User guide

Chapter 6. Following 197
NOTE DEFINE SCALING FIRST NOTE
If scaling is desired within a stored program, you must enable scaling (SCALE1) and define the
scaling factors (SCLA, SCLV, SCLD, & SCLMAS) prior to defining (DEF), uploading (TPROG), or
running (RUN) the program. This allows the 6000 Series product to store, display, and execute
the scaled distance, acceleration, and velocity values within the stored program. This can be
accomplished by defining all scaling factors via a terminal emulator just before defining or
downloading the program; or you can put the scaling factors into a startup (STARTP) program
(stand-alone controllers only) or a program that must be run prior to defining or downloading
the program.
NOTE FRACTIONAL STEP TRUNCATION NOTE
If you are specifying master distance values (FOLMD), when the master distance scaling
factor (SCLMAS) and the distance value are multiplied, a fraction of one step may possibly be
left over. This fraction is truncated when the distance value is used in the move algorithm.
This truncation error can accumulate when performing several moves over the specified
master distance. To eliminate this truncation problem, set the master scale factor (SCLMAS) to
1, or a multiple of 10.
Example
Distance Scaling
Scenario
Typically, the master and slave scale factors are programmed so that master and slave units are
the same, but this is not required. Consider the scenario below as an example.
The master is a 1000-line encoder (4000 counts/rev post-quadrature) mounted to a 50 teeth/rev
pulley attached to a 10 teeth/inch conveyor belt, resulting in 80 counts/tooth (4000 counts/50
teeth = 80 counts/tooth). To program in inches, you would set up the master scaling factor
with the SCLMAS8ØØ command (80 counts/tooth ∗ 10 teeth/inch = 800 counts/inch).
The slave axis is a servo motor with position feedback from a 1000-line encoder (4000
counts/rev). The motor is mounted to a 4-pitch (4 revs/inch) leadscrew. Thus, to program in
inches, you would set up the slave scaling factor with the SCLD16ØØØ command (4000
counts/rev ∗ 4 revs/inch = 16000 counts/inch).
Finding the Scale
Factors
If the SCLD (slave) and SCLMAS (master) scale factor values are not immediately obvious, use
the procedure below for help.
Slave (applicable to servos, and steppers with encoder feedback):
1. Disable scaling with the SCALEØ command.
2. Servos: Issue the TFB command to display the position (based on the active feedback
source).
Steppers: Issue the TPE command to display the encoder position.
Write down this value for later comparison.
3. Making sure the feedback device is monitoring movement of the slave, move the slave
a known distance in the desired units. For instance, if you want to program in 5-inch
units, move the slave 5 inches. This could be done in the jog or joystick modes, or
perhaps by disabling the drive (DRIVEØ) and physically moving the slave.
4. Issue the position status command (TFB or TPE) again. The difference between the
position values before and after the move, divided by the move distance in step 3, is the
value you should use in the SCLD command parameter.
Master:
1. Disable scaling with the SCALEØ command.
2. Issue the TPMAS command to display the position. Write down this value for later
comparison.
3. Move the master input a known distance in the desired units. For instance, if you are
going to follow the motion of a conveyor belt and you want to program in 6-inch
increments, move the conveyor 6 inches.
4. Issue the TPMAS command again. The difference between the TPMAS values before and
after the move in step 3, divided by the distance of the move, is the value you should
use in the SCLMAS command parameter.