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Gas-assisted injection molding (GAIM) is a process modification that promises big returns by reducing major costs associated with manufacturing plastic parts. Nitrogen is an inert, dry, non-toxic and odorless gas; its ability to contact melts at high temperatures – without introducing oxidation or splay – makes it an ideal candidate for GAIM. With GAIM, the purity of nitrogen gas required for clean part production varies, based on the polymer type and additive package used.
Linde offers a complete nitrogen GAIM package. Our specially trained application engineers can help design a turn-key operation that’s perfect for your use. Linde supplies cylinder gas to get you started and works with you as you grow.
Linde never stops developing new technologies and equipment that improve the injection molding process and offer customers a competitive edge.
GAIM with Reversed Inner Cooling
During the standard GAIM process, material is melted and injected into a cavity mold. As the melt begins to solidify, the area in contact with the mold walls hardens first. Nitrogen gas is then injected into the melt, pressurizing it from the inside out and pushing the molten material against the contours of the cavity. Upon sustaining an adequate material cure, the nitrogen is vented, the mold opened and the part ejected.
This process allows control of the melt flow, increased dimensional accuracy, reduced resin consumption and shortened cooling and cycle times.
Linde has added an additional step, creating GAIM with reversed inner cooling (PDF 197 KB). Here the already-available high-pressure nitrogen normally used in GAIM flows back through the product and cools the product from the inside. (To facilitate this, a second injector and a gas switch-over module must be installed.)
GAIM with reversed inner cooling offers several advantages:
Shorter cycle time (up to 30%)
Higher measurement accuracy
Low investment cost
Less clogging of piping by plastic residues
DESY 300/100 GAIM Supply System
With the PRESUS booster system liquid nitrogen is compressed up to 4700psi (325 bar) and sent into a high-pressure vaporizer. For pressure requirements over 4000psi, an additional low-energy consumption booster can be used.
The advantages of this system include:
Very low energy requirements, due to cost-effective liquid compression
Pumps exactly the quantity of nitrogen required by the user, even when strong demand fluctuations occur
Consistently high-quality output, because of the very pure and oil-free nitrogen
Injection Molding with CO2 Spot-Cooling
Uniform temperature distribution on the cavity surface is crucial to high-quality mold-injection results and short cycle times. Conventional water-cooling of long, thin cores or other difficult-to-access areas leads to severe problems:
Unwanted pressure losses
Surface defects on output
Long cooling times
CO2 spot-cooling technology is used with water cooling, and is applied to mold sections where conventional water cooling is not feasible. Liquid CO2 flows under high pressure (approx. 60 bar) through small and flexible capillary tubes (outer diameter, 1.6 mm) exactly to where cooling is required. The CO2 expansion cools the mold, and the newly gaseous carbon dioxide leaves the cavity through exhaust channels.
Advantages of CO2 Spot-Cooling
The use of liquid carbon dioxide (PDF 162 KB) to efficiently cool mold hot spots (e.g., very thin parts, small cores and areas with material accumulations) can result in enormous cooling time reductions and quality improvements. Its advantages include:
Effective cooling of mold hot spots
Shorter cycle times (50% or more), because of enormous shortening of cooling times
Very narrow areas of the mold can be cooled
Even temperatures over the whole part
Separate cooling of thick-walled areas feasible
Existing molds can be retrofitted
Linde can perform a thermal analysis of your existing molds, calculate CO2 consumption, design and engineer CO2 cooling, and provide support for demos and system start-up. Contact Us to discuss how we can help.