View source for Gas-assisted injection molding

{{short description|Type of plastics manufacturing process}}
{{Use American English|date=November 2020}}
{{Use mdy dates|date=November 2020}}
{{Infobox industrial process
| name           = Gas-assisted injection molding
| image          = File:Gas-assisted injection moulding concept.jpg
| caption        = Basic concept diagram of gas-assisted injection molding
| type         = [[Injection molding]] process
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'''Gas-assisted injection molding '''is a molding process where an inert gas is injected into the melted plastic pushing it further into the [[Molding (process)|mold]] and resulting in hollow parts.<ref>{{Cite web |last=Seong-Yeol Han, Jin-Kwan Kwag, Cheol-Ju Kim, Tae-Won Park, Yeong-Deug Jeong |title=A new process of gas-assisted injection molding for faster cooling |url=https://www.sciencedirect.com/science/article/abs/pii/S092401360400490X |website=ScienceDirect}}</ref>
==Basic concept==
[[File:Principle of fluid injection moulding neutral.svg|thumb|Gas-assisted injection molding to provide an internal hollow shape (Green and blue colors indicate inert gas and polymer melt respectively)]]
The basic concept of the gas-assisted molding process is quite similar to the regular [[injection molding]] process. In gas-assisted molding, the plastic material is injected into the mold cavities like the regular [[injection molding]] process but only up to 70%~80% of the [[Molding (process)|mold]] volume. The melted plastic in contact with the mold walls begins to solidify, then nitrogen gas is injected into the mold through strategically designed and placed gas inlets, providing pressure that pushes the plastic into the mold extremities. The path of the bubble is controlled by taking the path of least resistance through the hottest, least viscous plastic, which keeps it centered from the colder walls of the mold. Finally the [[Molding (process)|molded]] part is ejected like the regular injection molding process.<ref>{{Cite web |url=https://nrc-publications.canada.ca/eng/view/accepted/?id=edcc21d9-0044-4ea2-bf9f-1e1995346db9 |website=NRC Publications Archive, from National Research Council Canada|title=Real-time diagnostics of gas/water assisted injection molding using integrated ultrasonic sensors |language=en |access-date=9 November 2020}}</ref>
==Advantages==
This process forms hollow parts that are cheaper than traditionally [[injection molded]] equivalents. Molded parts also cool faster in this process. There is also usually less shrinkage as the thicker wall sections are hollow.<ref>{{Cite web|url=https://dienamics.com.au/blog/what-is-gas-assisted-injection-moulding/|website=Dienamics|title=What is gas assisted injection moulding?|language=en|access-date=9 November 2020}}</ref>
Some of the benefits of this process are:<ref>{{Cite web|url=https://www.ptonline.com/articles/external-gas-molding-squeezes-out-sinks|website=Plastics Technology|title=External Gas Molding Squeezes Out Sinks|language=en|access-date=10 November 2020}}</ref>
* Thicker parts
* Low clamp force
* Lightweight products
* Reduced part deformation (warpage)
* Minimal residual stresses
* No [[Injection moulding#Moulding defects|sink marks]]
* [[Sustainability|Greener]]
==Disadvantages==
This molding technique is very difficult to apply to multi-cavity molds, especially if the cavity sizes are dissimilar. Clear or transparent plastic materials are an inappropriate option for this technique as the cosmetic-appearance can deteriorate.<ref>{{Cite web |url=https://www.ptonline.com/articles/new-methods-expand-roles-of-gas-assist-molding |website=Plastics Technology |title=New Methods Expand Roles of Gas-Assist Molding |language=en |access-date=9 November 2020}}</ref>
==See also==
* [[Rotational molding]] (also produces hollow parts)
* [[Direct injection expanded foam molding]]
* [[Fusible core injection molding]]
* [[Metal injection molding]]
* [[Multi-material injection molding]]
* [[Reaction injection molding]]
==References==
{{reflist}}
==External links==
*[https://firstmold.com/ Precision Machining]
[[Category:Injection molding]]