I. Manufacturing Process
This aluminum cylindrical shell is designed for the water pressure resistance, corrosion resistance, and sealing requirements of diving environments. The core process utilizes a combination of CNC milling and turning machining and hard anodizing. The specific steps are as follows:
1. Raw Material Selection: 6061-T6 aluminum alloy (high overall strength, good weldability) or 7075 aluminum alloy (ultra-high strength, suitable for deep-water, high-pressure environments) is selected. Forged aluminum rod blanks are used (to reduce internal porosity and improve water pressure resistance).
2. Blank Pretreatment: The aluminum rod undergoes solution treatment and aging to eliminate internal stress. Straightening ensures roundness and prevents deformation after machining. The blank is then sawn to obtain a fixed length.
3. CNC Milling and Turning Machining:
◦ Using a milling and turning machining center, the outer cylindrical contour is first formed by turning, followed by inner boring to ensure the roundness and surface finish of the cavity.
◦ Milling/drilling and tapping of end face grooves, positioning holes, and sealing grooves (O-ring grooves), as well as machining of external anti-slip teeth and assembly bosses.
◦ For deep-water sealing requirements, the sealing surface is precision turned and polished, with a roughness controlled below Ra0.8μm.
4. Surface Treatment:
◦ Hard Anodizing: The core process, with an oxide layer thickness controlled at 15~50μm (upper limit for deep-water applications), and a hardness ≥HV400, achieving seawater corrosion resistance, wear resistance, and impact resistance; the black oxide layer also reduces underwater reflectivity, meeting the concealment requirements of diving equipment.
◦ Sealing Surface Treatment: The sealing groove and mating surface are passivated to prevent the oxide layer from affecting sealing accuracy. Some key surfaces can be nickel-plated to enhance sealing performance and wear resistance. 5. Post-processing and Inspection: After deburring, a water pressure test (simulating the pressure at actual diving depth) and dimensional inspection are performed. A waterproof leak test is conducted after assembling the seals. The hardness and thickness of the oxide layer are tested to ensure compliance with diving environment requirements.
II. Machining Accuracy
This housing must meet the sealing, pressure resistance, and assembly requirements of diving equipment. The core accuracy indicators are as follows:
1. Dimensional Accuracy:
◦ Inner hole diameter tolerance: ±0.01~±0.03mm, ensuring compatibility with internal components (such as sensors and battery modules).
◦ Sealing groove dimensions (width/depth): tolerance ≤±0.02mm, ensuring uniform O-ring compression for waterproof sealing.
◦ Positioning hole position accuracy: ≤0.05mm, ensuring precise assembly.
◦ Outer circle diameter tolerance: ±0.05mm, for compatibility with external protective sleeves/mounting bases.
2. Geometric Tolerances:
◦ Roundness: Inner hole/outer circle ≤ 0.02mm, to prevent deformation under high pressure that could lead to seal failure.
◦ Cylindricity: Overall cylinder ≤ 0.03mm/100mm, to ensure uniform pressure resistance.
◦ Perpendicularity: End face to axis ≤ 0.02mm, to ensure tight sealing surface contact.
3. Surface Finish:
◦ Sealing surface roughness Ra 0.4~0.8μm, to reduce seal wear and improve waterproofing.
◦ Outer surface (after hard anodizing) roughness Ra 1.6~3.2μm, non-sealing, non-outer surface roughness Ra 6.3μm is sufficient.
III. Industry Applications
These hard anodized aluminum cylindrical shells, with their pressure resistance, corrosion resistance, lightweight design, and electromagnetic shielding properties, have become core components in the diving industry. Specific applications include:
1. Diving Detection Equipment:
◦ Underwater sensor housings (such as depth sensors, water quality analyzers, and sonar probe chambers), protecting internal precision components from seawater corrosion and water pressure impacts.
◦ Waterproof housings for underwater cameras/photographic lights; the hard anodized layer reduces underwater impact and wear, and the black appearance reduces glare interference during shooting.
2. Diving Equipment Accessories:
◦ Core module housings for dive computers; waterproof chambers for underwater communicators; lightweight design reduces the weight burden on divers.
◦ Valve housings for dive regulators; protective casings for the pressure sensors in breathing apparatus; utilizing the impact resistance of aluminum alloy to adapt to complex underwater environments.
3. Underwater Operation Equipment:
◦ Power module/control module housing for small ROVs, pressure-resistant design suitable for deep-water operations (e.g., 100-500 meters).
◦ Hydraulic component housing for underwater salvage tools, control box housing for underwater welding equipment, corrosion-resistant properties suitable for long-term seawater immersion.
4. Marine Scientific Research Equipment:
◦ Sensor protective casing for marine environmental monitoring buoys, probe housing for seabed geological detectors, hard oxide layer to resist marine organism adhesion and seawater corrosion.
