Process and Inspection
Process and Inspection Description
1. Process Description
(I) Travel Mechanism
High-strength alloy steel is selected and initially formed through precision die forging after mechanical property testing. Machining is then performed via CNC machining centers to complete milling and boring operations, with critical surface roughness controlled to ≤ Ra 1.6. Quenching and tempering treatments are applied to enhance strength and toughness. Finally, zinc plating or spray coating is applied to ensure compliance with anti-corrosion performance standards.
(II) Hydraulic Pump
Key components such as the pump body and rotor are machined using high-precision equipment, with the cylindricity error of the pump body’s inner cavity controlled within 0.005 mm. Assembly is carried out in a cleanroom environment in a specified sequence, with the clearance between the plunger and cylinder barrel is controlled within 0.01 to 0.02 mm. Bolts are tightened using torque wrenches. After assembly, each pump undergoes no-load and load testing during which pressure and flow are adjusted to ensure stable output, the compliant noise levels and leakage should be within specified standards.
(III) Slewing Mechanism
After cutting, the steel plate is formed using CO2 gas shielded welding. Post-welding non-destructive testing is performed to eliminate cracks. Gears are processed through hobbing and shaving, with tooth surface roughness maintained between Ra 0.8–1.6 μm. Interference fits between gears and shafts are strictly controlled. During final assembly, bearing preload is accurately adjusted. Running-in tests monitor temperature and vibration to ensure smooth and efficient rotation.
(IV) Slewing Bearing
The raceways are manufactured from high-quality bearing steel through forging, turning, and grinding processes, achieving a surface hardness of HRC 58-62. a roundness error of ≤0.003 mm, and a surface roughness of Ra 0.4-0.8μm. The rolling elements are assembled in a clean-controlled environment, and maintain the racks with wear-resistant materials to ensure that the distribution is even and the gaps are reasonable. The seals are installed and tested to be leak-free.
(V) Travel and Slewing Motors
The stator and rotor are manufactured through powder metallurgy or precision casting, followed by precision CNC grinding. The flatness of the mating surface with the port plate is controlled within 0.002 mm. Assembly is conducted in a constant temperature and humidity environment with strict control over shaft-bore clearance. Performance is validated through pressure and volumetric efficiency testing. The displacement adjustment mechanism is debugged under simulated working conditions to optimize the pressure-flow characteristics, ensuring high efficiency and energy savings.
2. Inspection Standards and Methods
(I) General Standards
Critical dimensions (e.g., hydraulic pump plunger diameter) shall have a tolerance of ≤±0.01 mm, measured with a CMM (Coordinate Measuring Machine) or equivalent.
Mechanical properties of raw materials and finished products shall be tested in accordance with GB/T 228 and GB/T 231 standards, using a universal testing machine or equivalent.
Seal integrity shall be validated by holding at 1.5 times the working pressure for 5 minutes, with leakage ≤ 0.1 mL/min, tested with a pressure test bench or equivalent.
(II) Specific Tests
Travel Mechanism: Fatigue strength tested via million-cycle loading tests; wear rate measured on test bench ≤ 0.05 mm / 1000 hours.
Hydraulic Pump: Volumetric efficiency ≥ 90% (model-dependent); noise level ≤ 75 dB(A-weighted) measured in a semi-anechoic chamber.
Slewing Mechanism: Rotation angle error≤±0.1°under no-load conditions; transmission efficiency ≥92% (at rated operation).
Slewing Bearing: Load-induced deformation≤10% of design value; wobble clearance≤ 0.03 mm.
Motor: Output torque deviation ≤±5%; response time≤0.2 s.
The integrated approach of precision manufacturing and rigorous testing guarantees the hydraulic assembly’s quality and ensures high efficiency and reliability in excavator operation.
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location
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No. 34-19, Mingzhu West Road, Zhifu District, Yantai City, Shandong Province
