Grease lubrication

The advantages of grease lubrication are as follows:

• little requirement for design work; it may be possible to dispense with a central lubrication system
• the possibility of long term lubrication
• the use of reservoir lubrication.

Flowable grease lubrication

Due to the risk of increased lubricant egress, flowable greases of grades NLGI 00 and NLGI 000 should be used in accordance with the guide values for oil lubrication.

In the case of flowable greases of grade NLGI 0, the lubricant quantity and relubrication interval should be taken from the chapter Grease lubrication.

In clean environmental conditions, the impulse quantity can in certain circumstances be reduced to approx. 20% of the oil impulse quantity stated in the tables.

Minimal lubricant quantity metering unit

For the minimal lubricant quantity metering unit, only flowable greases of grades NLGI 00 and NLGI 000 are permissible.

Lithium soap and lithium complex soap greases with a mineral oil base and EP additives are recommended.

Base oil viscosity

The base oil viscosity is shown in the table:

^**For initial greasing with grease KP2N–20 to DIN 51825.

^**For initial greasing with grease KP2K–30 to DIN 51825.

Grease lubrication

Lithium soap and lithium complex soap greases with a mineral oil base are recommended.

Base oil viscosity

The base oil viscosity is shown in the table:

Miscibility

Greases may be mixed if:

• they have the same base oil type
• they have matching thickener types
• they have similar base oil viscosities: the difference must be no more than one ISO VG grade
• they have the same consistency (NLGI grade).

In case of doubt, please contact us.

Initial grease quantity

Carriages that are not connected to a central lubrication system must be greased before mounting with the initial grease quantity, see tables.

Linear recirculating ball bearing and guideway assemblies KUVE..-B

• Standard designs are delivered with a basic greasing, which must be supplemented before commissioning.
• KUVE25-B..-HS (design High-Speed) systems are supplied with an initial greasing.
• KUVE..-B..-UG is supplied without basic greasing, which means that it only has a preservative (the suffix for this option is -UG).

Initial grease quantities
for RUE

Initial grease quantities
for KUSE

Initial grease quantities
for KUVE
with basic greasing

^**KUVE25-B..-HS (design High-Speed) systems are supplied with an initial greasing.

Initial grease quantities
for KUVE..-UG
with preservative
(without basic greasing)

Initial grease quantities
for KUVS

^** KUVS systems are supplied with an initial greasing.

Calculation of the lubrication interval

Grease operating life

Since it is not possible to calculate all the influencing factors, the precise grease operating life can only be determined under operating conditions. The approximation equation below, however, can be used to determine a guide value for many applications:

tfG	h	Guide value for grease operating life in operating hours
tf	h	Factor for basic lubrication interval in operating hours, ➤ Figure
KP, KW, KU		Correction factors for load, stroke length and environment, see link.

Basic lubrication interval

The basic lubrication interval t_f is valid under the following conditions, ➤ Figure:

• bearing temperature ＜ +80 °C
• load ratio C₀/P = 20
• no disruptive environmental influences
• stroke ratio between 10 and 50, ➤ Figure.

Speed parameter

The speed parameter is defined as follows:

GKW		Speed parameter, ➤ Figure
vm	m/min	Mean travel velocity
KLF		Bearing factor, see table.

Determining the basic lubrication interval

t_f = basic lubrication interval · GKW = speed parameter ·

 Relubrication possible ·

 Regreasing necessary

The bearing factor K_LF takes account of the internal and external structure of the bearing, such as lubricant reservoirs, wipers and additional lubrication devices that influence the grease operating life.

Bearing factor K_LF for delivered condition

^**Valid only with mounting on both sides of the long term lubrication unit KIT on the carriage.

Correction factor for load K_P

The correction factor K_P takes account of the strain on the grease at a load ratio of C₀/P ＜ 20, ➤ Figure.

Correction factor
for load

K_P = correction factor for load · C₀/P = load ratio

Correction factor for
stroke K_W

The correction factor K_W takes account of the displacement distance to be lubricated, ➤ Figure. It is dependent on the stroke ratio.

Correction factor for stroke length

K_W = correction factor for stroke length · H_v = stroke ratio

Stroke ratio

If the stroke ratio is ＜ 10 or ＞ 50, the grease operating life is reduced due to the risk of fretting corrosion or the loss of grease.

The stroke ratio is calculated as follows:

Hv		Stroke ratio
L1	mm	Effective saddle plate length
H	mm	Stroke length.

If the stroke length is very small (＜ 2  ·  L₁), the grease operating life may be shorter than the calculated guide value. In such cases, special greases are recommended.

Correction factor for
environment K_U

The correction factor K_U takes account of shaking forces, vibrations (a cause of fretting corrosion) and shocks as well as environmental influences (contamination and operating media), see table.

Environmental influence and correction factor

Relubrication interval

If the guide value for the grease operating life t_fG is less than the required operating duration of the linear unit, relubrication must be carried out.

Relubrication must be carried out at a time when the old grease can still be forced out of the carriage by the new grease.

A guide value for the relubrication interval for most applications is:

tfR	h	Guide value for relubrication interval in operating hours
tfG	h	Guide value for grease operating life in operating hours
tfE	h	Required operating duration in hours.

Relubrication of the guidance system

Relubrication should be carried out at a stage no later than half the grease operating life.

For the relubrication of monorail guidance systems, Schaeffler offers matched lubrication connectors, depending on the wiper KIT combination.

Lubricating grease

Relubrication should be carried out using the same grease as for initial greasing; if different greases are to be used, the miscibility and compatibility of the greases must first be checked.

Relubrication quantity

The relubrication quantity is approx. 50% of the initial grease quantity. In the case of KUVE, the relubrication quantity is 50% of the initial grease quantity without basic greasing, see link. Relubrication should be carried out wherever possible with several partial quantities at various times instead of the complete quantity at the time of the relubrication interval.

Relubrication procedure

Relubrication should be carried out with the carriage still warm from operation and the carriage should be moved during relubrication. The minimum stroke is four times the saddle plate length; saddle plate length (L₁).

Long term lubrication units are a component of the KIT series 400.

Influence of grease on friction behaviour

During commissioning and relubrication, the coefficient of friction increases temporarily due to the fresh grease. After a short running-in period, however, the coefficient of friction returns to its original lower value.

The friction behaviour is determined significantly by the character­istics of the grease used. The consistency and base oil viscosity serve as approximate guide values.