plaquette MACHLINE - Ntn-snr.com

Installation: rules to follow
Run-in procedure
The run-in procedure has a considerable influence
on the accuracy of spindle rotation and its service
life. The procedure must be carried out in steps,
depending on the spindle type and temperature
rise. The rotation speed of the first step must be at
a low enough N.Dm (of the order of 10 5 ) to be certain
that the lubrication film is established.
Run-in time at each step depends on the time
required for bearing temperature to stabilise. As
soon as the temperature is stabilised, move on to
next step.
T°
Example of run-in cycle
of a spindle at 15,000 rpm.
1,000 rpm.
Step 1
3,500 rpm.
Step 2
7,000 rpm.
Step 3
15,000 rpm.
Step 4
Time
Characteristic failures
Spalling failures due to material fatigue are
extremely rare on MachLine spindle bearings.
Spindle failures are more characterized by deviation
of a certain number of factors observed and measured
on the manufactured components, which
indicate the requirement for spindle maintenance.
These factors are:
- Difficulties in maintaining dimensions.
- Increasing geometrical defects such as circularity
or radial run-out.
- Poor surface finish.
- Unusual surface condition (chatter marks, vibration,
etc.).
- Abnormal noises in operation.
In 70 % of cases failures are linked to lubrication
problems and in 10 % of cases, linked to the sealing
system or a sudden impact between the part
and the tool which can cause damage to spindle
and bearings.
The bearing itself is rarely the cause
of premature failure.
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