A comprehensive maintenance guide covering lubrication intervals by product type (HGR, SFU, LM, MGN), seal and wiper replacement timing, raceway wear pattern diagnosis, and a scheduled maintenance template for linear guideways and ball screws.
Why Maintenance Planning Determines Linear Motion System Lifespan
Linear guideways and ball screws are designed for service lives measured in thousands of kilometers of travel. Yet in practice, over 60% of premature failures stem from maintenance neglect - not from design deficiencies or material defects. A structured maintenance program addressing lubrication intervals, seal inspection, and wear diagnosis extends actual service life to match the calculated L10 rating and prevents unplanned production stoppages.
This guide covers the three pillars of linear motion maintenance: lubrication management, seal and wiper replacement, and wear pattern diagnosis - with specific intervals and procedures for Dongfeng's HGR guideway, LM bearing, and SFU ball screw product lines.nes.
Lubrication Management: The Single Most Critical Factor
Grease vs Oil Selection
Grease is the default lubricant for most industrial linear motion applications. It is retained inside the carriage or nut by wipers or seals, requiring less frequent replenishment than oil. The standard recommendation is a lithium-complex soap grease with a base oil viscosity of 100-200 cSt at 40°C (ISO VG 100 to VG 220). For cleanroom or food-grade applications, PTFE-based synthetic greases are available.
Oil lubrication is specified for high-speed applications (DN value > 50,000, where D = ball diameter in mm and N = rotational speed in rpm) and for systems requiring heat dissipation through circulating oil. Oil provides better cooling but requires a sealed circulation system, making it more complex and expensive to maintain.in.
Re-greasing Intervals by Product Type
| Product | Standard Load | Heavy Load (C2 Preload) |
|---|---|---|
| HGR Guideway Carriage | Every 100 km or 6 months | Every 500 km or 3 months |
| SFU Ball Screw Nut | Every 500-1000 km or 6 months | Every 250-500 km or 3 months |
| LM Linear Bearing | Every 50 km or 3 months | Every 25 km or monthly |
| MGN Miniature Guide | Every 50 km or 6 months | Every 25 km or 3 months |
Re-greasing Procedure for Ball Screws
- Clean the screw: Wipe the exposed screw shaft with a lint-free cloth to remove old grease and debris. Do not use solvents that could wash grease out of the nut interior.
- Locate the lubrication port: Find the grease nipple or wiper slot on the nut body. If no port exists, apply grease directly to the screw shaft at the nut entry point.
- Apply grease: Using a manual grease gun, inject 2-5 g of grease (amount varies by screw diameter: 2 g for Ø16 mm, 5 g for Ø40 mm). Do not over-grease - excess grease forces wiper seals outward and attracts contamination.
- Distribute grease: Jog the screw through 5-10 full strokes at low speed to distribute grease evenly inside the nut. Listen for a change from dry, metallic rolling to smooth, damped rolling sound.
- Wipe excess: Remove grease pushed out past the wipers. A thin film on the screw shaft is normal; a thick accumulation is not.
Seal and Wiper Replacement
Seals and wipers are the first line of defense against contamination - the leading cause of premature linear motion failure. In environments with dust, metal chips, coolant, or abrasive particles, seal condition directly determines carriage and nut lifespan.
When to Replace Seals
- Visual inspection: Cracked, deformed, or missing seal lips indicate immediate replacement is needed.
- Running torque change: A 20% or greater drop in drag torque (with no preload change) suggests seal wear has reduced contact pressure.
- Contamination evidence: Grease exiting the carriage appears dark or gritty - contaminant particles have penetrated the seal.
- Scheduled replacement: Replace seals at 50% of the expected carriage service life, typically every 12-18 months in standard environments or every 6 months in contaminated environments.
Dongfeng provides replacement seal kits for all HGR carriage sizes (HGH15-HGH45, HGW15-HGW45) and SFU ball screw nuts. Seal kits include the end seals, side seal strips, and bottom scrapers where applicable. Installation requires removing the carriage from the rail - use the included removal tool to prevent ball spillage.
Wear Diagnosis: Reading the Raceway
The raceway surface records the history of operating conditions. When performing scheduled maintenance, examine the raceway and ball surfaces under 10x-30x magnification to identify developing issues before they become failures.
Normal Wear Pattern
A uniform, narrow track along the full raceway length with a polished surface (no visible scratches or pitting) indicates normal operation. The bearing is correctly specified, properly lubricated, and operating within its rated load. No action needed beyond scheduled re-greasing.
Uneven Wear Track
If the wear track is wider on one side or shows an elliptical pattern, the carriage experienced uneven loading from misalignment or moment loads exceeding the design specification. Check rail mounting surface flatness (should be ≤5 µm/1,000 mm for grade P) and verify the applied load is within the carriage's rated dynamic load (C).(C).
Raceway Discoloration
Brown or blue tinting on the raceway indicates heat damage from insufficient lubrication. If discoloration is visible, measure the raceway hardness - a drop of more than 2 HRC from the specified 58-62 HRC means the component is compromised and should be replaced. Review the lubrication interval and grease type to prevent recurrence.
Pitting and Spalling
Surface pitting (small voids) indicates fatigue initiation. If pitting covers less than 10% of the raceway width, the carriage may continue service with shortened inspection intervals. If spalling (material detachment) is present, replace the carriage immediately - detached material will circulate through the ball circuit and accelerate failure of the replacement if the rail surface is also damaged.
Maintenance Schedule Template
| Interval | Task | Product Scope |
|---|---|---|
| Daily | Visual check for abnormal noise, vibration, or grease leakage | All axes |
| Weekly | Wipe exposed screw shafts and rail surfaces; check for contamination | SFU ball screws, HGR rails |
| Monthly | Re-grease LM bearings and MGN guides in contaminated environments | LM, MGN series |
| Quarterly | Re-grease HGR carriages and SFU nuts; inspect seal condition | HGR, SFU series |
| Semi-annually | Full raceway inspection under magnification; drive torque measurement | All axes |
| Annually | Replace seals in contaminated environments; CMM parallelism check on precision axes | HGR, SFE series |
Document each maintenance action with the date, axis identification, grease type and quantity used, and observations from the visual inspection. This maintenance log becomes invaluable for diagnosing recurring issues and planning replacement schedules before failures occur. Dongfeng Bearing provides maintenance schedule templates and seal kit part numbers for all product lines - contact our technical support team for product-specific guidance.