A ball screw should not be maintained only when noise, backlash or positioning error has already appeared. By that stage, lubricant failure, contamination or raceway damage may already have developed.
For many normally operating ball screws, a useful starting point is to inspect and replenish lubrication after approximately 100 km of linear travel or every 3 to 6 months. However, this is not a universal replacement interval. The final schedule must reflect stroke, cycle rate, load, speed, temperature, contamination, mounting direction and daily operating time.
Ball screw maintenance also includes cleaning, seal inspection, support-bearing checks, backlash monitoring and alignment verification. Lubrication is only one part of the complete maintenance plan.
Ball Screw Maintenance Is More Than Relubrication
The phrase "ball screw maintenance" is often used as if it means adding grease. In practice, the maintenance program should include several separate tasks.
| Maintenance Task | What It Includes | Main Purpose |
|---|---|---|
| Routine observation | Noise, vibration, temperature, grease leakage and visible contamination | Detect changes before permanent damage develops |
| Cleaning | Removal of dust, chips, coolant residue and contaminated lubricant | Prevent abrasive particles from entering the nut |
| Relubrication | Replenishment of compatible grease or verification of oil supply | Maintain a lubricant film between the balls and raceways |
| Mechanical inspection | Nut mounting, support bearings, coupling, locknut, seals and covers | Separate ball nut problems from surrounding component problems |
| Performance measurement | Backlash, repeatability, motor current, torque and temperature trend | Identify gradual wear or loss of preload |
A maintenance schedule should cover the screw shaft, ball nut, seals, lubrication and surrounding transmission components.
Why a Fixed Monthly Interval Is Not Enough
Calendar time alone does not show how much rolling contact has occurred inside the ball nut. A machine running continuously with a long stroke may reach the reference travel distance in days, while a laboratory axis used occasionally may not reach it for several years.
For a reciprocating axis in which one complete cycle contains one forward stroke and one return stroke:
Enter the stroke in meters to obtain daily travel in meters. Divide the result by 1,000 to convert it into kilometers.
Example 1: Continuous Automation Axis
Consider a machine with a 400 mm one-way stroke, 20 complete cycles per minute and eight operating hours per day.
Daily travel:
2 × 0.4 m × 20 × 60 × 8 = 7,680 m/day
7,680 m/day = 7.68 km/day
The axis reaches 100 km in approximately 13 operating days.
Waiting three or six months to inspect this machine may be much too long unless it uses a lubrication system and product specification designed for a significantly extended interval.
Example 2: Intermittent Laboratory Equipment
Now consider a 100 mm stroke, five complete cycles per minute and two operating hours per day.
Daily travel:
2 × 0.1 m × 5 × 60 × 2 = 120 m/day
120 m/day = 0.12 km/day
The axis would require approximately 833 operating days to reach 100 km.
In this case, lubricant aging, moisture and long idle periods may make the calendar interval more important than accumulated travel.
Practical Ball Screw Maintenance Schedule
The machine manufacturer's maintenance manual and the exact ball screw specification should take priority. When no detailed schedule is available, the following table can be used as a starting framework and adjusted according to inspection results.
| Suggested Trigger | Inspection or Maintenance Work | Required Action |
|---|---|---|
| Before startup or during routine operator checks | Look for chips, dust, coolant, rust, grease leakage, damaged covers and abnormal noise | Clean contamination and investigate any change before full-speed operation |
| During the first weeks after commissioning | Record normal nut temperature, motor current, sound and running resistance | Establish a baseline for later comparison |
| Approximately every 100 km or 3–6 months | Inspect grease condition, seals, exposed raceways and lubrication access | Replenish compatible lubricant as required and revise the interval from actual results |
| Every planned machine shutdown | Check nut housing, support units, locknut, coupling, lubrication lines and mounting bolts | Correct looseness, leakage, misalignment or blocked lubrication supply |
| Every 6–12 months or during accuracy verification | Measure backlash, positioning repeatability and support-bearing axial play | Compare results with commissioning records and machine accuracy requirements |
| After a collision, overload or coolant ingress | Inspect the screw, nut, bearings, coupling, alignment, seals and lubricant immediately | Do not wait for the next scheduled maintenance date |
| Before restarting after long storage | Check corrosion, hardened lubricant, seal condition and smooth movement | Apply suitable fresh lubricant before normal operation |
Conditions That Require a Shorter Maintenance Interval
The maintenance interval should be shortened whenever the lubricant or raceway is subjected to higher mechanical, thermal or environmental stress.
| Operating Condition | Why It Matters | Maintenance Response |
|---|---|---|
| Continuous multi-shift operation | Travel accumulates quickly and lubricant is repeatedly sheared | Base the interval mainly on travel distance and operating condition |
| High speed | Higher speed can increase temperature and grease agitation resistance | Monitor temperature and torque and confirm lubricant speed suitability |
| Heavy or fluctuating axial load | Contact stress increases and the lubricant film is more difficult to maintain | Inspect lubricant condition and operating temperature more frequently |
| Short repetitive stroke | Lubricant may not redistribute across the complete loaded raceway | Inspect for dried contact zones and use periodic longer strokes where possible |
| Dust, wood powder or abrasive particles | Particles can mix with grease and act as an abrasive | Increase cleaning and seal inspections and use an external cover |
| Coolant, water or cleaning chemicals | Liquid may wash lubricant away or cause corrosion | Check seals, covers, lubricant contamination and exposed surfaces frequently |
| Vertical mounting | Gravity and the lubrication-port position may affect lubricant distribution | Confirm that lubricant reaches all ball circuits in the actual orientation |
| High or low temperature | Grease consistency and oil viscosity change with temperature | Use a lubricant confirmed for the actual temperature range |
What to Check During Routine Inspection
Routine inspection should compare the machine with its normal operating baseline rather than relying only on whether the screw still moves.
Check the Exposed Screw Surface
Look for:
- Dust, chips or abrasive particles stuck to the lubricant
- Dry or uncoated sections of the raceway
- Dark, hardened or discolored grease
- Water, coolant or chemical contamination
- Rust, scratches, dents or visible pitting
- Grease pushed out excessively around the nut seals
Do not blow compressed air directly toward the ball nut seals. High-pressure air can push contamination into the ball circulation system.
Observe Noise and Movement
Pay attention to:
- Clicking or repetitive noise at the same position
- Grinding or dry rolling noise
- Resistance that changes along the stroke
- Jerking during low-speed movement
- Vibration that increases with rotational speed
- A noticeable delay when the axis reverses direction
Noise alone does not confirm that lubrication is the only problem. Localized raceway damage, a bent shaft, misalignment, loose support bearings or coupling problems can create similar symptoms.
Monitor Temperature and Motor Load
Record the normal ball nut temperature and motor current after commissioning. Later measurements should be taken under a similar load, speed and operating period.
A gradual increase may indicate insufficient lubrication, excessive grease, contamination, rising preload, support-bearing problems or installation distortion. A single absolute temperature limit cannot diagnose every machine, so the change from the established baseline is often more useful.
How to Relubricate a Grease-Lubricated Ball Screw
The correct grease type, quantity and supply point should follow the machine or ball screw specification. The procedure below provides a general maintenance sequence.
- Isolate the machine. Disconnect power and prevent unexpected movement before reaching into the axis.
- Identify the existing lubricant. Use the same compatible lubricant unless a controlled lubricant-change procedure has been approved.
- Clean the grease nipple and surrounding area. Dirt around the fitting can be injected directly into the nut if it is not removed first.
- Remove visible contamination from the exposed screw. Use a clean, lint-free cloth and a cleaning method compatible with the lubricant, seals and machine environment.
- Apply lubricant slowly. Inject grease through the nut's lubrication port where one is provided. Avoid high pressure that could damage or displace a seal.
- Distribute the lubricant. Move the nut or rotate the screw slowly through several strokes so that grease spreads through the ball circuits.
- Perform a low-speed break-in. Run the axis through several full strokes before returning to normal speed and load.
- Wipe away displaced excess grease. Excess lubricant around the seals can collect dust and contaminate surrounding components.
If the nut has no grease nipple or oil hole, suitable grease may be applied directly to the screw raceway, followed by several slow strokes to help carry lubricant into the nut.
For lubricant selection, grease quantity and oil-versus-grease considerations, see Ball Screw Lubrication: Oil vs Grease, Interval Guide and Best Practices .
Maintenance of Oil-Lubricated and Automatic Lubrication Systems
A ball screw connected to a centralized oil or grease system should not be treated as maintenance-free. The system may appear to be operating while a blocked line or metering unit prevents lubricant from reaching one nut.
Regularly check:
- Reservoir oil or grease level
- Lubricant condition and contamination
- Pump operation and pressure indication
- Metering valves and distributors
- Blocked, cracked or leaking supply lines
- Whether lubricant reaches every ball nut
- Filter condition
- Machine alarms related to low level or low pressure
The oil delivery quantity and timing depend on the ball screw diameter, stroke, speed, heat-control requirement and lubrication-system design. Do not replace the programmed oil supply with a general three-month or six-month rule.
Inspect the Complete Ball Screw Drive System
A ball nut is only one component in the drive system. Noise, axial play, heat and positioning error may originate from the support bearings, locknut, coupling, motor or driven table.
Support bearings, locknuts, couplings and mounting alignment should be inspected together with the ball screw nut.
| Component | What to Check | Possible Symptom |
|---|---|---|
| Ball screw nut | Lubrication, seals, backlash, noise and smoothness | Rough movement, lost preload or contaminated raceways |
| Fixed-side support bearings | Heat, noise, axial play, locknut tightness and bearing preload | Positioning error, vibration or heat incorrectly blamed on the nut |
| Supported end | Bearing condition, shaft movement and mounting security | Shaft vibration or inconsistent support |
| Coupling | Loose clamping screws, cracking and motor-to-screw alignment | Reversal error, vibration or intermittent drive |
| Nut housing | Mounting-bolt tightness and whether the housing is forcing the nut out of alignment | Uneven torque and localized wear |
| Linear guide system | Parallelism, lubrication and table resistance | Extra motor load incorrectly attributed to the ball screw |
| Covers and seals | Tears, gaps, wear and interference through the full stroke | Lubricant loss or contamination entering the nut |
For a detailed comparison of failure symptoms and root causes, see What Causes Premature Ball Screw Failure and How Can It Be Prevented? .
Warning Signs That Require Immediate Inspection
Do not wait for the scheduled maintenance date when any of the following changes appear.
| Warning Sign | Possible Cause | First Check |
|---|---|---|
| Nut temperature continues rising | Too little or too much lubricant, excessive preload or misalignment | Lubrication quantity, motor current and alignment |
| Noise at one repeatable shaft position | Local dent, raceway damage, contamination or shaft defect | Corresponding screw-raceway area |
| Resistance changes through the stroke | Bent shaft, alignment error, contamination or damaged raceway | Shaft runout, mounting alignment and guide resistance |
| Backlash increases | Raceway wear, loss of preload, loose support bearing or coupling | Nut clearance and complete axial drive chain |
| Grease contains metallic particles | Internal wear or damaged rolling contact surfaces | Ball nut and screw raceways before adding more grease |
| Rust or coolant inside the protected area | Damaged seal, cover failure or unsuitable corrosion protection | Source of liquid entry and raceway condition |
Special Maintenance for Short-Stroke Motion
A high-frequency axis with a very short stroke may repeatedly load only a limited area of the screw raceway. Lubricant can dry or move away from the contact zone without being redistributed over a longer distance.
Where the machine design and safety controls permit it, schedule an occasional longer maintenance stroke to distribute lubricant over a wider raceway area. The suitable frequency depends on the actual stroke, load, lubricant and nut design.
If a longer stroke cannot be performed, use closer condition monitoring and confirm a lubricant intended for small-amplitude reciprocating motion.
Maintenance Before Restarting After Long Storage
Lubricant can deteriorate during storage even when the ball screw has not accumulated travel. Moisture and condensation may also cause corrosion on exposed raceways.
Before restarting:
- Inspect the complete screw for rust, stains and physical damage.
- Check whether the grease has hardened, separated or collected contamination.
- Clean the screw using a method compatible with the seals and lubricant.
- Apply suitable fresh lubricant before normal movement.
- Rotate or move the assembly slowly through the usable stroke.
- Check the support bearings, locknut and coupling.
- Perform a low-speed test before restoring normal speed and load.
Keep a Ball Screw Maintenance Record
A maintenance record makes it possible to change the interval according to real machine performance instead of relying permanently on a general estimate.
Record:
- Maintenance date
- Accumulated travel or machine operating hours
- Lubricant brand, type and batch where available
- Amount of lubricant added
- Grease color and contamination condition
- Nut temperature before and after maintenance
- Motor current or drive-load reading
- Noise, vibration and movement observations
- Backlash or repeatability measurement
- Repairs or adjustments made to bearings, coupling, alignment or covers
If the lubricant remains clean and the operating baseline is stable at every inspection, the interval may be reviewed carefully. If grease repeatedly appears dry, contaminated or overheated before the planned date, shorten the interval and correct the underlying condition.
Frequently Asked Questions
Should every ball screw be lubricated every three months?
No. Three to six months is only a general reference for normal conditions. A continuously operating long-stroke axis may require maintenance much sooner based on accumulated travel, while a specially lubricated or low-use system may have a longer approved interval.
Is 100 km the service life of a ball screw?
No. It is a commonly used starting reference for relubrication under normal conditions. Ball screw fatigue life may be many thousands of kilometers and must be calculated from the dynamic load rating, actual axial load and duty cycle.
Can I add a different grease if the original type is unknown?
Mixing incompatible grease types can reduce lubrication performance or form deposits. Identify the original lubricant from the machine documentation where possible. If the lubricant must be changed, remove the old material as completely as the approved maintenance procedure allows.
Does a new ball screw require lubrication before use?
Confirm the delivery condition before installation. Rust-preventive oil used for transportation should not automatically be treated as the operating lubricant. Clean and lubricate the assembly according to the supplied specification before commissioning.
Why does the nut feel tighter immediately after greasing?
Fresh grease can temporarily increase agitation resistance. Run the axis slowly through several strokes to distribute the grease. If resistance or temperature remains unusually high, check whether too much lubricant was added or whether another mechanical problem is present.
When should a ball screw be replaced instead of maintained?
Replacement should be considered when backlash no longer meets the machine requirement, raceways show pitting or severe corrosion, the return system is damaged, or movement remains rough after lubrication, alignment and support-bearing problems have been corrected.
Contact DLY
Send DLY your ball screw model, diameter, lead, stroke, operating speed, daily running time, load, mounting direction, lubrication method and working environment. We can help review the ball screw specification, replacement dimensions and maintenance considerations for your application.
View the DLY ball screw product range for rolled ball screws, ground ball screws, different nut structures and machined ball screw assemblies.
Email: export@dlybearing.com
