Comparison of Switchover Methods for Injection Molding. David O. Kazmer, Sugany Velusamy, Sarah Westerdale, and Stephen Johnston Plastics Engineering Department University of Massachusetts, Lowell Priamus Users Group Meeting September 30 th , 2008. Agenda. Motivation
Comparison of Switchover Methods for Injection Molding
David O. Kazmer, Sugany Velusamy, Sarah Westerdale, and Stephen Johnston
Plastics Engineering Department
University of Massachusetts, Lowell
Priamus Users Group Meeting
September 30th, 2008
Where is it going tocome from?
Attributes of highly productive molders
Switchover is the point at which the filling phase ends and packing phase starts
From a controls perspective, there is a switch in the system’s boundary conditions and stiffness
Various methods for switchover:
Tie Bar Deflection
Other studies have been conducted.
This study is more comprehensive with respect to number of methods and also long term variation.
Seven Switchover Methods
Tensile Cavity Pressure
Six Measured Attributes
Impact Thickness (mm)
Impact Weight (g)
Impact Width (mm)
Tensile Thickness (mm)
Tensile Weight (g)
Tensile Width (mm)
100 consecutive molding cycles were monitored & data acquired
The average & standard deviation was calculated to measure of short term variation
Switchover values for each method were determined to provide same part weight
DOE performed to impose long term variation
Good process robustness
Very poor process robustness
Good process robustness
Best process robustness
Different switchovers are best for different attributes
Short Run Variation (%)
Long Run Variation (%)
Cavity temperature provided the most robustness against changes the process settings.
Place the sensor near but not at the very end of flow due to small control system delays (speed matters)
Cavity pressure provided reasonable switchover control but had susceptibility to changes in melt temperature and velocity.
Position control provided reasonable control but roughly twice the variation of cavity temperature.
Injection time is the least reproducible method for the transfer from fill to pack, with literally 10 times the variation of temperature control.
In-mold instrumentation is vital to achieving process robustness, automatic quality control, and competitiveness.
National Science Foundation grant numberDMI-0428366/0428669
Priamus System Technologies