Nitrogen for Injection Molding and Film Extrusion Plants
Nitrogen Generator for Plastic Injection Molding
On-site nitrogen for gas-assist injection molding (GAIM), film extrusion, and resin moisture protection. Dry, inert nitrogen delivered to the molding machine at typical 150 to 175 PSI feed pressure, with a dewpoint of negative 40 degrees Fahrenheit.
Purity range available
Typical molding-machine delivery pressure
Typical payback
Service life
Plastic injection molding uses nitrogen in three roles. In gas-assist injection molding (GAIM), high-pressure nitrogen is injected into the molten polymer to displace material from the part core, hollow out thick wall sections, pack out sink marks, and reduce part weight and cycle time. In film extrusion and blown-film lines, dry nitrogen inerts the resin path and, on oxygen-sensitive resin grades, pressurizes the film bubble to keep oxygen off the inside surface. In resin handling and drying, dry nitrogen blankets hoppers and dryer purge cycles so hygroscopic engineering resins do not absorb moisture between drying and the screw.
Gas Generation Solutions designs on-site nitrogen systems for injection molding plants and film extrusion lines. Engineering resins, medical-grade molding, and gas-assist on quality-critical parts typically run nitrogen at 99% to 99.9% purity, which is the tier where surface and structural quality drive yield. Our PSA and membrane systems cover the full 95% up to 99.9995% range when the same generator also feeds adjacent processes on a shared nitrogen header. In business since 1979, we serve injection molders, film extruders, medical-device manufacturers, automotive component plants, and consumer-product producers across the United States, Mexico, and Canada.
Below, we cover where nitrogen acts in the GAIM cycle, the defects it prevents, purity tiers and technology choice, system sizing at 150 to 175 PSI typical delivery, and payback economics.
Customer install and sample parts
GGS nitrogen for plastic injection molding plants
A skid-mounted system at a customer molding plant, plus sample molded parts produced under on-site nitrogen.
How nitrogen acts in GAIM
Where nitrogen acts in the gas-assist injection molding cycle
Gas-assist injection molding (GAIM) is the headline use of nitrogen in plastic injection molding. The same on-site generator also feeds film extrusion bubble pressure and dry-blanket resin handling on lines that run sensitive engineering resins.
STEP 1
Mold closes and the polymer shot starts
The mold clamps and the screw injects molten polymer into the cavity. In GAIM, the polymer shot is sized so that the cavity is partially filled, leaving room for nitrogen to displace material and form internal channels. Conventional injection molding fills the cavity completely; GAIM does not.
STEP 2
Nitrogen injects into the molten polymer core
High-pressure nitrogen is introduced through a gas pin or gas needle in the mold or through the nozzle. The gas follows the path of least resistance through the still-molten core of the part, displacing polymer outward to fill the rest of the cavity and forming hollow channels in thick wall sections.
STEP 3
Nitrogen holds pressure as the part cools
Nitrogen pressure is held inside the part during cooling. The internal gas pressure replaces the packing pressure of conventional injection molding, so the part cools against the mold wall under uniform pressure. This packs out sink marks at thick sections and reduces internal stress in the finished part.
STEP 4
Nitrogen vents and the part ejects
Before the mold opens, nitrogen pressure is released back through the gas pin or vented from the part. The mold opens and ejects a part with hollow internal channels that would not be moldable as a solid section. Cycle time is typically shorter than the equivalent solid molding because the part cools against the mold wall instead of through a thick polymer core.
Other places nitrogen shows up in a molding plant: In film extrusion and blown-film lines, dry nitrogen inerts the resin path and, on oxygen-sensitive resin grades, pressurizes the film bubble to keep oxygen off the inside surface. In resin handling, dry nitrogen blankets hopper space and dryer purge cycles so hygroscopic engineering resins (nylon, PC, PET, PEEK, PEI) do not pick up moisture between drying and the screw. The same on-site generator can feed all three uses through a shared nitrogen header.
Why nitrogen at the molding machine
What dry, inert nitrogen prevents in plastic injection molding
Nitrogen earns its place in the molding plant by addressing four distinct quality and cost problems that come up across gas-assist molding, film extrusion, and engineering-resin handling.
Sink marks and voids on thick sections
Conventional packing pressure cannot reach the core of a thick wall before the surface freezes off, leaving sink marks on the outside and voids inside. In GAIM, nitrogen pressure inside the part packs from the inside out and replaces the missing volume with a hollow gas channel, so thick sections finish flat and dimensionally correct.
Splay, silver streaking, and surface defects from wet resin
Hygroscopic resins (nylon, PC, PET, ABS) absorb moisture from ambient air. Moisture in the melt outgasses at process temperature and shows up as silver streaks, splay, surface defects, or weak weld lines. A dry nitrogen blanket on the dryer and the hopper between drying and the screw keeps moisture out of the resin path.
Polymer oxidation at high process temperatures
Engineering resins such as PEEK, PEI, PPS, and certain medical-grade polymers run at melt temperatures where oxygen contact during melt residence drives polymer chain scission, discoloration, and loss of mechanical properties. Inert nitrogen in the resin handling and feed path keeps oxygen out of the high-temperature zone.
Cycle time and material cost on heavy-wall parts
A solid thick-wall part has to cool through its entire cross section before ejection. Hollowing the core with nitrogen in GAIM removes material from the slowest-cooling region, so cycle time drops, and a part that previously had to be designed thick for stiffness can use less polymer per shot without losing structural performance.
Purity and technology
Match purity to the resin and the role nitrogen plays
Engineering resins, medical-grade molding, and gas-assist on quality-critical parts typically run nitrogen at 99% to 99.9%. That tier is the one where surface and structural quality drive yield. Lower-purity nitrogen works for general gas-assist on commodity resins; higher-purity nitrogen serves a narrower set of specialty molding applications.
Engineering and medical molding
99% to 99.9%
Engineering resins, medical-grade, GAIM on quality-critical parts
- Gas-assist injection molding (GAIM) on visible structural parts
- Engineering resins such as nylon, PC, PET, ABS
- Medical-device molding and consumer-product housings
- Film extrusion on oxygen-sensitive resin grades
- PSA system at this purity range
Lower-cost tier
95% to 99%
General gas-assist on commodity resins
- GAIM on commodity polypropylene or polyethylene parts
- Basic film extrusion bubble pressure with non-sensitive resins
- Hopper and dryer blanket on standard commodity grades
- Lowest cost per cubic foot of generated nitrogen
- Membrane or low-purity PSA
Specialty tier
99.99% to 99.9995%
High-purity engineering plastics and downstream high-purity feed
- High-temperature engineering polymers such as PEEK, PEI, PPS
- Cleanroom medical molding with tighter ppm-level oxygen limits
- Plant also runs reflow soldering or metal 3D printing on the same supply
- PSA with carbon polishing or specialty filtration
PSA versus membrane for plastic injection molding
Choose membrane when
- Purity needed is 95% to 99%
- Steady-state demand for hopper blanket or basic GAIM on commodity resins
- Lowest capital cost is the priority
- The plant has limited footprint or simpler maintenance is preferred
Choose PSA when
- Purity needed is 99% or higher
- Engineering resins, medical-grade molding, or GAIM on visible structural parts
- Customer wants room to grow into 99.9% or 99.99% later
- Multiple molding machines or shared header with other plant processes
Sizing and economics
Right-size the generator before you buy
A molding-plant nitrogen system is sized to the gas demand at the molding machine, the purity required by the resin and the role nitrogen plays, and any other points in the plant that share the same nitrogen header. We measure actual flow before we recommend a size.
Three things we ask for sizing
Per-machine flow demand
Flow at the molding machine depends on press tonnage, shot size, GAIM gas channel volume, cycle time, and how many machines run concurrently. We use measured flow data from a free wireless flow meter rental on your existing gas line to size the generator to your actual demand instead of nameplate estimates.
Purity required by resin and use
Engineering resins, medical-grade molding, and gas-assist on quality-critical parts typically run nitrogen at 99% to 99.9%. If the plant runs high-temperature engineering resins, medical-grade molding, or shares the nitrogen header with reflow soldering or metal 3D printing, we size the generator to the highest-purity demand on the header.
Delivery pressure to the molding machine
Most molding machines and GAIM units take a 150 to 175 PSI nitrogen feed. Some GAIM systems have an on-machine pressure intensifier that boosts the feed for the actual gas-injection pressure at the gas pin. Tell us the pressure at the inlet and the run length from the generator and we will size the receiver and piping to hold pressure during peak draw.
Payback economics
Cost reduction vs. delivered cylinders, dewars, and bulk liquid nitrogen
Typical payback for a multi-shift molding plant
Service life with sealed sieve beds and routine maintenance
Not sure what your molding machines actually pull? Rent a flow meter free
We rent wireless data-logging flow meters at no cost. Install on your existing nitrogen line for a week and get an exact SCFH-by-shift profile before sizing.
Frequently asked questions
What purity of nitrogen is needed for plastic injection molding?
Engineering resins, medical-grade molding, and gas-assist injection molding (GAIM) on quality-critical parts typically run nitrogen at 99% to 99.9% purity. Sensitive engineering resins like nylon, PC, PET, and ABS sit in this tier. General gas-assist on commodity polypropylene or polyethylene parts can run on 95% to 99% nitrogen at lower cost. High-temperature engineering polymers such as PEEK, PEI, and PPS, plus cleanroom medical molding with tighter ppm-level oxygen limits, run at 99.99% to 99.9995%. Our PSA and membrane systems cover the full 95% up to 99.9995% range and are sized to the highest-purity demand on the same nitrogen header.
What is gas-assist injection molding (GAIM) and why does it use nitrogen?
Gas-assist injection molding is an injection molding process where high-pressure nitrogen is injected into the molten polymer through a gas pin or gas needle. The nitrogen displaces material from the part core, forms hollow channels in thick wall sections, packs out sink marks, and reduces internal stress. Cycle time drops because the part cools against the mold wall instead of through a thick polymer core, and material per shot drops because the core is hollow. Nitrogen is used because it is inert, dry, available on demand from an on-site generator, and does not introduce moisture, oxygen, or combustion risk to the molten polymer.
What pressure does the nitrogen feed need for plastic injection molding?
Most plastic injection molding machines and gas-assist injection molding (GAIM) units take a 150 to 175 PSI nitrogen feed at the inlet. The actual gas-injection pressure inside the part is typically much higher; many GAIM systems include an on-machine pressure intensifier that boosts the feed pressure to the working pressure at the gas pin. We size the generator to deliver the 150 to 175 PSI feed reliably and let the molding-machine intensifier handle the boost. Generator output pressure ranges from 75 PSI up to 6,000 PSI across the product line, so other pressure requirements are also supported.
Why does dewpoint matter for plastic injection molding?
Hygroscopic resins (nylon, PC, PET, ABS, and most engineering polymers) absorb moisture from the air. Moisture in the melt outgasses at process temperature and shows up as silver streaks, splay marks, surface defects, weak weld lines, and in some cases hydrolytic degradation of the polymer chain. A dry nitrogen blanket on the resin dryer and the hopper space between drying and the screw keeps moisture out of the resin path. Our nitrogen generators deliver dry nitrogen with a dewpoint of negative 40 degrees Fahrenheit, which is well below the dewpoint required for any standard injection molding application.
Can on-site nitrogen replace delivered cylinders, dewars, or bulk liquid nitrogen for a molding operation?
Yes. Molding plants running multi-shift presses typically save up to 90% on nitrogen cost by switching from delivered gas to on-site generation. Cylinders run roughly $6 to $10 per CCF, dewars run $4 to $6 per CCF, and bulk liquid nitrogen runs $0.50 to $1.50 per CCF before boil-off losses. On-site generation lands at $0.05 to $0.15 per CCF depending on local power cost. Payback is typically 12 to 14 months.
How much does a nitrogen generator for plastic injection molding cost?
Pricing scales with flow, purity, pressure, and any custom requirements. Single-machine molding plants with one shift typically start near $15,000. Multi-machine molding operations with continuous GAIM nitrogen and shared resin-blanket supply usually run $40,000 to $150,000. Large facilities feeding multiple molding machines, film extrusion lines, and other plant processes from the same generator reach $200,000 to $500,000. Payback is typically 12 to 14 months across system sizes.
Should I use PSA or membrane for plastic injection molding?
Membrane is a strong fit when purity needed is 95% to 99% and demand is steady, because capital cost is lower and there are no sieve beds to maintain. PSA is the right choice when purity needed is 99% or higher, when the plant runs engineering resins or medical-grade molding, when GAIM is used on visible structural parts, or when multiple molding machines or other plant processes share the same nitrogen header. We quote both technologies on most molding projects and recommend the one that fits the resin, the role nitrogen plays, and the rest of the plant.
How do I find out what size generator my injection molding plant needs?
Start with the per-machine flow rate at the GAIM unit or molding machine inlet, the number of machines running concurrently, and the duty cycle. If the same nitrogen also feeds film extrusion bubble pressure, dryer and hopper blanket supply, or other plant processes, list those flow rates and target purities. We provide free wireless flow meter rental to measure actual consumption over a representative period. Email your equipment specs and any measured flow data for a same-day quotation. Call 760-505-1300.