Okuma OSP 5000, Электротехническое обслуживание, Учебное пособие

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Okuma America Corporation
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Rev. 8-21-01
Absolute Position Encoder
This Okuma patented device is used for axis speed and position feedback. The D6 type is only
used on DC axis servo systems (LDU’s). The axis servo systems which utilize the BL motor
(BDU, BLD, or BLIID) use the E,F,FB, or FC type absolute position encoder. The E and F types
are being phased out. If an E or F type is replaced, it is replaced with an FB or FC. The FC type
absolute position encoder is the newest and is physically shorter (approx. 3/4 of an inch) then the
older styles. Hence, the FB,F, or E types cannot take the place of an FC. The E, F, FB, and FC
types are capable of making 2048 revolutions before turning over(back to zero). An HC type
absolute position encoder has been developed for high speed turrets and rotary tables. The
output shaft of the HC can turn 7200 revs before turning over.
The absolute position encoder uses a multi-pole resolver (MPR) for lower digit positioning
(.0001) along with pulse type heads for upper digit positioning (123.4560). The control sends a
5 kHz sine and cosine signal to the MPR in the absolute position encoder. The CNC control
generates a clock signal (81.92 Mhz) which it compares to the phase offset between the sine
signal and the MPR feedback signal. The control counts the number of clock pulses per phase
shift and multiplies this number by the distance per pulse. Every time the output shaft of the
absolute position encoder turns 36°, there is a 360° offset between the sine signal and the MPR
feedback signal. This equates to 16384 clock pulses per tenth of a revolution. This The E8-1
rotor rotates one position for every 360° phase shift. This feedback signal is sent back to the
OSP control. The parallel pulse signals from the pulse type heads are digitized inside the en-
coder and also sent back serially to the OSP control.
The absolute position encoder is physically attached to the BL motor. In some cases this encoder
is used on ATC magazines which are hydraulically driven. This encoder is referred to as an
encoder with shaft. This encoder has a casing around it with a shaft sticking out where as the
more common absolute position encoder has no casing around it and has a coupler that is
mounted onto a shaft in the BL motor.
Procedure for Replacing Absolute Position Encoders
Removing Encoder From Motor
1. Unscrew the four clamping bolts (M4 or M5) to remove the back cover of the motor.
2. Remove the cover and resin frame. It may not be easy to remove by hand due to the
adhesion of packing. In this case, the cover can be removed by lightly hitting the cover
with a soft hammer. Positively prohibit hitting it with a metallic hammer or hitting it
hard with a soft hammer since the parts may be broken.
3. Disconnect the encoder input/output connector (ribbon cable) by pulling down the lock
levers on both sides of the connector.
4. The encoder diaphragm is attached to the motor chassis by four special long head bolts.
Remove these bolts to detach the encoder diaphragm from the chassis of the motor.