Festo EXCM-10, Repair Instructions

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46 / 52 Festo 7EXCMc_en
4.2.4.5 Adjusting the toothed belt pretensioning
Caution
The toothed belt pre-tension has a direct influence on the service life of the toothed belt and the performance of the
planar surface gantry. The toothed belt pretension must therefore be checked extremely carefully.
Before the toothed belt pre-tension can be measured, the slide must be moved back and forth a number of times so
that the toothed belt can fully settle and differences in tension can be compensated.
The toothed belt pretensioning is determined by measuring the fundamental
oscillation (natural frequency) of the toothed belt with a fixed and freely
oscillating strand length (L). As the freely oscillating strand length (L) cannot be
measured directly, the distance (L1) between the motor pulley housing (a) and
the cover of the Y-axis (b) is used as a reference. This distance can be adjusted
by offsetting the Y-axis. The oscillation measurement is then carried out at this
point.
1. Set the distance (L1) between the motor pulley housing (a) and the cover of
the Y-axis (b) to 90 mm, see the drawing above.
Caution
The pretension of the toothed belt is not an indicator of wear!
The values specified here are relate to a new toothed belt.
The toothed belt is set to the specified value in the factory, and is thus maintenance-free for its entire service life.
The pretension of the toothed belt reduces due to storage time and operation. This is not an indication of wear; it is a
normal process that must not be changed by retensioning the toothed belt.
The toothed belt pretension must therefore only be set after renewing the toothed belt.
Note
The belt must be able to oscillate freely.
To assess the toothed belt pre-tension, several measurements should be
taken to balance out any measurement tolerances.
2. Hold the acoustic frequency meter towards the centre of the distance (L1)
between the motor pulley housing (a) and the Y-axis (b) as described in the
accompanying operating instructions.
3. Make the toothed belt oscillate by striking it with a thin, heavy object, such
as an Allen key or pin punch.
The acoustic frequency meter must not touch the oscillating toothed belt.
4. If the measured natural frequency is within the allowable range of 271 Hz
to 280 Hz , the threaded pins in the pulley housings can be tightened with a
tightening torque of 2.4 Nm ±10 %.
Example representation