Gas assist injection molding solves a narrow but expensive set of problems: thick sections that sink, ribs that telegraph through cosmetic surfaces, large parts that demand more clamp tonnage than the machine can deliver, and parts that end up heavier than the application needs. Maidder Technology designs and runs gas-assist molds in-house at our Dongguan facility, from DFM through PPAP.
What Is Gas Assist Injection Molding?
Gas assist injection molding, also called gas-assisted molding, uses pressurized nitrogen injected into the polymer melt to create internal hollow channels inside the part. The gas follows the path of least resistance, normally the thickest section, which the designer converts into a gas channel. Gas pressure packs the melt against the cavity walls from the inside, holds it during cooling, and is vented before the mold opens.
Two common methods are used in production:
- Short shot (gas displacement): the cavity is partially filled, then gas is injected and pushes melt toward the extremities. Suited to tubular shapes and long flow paths.
- Full shot (gas expansion into overflow): the cavity fills completely and gas expands into overflow cavities, hollowing thick sections. Common for handles, ribs, and bosses.
Either way, the outcome is the same: a part with hollow internal geometry, molded at lower injection pressure and lower clamp force than a solid version.
Benefits of Gas-Assisted Molding
Sink reduction over ribs and bosses
Thick ribs and bosses pull material inward as they cool, and the surface above them sinks. A gas channel running through or beside that thick section packs it from within, so the cosmetic surface stays flat. This is the most common reason customers ask about gas assist.
Weight reduction without losing stiffness
Hollow channels replace solid plastic. Material is pushed to the outer walls, where it contributes most to stiffness, so a gas-assist part can be substantially lighter than its solid equivalent while carrying the same load.
Large parts on realistic tonnage
Internal gas pressure takes over part of the packing duty, which lowers cavity pressure and clamp tonnage requirements. Parts that would otherwise need a very large press can run on a mid-size machine, which affects both tooling cost and lead time.
Hollow sections and integrated features
Handles, grips, tube-like forms, and hollow frames can be molded as one part instead of assembled from several. Fewer components means fewer assembly steps and fewer joints that can fail or leak.
Cycle time and dimensional stability
Gas packing holds pressure evenly along the channel during cooling. That reduces warpage and can shorten hold time compared with a solid thick section.
Where Gas Assist Is the Right Choice
- Handles and grips — cooler handles, tool handles, appliance handles, and carry frames with molded-in hollow cores.
- Housings and enclosures — thick-walled covers where sink over internal bosses is a visible defect.
- Automotive parts — structural frames, trim carriers, and roof-related components where stiffness-to-weight matters.
- Large containers and boxes — panels and tubs with heavy reinforcing ribs, in the same family as large-format container programs.
If a part is thin and uniform in wall thickness, gas assist adds tooling complexity without adding value. It earns its place where wall thickness varies sharply, or where weight and stiffness are in direct conflict.
Our Gas-Assist Capability, In-House
Gas-assist molds are designed and built at Maidder alongside multi-cavity molds, auto-unscrewing molds, 2K molds, overmolds, and collapsible-core molds. We build molds up to 15 tons. Product development, 3D printing, mold and fixture manufacturing, injection molding, and assembly are handled as a one-stop process, with design, CNC machining, EDM, and wire cutting all performed in-house by an independent design department. A gas channel recommendation is never handed off to a third party.
Our engineering team brings 15 years of experience. For complex, high-precision products we provide free Moldflow analysis and a DFM report before steel is cut, so gas channel layout, gate location, and wall thickness are settled on screen rather than on the sampling floor. See our DFM and Moldflow analysis page for how that review works.
Molding runs on Yizumi and Tairui injection machines from 130T to 500T, with 24-hour shifts.
Quality control covers first-article inspection, in-process patrol inspection with traceability, process testing, per-product batch trace codes, and a PPAP approval process. Measuring equipment includes CMM, vision measuring instruments, calipers, a colorimeter, and a melt flow indexer, with Minitab used for statistical analysis.
Certifications: ISO 9001 and ISO 14001:2015. For applicable food-contact programs, tell us your application and target market; we will confirm suitable materials and documentation for your program. Certificates available upon request.
Project Experience
Maidder was founded in 2016 in Hengli Town, Dongguan City, Guangdong. Our founder's pre-2016 career was as a mold design engineer from 2006 to 2016, before starting the company.
Company project experience includes:
- HP printer base ECN project, 2020: part F0V63-90005, engineering change with add/remove steel, welding and remake of CAV/COR inserts, Rev 4.9 to Rev 12.1, mod cost USD 25,000, documented 3-week lead time, customer-approved change order.
- Hard cooler ODM programs: folding coolers, multi-size hard coolers, and cooler boxes with secondary foam injection.
- Large-format containers: panels and tubs with heavy reinforcing ribs.
- Automotive components: structural frames, trim carriers, and roof-related components where stiffness-to-weight matters.
Working With Maidder
- No MOQ (negotiable).
- Orders under 3,000 pcs incur a machine setup fee.
- Molds belong to the customer, with free maintenance and 1-year free storage.
- Batch quality issues answered within 1 day.
- Production for North America, Europe, and Japan, with, according to company information, a Cambodia production base and OEM Cambodia service as an alternative manufacturing origin.
Start With a DFM Review
Send the 3D file, target resin, and annual volume. The Engineering Team returns a DFM report with a gas-assist recommendation, gas channel layout, gate and ejection notes, and an honest assessment of whether gas-assisted molding is worth the added tooling complexity for your part. If it is not, we will say so.
- Email: [email protected]
- Phone: +86 137 13040698
- Location: Hengli Town, Dongguan City, Guangdong, China
The Sales Team and Engineering Team are available for technical calls on gas-assist mold design, multi-cavity mold manufacturing, and injection molding services.