Rockwell Automation 1746-BLM Blow Molding Module Installation Instructions - Manual (Page 15)

Blow-molding Module 15
Publication 1746-IN014B-EN-P - January 2001
Monitoring Mandrel Position
Instantaneous mandrel position may be monitored by reading the current process
variable from the module’s input file. Several other values of interest are also
available for each axis (e.g. control output, profile step, etc.). Process variable
profiles may be read from the module’s M1 file.
Controlling Ram Velocity
Accumulator ram velocity is controlled in position-based mode by specifying ram
velocity as a function of ram position. As with mandrels, rams are calibrated for
zero-scale and full-scale positions. Velocity is then expressed as velocity = change
of position/millisecond. By convention, the fully-forward ram position is the
zero-scale calibration point, while the fully-retracted ram position is the full-scale
calibration point. This implies that negative velocities result in moving the ram
forward.
Velocity can be controlled in either open loop or closed loop. You select
closed-loop velocity control by setting the appropriate axis’ velocity-control bit in
the module output file. Since hydraulic valves generally provide a constant
hydraulic flow with a constant command input, setpoints in open-loop mode
inherently specify velocity. Once closed-loop velocity control is enabled, hold value
#2 is interpreted as shotsize, and the axis’ step synchronization output is enabled as
an at-shotsize indicator.
Operation by Controlling Ram Velocity
Normally, ram velocity is controlled in closed loop using a single module analog
I/O pair. A velocity profile (as opposed to a position profile) is necessary since the
independent axis is the ram position. The remaining three analog I/O pairs are
available for controlling machine heads.
Operation by Monitoring Ram Velocity
This mode of operation is identical to operation with ram velocity control, except
ram position is monitored only (a velocity profile for the ram is not used). You can
control up to three machine heads per 1746-BLM. The resulting unused analog
output is available for general (open-loop) use.