Okuma OSP 5000, Electrical Maintenance, Training Manual

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Okuma America Corporation
CONSTR CONSTR
CONSTR CONSTR
CONSTRUCTION UCTION
UCTION UCTION
UCTION
Rev. 8-21-01
Connecting the encoder input/output (ribbon cable) connector.
Since this connector has a protruding portion to prevent an error during insertion, care should be
paid to its insertion direction. (Insert the connector with its protruding portion pointed at the
center (inside) of shaft. Turn the lock levers towards the inside. At this time, check for a click-
ing noise. If the connector is not inserted sufficiently, the clicking noise will not be heard or felt.
Install the cover and resin frame
The installation of the encoder is completed.
At this point, refer to the Parameter section to redefine the Stroke End Limits and Zero Offsets.
If the absolute position encoder is replaced on a machining center, only the Zero Offset has to be
redefined.
MPR
Some machines have an MPR (MultiPolar Resolver) mounted directly to the ballscrew. This
MPR is the same as the MPR in the absolute position encoder. The MPR is used in conjunction
with the absolute position encoder to provide greater accuracy. This resolver has eight poles;
four sine poles and four cosine poles. The sine and cosine signals are generated by the OSP
control. As the stator (located in the center of the eight poles) rotates, a feedback signal is
generated. This feedback signal will be phase shifted up to 360 degrees depending on the
position of the stator which is directly coupled to the output shaft of the MPR. As mentioned
above, the OSP generates a clock signal which it compares to the phase shift between the feed-
back and sine signals. There is a set number (163,840) of clock signals within a 360 degree
phase shift. By knowing the distance the axis travels for each clock pulse, the control counts the
number of clock pulses per 360 degree phase shift and multiplies the number by this set distance
to determine how much the axis has traveled.
Inductosyn
The bigger the machine, the longer the axis ballscrew. The longer the ballscrew , the more room
there is for error due to heat expansion of the ballscrew. An inductosyn feedback system is a
practical way of compensating for ballscrew growth. It is also used on machines requiring high
accuracy positioning. An inductosyn feedback used in conjunction with the absolute position
encoder enables the control to detect axis positioning in units of .1 microns.
An inductosyn transducer is a high accuracy multi-pole position data device. There are linear
and rotary inductosyns. The linear inductosyn uses an inductive scale that is attached to the
table of the machine. A reference signal is sent to this scale. On the other side is the slider
which has a sine and cosine pickup coil. As the slider is moved across the face of the scale, two
signals are induced (sine & cosine) which are 90° out of phase. These two signals are sent to the
preamp board where they are combined and sent back to the OSP control as the POS(position)
signal.