Custom Gas Assisted Injection Molding Manufacturer in China
Specialized in nitrogen gas-assist tooling and production for automotive, appliance, electronics, and industrial parts. Cut material cost up to 40% with DFM, MoldFlow, and mass production under one manufacturer.
- Internal and external gas-assist tooling — internal for most applications
- Nitrogen control: 2,000–5,000 psi, 99.9% purity
- HASCO/DME export-grade mold standards
- Presses from 90T to 3,300T, no MOQ
- Free DFM review in 48 hours
What Is Gas Assisted Injection Molding (And Why Most Projects Fail)
How Gas-Assist Molding Works in One Paragraph
Gas-assisted injection molding (GAIM) is a plastic injection process that injects high-pressure nitrogen into molten resin before it solidifies, displacing material in thick sections to form hollow channels. This reduces part weight, eliminates sink marks, packs resin against the cavity wall at constant internal pressure, and cuts material cost up to 40%. It is the standard process for handles, automotive trim, appliance housings, and large structural panels.
5 Pain Points That Kill Gas Assist Projects
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1
Dual-parameter sensitivity.
You're tuning shot size, melt temperature, gas delay, gas pressure, and hold time at once. A 0.2-second shift in gas timing scraps the shot.
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2
Gas blowout and fingering.
When gas pressure exceeds the strength of the plastic skin, nitrogen punches through the cavity wall — internal voids and visible defects on the A-surface.
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3
Trapped gas, burn marks, and short shots.
Inadequate venting compresses trapped air past the resin's degradation point, scorching the cavity surface or leaving incomplete fills.
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4
Asymmetric gas channels and warpage.
Gas follows the path of least resistance. Unbalanced channel volume produces uneven wall thickness and post-mold warp that cannot be tuned out at the press.
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5
Hidden tooling cost surprises.
Quotes that exclude the gas-assist controller, nitrogen unit, modified nozzle, or trial rounds turn into mid-project change orders.
After 20+ years building and tuning gas assisted injection molding tools — with customers in their 10th and 15th year of continuous work — our founder-led engineering team has fixed every one of these in real shots, not theory.
The next section breaks down how the four-step gas-assist cycle controls each defect.
How Gas Assist Injection Molding Works: 4-Step Process
Every gas assisted injection molding cycle runs four tightly synchronized stages. Miss the timing on one and the shot becomes scrap.
Short Shot (70–90% Mold Fill)
Molten resin fills 70%–90% of final part volume. Exact ratio depends on wall thickness, gas channel layout, and resin viscosity — tuned during MoldFlow analysis before any steel is cut.
Nitrogen Gas Injection (2,000–5,000 psi)
Before the polymer skin sets, high-purity nitrogen enters through the machine nozzle or gas pins built into the mold at 2,000 to 5,000 psi (138–345 bar). Pressure is matched to part geometry and resin grade.
Gas Core Formation
Pressurized nitrogen displaces molten plastic from thick sections into ribs, bosses, and end-of-flow areas. Resulting gas channels occupy 40%–60% of the original cross-section, leaving a uniform outer skin.
Pack, Cool, Vent & Eject
Internal gas pressure holds resin against the cavity wall through cooling — sink marks and shrinkage voids are eliminated. Gas is bled through a controlled vent path before mold opening, never released against the operator.
Knowing the cycle is half the work. The next module compares this process to conventional injection across eight engineering and cost dimensions — and clears up the most common misconception about whether gas-assist needs a special machine.
Gas Assisted Injection Molding vs Conventional: 8-Point Comparison
Eight engineering and cost dimensions, side by side — including the surface-quality difference you can see between a gas-assist part and a conventionally molded one.
| Dimension | Gas Assisted | Conventional |
|---|---|---|
| Wall thickness range | 1.5–4 mm + ribs/bosses up to 8 mm | 1.5–3 mm uniform |
| Sink marks on thick areas | Eliminated | Common defect |
| Cycle time on thick parts | Reduced 20–30% | Baseline |
| Required clamp force | Lower (smaller press possible) | Higher |
| Material cost | Down up to 40% (handles up to 70%) | Baseline |
| Surface finish on thick sections | Class A achievable | Sink-prone |
| Equipment | Standard press + N₂ unit + gas-assist nozzle | Standard press only |
Do You Need a Special Injection Machine? (No)
This is the most common misconception we hear from buyers new to gas assisted injection molding. You do not need a dedicated machine. A standard injection press, a nitrogen control unit, and a gas-assist nozzle is all the hardware required. The mold itself carries the gas channels and gas pins. Any of our 90T–400T presses configures for gas-assist within hours.
Internal vs External Gas Assist
Internal gas assist routes nitrogen through gas pins to hollow thick structural sections — handles, brackets, tubular geometries. This applies to most KTM customer programs.
External gas assist introduces gas between the part and cavity wall to press resin flat — used on large appliance panels and visible trim to remove sink on Class A surfaces.
Comparing gas assist with structural foam molding instead? Read our gas assist vs structural foam molding guide →
The next module quantifies the four engineering benefits this comparison hides — and puts a dollar figure behind each one.
4 Key Benefits of Gas Assisted Injection Molding
The business case rests on four measurable outcomes, documented across KTM production runs in automotive, appliance, and industrial parts.
Material Cost Reduction up to 40%
Hollow gas channels displace 40%–60% of volume in thick sections. Across our trim and handle programs, material savings range 10–40%, with one ABS automotive trim component reaching 38% weight reduction. Resin savings flow directly to your unit price.
Sink Marks Eliminated
Constant internal nitrogen pressure (2,000–5,000 psi) packs resin uniformly against the cavity wall. Thick ribs, bosses, and wall-thickness transitions that sink under conventional packing come out flat — even on textured A-surfaces.
Cycle Time Reduced 20%–30%
Hollow cores dissipate heat from the inside. Less mass to cool delivers cycle reductions of 20%–30% on thick-walled parts versus solid molding — a direct hit to per-part cost on long-running tools.
Lower Clamp Force = Smaller Machine
Internal gas pressure distributes load evenly. Parts that demand a 600T press in conventional molding often run reliably on 400T or smaller with gas-assist, lowering both your hourly machine rate and capital exposure.
Want to see which of these four numbers move most on your part? The industry breakdown below shows where gas-assist hits hardest by sector.
Industries We Serve with Gas Assisted Injection Molding
KTM ships gas assisted injection molding parts to OEMs across four industries. Each card reflects part categories we've molded and exported, with current destination markets.
Automotive Gas Assist Injection Molding
Interior trim panels, grab handles, seat structural members, mirror housings, HVAC vent components. Resins: ABS, PC/ABS, PA6, PA66+30% GF. Active programs to OEM and Tier-1 buyers in the USA, Mexico, Germany.
Home Appliance Gas Assist Molding (Handles & Housings)
Kettle handles, vacuum cleaner housings, refrigerator side panels, washing machine front frames. Gas-assist eliminates sink at wall-thickness transitions where conventional packing fails. Materials: ABS, PP, PA. Programs to USA, Mexico.
Electronics Gas Assist Molding
Printer enclosures, monitor housings, POS terminal shells, frames for industrial control panels. Gas channels routed under ribs preserve Class A faces. Resins: ABS, PC, PC/ABS. Exports to USA, Europe.
Industrial Gas Assist Components
Structural brackets, pipe fittings, irrigation manifolds, toolbox frames. PP, HDPE, and glass-filled grades for stiff, weight-sensitive parts. Active programs in Europe, Canada.
If your part fits one of these four categories, the closest reference build is in our case file. But before the cases — the engineering rules that decide whether your geometry is even shot-ready.
Gas Assist Injection Molding Design Guide & DFM Best Practices
Most gas-assist defects trace to geometry decisions made before steel is cut. The parameters below are the engineering envelope our DFM team verifies on every part we quote.
Wall Thickness Guidelines
Nominal walls 1.5–4 mm, uniform within ±10%. Thick sections targeted for gas channels run 6–12 mm. Abrupt transitions cause uneven gas penetration — taper at 3:1 minimum.
Rib & Boss Geometry
Ribs and bosses sized at 60%–80% of nominal wall thickness. Anything thicker becomes a sink risk in conventional injection but a gas channel candidate in GAIM. Boss-to-wall fillet radius minimum 0.5 mm to seat gas pins cleanly.
Gas Channel Layout
Channel diameter 2× to 3× nominal wall thickness. Routes must be symmetric across the part — gas seeks the path of least resistance, and asymmetry produces warpage that no press tuning can fix. Channel volume targets 40%–60% of the thick-section cross-section.
Pressure & Injection Timing
Gas pressure 2,000–5,000 psi, triggered at 70%–90% mold fill. Glass-filled grades (PA66+30% GF, PBT+GF) require pressures at the upper end and 5–8% more melt temperature than virgin resin.
Material Selection Matrix
| Resin | Use Case | Gas Pressure | Notes |
|---|---|---|---|
| ABS / PC-ABS | Trim, housings | 2,000–3,000 psi | Excellent surface |
| PP / HDPE | Industrial brackets | 2,500–3,500 psi | Forgiving process window |
| PA6 / PA66 | Structural handles | 3,000–4,500 psi | Dry resin to <0.2% moisture |
| PA66+30% GF | Load-bearing parts | 4,000–5,000 psi | Highest stiffness gain |
| PC | Electronics enclosures | 2,500–3,500 psi | Avoid clear grades |
| PBT | Connectors, structural | 3,000–4,000 psi | Watch shrink anisotropy |
Download Free Gas Assist DFM Checklist (PDF) — 12-point geometry audit our engineers run before quoting. Email-gated.
Download ChecklistThese rules drove every build in our case file — the four reference projects below show what the parameters look like on real parts.
Itemized Quote · No Hidden Fees · 24-48 Hours
Engineer-to-engineer reply within 12h. Upload STEP/STP/IGES.
KTM Gas Assist Capabilities & Why Source from China
KTM runs gas assisted injection molding tooling and production from a single Dongguan facility. Our founder leads the technical floor, English-speaking engineers handle direct OEM communication, and every step is documented for export buyers.
Injection Machines & Tonnage (90–3300T)
40 in-house injection machines from 90T to 400T, mixing FANUC and Haitian presses with robotic arms for 24-hour production. For larger parts, our qualified partner network covers 450T, 600T, 1,000T, 1,600T, 2,100T, and 3,300T — including dedicated nitrogen gas-assist setups and 2K two-shot machines.
Tool Steel & Mold Life Matrix
Steel selected against expected shot count: P20 (~300k shots), 718H (~500k), NAK80 (~500k, fine polish), H13 (1M+, high-temp resins), S136 (1M+, optical or corrosive resins), 2738 (mid-volume, pre-hardened). Material certificates and hardness reports ship with every mold.
HASCO & DME Mold Standards
Export tooling built to HASCO or DME on request — interchangeable components, standardized ejector layouts, documented BOM. North American and European production teams plug our tools into their presses without retrofit.
English Project Engineering Team & Founder-Led Technical
Our founder holds a degree in mold design and manufacturing and has run tooling floors for 20+ years. He still signs off on gas channel layouts and DFM reviews himself — this is a technical-led shop, not a sales-led one. Engineers reply to technical questions within 48 hours in English. Video calls are standard during DFM, T1, and PPAP.
Inspection & Quality Reports
CMM dimensional reports, SODICK mirror EDM verification, 2D projector measurement, hardness testing, full pin and ring gauge sets. Every shipment includes traceable inspection data — material certs, dimensional reports, and trial summaries on file under our ISO 9001 system.
Why Source from Dongguan, China
Dongguan is the densest tooling cluster in Asia. H13 and 718H steel, HASCO components, and standard mold bases are sourced within 24 hours. Customers cut tooling spend 40%–50% versus North American or European shops. Active gas assisted injection molding programs ship to the USA, Mexico, Costa Rica, Canada, and 12 European countries — including clients in their 10th and 15th year of continuous work with KTM.
The same equipment and engineering process produced the four gas-assist builds below.
Gas Assisted Injection Molding Case Studies
Each build below started with a defect or constraint conventional injection couldn't solve.
Case 1 — Automotive ABS Housing | Sink Mark Elimination | USA
- Problem:
- 6 mm reinforcement boss showed visible sink on Class A face
- Solution:
- Gas channel routed through boss center
- Process:
- Nitrogen at 2,800 psi, triggered at 82% fill
- Cycle:
- 50s · Tooling: 1×1 · Material: ABS
- Result:
- Sink eliminated at T2
Case 2 — Electronics PA6 Cover | Hidden Gas Channels | Europe
- Problem:
- Printer enclosure required flat Class A face with internal stiffening ribs
- Solution:
- Gas channels tucked under rib network — cosmetic surface untouched
- Cycle:
- 60s · Tooling: 1×2 · Material: PA6
- Result:
- Class A surface preserved, ribs hollowed for stiffness
Case 3 — Home Appliance Handle | 38% Weight Reduction | Mexico
- Problem:
- Washing machine grab handle in PA66+30% GF carried a 12 mm solid core
- Solution:
- Gas-assist hollowed core to 4 mm wall
- Cycle:
- 45s · Tooling: 1×2 · Material: PA66+30% GF
- Result:
- Part weight down 38%, no loss in pull-test load
Case 4 — Industrial PP Bracket | 29% Cycle Reduction | Europe
- Problem:
- Irrigation manifold bracket ran 92s in conventional injection
- Solution:
- Gas-assist hollowed structural ribs
- Cycle:
- 65s · Tooling: 1×4 · Material: PP
- Result:
- 29% faster cycle at the same press tonnage
Each build was quoted line-item before steel was cut. The next section explains how that quote is structured.
Gas Assist Injection Molding Cost & Pricing Transparency
Pricing on a gas assist project breaks into tooling, trials, and per-part molding. Here's what drives each line — and what triggers any change after the quote is signed.
Tooling Cost by Tool Steel Grade
Approximate ranges for a single-cavity gas-assist mold by steel grade:
P20
low-volume
$2,500–6,000
718H / NAK80
mid-volume
$6,500–14,000
H13
high-volume, high-temp resins
$8,000–18,000
S136
high-volume, corrosion or optical
$11,000–24,000
Cavity count, sliders, lifters, hot runner, gas channel complexity, and the detail level of your project determine final tooling price.
Prototype vs Production Tooling
Prototype tools in P20 or 1.1730 run 30%–50% lower than full production steel like H13 or S136. Useful when annual volume is under 20k, or when geometry is still moving and you want validation before committing H13.
Trial Shot Policy (No Hidden Fees)
Three rounds of tool trials are included as long as part drawing and specifications remain unchanged from the signed DFM. If a defect traces to our process, we own the rework. If you revise geometry, wall thickness, or material after tool steel is cut, the modification is quoted separately and signed before any work starts — no surprise invoices, no mid-project markups.
Export Tool vs In-House Production
Export the tool to your own press if you run nitrogen-assist in-house — built to HASCO or DME for direct fit, with material certs and CMM reports on delivery. Or leave the tool at KTM for production: no MOQ, prototype runs through 1M+ parts, with full inspection reports per shipment.
Before you commit to a quote, the next section lists four scenarios where gas-assist isn't the right call — we'll tell you upfront.
When NOT to Use Gas Assisted Injection Molding
Gas assist isn't right for every part. We say so upfront when a different process fits better.
Skip gas assist if your part is:
Transparent or clear-plastic.
Gas channel ghosting shows under backlight. PMMA and clear PC run better in conventional injection.
Ultra-thin with uniform walls under 1.5 mm.
No thick section to displace — you add complexity without the benefit.
A multi-cavity tool with mismatched cavity sizes.
Gas flows to the path of least resistance; dissimilar cavities fill unevenly.
A hollow channel with tight internal ID tolerance.
Gas core diameter varies ±5%–8% — rules out medical fluid paths and optical light pipes.
If your drawing fits any of these, we'll point you to conventional injection molding or 2K/two-shot molding instead. The honest call is the cheaper call.
Still weighing whether gas assist fits your part? The questions below cover what buyers ask before sending drawings.
Gas Assisted Injection Molding FAQ
Have a drawing ready? The next step takes 48 hours.
Q1: What is gas assisted injection molding?
Gas assisted injection molding (GAIM) is a process that injects high-pressure nitrogen into molten resin during the injection cycle, displacing plastic in thick sections to form hollow channels. The result: lower part weight, no sink marks on thick areas, shorter cycles, and material savings up to 40%.
Q2: Can an existing conventional mold be converted to gas assist?
Sometimes. We review your tool drawings to check wall thickness, gating, and ejector layout. About 40% of conventional molds accept retrofitted gas channels and pin gates. The rest need a new core insert — still cheaper than cutting a fresh tool from scratch.
Q3: What gas is used in gas assist injection molding?
Nitrogen at 99.9% purity or higher. Nitrogen is inert and dry — it won't react with hot resin or introduce moisture. Compressed air causes voids and oxidation. Our nitrogen units feed gas at 2,000–5,000 psi through dedicated controllers.
Q4: Do I need a special injection machine for gas assist?
No. Any standard injection press runs gas assist once paired with a nitrogen control unit and a gas-assist nozzle. The press itself doesn't change. We run gas assist parts on our in-house presses without machine-side modifications beyond the nozzle.
Q5: What's the difference between conventional and gas assisted injection molding?
Conventional fills the cavity with solid plastic. Gas assist injects nitrogen into a short shot, hollowing thick sections. Result: less resin per part, no sink marks on thick ribs, shorter cycles, lower clamp tonnage on the same press.
Q6: What materials work with gas assist molding?
Most engineering thermoplastics: PC, ABS, PP, PA6, PA66 with up to 30% glass fiber, PBT, and PC/ABS blends. Glass-filled grades need higher melt temperatures and gas pressure. We avoid transparent PMMA and crystal PC because gas channel marks show under backlight.
Q7: What is internal vs external gas assist injection molding?
Internal injects nitrogen into the part itself, hollowing thick handles, tubes, and structural ribs. External injects nitrogen between the part and cavity wall to press resin flat — used on large flat panels to remove sink marks.
Q8: How much does gas assisted injection molding cost?
Tooling depends on part size, cavity count, and steel grade. Per-part costs typically drop 15%–35% versus solid molding due to reduced resin and shorter cycles. The cost section above shows full tooling ranges by steel grade and trial-shot policy.
Q9: What are the disadvantages of gas assisted injection molding?
Process sensitivity (gas pressure, timing, and melt temp must stay synchronized), risk of gas blowout on thin walls, limits on transparent resins, and higher initial setup than standard molding. The "When NOT to Use" section above lists the part categories where we recommend a different process.
Q10: Who makes gas assisted injection molds in China?
KTM builds gas assist tooling and production in Dongguan. Our founder has led mold technical work for over 20 years. We've shipped tools and parts to clients in the US, Mexico, Canada, and 16 European countries. ISO 9001 certified, HASCO/DME standards, no MOQ.
Get Your Free Gas Assisted Injection Molding DFM Review
Ready to cut material cost on your next gas-assist part? Upload your STEP, STP, or IGES file. Our engineers reply within 48 hours with a preliminary DFM, gas channel layout review, and an itemized quote. We sign your NDA before opening any drawings.
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