Gas Assist Injection Molding: Linde's PRESUS™ N10
Product Announcement from Linde North America, Inc.
In the gas assist injection molding process (GAIM), nitrogen is injected under high pressure into the melted polymer that has not yet completely filled the mold. The gas displaces the melt from the core of the molded part and presses it against the cavity wall. This creates a void in the core of the part - the amount of material used and the molded part weight drop considerably. After solidification of the molded part, the gas is released.
Benefits of gas assist injection molding (GAIM):
• Improved product quality, specifically, better surface finish, no sink marks, less warpage, greater dimensional accuracy
• Shorter cycle time because of faster cooling
• Reduced clamping force requirement
Until now, the major problem with GIM has been compressing the gaseous nitrogen to high pressures economically and with a high degree of purity. This operation requires a great deal of energy and significant maintenance on the compressors. In addition, the oil lubrication in the compressors contaminates the nitrogen, reduces product quality and process reliability.
A suitable supply of high-pressure nitrogen significantly reduces the costs for injection molding. The pressure boosting system PRESUS™ N10, developed and patented by Linde, offers an interesting alternative to the traditional method of nitrogen supply.
PRESUS™ N10 compresses liquid nitrogen to a pressure of up to 300 bar. The liquid nitrogen then vaporizes in a high-pressure evaporator. Avery low energy consumption in combination with absolutely pure and oil-free gas are the main advantages of this system. In contrast to conventional cryo-pumps, the system automatically adjusts to the amount of gas used - even in the event of highly variable consumption. When higher pressures are needed (over 300bar), an auxiliary compressor that requires a small amount of energy can be added.