Custom NMRV Worm Gearbox Manufacturers

What are the key points of leakproof design for the sealing structure of NMRV worm gearbox?

1. Optimization and matching of sealing materials
The performance of sealing materials is the basis of leakproof design, and multiple indicators such as wear resistance, corrosion resistance, high temperature resistance and elasticity must be taken into account. NMRV worm gearbox adopts high-strength aluminum alloy casting housing, which has good heat dissipation and corrosion resistance (Hangzhou Hengbai Reducer Co., Ltd has its own foundry, which can accurately control the shell material composition and casting process), providing a stable installation foundation for the sealing structure. In the selection of sealing elements, the following schemes are usually adopted:
Selection of main seal material
Rubber seals: such as nitrile rubber (NBR), which has excellent oil resistance, is suitable for lubricating oil environment, and has moderate cost. It is a common material for static and rotary seals of reducers. Hangzhou Hengbai Reducer Co., Ltd's testing laboratory can conduct strict tests on the hardness, tensile strength and other indicators of rubber parts to ensure that the seals remain elastic during long-term operation.
Polytetrafluoroethylene (PTFE): It has the characteristics of corrosion resistance and low friction coefficient. It is often used for sealing high-speed rotating shafts. It can be combined with rubber parts to form lip seals to improve sealing reliability. For example, at the high-speed shaft end of the worm gear transmission, the use of mechanical sealing rings made of PTFE can effectively reduce the risk of leakage caused by wear.
Application of auxiliary sealing materials
Sealants: Used for static sealing of the housing joint surface, such as epoxy resin glue or silicone sealant. During the product assembly process, the microscopic gap on the housing surface is eliminated by accurately controlling the thickness of the glue layer (usually 0.1-0.3mm) to prevent lubricating oil from seeping out from the joint surface.
Metal bellows: Under high temperature or high pressure conditions, stainless steel bellows can be used as sealing elements. It has strong elastic compensation ability and can adapt to the slight deviation of the shaft to avoid sealing failure caused by mechanical vibration.
2. Diversified design of sealing structure
The sealing structure of the NMRV gearbox needs to be designed according to the leakage risk of different parts (such as the shaft extension, the housing joint surface, the bearing chamber, etc.). The following are the key points of leakage prevention technology in key parts:
Rotary seal at the extension of the shaft
The extension of the shaft is the focus of dynamic sealing. Common causes of leakage include seal wear, insufficient shaft surface roughness or axial movement. The design points are as follows:
Lip seal structure: single lip or double lip seal design is adopted, the lip direction is toward the lubricating oil side, and the spring force is used to make the lip close to the shaft surface. In the NMRV worm gear box, the lip angle is optimized (usually 15°-25°), and the shaft surface is polished (roughness Ra≤0.8μm) to reduce friction heating and wear.
Labyrinth seal auxiliary: a labyrinth structure is added to the outside of the lip seal to block oil leakage through multi-stage gaps. The labyrinth gap is usually designed to be 0.2-0.5mm, and a spiral groove structure is adopted (the rotation direction is opposite to the shaft rotation direction), and the leaked oil is thrown back to the bearing chamber by centrifugal force.
Shoulder and retaining ring design: A shoulder is set at the shaft extension to limit the axial movement of the seal, and it is fixed with an elastic retaining ring to prevent the seal from shifting and failing due to shaft movement.
Static sealing of the shell joint surface
The leakage of the shell joint surface (such as the joint of the upper and lower boxes) is mainly caused by insufficient processing accuracy or uneven bolt preload. The key points of leak-proof design include:
High-precision processing technology: The CNC processing factory uses a five-axis linkage machining center to ensure that the joint surface flatness is ≤0.03mm/m and the roughness Ra≤3.2μm, reducing microscopic leakage channels.
Bolt preload optimization: Use a torque wrench to evenly apply preload, and control the bolt spacing at 80-120mm to avoid local stress concentration and deformation of the joint surface. For large reducers, elastic washers or disc springs can be used to compensate for the preload attenuation caused by vibration.
Seal groove design: Open an annular seal groove on the joint surface, embed a rubber seal strip or apply sealant to form a multiple sealing barrier. The ratio of groove width to depth is usually 1:1, ensuring that the sealing material fully fills the gap.
Sealing isolation between bearing chamber and oil pool
The seal between the bearing chamber and the oil pool needs to prevent lubricating oil from entering the bearing and causing overheating, while preventing foreign impurities from invading. The design scheme includes:
Oil slinger and oil baffle: an oil slinger is set on the inner side of the bearing. When the shaft rotates, the excess oil is thrown back to the oil pool by centrifugal force; an oil baffle is installed on the outer side of the bearing to prevent the oil from leaking to the shaft extension. The curvature of the oil slinger and the position of the oil baffle are optimized through fluid mechanics simulation to improve oil control efficiency.
Design of vent cap and balance hole: a vent cap is set on the top of the reducer to balance the internal air pressure and avoid leakage caused by increased internal pressure due to increased oil temperature; a balance hole is opened at the bottom of the bearing chamber to allow a small amount of infiltrated oil to flow back to the oil pool to prevent oil accumulation in the bearing chamber.
3. Working condition adaptability and environmental protection design
The application scenarios of NMRV reducers cover food processing, textile printing and dyeing, glass ceramics and other industries. Different working conditions have different requirements for sealing structures:
Sealing design under high temperature environment
In high temperature working conditions such as glass ceramic manufacturing, sealing materials are prone to lose elasticity due to thermal aging. Solutions include:
Upgrade of high temperature resistant materials: Use fluororubber (FKM) or silicone rubber (VMQ) to replace ordinary nitrile rubber, and the temperature resistance range can be increased to -40℃~200℃. The testing equipment can simulate high temperature environment (up to 250℃) to test the thermal deformation and sealing of the seal.
Cooling structure coordination: Add heat dissipation ribs on the surface of the casing, and cooperate with forced air cooling or water cooling system to reduce the temperature of the sealing area and slow down the aging of the material.
Protection against humid and corrosive environments
The food processing and textile printing and dyeing industries often face problems such as moisture, acid and alkali corrosion, and the sealing design needs to enhance the anti-corrosion ability:
Application of stainless steel materials: 304 or 316 stainless steel shafts are used at the shaft extension, and the seals are made of corrosion-resistant PTFE or hydrogenated nitrile rubber (HNBR), and epoxy resin anti-corrosion coating is sprayed on the surface of the casing.
Hydrophobic sealing structure: A hydrophobic groove is set in the labyrinth seal gap to guide the discharge of condensed water or corrosive liquids to avoid accumulation in the sealing area.
High dust and particle environment sealing
In mining machinery or powder processing scenarios, dust intrusion will aggravate the wear of seals. The key points of leak-proof design include:
Multiple dustproof seals: The "labyrinth seal + dustproof seal ring + dust-slinging ring" combination structure is adopted. The first labyrinth blocks large particles of dust, the second dustproof ring (such as felt seal) filters fine dust, and the dust-slinging ring removes attached particles through rotating centrifugal force.
Positive pressure sealing technology: Apply a slight positive pressure (5-10kPa) to the reducer through an external air source, so that the internal air pressure is higher than the external dust environment, preventing dust from intruding. Hangzhou Hengbai Reducer Co., Ltd can customize sealing components with air source interfaces according to customer needs.
4. Assembly process and quality control
The leak-proof performance of the sealing structure not only depends on the design, but also requires strict assembly process and quality inspection. The following measures are taken to ensure the reliability of the seal:
Cleanliness control: Ultrasonic cleaning of parts before assembly to remove impurities such as metal debris and oil stains to prevent particles and foreign matter from damaging the sealing surface.
Seal installation specifications: Use special tools to install seals to avoid lip folding or scratching; for seals with interference fit, use heating or freezing assembly process to ensure that they are installed in place.
Leakage test: After assembly, perform air pressure or oil pressure leakage test, maintain pressure at 0.05-0.1MPa for 30 minutes, and the pressure drop is ≤0.005MPa for qualified. The company's testing laboratory is equipped with a helium mass spectrometer leak detector, which can detect micro leaks on precision seals.
5. Maintenance convenience and life optimization
The sealing structure design of the NMRV gearbox must take into account maintenance needs and reduce user costs. For example:
Maintenance-free sealing design: built-in permanent lubricant to reduce seal damage caused by improper lubricant replacement; some models use self-lubricating sealing materials, and no lubricant needs to be added regularly.
Easy to replace structure: The seal adopts a standardized design, and the removable end cover or modular structure is convenient for quick on-site replacement and shortens downtime.