1.10.1 Functions of Lubrication
Adequate lubrication and subsequent relubrication with a lubricant suitable for operating and environmental conditions is essential for reliable operation and long service life of SCHNEEBERGER MONORAIL guideways.
Lubrication performs the following functions:
- Separating metal rolling contacts by forming a stable lubricating film
- Minimizing wear
- Reducing friction between rolling elements and raceways and between rolling elements themselves
- Reducing sliding friction of seals
- Preventing corrosion
- Reducing running noise
Lubrication system function diagram
In addition, lubrication can perform other functions:
- Heat dissipation or flushing out contaminants (in the case of oil lubrication)
- In combination with the sealing system, preventing ingress of liquid or solid foreign matter (in the case of grease lubrication)
Effect of Lubrication on Function and Service Life
Therefore, lubrication has an important influence on the function and service life of linear guideways.
However, a prerequisite for the lubrication system to achieve optimum efficiency is the selection of a lubricant suitable for operating and environmental conditions, as well as proper functioning of the sealing system. The task of the seals is to retain the lubricant in the carriage and prevent ingress of liquid or solid foreign particles into the carriage interior. Therefore, seals should prevent lubricant contamination or discharge.
Note: Personal Injury and Component Damage Due to Malfunction
Insufficient lubricant or selection of unsuitable lubricant, along with contamination and overload, are the most common causes of linear guideway failure.
Please ensure correct operating conditions and regular lubrication.
1.10.2 Lubricant Types
SCHNEEBERGER MONORAIL guideways can use grease, fluid grease, or oil as lubricants.
Note: Lubricants containing solid lubricant additives (such as graphite, MoS2, or PTFE) are not suitable for SCHNEEBERGER MONORAIL guideways as they form harmful deposits on rolling element raceways.
Lubricant Application Methods
Lubricant can be applied manually (e.g., using a grease gun), or supplied automatically using a centralized lubrication system, or an additional lubricant dispenser can be installed on the carriage (see Section 4.15.9 - Lubrication Plate SPL).
Using a centralized lubrication system generally guarantees consistent and reliable lubricant supply. In special cases, oil-air lubrication is also used, which is a minimum quantity lubrication method. For application knowledge regarding lubrication requirements under specific operating conditions, please refer to Section 4.15.8.
Key factors in selecting lubricant type and implementation:
Application Type
Machine tools, handling equipment, cleanrooms, etc.
Operating Conditions
Speed, stroke, force, vibration, etc.
Machine Configuration
Configuration of machine and surrounding structure
Accessibility
Accessibility of guideways
1.10.3 Lubricant Properties
Lubricating Oil
Mineral oils or artificially produced synthetic oils can be used as lubricating oils, combined with additives to provide properties such as anti-aging, corrosion protection, anti-foaming, and improved pressure resistance. Lubricating oils are classified into different grades according to their viscosity per DIN 51519.
Characteristics of lubricating oil:
- Easier penetration into carriage, better dispersion effect than grease
- Effective heat dissipation
- Easier to flow out of carriage than grease
- Affected by gravity, thus requiring higher design consideration depending on mounting orientation
- Provides flushing effect
Lubricating Grease
Lubricating grease consists of base oil (usually mineral oil), thickener (metal soaps, simple soaps, complex soaps (calcium, lithium, sodium, etc.)) and various additives (e.g., anti-oxidation, anti-corrosion, and improved pressure resistance). Lubricating grease is classified into various NLGI grades (National Lubricating Grease Institute) according to its consistency and/or strength per DIN 51818.
Characteristics of lubricating grease:
- Prevents running noise
- Supports scraper effectiveness due to its solid consistency
- Blocks contaminant ingress into carriage
- Stays positioned at lubrication point
- Sustained release/deposit effect due to thickener action
- Has lasting effect, supports extended relubrication intervals
- Thickener also provides certain emergency running properties
Fluid Grease
Fluid grease is low-viscosity grease, therefore:
- Suitable for use in centralized lubrication systems
- Has soft, fluid-like consistency
Lubricant Miscibility
Mineral oil-based lubricating oils can be mixed with each other when they have the same classification and their viscosity difference does not exceed one ISO-VG grade.
For synthetic oils, please consult the lubricant manufacturer.
Changing Lubricants
Subsequent change from oil lubrication to grease lubrication can be safely completed, provided the different lubricants are compatible.
Important: Changing from grease lubrication to oil lubrication is not possible. After initial lubrication, grease remains in narrow lubrication channels, which impedes oil flow, meaning adequate oil lubrication supply cannot be guaranteed.
1.10.4 Recommended Lubricants
Lubricants recommended by SCHNEEBERGER:
| Lubrication Type | Recommended Product |
|---|---|
| Oil Lubrication | Mineral oil CLP (DIN 51517) or HLP (DIN 51524), viscosity range ISO VG 32 to ISO VG 100 (DIN 51519); Slideway oil CGLP (DIN 51517), viscosity grade up to ISO VG 220 |
| Grease Lubrication | Lubricating grease KP2K (DIN 51825) |
| Fluid Grease Lubrication | Fluid grease GP00N or GP000N (DIN 51826) |
1.10.5 Lubricant Specifications and Additives
Viscosity
Viscosity is a measure of flow resistance based on internal friction of liquid. Lubricating oils are classified into different grades according to viscosity per DIN 51519. Low viscosity indicates thin flow, high viscosity indicates thick lubricant. For example, water has an ISO-VG grade of 1.
ISO Viscosity Grades (DIN 51519)
| ISO Grade | Viscosity (mm²/s, 40°C) | Minimum (mm²/s) | Maximum (mm²/s) |
|---|---|---|---|
| ISO VG 32 | 32 | 28.8 | 35.2 |
| ISO VG 46 | 46 | 41.4 | 50.6 |
| ISO VG 68 | 68 | 61.2 | 74.8 |
| ISO VG 100 | 100 | 90 | 110 |
| ISO VG 150 | 150 | 135 | 165 |
| ISO VG 220 | 220 | 198 | 242 |
Consistency
The resistance of grease to deformation is defined as its consistency. This specification is used to classify lubricating greases. For this purpose, DIN 51818 divides lubricating greases into 9 different NLGI grades. Worked penetration serves as the assessment parameter for classification, indicating the depth to which a standard cone can penetrate the lubricant under gravitational force.
For SCHNEEBERGER MONORAIL guideways, greases with NLGI grades 000 to 3 are used.
NLGI Grades (DIN 51818)
| NLGI Grade | Grease Type | Consistency | Worked Penetration (0.1 mm) | Application |
|---|---|---|---|---|
| 000 | Fluid grease | Fluid | 445 - 475 | For centralized lubrication systems, gear lubrication, SCHNEEBERGER MONORAIL guideways |
| 00 | Viscous | 400 - 430 | ||
| 0 | Semi-fluid | 355 - 385 | ||
| 1 | Soft grease | Very soft | 310 - 340 | |
| 2 | Soft | 265 - 295 | SCHNEEBERGER MONORAIL guideways | |
| 3 | Smooth | 220 - 250 | ||
| 4 | Almost solid | 175 - 205 | Sealing grease | |
| 5 | Hard grease | Solid | 130 - 160 | |
| 6 | Very solid | 85 - 115 |
Additives
Industrial lubricants are usually blended with various additives. These additives provide specific properties or improve performance of the lubricant:
| Additive Type | Purpose |
|---|---|
| Antioxidants | Prevent lubricant deterioration |
| VI-improver | Reduce viscosity dependence on temperature |
| EP additives | Improve pressure resistance (for high loads; EP = Extreme Pressure) |
| Corrosion inhibitors | Prevent corrosion and rust |
| Foam inhibitors | Prevent foam formation (improve force transmission) |
1.10.6 DIN 51502 Lubricant Short Description
Structure of Lubricating Oil Short Description
Example: C-L-P-PG-68
| Component | Meaning |
|---|---|
| C | Lubricating oil type |
| L | Additive identification letter (corrosion protection, anti-aging) |
| P | Additive identification letter (anti-wear, anti-friction, load capacity) |
| PG | Additional identification letter for synthetic lubricants |
| -68 | Viscosity, ISO-VG grade |
Lubricating Oil C, CL, CLP (DIN 51517)
Lubricating oil CLP:
Mineral oil (C) with additives for improved corrosion protection and anti-aging (L),
and reduced wear in mixed friction zone (P).
Slideway oil CGLP:
Slide and slideway oil (CG) with particularly good sliding properties and adhesiveness (G),
with additives for improved corrosion protection and anti-aging (L),
and reduced wear in mixed friction zone (P).
Hydraulic Oil HL, HLP, HVLP (DIN 51524)
Hydraulic oil HLP:
Hydraulic oil (H) with additives for improved corrosion protection and anti-aging (L),
and reduced wear in mixed friction zone (P).
Structure of Lubricating Grease Short Description
Example: K-P-2-K-(-30)
| Component | Meaning |
|---|---|
| K | Lubricating grease type |
| P | Additional letter for base oil type and additives |
| 2 | Consistency, NLGI grade |
| K | Maximum operating temperature and water performance specification |
| -30 | Minimum operating temperature (°C) |
Lubricating Grease K (DIN 51825)
Lubricating grease KP 2K:
Lubricating grease for roller bearings, plain bearings, and sliding surfaces (K),
with additives to reduce friction and wear in mixed friction zone and/or improve
load capacity (P), consistency grade NLGI 2, maximum operating temperature 120°C (K).
Lubricating Grease OG (DIN 51825)
Lubricating grease OGP 2K:
Lubricating grease for open gears (OG), with additives to reduce friction and wear
in mixed friction zone and/or improve load capacity (P), consistency grade NLGI 2,
maximum operating temperature 120°C (K).
Lubricating Grease G (DIN 51826)
Lubricating grease GP 00/000N:
Lubricating grease for closed gears (G), with additives to reduce friction and wear
in mixed friction zone and/or improve load capacity (P), consistency grade NLGI 00/000
(fluid grease), maximum operating temperature 140°C (N).
1.10.7 Determining Factors for Lubricant Selection
A suitable lubricant should be selected in cooperation with the lubricant manufacturer. The following factors should be considered:
- Type of use: Machine tools, handling equipment, cleanrooms
- Operating conditions: Speed, stroke, force, vibration
- Environmental influences: Temperature, coolant lubricant, contaminants
- Linear guideway: Ball/roller, size, mounting orientation, accessibility
- Lubricant supply: Manual, centralized lubrication system, lubrication intervals, compatibility with other lubricants
- Other: Lubricant service life, certifications/specifications, materials, environmental factors, cost-effectiveness