Rockwell Automation 1746-BLM Blow Molding Module Installation Instructions - Manual (Page 14)

14 Blow-molding Module
Publication 1746-IN014B-EN-P - January 2001
Step: 3 Module operation with an accumulator machine
Position-based Operation
In position-based mode, setpoint profiles are specified as a function of the position
of a second, independent axis position. Here the independent axis corresponds to
the accumulator ram position, while the dependent axis corresponds to mandrel
position (or ram velocity).
Conceptually, the shot size of the independent axis is divided into 256 segments.
When the accumulator ram position falls within the range of a particular segment,
the number of that segment is used as an index into the setpoint profile to
determine the current setpoint for the mandrel position (or ram velocity).
Controlling Mandrel Position
Static control: Mandrel position may be controlled statically by means of the three
axis-hold values and corresponding hold-value control bits accessible via the
module output file. The hold values are prioritized with hold value #0 being highest
priority and hold value #2 being lowest.
In absence of an active profile, the highest priority enabled hold value becomes the
position setpoint. By convention, the fully-closed mandrel position is the zero-scale
calibration point, while the fully-open mandrel position is the full-scale calibration
point.
Dynamic control: Mandrel position may be controlled dynamically by
downloading a setpoint profile to the module’s M0 file and setting the profile
enable bit. Then, upon detecting the independent axis position at shot size, the
module will automatically update the mandrel position once per millisecond
through the last profile setpoint.
The last setpoint is maintained until all of the following are complete:
•
profile enable bit is cleared
•
independent axis is again at shot size
•
profile enable bit is set again, which starts the next profile
IMPORTANT
Although you may specify profile sizes less than 256 in the
config file, the module expands these to 256-point profiles
after downloading from shared memory. Internally to the
module, all profiles are 256 points in length. Similarly, process
variable profiles are compressed from the module’s 256-point
internal representation to your desired profile size prior to
uploading.