Proper lubrication is the key to the continued performance and reliability of lead screw assemblies.
Prolong acme screw assembly reliability and life
The coefficient of friction, wear life, and resulting torque to drive lead screws and acme screw assemblies are highly controlled by the ability of the engineered plastic to supply sufficient lubrication to the nut and screw interface.
Many factors have to be considered when designing and selecting a precision acme screw. Environment, operating load, accuracy, and speed are important factors to consider in the design decision. Unlike ball screws, acme lead screws with bronze or polymer acme nuts tend to have higher friction and more wear - making proper lubrication a vital part of the performance and increased life.
Benefits of a proper lubrication
There are several main benefits of using proper lubrication, including:
- Sheer Stability
- High-Temperature Resistant
- Corrosion Protection
- Separation Resistant
- Extreme Pressure Properties
- Shelf Stable
- Water-Resistant
Extend life and longevity
Precision acme screws are manufactured from high-quality materials with excellent dynamic properties. A specific life cannot be predicted because of the variable effects of friction, lubrication, and cleanliness. Proper lubrication, regular maintenance, and operation within specified limits will extend the screw's life and longevity.
The application determines lubrication intervals. It is required that screw assemblies are lubricated often enough to maintain a lubricant film on the screw.
For service planning, document axial load, screw speed and lead, duty cycle, cleanliness, temperature, and lubrication access for the assembly; these application conditions establish the maintenance interval.
Importance of efficiency
The efficiency of precision acme screw assemblies ranges from 15% to 85%. These efficiencies are dependent upon the nut material, lubrication, lead, and thread form.
For positioning applications, specify anti-backlash requirements with drive torque: Helix offers self-adjusting, maintenance-free anti-backlash assemblies, and anti-backlash preload can increase drag torque.
Temperature precautions
With proper lubrication, acme screws with bronze nuts operate efficiently between 15°F and 350°F, and plastic nuts between 15°F and 175°F.
Proper lubrication must be provided to achieve a satisfactory service life for your acme screws and acme screw assemblies. It is required that screw assemblies are lubricated often enough to maintain a lubricant film on the screw.
Lack of lubrication
Lack of lubrication can reduce the life and performance of the acme screws and the entire machine. Frequently, a lack of lubrication can cause erratic drag torques and unpredictable wear.
Track drag torque at scheduled service alongside lubricant-film condition; erratic drag torque is an actionable wear and lubrication indicator.
Specifying a lubricant
Even self-lubricated nuts can benefit from using light grease and can also reduce heat in these units.
Excellent and consistent lubrication has long-term benefits and is more critical to an application than whether the screw was cut or rolled. When maximum performance is required in the most demanding applications, using the proper lubricant and the proper amount can help you reach full productivity.
Specific applications require more/less lubrication, external/internal lubrication, and more/less maintenance.
There are a broad range of nut materials and application-specific options for vacuum, chemicals, temperature swings, FOD, high load, and healthcare environments. When lubricants are applied correctly, they can provide unique capabilities that may be difficult to obtain without using any lubricant.
FAQ
What should I include in a lead-screw application review?
Specify axial and radial load, screw speed and lead, duty cycle and cycle count, horizontal or vertical orientation, required life, backlash over life, temperature range, dust, chips, washdown or chemicals, and lubrication access.
What maintenance belongs in a precision ball-screw plan?
Include an effective lubrication and contamination-control strategy with the predictable-life, high-efficiency, minimized-backlash objectives documented for the precision ball-screw offering.
For any questions, please reach out to our US-Based Application Engineers.
