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Fadal Manuals

Motor Encoders



Fadal Manuals - Complete Documentation Resource


Spindle Drive - One of the most common problems with a spindle drive running in the Vector mode is caused by the spindle motor encoder.  Missing encoder pulses will basically confuse the drive and cause vector miscalculations which result in too much current output to the motor.  One sign is that the load meter will usually "peg" or pulsate.  Another sign is the RPM will not be stable.  Too often the drive is misdiagnose as being "bad" when it's actually the encoder causing the problem.


The best method of testing is to use a oscilloscope to view the A/B channels.  Pulse errors can easily be detected.  With our new Baldor H2 drive, we simply switch the drive into open loop Inverter mode and you can see the encoder RPM calculations changing erratically with the drives diagnostics feature.  With the older Baldor drives, as you rotate the spindle, the drive keypad will display the calulated rpm.
One simple way to manually test an encoder is by using a FLUKE meter, set it to AC input.  When checking from the encoder supply power common to one of the A+,A-,B+,B- encoder signals on the spindle drive encoder input terminal, you should see approximately 2.8 VAC when turning the spindle at the orientation speed.  The digital pluses look like an AC voltage to a FLUKE meter.
Another important way to test the encoder is by checking the state of each channel.  With a voltmeter in the DC setting, from encoder supply power ground to the A+ encoder input, you should measure either 0 or 3.5 VDC.  The state is either high or low.  If A+ is high (3.5 volts) then the A- channel must be low; A+ and A- can never be the same.  The same logic goes for the B+ and B- channels.  If you rotate the spindle and let it stop, you'll should see the states changing.

More Information  Spindle Drive Functional Diagram:
Link for more information about the Spindle Drive System and possible failiures.

Testing Motor Encoders
- A simple way to test the motor encoder is by using the control diagnostics.

At ENTER NEXT COMMAND enter the DI command then type G 0 3000 and press ENTER to begin the diagnostics.  They are menu driven and easily navigated.  Locate the function TEST ENCODERS (1010-4).

The display shows the encoder data for all the axis boards.  Press the Emergency Stop button and rotate the motor by turning the Ballscrew.  The counter will change if the encoder is sending pulses.  All the encoder ports are the same, so you can move the connector to another board to verify that the board itself is not a problem.  The axis motors have one index pulse per revolution, this is used only one time for the Cold Start procedure.  The spindle encoder does not have an index pulse.

To exit Diagnostics; you'll need to power off/on the machine.


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