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Roller Bearings and Lubrication

May 24, 2011 - Rockford, IL  -  Posted by Tech Team

Lubrication

Roller Lubrication

All smaller rollers (in the Redi-Rail®, Integral-V™, V-Guide, Commercial Rail, Hardened Crown Roller families, and smaller diameter Hevi-Rail® bearings) are lubricated for long life.  No additional lubrication is necessary.  The rollers are sealed (or shielded) against the operating environment to prevent egress of lubricant, and prevent ingress of contaminants.  Some larger rollers (in the Hevi-Rail family) are supplied with a grease access point and can be re-lubricated using a zerk fitting. 

Raceway/Guideway Lubrication

To ensure long life, it is necessary to have a thin film of lubrication on the Raceway/Railway at all times.  When properly applied, lubrication:

  • Reduces wear
  • Reduces stress on the contact surfaces
  • Reduces friction (and therefore heat buildup)
  • Allows for operation at specifications in this catalog (de-rating is required for un-lubricated applications)
  • Helps protect the metal surfaces against corrosion (rust and fretting corrosion)

Lubrication Type

Technical, environmental, ecological and economic factors will determine whether oil or grease should be used in an application.  One of the most significant factors in the lubrication selected is the environmental conditions.  If extreme conditions are expected, it is highly recommended that either PBC Linear or a representative from a lubrication company is consulted.  This includes heavy contamination, when the expected particle size is smaller than 0.1 mm (0.005 in) as small particles can more easily bypass seals and wipers.

CAUTION!  The compatibility of lubricants must always be checked!  This check should be done under both static and dynamic conditions and within the operating environment.  Some lubricants may have unexpected, negative reactions with the plastics, elastomers or non-ferrous metals within the products.  It is possible to draw upon previous and practical experience or guidelines from the lubricant manufacturer.  When in doubt, consult the lubricant manufacturer. 

Initial Lubrication (during installation)

PBC Linear Guides and Raceways are shipped with a preservative lubrication applied to the raceway.  During installation, it is necessary to apply additional lubrication.  Provided there are no application conflicts, PBC recommends high quality lithium soap grease as the initial lubricant.  This grease should be applied to the entire raceway, not just the portion used during normal operation.  Oil or grease may be used for re-lubrication. 

Note:  Coated/Plated rails, Commercial Rail, Hardened Crown Roller and Hevi-Rail® rails are typically shipped without any preservative lubrication.  See the Hevi-Rail® section for more details: sandblast and lightly oiled option is available for Hevi-Rail.

Periodic Lubrication/Maintenance

The lubrication interval is dependent on many operating and environmental conditions, such as load, stroke, velocity, acceleration, mounting position/orientation, type of lubrication used, temperature, humidity, UV exposure, etc.  The actual lubrication interval should be determined by tests conducted under actual application conditions. 

While the actual lubrication intervals are application specific and determined only through testing, the following guidelines can typically be used as a starting reference point under “normal” conditions:

  • Re-lubrication every 1,000 km; 50,000 cycles or six months (whichever occurs first).

Oil Filled Polymer Lubricator

Some PBC Linear products offer a high quality polymer lubricator.  PBC uses an advanced, oil filled porous polymer which has been tested to show better performance and longer life than similar wiper/lubricators made of oil or grease filled felt.  In some applications, this special lubricator will last the life of the application without additional re-lubrication. 

This lubricant within the polymer is NSF Registered for both H1 & H2 applications (Direct & Indirect contact with food).  It can also be used for wash down & industrial applications.  The lubrication within the polymer contains corrosion inhibitors, anti-oxidants & extreme pressure (E.P.) additives.  Table 1, below, shows some specific properties for the lubricant. 

Table 1:  Properties for Lubrication in Advanced Oil-Filled Plastic

Upper Temp Limit

Lower Temp Limit

Specific Gravity

Viscosity at 40°C cSt

Viscosity at 100°C cSt

99° (210°F)

-40° (-40°F)

0.86

150

16.5

Used Lubricants

Used lubricants should be disposed of using environmentally-friendly methods.  Most lubricant manufacturers have guidelines regarding their allowable storage, use and disposal.  In addition, some countries have regulations regarding storage, use and disposal of lubricants for occupational safety and/or environmental protection.  Furthermore, some companies may have adopted internationally accepted quality and standards policies (i.e. ISO14001) which will further regulate the use of lubricants within an application.

These guidelines and regulations must be followed.  Care should be exercised as to not specify a lubricant which is forbidden. 

Lubrication Failure

Contamination and Lack of Lubrication are the two primary causes of (ball based) linear guide failures.  Lack of lubrication will cause Fretting Corrosion which can cause permanent system damage and eventually lead to system failure.  As it applies to this product, Fretting Corrosion is a form of damage caused as a combination of corrosion and abrasive wear.  Fretting Corrosion can typically be seen as a reddish discoloration on either mating raceway (track or roller).  Fretting Corrosion can sometimes be confused with Rust.  Both are signs that additional lubrication is necessary and the re-lubrication period must be decreased. 

Operation in an Un-Lubricated Sate

While not recommended, it is possible to run most systems without lubrication; however, there will be significant reductions to maximum load, maximum speed and expected life.  Table 2, below, shows that a typical un-lubricated system will have a significantly reduced maximum load and a reduced maximum speed when compared to a properly lubricated system.

Table 2:  Typical Reductions for Max Load & Speed for Un-Lubricated Systems

Product

 

Lubricated

Un-Lubricated

Reduction

A

Max Load

kg

100

25

75%

Max Speed

m/s

2

1.5

25%

 

In addition to significant reductions in maximum load and speed, un-lubricated system will also experience an extreme reduction in expected life.  Table 3, below, shows the expected life for both a lubricated and un-lubricated system for two different products with two different applied loads.  The approximate reduction in lifetime has also been calculated. 

Table 3:  Typical Life Reductions for Un-Lubricated Systems

Product

 

Lubricated

Un-Lubricated

Reduction

Example B

Applied Load 1

kg

45.4

45.4

 --

Life 1

m

5,410,200

88,900

≈ 98%

Applied Load 2

kg

22.7

22.7

 --

Life 2

m

22,860,000

533,400

≈ 98%

Example C

Applied Load 3

kg

45.4

45.4

 --

Life 3

m

50,800,000

863,600

≈ 98%

Applied Load 4

kg

90.7

90.7

 --

Life 4

m

8,382,000

152,400

≈ 98%

 

Note:  Actual performance will vary depending upon specific application conditions.  PBC Linear has removed the actual product name from the examples listed above as the results may not be repeatable, depending upon specific application conditions.  While these values are typical, specific reductions should be determined by tests conducted under actual application conditions. 

 
 

 

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