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Chapter 10
Tuning Considerations
for Production Parts
Profile Requirements
10-8
In this section, we discuss the usage and effect of the following items:
Profile Requirements
Cushion, Shot Size, and Transition Setpoints
Unselected Valve Set-output Values
Logical Bridges and End-of-profile Set-output Values
Decompression Pullback
Acceleration and Deceleration Ramp Rates
Watchdog Timer and Profile Offsets
Pressure Alarm Setpoints
Pressure-limited Velocity vs. Position Profile
Expert Response Compensation
We assume you are familiar with conventions, terminology, and procedures
used in the Injection Molding Industry and in this manual.
A profile is a series of position (or time) and pressure (or velocity)
setpoints which uniquely define a phase of the injection molding process
for a given part. The complexity of the profile depends on your machine
and the part you want to mold.
Velocity Setpoints
Use velocity setpoints only for the injection velocity vs. position profile to
control the fill rate of various mold cavities with repeatability.
Do not be concerned if the reported velocity in the first segment of your
velocity vs. position profile does not match its setpoint. For example, the
velocity of the first segment could:
Undershoot if you programmed a short length or time. It takes time for
the hydraulics to overcome the inertia of the injection cylinder and
accelerate the ram (screw) to desired velocity.
Do NOT increase velocity gain constants to compensate. Excessive
gain may de-stabilize the velocity loop during the rest of the profile.
Overshoot if you configured a large post-decompression pullback after
plastication. The ram (screw) sees little resistance pushing plastic over
the post-decompression distance until the plastic reaches the mold gate.
Do NOT decrease velocity gain constants to compensate. Too little gain
may cause the velocity loop to be sluggish during the rest of the profile.
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