CO2: Cooler than nitrogen any day
When weight reduction isn’t the primary goal but the focus is on quality and cycle time reduction, Gas Injection Moulding (GIM) is increasingly used today. “For thick walled plastic parts like fridge handles, car door panels and bike racks, surface quality is important,” explains Andreas Praller, Senior Application Expert at the Linde Gases Division, “but without internal pressure in the mould, the plastic just shrinks, creating an unacceptable finish.”
In regular GIM, high-pressure nitrogen (50 to 340 bar) is used to ensure dimensional stability, but Linde’s PLASTINUM® Gas injection moulding solution takes efficiency to the next level by replacing gaseous nitrogen with liquid CO2. “CO2 can reduce cycle times by up to 30%,” explains Praller, “it has a much greater cooling potential than nitrogen due to its much higher density at typical GIM pressures.”
In fact, it performs at a comparable level to the more niche water injection moulding (WIM) in terms of heat removal capacity and cycle times. The difference is, it doesn’t leave any moisture on the products or tools, thus eliminating an additional drying step in the fluid injection cycle. “It’s the perfect solution for the best of both worlds” explains Praller.
CO2 is particularly beneficial where an automotive manufacturer wants to produce as many parts as possible with the same machine: “Switching from N2 to CO2 is very straightforward and can immediately increase your capacity due to reduced cycle times,” says Kirchpfening.