moulds | Temperature control
Cooling moulds with CO2
Industrial gases group Linde has developed a system for cooling
mould ‘hot spots’ using liquid CO2. Mikael Orsén, James Stanley and Andreas Praller explain how
Main image:
Integrating CO2 cooling into the thin central fi llet of this headlamp
housing mould cut cycle time
Water is a highly effective cooling medium for injection moulds. However, water cooling reaches its limits where the space for placement of cooling channels in the mould is restricted. Liquid carbon dioxide (CO2
) has
been used as an addition to existing water-based mould temperature control systems to effectively cool localised hot spots and, where properly applied, can result in dramatically shorter cycle times, improved quality, and lower cost. This article looks at work carried out by industrial gases group Linde in applica- tion of liquid CO2
in injection mould cooling. Injection moulding is a fast developing technology
that continues to push and exceed established limits in terms of part design and performance across a wide range of industrial markets, from medical and automo- tive through to packaging and construction. A common theme across all sectors, however, is the demand for higher quality and lower cost. That places intense demands on mould cooling technology. In most injection moulding applications, cooling
52 INJECTION WORLD | June 2014
accounts for the greatest part of the production cycle. Water-based cooling has proven a highly effective means of mould temperature control. However, in many moulds the overall cooling time is determined by localised areas of the mould - so-called hot spots - that cannot be cooled using water, or can only be cooled to an inadequate extent. Examples of such diffi cult-to-reach parts of the mould include long thin cores, fi llets, slides and ejectors. Even where it is possible to reach these challenging areas with water, good mould temperature control can be compromised by the risk of the neces- sarily thin water channels becoming clogged by deposits. Small cooling channel diameters can also cause high pressure losses in the cooling system. An alternative technology for cooling diffi cult-to-
reach hot spots is to use liquid carbon dioxide (CO2
addition to the existing water temperature control system. The system uses special CO2
time the injection of CO2 through stainless steel
capillary tubes inserted into small chambers in the metal of the mould (Figure 1). The chambers may be either drilled into the mould itself or may be formed by hollow core pins. The CO2
cooling technology has been adopted by an
automotive vehicle headlight manufacturer to overcome problems in moulding headlight housings (shown in the main image) using a two cavity-mould. The company was experiencing problems cooling the centre, thin mould fi llet. With no cooling in this area in the initial tool construction, the fi llet area heated up strongly
www.injectionworld.com ) in solenoid valves to
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