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6-10 Operation
MN1928
6.4.2 Selecting a scale
Mint defines all positional and speed related motion keywords in terms of encoder quadrature
counts (for servo motors) or steps for stepper motors. The number of quadrature counts (or steps)
is divided by the
SCALEFACTOR
allowing you to use units more suitable for your application. The
unit defined by setting a value for scale is called the
user unit
(uu).
Consider a servo motor with a 1000 line encoder. This provides 4000 quadrature counts for each
revolution. If
SCALEFACTOR
is not set, a Mint command that involves distance, speed, or
acceleration may need to use a large number to specify a significant move. For example
MOVER(0)=16000
(Move Relative) would rotate the motor by 16000 quadrature counts - only
four revolutions. By setting a
SCALEFACTOR
of 4000, the user unit becomes revolutions. The
more understandable command
MOVER(0)=4
could now be used to move the motor four
revolutions.
The same concept applies to stepper motors, where the scale can be set according to the number
of steps per revolution. Typically, this would be 200 for a motor with a 1.8° step angle, or 400 if
driven in half step mode. By setting a
SCALEFACTOR
of 200 (or 400 if driven in half step mode),
the user unit becomes revolutions.
In applications involving linear motion a suitable value for
SCALEFACTOR
would allow commands
to express values in linear distance, for example inches, feet or millimeters.
1. In the Toolbox, click the Parameters icon.
2. Click the Scale tab.
3. Click in the Axis drop down box to select the
axis. Each axis can have a different scale if
required.
4. Click in the Scale box and type a value.
5. Click
Apply
.
This immediately sets the scaling factor for
the selected axis, which will remain in the
NextMove ES until another scale is defined
or power is removed from the NextMove ES.
See section 6.11 for details about saving
configuration parameters.
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