacturing fields such as aerospace, precision instruments, and chemical equipment, many metal workpieces (such as irregularly shaped cavity parts made of titanium alloys and aluminum alloys) not only need to possess excellent mechanical properties, but their surfaces (especially complex internal cavity surfaces) also require anodizing or platinum plating treatment to obtain special functions such as corrosion resistance, high temperature resistance, low friction, or high conductivity. During the anodizing and platinum plating process, the adaptability, conductivity, and sealing stability of the tooling fixtures directly determine the processing quality of the workpiece.

[0003] In existing technologies, commonly used tooling fixtures for workpieces with complex internal cavities have several limitations: First, the contact structure of traditional fixtures is mostly rigid, making it difficult to achieve a complete fit with irregular internal cavity walls. This leads to poor conductivity in localized areas of the cavity, resulting in uneven oxide film thickness and incomplete plating, especially in dead corners with corners or blind holes, making it even more difficult to guarantee processing quality. Second, the conductive connection mechanism lacks flexibility. When the depth or dimensions of the workpiece cavity change, a special fixture must be replaced, increasing manufacturing costs and reducing processing efficiency. The platinum electroplating process places extremely high demands on the conductivity and chemical inertness of the fixture. Existing fixtures often use ordinary metal materials for their conductive contact layers, which are easily corroded by the electrolyte over long-term use, affecting conductivity and potentially contaminating the plating solution, increasing subsequent processing costs. Therefore, it is necessary to develop a tooling fixture that can adapt to complex internal cavity structures, provide stable conductivity, ensure reliable sealing, and has strong adaptability to solve the above problems. Summary of the Invention

[0004] The technical problems to be solved by the present invention are the low efficiency of manual line-following method, the insufficient positioning accuracy of single sensor, the poor applicability of fixed monitoring device, and the weak data processing and fusion capability. In view of the shortcomings of the prior art, an anodizing or electroplating platinum tooling fixture suitable for complex internal cavities is provided.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a fixture for anodizing or electroplating platinum with complex internal cavities, comprising a fixture body, an internal cavity adapter component, a conductive connection mechanism, and a sealing and positioning unit; the fixture body is a frame structure used to support the workpiece to be processed; the internal cavity adapter component is detachably connected to the fixture body and can extend into the complex internal cavity of the workpiece to be processed and fit against the internal cavity wall; one end of the conductive connection mechanism is connected to an external power source, and the other end is electrically connected to the fixture body and the internal cavity adapter component respectively; the sealing and positioning unit is disposed at the connection between the fixture body and the workpiece to be processed, and is used to achieve sealing and fixing of the workpiece and the fixture.

[0006] Furthermore, the inner cavity adaptation component includes an elastic support frame and a conductive contact layer. The elastic support frame is composed of several flexible metal rods hinged together, which can adaptively adjust the bending angle according to the shape of the inner cavity. The conductive contact layer covers the outer side of the elastic support frame, and the surface of the conductive contact layer is provided with several conductive protrusions, which elastically abut against the inner cavity wall.

[0007] Furthermore, the elastic support frame is provided with an air-expansion adjustment structure, which includes micro air bags and an inflation port. The micro air bags are distributed along the length of the frame. After being inflated through the inflation port, they can drive the elastic support frame to expand towards the inner cavity wall, so that the conductive contact layer and the inner cavity wall maintain a preset pressure fit.

[0008] Furthermore, the conductive connection mechanism includes a main conductive rod, branch conductive components, and conductive clamps; the main conductive rod is vertically fixed to the top of the fixture body, and a power terminal is provided at its top end; one end of the branch conductive component is connected to the main conductive rod, and the other end is connected to the outer surface and inner cavity of the workpiece to be processed through the conductive clamps respectively, and a conductive silicone pad is provided on the inner side of the conductive clamps.

[0009] Furthermore, the sealing and positioning unit includes an annular sealing gasket and a quick-locking structure; the annular sealing gasket is made of fluororubber material resistant to electrolyte corrosion, and its cross-section is stepped, which can be adapted to the stepped structure of the workpiece end face; the quick-locking structure includes several eccentric locking buckles evenly distributed on the fixture body, which can press and fix the workpiece on the annular sealing gasket after rotation, for sealing.

[0010] Furthermore, it also includes an electrolyte guiding component, which includes a guiding pipe and a diverting nozzle; one end of the guiding pipe is connected to an external electrolyte supply system, and the other end extends into the interior of the fixture body; the diverting nozzle is located at the end of the guiding pipe, and some of the diverting nozzles are integrated with the inner cavity adapter component, which can directly guide the electrolyte to the dead corner area of ​​the workpiece's inner cavity.

[0011] Furthermore, the conductive contact layer is made of platinum alloy material with a thickness of 0.1-0.3 mm, and a thermally conductive insulating layer is provided between the conductive contact layer and the elastic support frame, the thermally conductive insulating layer being made of aluminum nitride ceramic material.

[0012] Furthermore, the fixture body is provided with several position-adjustable support blocks. The support blocks are connected to the fixture body through a screw slide mechanism, which can adjust the support position according to the shape and size of the workpiece, so that the center of gravity of the workpiece coincides with the center of the fixture body.

[0013] Furthermore, the branch conductive component is a telescopic structure, including a fixed section and a telescopic section. The fixed section is fixedly connected to the main conductive rod, and the telescopic section is slidably engaged with the fixed section through a spring pin. The length adjustment range of the telescopic section is 50-200mm to adapt to the inner cavity of the workpiece of different depths.

[0014] Furthermore, the outlet end of the diverting nozzle is provided with a rotatable guide vane. The guide vane is driven by a micro motor and can change the spray direction of the electrolyte to achieve all-round flushing of the inner cavity wall.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention effectively solves the problem of traditional fixtures being unable to adapt to complex internal cavity workpieces through a detachable and self-adjusting internal cavity adapter component. The elastic support frame combined with the air-expansion adjustment structure can flexibly adjust its shape according to the shape of the internal cavity and maintain a stable fit. Combined with the platinum alloy conductive contact layer with conductive bumps on the surface, it ensures the uniformity and reliability of conductivity of the internal cavity wall. At the same time, the design of the retractable branch conductive component and the position adjustable support block further improves the adaptability of the fixture to workpieces of different sizes and depths, reduces the opening cost of special fixtures, and improves equipment utilization.

[0016] 2. This invention significantly improves the processing quality and efficiency of prototype oxidation and platinum electroplating through multi-structure collaborative design; the sealing and positioning unit adopts a corrosion-resistant fluororubber annular sealing gasket and a quick-locking structure, which not only achieves reliable sealing between the workpiece and the fixture, avoiding electrolyte leakage, but also simplifies the clamping process; the electrolyte guiding component, through the diversion nozzle and rotatable guiding blade integrated into the inner cavity adapter component, accurately guides the electrolyte to the dead corners of the inner cavity and achieves all-round flushing, ensuring the uniformity of the inner cavity surface treatment; the setting of the thermally conductive insulation layer can avoid the impact of local overheating on the processing quality, ultimately achieving high quality and high consistency of the surface treatment of complex inner cavity workpieces. Attached Figure Description

[0017] The present invention will now be described in further detail with reference to the accompanying drawings.

[0018] Figure 1 : Schematic diagram of the overall structure of the present invention; Figure 2 Top view of the overall structure of the present invention.

[0019] The components include: 1. Fixture body; 2. Inner cavity adapter assembly; 21. Elastic support frame; 22. Conductive contact layer; 23. Air expansion adjustment structure; 3. Conductive connection mechanism; 31. Main conductive rod; 32. Branch conductive component; 33. Conductive chuck; 4. Sealing and positioning unit; 41. Annular sealing gasket; 42. Quick locking structure; 5. Electrolyte flow guiding assembly; 51. Flow guiding tube; 52. Flow dividing nozzle; 6. Support block. Detailed Implementation

[0020] To better understand the present invention, the content of the invention is further clearly illustrated below with reference to embodiments and accompanying drawings. However, the scope of protection of the present invention is not limited to the embodiments described below. Numerous specific details are set forth in the following description to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without one or more of these details.

[0021] Example 1, see Figure 1 The fixture includes a fixture body 1, an inner cavity adapter component 2, a conductive connection mechanism 3, and a sealing and positioning unit 4. The fixture body 1 is a frame structure used to support the workpiece to be processed. The inner cavity adapter component 2 is detachably connected to the fixture body 1 and can extend into the complex inner cavity of the workpiece to be processed and fit against the inner cavity wall. One end of the conductive connection mechanism 3 is connected to an external power source, and the other end is electrically connected to the fixture body 1 and the inner cavity adapter component 2 respectively. The sealing and positioning unit 4 is set at the connection between the fixture body 1 and the workpiece to be processed, and is used to achieve the sealing and fixing of the workpiece and the fixture. The fixture body 1 is provided with several position-adjustable support blocks 6. The support blocks 6 are connected to the fixture body through a screw slide mechanism, and can adjust the support position according to the outer dimensions of the workpiece so that the center of gravity of the workpiece coincides with the center of the fixture body 1.

[0022] It should be noted that the fixture body 1 is made of 304 stainless steel with a frame structure, and the overall dimensions are 600mm×400mm×500mm. The frame beams and longitudinal beams are detachably connected by bolts, which facilitates the adjustment of the internal space of the frame according to the workpiece size. Four leveling feet are provided at the bottom of the frame, and threaded holes are reserved at the top for installing the conductive connection mechanism 3. Three sets of support platforms for supporting the workpiece are welded in the middle. The surface of the support platforms is covered with a polytetrafluoroethylene insulation layer to avoid direct conductive interference between the workpiece and the fixture body 1.

[0023] During use, the assembled fixture is placed in the anodizing tank or platinum plating tank, and the leveling feet are adjusted to keep the fixture horizontal. The workpiece to be processed is installed on the fixture body 1, and the inner cavity adapter component 2 is inserted and clamped by the conductive chuck 33. After checking the sealing and conductivity of each connection part, the external power supply is turned on and the electrolyte circulation system is started. Anodizing or platinum plating can then be carried out. During the processing, the insulation design of the fixture body 1 and the precise conduction of the conductive connection mechanism 3 ensure that the current is evenly transmitted to the outer surface and inner cavity wall of the workpiece.

[0024] Technical benefits: By adopting a frame-type fixture body 1, the frame structure can be adjusted to adapt to workpieces of different sizes. The detachable inner cavity adapter component 2 can be flexibly adjusted according to the shape and depth of the inner cavity. The hinged elastic skeleton combined with the conductive protrusion design improves the contact rate between the contact layer and the inner cavity wall, solving the problem that traditional rigid fixtures cannot fully cover complex inner cavities and effectively avoiding the phenomenon of leakage in the inner cavity dead corners. At the same time, the conductive connection mechanism 3 adopts a pure copper main conductive rod 31 and a multi-branch conductive component 32 design, which controls the conductivity resistance between the outer surface of the workpiece and the inner cavity adapter component 2 to within 0.5Ω, while enhancing sealing reliability and ease of operation, and reducing the cost of use and maintenance difficulty.

[0025] Example 2, see Figure 2 The inner cavity adapter component 2 includes an elastic support frame 21 and a conductive contact layer 22. The elastic support frame 21 is composed of several flexible metal rods hinged together, which can adaptively adjust the bending angle according to the shape of the inner cavity. The conductive contact layer 22 covers the outer side of the elastic support frame 21, and the surface of the conductive contact layer 22 is provided with several conductive protrusions, which elastically abut against the inner cavity wall.

[0026] It should be added that the elastic support frame 21 uses TC4 titanium alloy as the base material for the bendable metal rods, with a tensile strength ≥895MPa and an elongation ≥10%, meeting the bending and support requirements after hinge. The length of a single metal rod segment is set to 50mm, and the diameter is 12mm. Each segment has 8mm diameter hinge holes machined at both ends. Adjacent segments are rotated and connected by 6mm diameter stainless steel pins. An adjustable bending angle range of 5°-175° is reserved between adjacent segments. Based on the depth of the workpiece's inner cavity, 9 metal rod segments are selected and hinged to form an elastic support frame 21 with a total length of 450mm. A 50mm diameter connecting flange is welded to the first end of the frame for connection with the fixture body 1, and a 10mm diameter guide head is installed at the end for easy insertion into the inner cavity.

[0027] The conductive contact layer 22 is made of Pt-Ir alloy with a resistivity ≤10.5×10⁻ 8It exhibits excellent resistance to electrolyte corrosion (Ω·m). The alloy is cold-rolled into a 0.2mm thick foil, which is then laser-cut into a tubular structure compatible with the elastic support frame 21. A 5mm wide expansion joint is pre-installed in the tube to accommodate bending deformation of the frame. The alloy foil is then wrapped around the elastic support frame 21 using a high-temperature brazing process. The brazing temperature is controlled at 850℃, and the holding time is 15 minutes, ensuring a bonding strength ≥20MPa. Subsequently, conductive bumps are formed on the contact layer surface using a stamping process. The bumps are hemispherical, 3mm in diameter and 1.5mm in height, distributed in a 12mm×12mm matrix. The bumps and the contact layer are integrally formed.

[0028] The inner cavity adapter assembly 2 is bolted to the support seat of the fixture body 1 via a connecting flange. A PTFE sealing gasket is installed at the flange. After the workpiece is hoisted onto the fixture body 1, the elastic skeleton 21 is manually pushed into the inner cavity. When the guide head at the end of the skeleton contacts the inner cavity wall, the bending angle of the metal rod is adjusted segment by segment according to the corner position of the inner cavity. At the 120° corner, the three adjacent metal rod segments form an adapter angle, ensuring that the conductive protrusions contact both sides of the corner wall. In the blind hole area, at a depth of 80mm, the bending angle of the two end metal rod segments is adjusted to 90°, so that the protrusions fit the bottom and side wall of the blind hole. After debugging, the skeleton position is fixed by the positioning pin at the flange to ensure the stability of the skeleton shape during processing.

[0029] The conductive contact layer 22 is electrically connected to the branch conductive component 32 of the conductive connection mechanism 3 via a copper conductive sheet on the connecting flange. The contact resistance between the conductive sheet and the contact layer is ≤0.1Ω. The elastic support frame 21 is integrated with the diversion nozzle 52 of the electrolyte diversion assembly 5. A diversion channel with a diameter of 5mm is reserved inside the frame. The diversion nozzle 52 guides the electrolyte to the dead corner of the inner cavity through the channel. The nozzle outlet is 5mm away from the conductive protrusion to avoid the electrolyte impact affecting the contact stability of the protrusion.

[0030] Technical Effects: The multi-segment hinged structure of the elastic support frame 21 can flexibly adapt to the corners, diameter changes, and blind hole areas of the inner cavity. At a 120° corner, the contact area of ​​the protrusions reaches over 95% of the corner wall surface, and the blind hole area achieves full wall coverage, solving the "dead corner" problem of traditional rigid structures. It ensures stable conductivity and improves processing uniformity: the low resistivity of the Pt-Ir alloy conductive contact layer 22 keeps the overall conductivity of the component below 0.3Ω. The matrix-distributed conductive protrusions increase the contact pressure with the inner cavity wall, with a protrusion contact pressure ≥0.8MPa, effectively reducing contact resistance fluctuations, with a fluctuation amplitude ≤0.05Ω. After anodizing, the oxide film thickness on the inner cavity wall is 7-9μm, and the thickness difference between the corner and blind hole areas and the main inner cavity area is ≤0.3μm, far superior to existing technologies with a thickness difference ≥1μm, meeting the surface quality requirements of precision components. Enhanced structural reliability and service life: The high strength of the TC4 titanium alloy skeleton allows the component to withstand radial pressure ≥50N without permanent deformation. The Pt-Ir alloy contact layer is resistant to anodic oxidation electrolyte corrosion. After 500 cycles of processing, the contact layer shows no corrosion spots, and the wear of the bumps is ≤0.1mm. The service life of the component is more than 3 times longer than that of existing copper contact structures. The matrix bump design ensures effective contact while reducing the friction area between the contact layer and the inner cavity wall, thus reducing the risk of surface scratches on the workpiece (scratch rate reduced from 8% in existing technologies to 0.5%).

[0031] Optionally, the elastic support frame 21 is provided with an air-inflating adjustment structure 23. The air-inflating adjustment structure 23 includes micro air bags and an inflation port. The micro air bags are distributed along the length of the frame. After being inflated through the inflation port, they can drive the elastic support frame 21 to expand towards the inner cavity wall, so that the conductive contact layer 22 and the inner cavity wall maintain a preset pressure fit.

[0032] In addition, the micro airbag is made of acid- and alkali-resistant fluorosilicone rubber, and is formed into a cylindrical structure with a diameter of 8 mm and a length of 45 mm. The wall thickness of the airbag is 0.5 mm, and the bursting pressure is ≥ 0.8 MPa, meeting the usage requirements in the electrolyte environment. An installation hole with a diameter of 10 mm is machined along the axis inside each bendable metal rod. One micro airbag is embedded in a single metal rod, and both ends of the airbag are fixed by special sealing plugs. The sealing plugs and the inner wall of the metal rod are in interference fit with an interference amount of 0.2 mm. The micro airbags in adjacent metal rods are connected in series through a fluoroplastics gas pipe with a diameter of 2 mm. The gas pipe is buried in the reserved hole at the hinge of the metal rod to avoid being damaged under pressure during hinge rotation. The inflation interface is made of brass and is designed in an L-shaped structure. One end is connected to the head of the series-connected gas pipe through a thread, and the other end extends to the outside of the connection flange of the elastic support framework 21. A one-way valve is installed at the interface to prevent gas leakage, and the range of the pressure sensor is 0 - 0.5 MPa with an accuracy of ± 0.01 MPa. The pressure sensor is connected to an external digital display pressure controller through a wire to achieve real-time monitoring and feedback of the inflation pressure; the inflation interface is connected to the output pressure of a micro air pump of 0 - 0.5 MPa and a flow rate of 5 L / min through a high-pressure gas pipe, and an electromagnetic control valve is connected in series in the gas path to control the inflation and deflation processes. The metal rods embedded with micro airbags are hinged by pins to form the elastic support framework 21, and the gas pipes at the hinge are connected by flexible joints to ensure unobstructed gas paths during bending. After the conductive contact layer 22 is coated on the outside of the framework, a 0.3-mm expansion allowance is reserved at the position corresponding to the micro airbag, which is achieved by laser cutting a reserved annular groove to avoid the contact layer being torn due to stress when the airbag expands. After the gas path of the entire pneumatic expansion adjustment structure 23 is assembled, an airtightness test is carried out. Compressed air of 0.3 MPa is filled into the gas path, and the pressure is maintained for 30 min. If the pressure drop is ≤ 0.01 MPa, it is qualified; after the inner cavity adapter component 2 integrating the pneumatic expansion adjustment structure 23 is inserted into the inner cavity of the workpiece, first manually adjust the bending angle of the framework to adapt to the general shape of the inner cavity, and then start the air pump to inflate. The preset pressure value is set through the pressure controller, 0.2 MPa for the variable diameter section and 0.15 MPa for the arc surface. When the pressure sensor feedback reaches the preset value, the electromagnetic control valve automatically closes, and the airbag maintains a stable expansion state, pushing the metal rod to expand towards the inner cavity wall direction, so that the conductive bumps tightly abut against the inner cavity wall. After processing, the electromagnetic control valve is opened to deflate, and the airbag contracts, and the component can be easily taken out of the inner cavity.

[0033] Technical Benefits: Precise pressure control and improved contact stability: Through closed-loop control of a pressure sensor and electromagnetic control valve, the contact pressure control accuracy between the conductive protrusions and the inner cavity wall reaches ±0.02MPa. Differentiated pressure values ​​can be set according to the structural characteristics of different areas of the inner cavity, with contact pressure fluctuations between the variable diameter section and the arc-shaped surface ≤5%. Compared to manually adjusted elastic frames, this structure improves the consistency of contact pressure, effectively avoiding poor conductivity or workpiece surface damage caused by uneven pressure. Enhanced adaptability to complex inner cavities and expanded application range: When the air bag expands, it can drive the elastic support frame 21 to achieve a radial expansion of 0-15mm, adapting to variable diameter inner cavities with a diameter difference within 80mm, significantly improving the fit rate of arc-shaped transition surfaces. For workpieces with 0.5-1mm unevenness errors on the inner cavity surface, the elastic deformation of the air bag can achieve adaptive compensation contact of the protrusions, solving the problem that rigid adjustment structures cannot adapt to uneven inner cavities.

[0034] Optionally, the conductive connection mechanism 3 includes a main conductive rod 31, a branch conductive component 32, and a conductive clamp 33. The main conductive rod 31 is vertically fixed to the top of the fixture body 1, and a power terminal is provided at its top. One end of the branch conductive component 32 is connected to the main conductive rod 31, and the other end is connected to the outer surface and inner cavity of the workpiece to be processed through the conductive clamp 33. A conductive silicone pad is provided on the inner side of the conductive clamp 33. The branch conductive component 32 is a telescopic structure, including a fixed section and a telescopic section. The fixed section is fixedly connected to the main conductive rod 31, and the telescopic section slides with the fixed section through a spring pin. The length adjustment range of the telescopic section is 50-200mm to adapt to the inner cavity of the workpiece of different depths.

[0035] It should be noted that the main conductive rod 31 is made of oxygen-free copper, with a resistivity of ≤1.72×10⁻ 8 Ω·m ensures excellent conductivity. The pole is machined into a cylindrical structure with a diameter of 25mm and a length of 600mm. The surface of the pole is tin-plated with a thickness of 5μm to prevent oxidation and corrosion. An M20 external thread is machined at the bottom of the pole to mate with a pre-set threaded hole at the center of the top of the fixture body 1. Conductive PTFE tape is wrapped around the thread to enhance conductivity and sealing.

[0036] A DT-35 copper power terminal block is welded to the top of the pole. The terminal block has an internal anti-slip wire clamping structure and connects to an external DC power supply via a 16mm² copper core cable. The branch conductive component 32 is made of multi-strand soft copper wire, externally covered with a 1.5mm thick, electrolyte-resistant polytetrafluoroethylene propylene insulation layer with a temperature range of -20℃ to 200℃. Three sets of branch conductive components 32 are provided, each with lengths of 800mm, 1000mm, and 1200mm depending on the connection location, to accommodate the connection requirements of different parts of the workpiece. One end of each branch conductive component 32 is securely connected to the main conductive rod 31 via a 25mm inner diameter copper clamp. Conductive grease is applied to the inside of the clamp, resulting in a volume resistivity ≤5×10⁻⁻⁻⁶. 4 Ω·cm, ensuring contact resistance ≤0.05Ω; the clamp is tightened with M8 bolts, and the pre-tightening torque is controlled at 15N·m to prevent loosening and poor conductivity.

[0037] The conductive chuck 33 is made of brass and comes in two specifications: an outer surface chuck and an inner cavity component chuck. The outer surface chuck has a C-shaped structure with an adjustable opening size range of 20-50mm to accommodate conductive areas of different thicknesses on the outer surface of the workpiece. The inner cavity component chuck has a "clamp-type" structure, with its inner diameter matching the connecting flange diameter of the inner cavity component 2. Fine-tuning of the diameter is achieved via bolts. Both types of chucks have a 5mm thick conductive silicone pad adhered to their inner sides with strong adhesive. The silicone pad has a volume resistivity ≤1×10⁻³Ω·cm and a Shore hardness of 60HA. The surface of the silicone pad is machined with a diamond-shaped anti-slip texture to increase friction with the contact surface. The other end of the branch conductive component 32 is connected to the conductive chuck 33 via a crimping process. The crimping joint is sealed with heat-shrink tubing to prevent electrolyte from seeping in and corroding the conductive core wire.

[0038] Technical Effects: Through the combined design of the oxygen-free copper main conductive rod 31 and the multi-strand soft copper branch conductive parts 32, the total resistance of the entire conductive connection mechanism 3 is controlled within 0.5Ω, ensuring stable current transmission during processing with a current fluctuation amplitude of ≤2%. The conductive silicone pad not only increases the contact area but also compensates for the microscopic unevenness of the contact surface, resulting in a uniform current density distribution between the outer surface of the workpiece and the inner cavity wall. After anodizing, the uniformity of the oxide film thickness on the workpiece surface is improved by 65%, effectively avoiding problems such as film peeling and color difference caused by uneven conductivity. Enhanced Adaptability and Expanded Application Range: The adjustable opening design of the "C"-shaped chuck can accommodate conductive areas of workpieces with a thickness of 20-50mm, while the "clamp-type" chuck is compatible with internal cavity component connection structures with a diameter of 45-55mm. Combined with branch conductive parts 32 of different lengths, this conductive connection mechanism 3 can adapt to various specifications of complex internal cavity workpieces without the need for custom-made conductive connectors for different workpieces, improving equipment versatility and reducing tooling manufacturing costs.

[0039] Optionally, the sealing and positioning unit 4 includes an annular sealing gasket 41 and a quick-locking structure 42; the annular sealing gasket 41 is made of fluororubber material that is resistant to electrolyte corrosion, and its cross-section is stepped, which can be adapted to the stepped structure of the workpiece end face; the quick-locking structure 42 includes a number of eccentric latches evenly distributed on the fixture body 1, which can press and fix the workpiece on the annular sealing gasket 41 after rotation, for sealing.

[0040] In addition, the annular sealing gasket 41 is made of FKM-26 fluororubber. This material has a volume expansion rate of ≤3% and a compression set of ≤15% in a working environment of 20%-50% sulfuric acid electrolyte and 50-80℃, meeting the requirements for corrosion resistance and sealing. Based on the double-step structure of the workpiece end face, the sealing gasket is designed with a corresponding double-step structure and a corresponding double-step interface. The total outer diameter is 405mm, the diameter of the first step is 325mm, the diameter of the second step is 255mm, the step height is 3.5mm, and the total thickness of the sealing gasket is 8mm. Three annular sealing grooves are opened on the inner wall to enhance the sealing effect. The quick-locking structure 42 uses eight eccentric locking buckles of model LS-80. The buckle body is made of 45 steel with heat treatment, the eccentric wheel diameter is 80mm, the eccentric distance is 8mm, and the maximum locking force can reach 5kN. Eight eccentric locking buckles are evenly distributed along the circumference of the support platform of the fixture body 1, with the center of the circle coinciding with the center of the sealing gasket. The spacing between adjacent buckles is 45°, and the buckle installation height is flush with the end face of the workpiece to ensure that the pressure is evenly applied to the stepped surface of the workpiece during locking. Each buckle is equipped with an operating handle with anti-slip texture. The handle is 120mm long and is connected to the eccentric wheel via a flat key. The rotation angle range is 0-90°. When rotated to 90°, the buckle is in a fully locked state. At the same time, a positioning pin hole is set at the end of the handle. Inserting the positioning pin can prevent the buckle from loosening during processing.

[0041] Technical Benefits: Achieves highly efficient and reliable sealing, eliminating electrolyte leakage: The precise fit between the double-step cross-section sealing gasket and the workpiece's stepped surface, combined with three annular sealing grooves, forms a "multi-seal" structure. The contact pressure on the sealing surface is uniformly and stably maintained at 2-3 MPa. After continuous operation for 8 hours in 80℃ sulfuric acid electrolyte, the leakage rate is ≤0.1 mL / h, far superior to traditional single-plane sealing structures with a leakage rate ≥5 mL / h. This effectively avoids problems such as fixture corrosion and plating solution contamination caused by electrolyte leakage. Improves workpiece positioning accuracy and stability: Eight evenly distributed eccentric latches ensure uniform force on the workpiece end face, with a radial positioning error ≤0.3 mm and axial runout ≤0.2 mm. This ensures the relative position stability between the workpiece and the inner cavity adapter component 2 during processing, reducing problems such as poor conductivity and uneven plating thickness caused by workpiece misalignment. Compared to bolt fastening methods, it improves workpiece positioning accuracy, meeting the positioning requirements of precision component processing.

[0042] Optionally, it also includes an electrolyte guiding component 5, which includes a guiding pipe 51 and a diverting nozzle 52. One end of the guiding pipe 51 is connected to an external electrolyte supply system, and the other end extends into the interior of the fixture body 1. The diverting nozzle 52 is located at the end of the guiding pipe 51, and part of the diverting nozzle 52 is integrated with the inner cavity adapter component 2, which can directly guide the electrolyte to the dead corner area of ​​the workpiece cavity. The outlet end of the diverting nozzle 52 is provided with a rotatable guiding vane. The guiding vane is driven by a micro motor and can change the spray direction of the electrolyte to achieve all-round flushing of the inner cavity wall.

[0043] It should be added that the guide pipe 51 is made of highly corrosion-resistant polyvinylidene fluoride (PVDF), with a wall thickness of 3mm and an inner diameter of 15mm. This material exhibits excellent chemical stability within a temperature range of -40℃ to 150℃ and can withstand the corrosion of anodic oxidation electrolytes such as sulfuric acid and oxalic acid, as well as platinum plating solutions. The guide pipe 51 consists of a main guide pipe 51 and branch guide pipes 51. One end of the main guide pipe 51 is connected to the external electrolyte supply system via a flange, with a flow rate of 0-50L / min and a pressure of 0-0.4MPa. The other end extends along the inner side of the fixture body 1 frame to below the support platform, branching into three branch guide pipes 51 via a tee connector—two extending upwards along the side of the fixture body 1 to both sides of the workpiece's outer surface, and one penetrating into the support platform of the fixture body 1 and integrating with the inner cavity adapter component 2. The branch guide pipes 51 are connected to the main guide pipe 51 using a socket-type connection, with PVDF clamps used at the interface for locking to ensure no leakage.

[0044] Eight flow-diverting nozzles 52 are provided, all integrally injection molded from VDF. The nozzle outlet diameter is set in two specifications: 3mm and 5mm, depending on the flow guidance requirements. Four of the 5mm diameter nozzles are external surface nozzles, fixed to the end of the branch flow guide pipe 51 extending to the outer surface of the workpiece by a pipe clamp. The nozzles are tilted at 45° towards the outer surface of the workpiece, and the distance between adjacent nozzles is 90° to ensure that the electrolyte evenly covers the outer surface of the workpiece. The other four nozzles are internal cavity nozzles. Two of the 3mm diameter nozzles are integrated with the elastic support frame 21 of the internal cavity adapter component 2. Mounting holes are opened on the metal rod of the frame corresponding to the corner of the internal cavity, and the nozzles are fixed to the frame by threads. The nozzle outlet is 8mm away from the conductive protrusion of the conductive contact layer 22 and faces the corner gap. The remaining two 3mm diameter nozzles are integrated at the guide head at the end of the frame, symmetrically distributed, with the outlet facing the bottom and side wall of the blind hole. All nozzles have streamlined flow guide cavities inside to reduce electrolyte flow resistance. For the two internal nozzles in special areas such as blind holes and corners, their outlet ends integrate rotatable guide vanes. These vanes are made of 1mm thick polytetrafluoroethylene (PTFE) and have a cross-shaped structure. The center of the vane is connected to the nozzle via a miniature bearing, and a sealing sleeve is fitted around the bearing to prevent electrolyte seepage. The vanes are driven by a 36BYJ46 miniature stepper motor with a power of 10W and a speed of 0-30 r / min. The motor is connected to an external controller via a waterproof cable. The controller can set the vane rotation angle from 0-360° or a continuous rotation mode according to processing requirements. The motor is fixed inside the elastic support frame 21, with a heat insulation pad between the motor and the frame to prevent processing heat from affecting motor performance.

[0045] Technical Benefits: Achieves comprehensive electrolyte coverage and eliminates processing dead zones: Through the coordinated design of the outer surface nozzles and the integrated nozzles within the inner cavity, the workpiece surface coverage is significantly improved. The electrolyte scouring intensity in the corner areas of the inner cavity is increased to 0.8 m / s, and the bottom of blind holes achieves 360° scouring without dead zones under the action of rotating blades. This completely solves the problems of electrolyte stagnation and untimely renewal in dead zones of the inner cavity in traditional flow guiding methods. Compared with non-directional flow guiding structures, the electrolyte renewal rate in various areas of complex inner cavities is increased by four times, ensuring the uniformity of oxide film growth and coating deposition, further improving electrolyte utilization efficiency and reducing production costs.

[0046] Optionally, the conductive contact layer 22 is made of platinum alloy with a thickness of 0.1-0.3 mm. A thermally conductive insulating layer is provided between the conductive contact layer 22 and the elastic support frame 21. The thermally conductive insulating layer is made of aluminum nitride ceramic material, which aims to enhance heat conduction and dissipation capabilities and improve processing quality. The thermal conductivity of aluminum nitride ceramic is as high as 180-200 W / (m·K), which is more than 5 times that of traditional alumina ceramic. It can quickly conduct local heat generated during processing from the conductive contact layer 22 to the elastic support frame, and then diffuse it to the fixture body 1 through the frame. Actual test data shows that at a current density of 10 A / dm², after adding this thermally conductive insulating layer, the temperature of the conductive contact layer 22 is reduced by 12-15℃ compared to the design without an insulating layer, and the temperature fluctuation of the inner cavity wall of the workpiece is controlled within ±1℃. This efficient heat dissipation capability can avoid defects such as oxide film cracking and coarse coating grains caused by local overheating, thereby increasing the density of the inner cavity oxide film and reducing the surface roughness of the electroplated platinum layer.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A fixture clamp suitable for anodizing or electroplating of platinum in complex internal cavities, characterized in that: The utility model provides a kind of electrolytic solution processing fixture, including clamp body (1), inner cavity adaptation assembly (2), electrically conductive connecting mechanism (3) and sealing positioning unit (4);The clamp body (1) is frame structure, for carrying the workpiece to be handled;The inner cavity adaptation assembly (2) can be detachably connected in the clamp body (1), and can extend into the complex inner cavity of the workpiece to be handled and be attached with inner cavity wall;The electrically conductive connecting mechanism (3) one end with external power supply is in communication, the other end is electrically connected with the clamp body (1) and inner cavity adaptation assembly (2) respectively;The sealing positioning unit (4) is arranged at the junction of the clamp body (1) and the workpiece to be handled, for realizing the sealing fixation of workpiece and clamp.

2. The anodizing or electroplating fixture clamp suitable for complex internal cavities of claim 1, wherein: The inner cavity adaptation assembly (2) includes elastic support framework (21) and electrically conductive contact layer (22), the elastic support framework (21) is articulated by several bendable metal rods, and can be self-adaptively adjusted according to the shape of the inner cavity; The electrically conductive contact layer (22) is coated on the outside of the elastic support framework (21), and the surface of the electrically conductive contact layer (22) is provided with a plurality of conductive bumps, and the conductive bumps are in elastic abutment with the inner cavity wall.

3. The anodizing or electroplating fixture clamp suitable for complex internal cavities of claim 2, wherein: The elastic support framework (21) is provided with a gas-filled adjusting structure (23) inside, the gas-filled adjusting structure (23) includes a micro gas bag and an inflation interface, the micro gas bag is distributed along the length direction of the framework, and after inflation through the inflation interface, the elastic support framework (21) can be driven to expand towards the inner cavity wall, so that the electrically conductive contact layer (22) is attached to the inner cavity wall with a preset pressure.

4. The anodizing or electroplating fixture clamp suitable for complex internal cavities of claim 1, wherein: The electrically conductive connecting mechanism (3) includes a main electrically conductive rod (31), a branch electrically conductive piece (32) and an electrically conductive chuck (33); The main electrically conductive rod (31) is vertically fixed on the top of the clamp body (1), and a power connection terminal is arranged at the top end thereof; One end of the branch electrically conductive piece (32) is in communication with the main electrically conductive rod (31), and the other end is connected with the outer surface of the workpiece to be handled and the inner cavity adaptation assembly (2) through the electrically conductive chuck (33), and the inside of the electrically conductive chuck (33) is provided with an electrically conductive silica gel pad.

5. The anodizing or electroplating fixture clamp suitable for complex internal cavities of claim 1, wherein: The sealing positioning unit (4) includes an annular sealing gasket (41) and a quick locking structure (42); The annular sealing gasket (41) is made of fluororubber material resistant to electrolyte corrosion, and its cross section is ladder-shaped, which can be adapted to the stepped structure of the end face of the workpiece; The quick locking structure (42) includes a plurality of eccentric locks uniformly distributed on the clamp body (1), and the eccentric locks can press and fix the workpiece on the annular sealing gasket (41) after rotation, for sealing.

6. The anodizing or electroplating fixture clamp suitable for complex internal cavities of claim 1, wherein: It also includes an electrolyte flow guide assembly (5), the electrolyte flow guide assembly (5) includes a flow guide pipe (51) and a shunt nozzle (52); One end of the flow guide pipe (51) is connected with an external electrolyte supply system, and the other end extends into the inside of the clamp body (1); The shunt nozzle (52) is arranged at the end of the flow guide pipe (51), and part of the shunt nozzles (52) are integrated with the inner cavity adaptation assembly (2), which can guide the electrolyte directly to the dead corner area of the inner cavity of the workpiece.

7. The anodizing or electroplating fixture clamp suitable for complex internal cavities of claim 2, wherein: The conductive contact layer (22) is made of platinum alloy material, the thickness is 0.1-0.3mm, and the conductive contact layer (22) is provided with a heat-conducting insulating layer between the elastic support framework (21), the heat-conducting insulating layer adopts aluminum nitride ceramic material.

8. The anodizing or electroplating fixture clamp suitable for complex internal cavities of claim 1, wherein: The support block (6) is connected with the fixture body through a screw rod sliding table mechanism, the support position can be adjusted according to the shape size of the workpiece, so that the center of gravity of the workpiece coincides with the center of the fixture body (1).

9. The anodizing or electroplating fixture clamp suitable for complex internal cavities of claim 4, wherein: The branch conductive piece (32) is a telescopic structure, including a fixed section and a telescopic section, the fixed section is fixedly connected with the main conductive rod (31), the telescopic section is slidably connected with the fixed section through a spring pin, and the length adjusting range of the telescopic section is 50-200mm, so as to adapt to the inner cavities of workpieces with different depths.

10. The anodizing or electroplating fixture clamp suitable for complex internal cavities of claim 6, wherein: The outlet end of the shunt nozzle (52) is provided with rotatable guide vanes, the guide vanes are driven by a micro motor, the injection direction of the electrolyte can be changed, and the inner cavity wall can be fully washed.

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