6Warner Electric • 800-825-9050 P-209-WE • 819-0517
Burnishing and Maintenance
Burnishing
Intimate metal to metal contact is essential between
the armature and the metal rings (poles) of the
magnet or rotor. Warner Electric clutches and brakes
leave the factory with the friction material slightly
undercut to assure good initial contact.
Normally, the desired wearing-in process occurs
naturally as the surfaces slip upon engagement. The
time for wear-in, which is necessary to obtain the
ultimate torque of the unit, will vary depending on
speed, load, or cycle duty.
If maximum torque is required immediately after
installation, the unit should be burnished by slipping
the friction surfaces together at reduced voltage. It is
recommended that the burnishings be done right on
the application, if at all possible.
Burnishing at high speed will result in a smoother
wear-in pattern and reduce the time for burnishing.
The voltage should be set at approximately 30% or
40% of the rated value.
The unit should be cycled on and off to allow
sufficient time between slip cycles to prevent
overheating.
When a Warner Electric brake or clutch is properly
assembled and installed, no further servicing,
lubrication, or maintenance should be required
throughout the life of the unit.
Maintenance
Wear Pattern: Wear grooves appear on the
armature and magnet surfaces. This is a normal
wear condition, and does not impair functioning of
the unit. Normally, the magnet and armature, as a
mating pair, will wear at the same rate. It is the usual
recommendation that both components be replaced
at the same time.
Remachining the face of a worn armature is not
recommended. If a replacement armature is to
be used with a used magnet, it is necessary to
remachine the worn magnet face. In refacing a
magnet: (1) machine only enough material to clean
up the complete face of the magnet; (2) hold the face
within .005” of parallel with the mounting plate; and
(3) undercut the molded facing material .002” - .004”
below the metal poles.
Heat: Excessive heat and high operating
temperatures are causes of rapid wear. Units,
therefore, should be ventilated as efficiently as
possible, especially if the application requires fast,
repetitive cycle operation.
Foreign Materials: If units are used on machinery
where fine, abrasive dust, chips or grit are dispelled
into the atmosphere, shielding of the brake may be
necessary if maximum life is to be obtained.
Where units are used near gear boxes or
transmissions requiring frequent lubrication, means
should be provided to protect the friction surfaces
from oil and grease to prevent serious loss of torque.
Oil and grease accidentally reaching the friction
surfaces may be removed by wiping with a rag
dampened with a suitable cleaner, which leaves no
residue. In performing this operation, do not drench
the friction material.
If the friction materials have been saturated with oil
or grease, no amount of cleaning will be completely
effective. Once such a unit has been placed back in
service, heat will cause the oil to boil to the surface,
resulting in further torque loss.
Torque Loss: If a brake or clutch slips or loses
torque completely, the initial check should be the
input voltage to the magnet as follows:
90-Volt Series: Connect a DC voltmeter with a
range of 0-100 or more directly across the magnet
terminals. With the power on and the potentiometer
turned up, a normal reading is 90 volts, although 85
to 95 is satisfactory. The reading should drop as the
potentiometer control is adjusted counterclockwise.
24-Volt Series: Use a DC voltmeter with a
range of 0-30 volts or more. A normal reading is
approximately 22-26 volts.
