All taught positions are based upon a reference point, or "0.00 mm" location.  If your actuator / controller combination features absolute encoders, homing is not necessary before teaching points. Incremental encoders will require homing before teaching points.

In general, there are four ways to teach points:

1. Jog the actuator(s) into position via Teach Pendant or software, and then teach the point.
2. Turn the servos off, move the actuator(s) into position manually, then teach the point.
3. Manually enter data into the point table via the Teach Pendant or software, then save it back to the controller.
4. Enter data into the controller via serial communication from a PLC or Industrial PC.

Once the position data is entered into the point table it will reside in the memory of the controller as long as the lithium battery lasts within the controller. (Note: SEL E/G, A/B, DS, SCARA have a battery. The SEL F/H and Robo Cylinder Controllers have Flash ROM and do not need a battery).

If the controller is powered up constantly, the battery is never used as the memory has constant power applied. Once power is dropped, the battery goes into backup mode.   Due to this method of operation, the life of the battery, and in turn, the life of the point data, programs and parameters, depends directly on how long the controller is powered down.

Teaching Points on the SCARA

The SCARA system works in a different manner where teaching points is concerned.  The encoders on the SCARA servos are absolute encoders, which require no homing upon power up under normal working conditions.  The encoder information is retained as long as the encoder battery is not fully depleted or disconnected for an extended period of time.

Before teaching points with the SCARA, the servos must be turned on in order to update the controller with the current encoder information. The controller, upon power up or after Estop, will come up with encoder information that is "default", and not the actual encoder position.

After the servos are turned on, the controller will have updated encoder information, and teaching points can be done as per usual.