Rockwell Automation 1771-QDC, D17716.5.93(Passport) PLASTIC MOLDING MODULE - Manual (Page 252)

Tune Your Machine
Chapter 10
10-24
High speed ejector operation while meeting the above objectives.
Molders want to achieve minimal machine cycle time while insuring
part quality, achieving repeatable ejector advance positioning, and
positive part ejection.
Profile Requirements
A profile is a series of position and pressure (or velocity) setpoints which
uniquely define a phase of clamp or ejector motion. The complexity of
the profile depends on your mold, clamp, and ejector mechanism. Next
we discuss required setpoints.
Velocity Setpoints for Clamp and Ejector Profiles
In general, choose velocity setpoints to move the clamp and ejector quickly
without damaging the machine, mold, or parts. Because of the clamp’s
large dynamic load, be very careful if you configure the clamp to operate at
high speeds because once accelerated, the moving platen/mold
combination is extremely difficult to stop in a short period of time.
When configuring velocity profiles:
Start with relatively low velocity setpoints.
Increase them in small increments while observing clamp motion and
repeatability at critical positions in the cycle.
Because of the inertia and momentum of moving large masses, remember:
Unless the first clamp close/open profile segment is of long duration,
actual velocities generally will undershoot setpoints. It takes time for
the hydraulics to overcome the clamp’s inertia and build adequate
pressure and flow to accelerate the clamp to the requested velocity.
Actual velocities of your second and/or third clamp close/open profile
segments generally will overshoot setpoints. Overshoot increases with
higher velocities. Once the platen/mold combination gains momentum,
it is difficult to slow it to the requested velocity.
Low Pressure Close (LPC) Pressure Setpoints
In general, use LPC pressure setpoints low enough to let obstructions (such
as sprues or un-ejected parts) resist mold closure and halt clamp movement
before the clamp reaches the mold-safe position. Use the low pressure
close watchdog timer to signal the PLC-5 processor that a mold-protection
fault has occurred.