User`s manual

Configuration
GFK-1742A Chapter 4 Configuration 4-13
4
configured to allow this. With this ratio, one user unit would represent .01 millimeters. 2540 user
units would represent 25.40 millimeters (one inch) of travel.
The example below illustrates how to meet the requirements that the User Units and Counts values
be within the range of 1 to 65,535, and the User Units to Counts ratio be within the range of 8:1 to
1:32.
The basic equation we need to satisfy is:
User Units (Load Movement per Motor Rotation)
÷
(Desired User Units Resolution)
Counts
=
Encoder Counts per Motor Rotation
The numerator and denominator must each fit within the RANGE limits. The reduced fraction
must fit between the RATIO limits. The decimal point is always implied, not used. The User
Units to Counts ratio is always expressed as an integer ratio.
Example Application
Use the User Units to Counts ratio to configure the DSM314 so you can program in engineering
units rather than encoder counts. As an example, assume a machine has a motor with a motor-
mounted quadrature encoder connected through a gear reducer to a spur gear. The spur gear is
mounted to the end of a pinch-roller shaft. The pinch roller feeds sheet material for a cut-to-length
application. The motion program will specify the length of cut sheets. The programmer wishes to
program in 0.01-inch resolution.
The following data is given:
•
2000 line encoder (x4 = 8000 counts per encoder revolution)
•
20:1 gear reduction
•
14.336 inch pitch diameter spur gear
•
Inch desired programming unit (.01)
Although several approaches are possible, the most straightforward is to base the
calculations on a single spur gear revolution.
1. First determine the number of User Units per spur gear revolution:
14.336 inch pitch diameter *
π
(pi) = 45.0378 inches circumference
45.0378 inches / 0.01 inch desired programming units = 4503.78 User Units per
revolution of spur gear
2. Then determine the number of encoder counts per spur gear revolution:
4 counts 20 motor revs.
2000 lines *
line
*
1 gear rev.
=
160,000 encoder counts
per spur gear revolution
3. Then check the value of the User Units to Counts ratio. The ratio must be in the 8:1
to 1:32 ( 8 to 0.03125) range and the two numbers must be in the 1 to 65535 range.
4503.78 User Units / 160,000 encoder counts = 0.02815 or 1:35.5