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Festo 7EGC_TB_KFb_en
4.3
Linear recirculating ball bearing guide system
The linear recirculating ball bearing guide system comprises a guide rail and the associated four rows (EGC-50, two rows)
of recirculating ball bearing units (roller carriages) with ball bearing chain. The system has negative operating clearance
in all sizes, i.e. it is pretensioned and therefore has no mechanical play. This results in high rigidity and load bearing ca-
pacity in all system directions, as well as more precise guiding. The specified pretension is achieved using the individual
components and their manufacturing tolerances.
The guide rail is a component part of the cylinder barrel module and cannot be renewed. If a defect occurs in the guide
rail, the entire toothed belt axis must be replaced.
Note
Festo recommends, as a basic principle, that you always replace the entire drive if a defect occurs in the linear recircu-
lating ball bearing guide system.
Replacement of the roller carriages is undertaken by users at their own risk.
The roller carriages cannot be renewed above a certain stroke length (dependent on the size and slide type, see table in
section
4.3.1 “Renewing the roller carriages”
). These roller carriages are paired with the guide rail, in other words they
form a single unit and are matched to each other in terms of both production and assembly.
Replacement of the toothed belt axis may be necessary under the following circumstances, for example:
The end of the linear recirculating ball bearing guide system's useful life has been reached as a result of material fatigue
and wear. Signs of fatigue appear on the material areas of the rolling components. Fine tears, pores and pits (depending
on the wear condition) as well as deformation occur. Pitting on the bearing surface of the guide rail can be observed
visually as the bearing surface is noticeably uneven. This can result in perceptible bearing clearance, impaired roll-off and
increased operating noise, etc.
Note
The application must be checked for the following causes in the event of premature failure due to increased wear:
•
Lack of lubrication; lubrication interval not adhered to (unlubricated operation).
• Use of a lubricating grease not contained in the specification.
•
Dirty and corrosive ambient conditions (dust, etc.).
•
Impact and vibration.
•
Technical limit data exceeded (torques, forces, speed, temperature range, etc.).
•
Flatness of the attachments screwed onto the slide, setpoint value < 0.01 mm (distortion).
•
The following must be checked in applications with parallel axes:
– Parallelism between the guide rails
– Height offset between the slides
Deviations result in distortion in the recirculating ball bearing guide, and therefore overloading of the guide
system. Parallelism and height offset cannot be assessed using the displacement force. The alignment should be
carried out by metrological means. If necessary, install an additional adjustment device as a design feature for
aligning the axes.
Note
Incorrect set values for the braking ramp during STOP conditions (e.g. emergency stop, quick stop) result in overloading
of the toothed belt axis and can destroy it or dramatically reduce its service life.
•
Check the settings for all braking ramps in your controller or the higher-order control system (deceleration values
and jerk).
•
Make sure that the deceleration values (braking deceleration, deceleration times) for the speed, the load to be
moved and the installation position (horizontal/vertical) as well as the specified maximum drive torque or the feed
force correspond to the permissible values for the toothed belt axis used.
•
Use the Festo “Positioning Drives” sizing software, available via the Festo website (
www.Festo.com
), to size the
toothed belt axis.
