The lubrication method should be selected flexibly according to the speed, load, working environment and precision requirements the ball screws. Its core purpose is to reduce friction, minimize wear and tear, restrain temperature rise and prolong service life. Below is a detailed analysis of the mainstream lubrication methods and their application scenarios.
I. Grease Lubrication: Balance convenience and economy
Applicable scenarios
Low and mediumspeed applications: such as machine tool feed system, automation equipment, 3C industry precision positioning tables.
Closed environment: such as vertical installation of ball screws (to prevent grease loss).
Long maintenance cycle: frequent refuelling needs to be reduced.
Lubricating properties require:
Base oil viscosity: selected according to temperature. Synthetic oil-based grease (polyalphaolefin PAO) should be used for low temperatures (e.g. below 80°C) and silicone oil or fluorine grease for high temperatures (e.g. above 80 ° C).
Consistency grade: According to the NLGI (American Grease Institute) standard, choose NLGI 2 (such as lithium based grease) for mediumspeed and NLGI 1 or 0 (to reduce agitation resistance) for high speed.
Additives: Extreme pressure abrasives (such as molybdenum disulfide and graphite) can improve carrying capacity, and rust inhibitors can inhibit corrosion in humid environments.
Fat supplementation cycle and quantity
Cycle: Grease refills every 2,000 to 5,000 hours or annually (see equipment manual for details).
Quantity: filling amount about 1/3-1/ 2 of the nut's interior space. Excessive packing may lead to excessive temperature (due to increased agitation resistance).
II. Oil Lubrication: Top choice for high speed, heavy loading.
Applicable scenarios
High-speed applications (line speed > 15m/min): such as high-speed machining centers, CNC grinding machines, robot joints, etc.
Heavy Load: Equipment such as stamping machines and die-casting machines that need to withstand impact loads.
Open environment: A continuous fuel supply is required to remove heat and ground debris.
Classification of oil lubrication methods:
Oil bath lubrication
How it works: Soak part of the nut into the oil tank and rotate the oil into the raceway.
Strengths: Simple structure, low cost.
Weaknesses: Suitable only for low speeds (linear speed ≤5m/min), where churning oil can cause excessive temperature.
Oil level control: oil level should be 1-2mm below nut minimum to prevent oil leakage.
Drip oil lubrication
How it works: Oil is regularly dripped onto the raceway via an oil cup or drip device,such as 1 to5 drips per minute.
Strengths: Controllable oil volume for medium speed (line speed 5-15m/min).
Weaknesses: Regular checks are needed to see if the oil circuit are blocked.
Oil mist lubrication
How it works: The lubricant is atomized and then transported through compressed air to the raceway to form an oil film.
Strengths: Good heat dissipation effect, suitable for high-speed (linear speed > 15m/min) and high temperature.
Weaknesses: The need for a matching oil mist generator is relatively high in cost and the oil mist can pollute the environment (installation of an oil mist exhaust device is required).
Circulating oil lubrication
How it works: Lube is pumped oil pump the oil tank to the nuts. Once cooled, it returns to the oil tank, forming a closed loop.
Advantages: Good heat dissipation and filtration effects, suitable for heavy load (if axial load is greater than 10kN) and high speed.
Weaknesses: The system is complex and requires periodic replacement of filters and oil.
Oil Selection Highlights:
Viscosity: Select according to temperature and speed. low-viscosity oil (such as ISO VG32) is used at high speed and high-viscosity oil is used under heavy load.
Abrasion resistance: The presence of extreme pressure additives such as ZDDP and sulfurized olefins can improve carrying capacity.
Antioxidant properties: prevent oil from oxidizing and deterioration, prolong oil replacement cycle.
III. Self-lubrication: special maintenance-free design
Applicable scenarios
Difficult environmentto maintain: e.g. space equipment, nuclear power plants and deep-sea probes.
Scenarios requiring high cleanliness: semiconductor manufacturing, food processing, etc.
Self-lubrication technology type:
Solid lubricant embedding: Solid lubricants such as molybdenum disulfide (MoS2) and polytetrafluoroethylene (PTFE) are embedded on the surface of a sphere or runway to release lubricating elements through friction.
Oily retentors: Retentors made of porous metals (such as bronze) or polymer materials (such as polyimides), pre-impregnated with lubricating oils, which are continuously supplied by capillary action.
Composite coating: DLC (diamond-like carbon) or MoS2/TiN composite coating sprayed on the raceway surface for abrasion resistance and self-lubrication.
Limitations
It has a relatively short service life and needs to be replaced in advance in accordance with working conditions.
Costs are relatively high.