Page 66 - Plastics News October 2024
P. 66
TECHNOLOGY NEWS
the higher you heat, the longer you need to wait
for the material to cool down.
Also, it is important to pay attention to variables
such as HDT and thermal conductivity. HDT is
the Heat Deflection Temperature, and it basi-
cally tells you how soon you may eject the part
out of the mold; the higher the HDT, the faster
your cycle time.
The same happens with thermal conductivity.
While polymers are inherently quite good at iso-
lating heat, you may find differences between
grades when it comes to the ability of the ma-
terial to transfer heat to the mold. So, you will
always want to choose a material with higher
thermal conductivity. This will shorten your cycle
time and therefore reduce energy consumption
associated to tempering in the mold.
Parametrization is The Key optimize.
The past couple of years I have been working Reducing speed in injection molding allowed to
with companies in the optimization of the mold- reduce the peak in energy consumption in this
ing process. A tool able to measure the energy region. When the screw run backwards, the en-
consumption at each step of the process has ergy was reduced by a proper combination of
proved to be very valuable at identifying poten- counterpressure and a progressive set up of ro-
tial improvement opportunities. tation speed.
The figure provided by Kern IoP demonstrates It was also evident that closing the mold too fast
energy consumption over cycle time for two dif- did not make a significant difference in cycle
ferent process setups. The curve shows all the time but it did on energy consumption. All these
process stages: closing the mold, volumetric in- optimizations where done using Kern IoP. The
jection, packing and holding, cooling and plas- resulting energy savings where 5,7%, without
tification, followed by mold opening. The area any modifications in material, mold or machine.
under each curve represents energy consump- Source – Plastics Engineering
tion over time, which serves as the parameter to
66 PLASTICS NEWS October 2024
