Jul 31, 2019
Water is mainly used as coolant in injection molding.
It is required as cold and hot water.
If a cooling device is not connected to an external water supply, but creates cold water through an internal module, the device is called autarkic temperature control.
In this case of self-sufficient temperature control, both the water replenishment and the cooling take place independently of an on-site cooling network.
With this double benefit, a mains-independent cooling and heating process with temperatures of 20 °C to 90 °C is possible.
Higher temperatures up to 400 °C are generated electrically.
Mostly mobile, the cooling and temperature control unit can be matched in its performance to the production process and stands next to the machine(s).
Temperature Control: Autarkic
temperature control with the
cooling system of the type STC.
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This glossary of plastic industry is provided by PLEXPERT Canada Inc.
Oct 6, 2019
Particularly important for the evaluation of the temperature on the mold surface is the knowledge about the temperature on the cavity
wall.
This temperature is called cavity wall temperature.
During continous production, the cavity wall temperature is higher than the mold temperature.
The reason for this is that the hot melt is in direct contact with the cavity wall during the injection time and heats up the cavity wall.
The temperature fluctuates during a cycle due to heating (injection phase) and cooling (cooling time).
The cavity wall temperature can be determined by special sensors mounted within the cavity wall.
Temperature control: The
mold surface
temperature measured in an 8-
cavity mold over time.
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This information and services are provided by:
This glossary of plastic industry is provided by PLEXPERT Canada Inc.
Jul 16, 2019
A coolant absorbs heat from the mold during the injection molding process. The transfer of the absorbed heat from one coolant to another heat transfer medium (like air, water, …) is done by a machine named heat exchanger.
Simplified, a heat exchanger allows the transfer of thermal energy from one heat transfer medium to another.
Heat exchangers are used whenever the needed temperature of a process is above the ambient temperature.
Default temperatures for injection molding are in between 30 °C to 80 °C.
Two basic types of heat exchangers can be distinguished:
1. Water-Air:
The absorbed energy will be released to the ambient air.
2. Water-Water:
The absorbed energy will be released to a secondary water circuit.
Aug 5, 2019
The flow behavior of a fluid is described by its type of movement.
A straight forward movement in separated layers with equal temperatures is called laminar flow.
A tube with Reynolds number lower than approximately 4000 will have this kind of flow behavior.
A coolant in injection molding with laminar flow will have its highest temperature near the mold wall.
The lowest temperatures will be found in the center of the cooling channel.
The fluid is heating up from the outside to the inside.
The mold will no longer cool down as soon as the outer layer of the coolant has absorbed the maximum amount of heat.
Because of the laminar flow there is no temperature exchange within the coolant.
The outer layer of the coolant stays hot.
This means that the coolant cannot sufficiently cool the mold anymore.
Therefore, laminar flow is not recommended for a coolant.
Sep 20, 2019
Like in the electrical engineering with cabels, the cooling channels in the injection mold may also have parallel connections.
There are two different possibilities to achive parallel cooling.
For the first one, the parallel connections are done directly next to the cooling device.
In order to have a flexible cooling of the mold, multiple cooling devices are needed.
However, sometimes there is only one cooling device available. In this case the flow rate of the cooling device is splitted up using a distributor block.
The second version of a parallel cooling can be found in the mold itself.
One cooling channel is split up in multiple parallel channels. Note that the same flow rate should be given through each of the channels otherwise the effectivity of the channel is reduced.
The advantage of parallel cooling is, that the channels are shorter and the starting situation is the same for each channel.
Especially for multiple cavity molds parallel cooling is a way where identical cooling can be reached for each cavity.
