Laser Wire Direct Closeout (LWDC) is a patented method of metal 3D printing developed by engineers at NASA’sMarshall Space Flight Center(MSFC) in Huntsville, Alabama.
专门为additive fabrication of nozzles，该方法在时间和价格上与传统制造技术具有竞争力。
Now in the process of licensing, NASA is looking to bring LWDC to the commercial sphere, “revitalizing and transforming” its “advanced manufacturing technologies for rocket engines.”
Precision manufacturing
LWDCis a directed energy deposition (DED) process, relying on a wire-based feedstock. In comparison withpowder bed fusion（PBF）增材制造技术，LWDC是一个自由形式的过程。
制造火箭推进的喷嘴的小狗oses is complex. The conical structure is manufactured with internal coolant channels, responsible for delivering high pressure fluid that protects the walls from overheating. In a regeneratively cooled nozzle, these channels must be sealed precisely to keep the coolant inside.
“The manufacturing process is further complicated by the fact that the hot wall of the nozzle is only the thickness of a few sheets of paper and must withstand high temperatures and strains during operation,” explains Paul Gradl, senior propulsion engineer at MSFC.
The LWDC process facilitates the precise closing of these channels. Engineers are now seeking other applications that could benefit from the process.
A traditional manufacturing competitive process
目的是通过强大的增材制造技术巩固传统喷嘴制造工艺的众多复杂步骤。
完成这项任务，LWDC过程还有可能减少数月的交货时间，并“大大降低”生产零件的相对成本。
在3D打印之后，使用LWDC技术进行的喷嘴是在MSFC上测试的热火，“在高燃烧室压力和温度下积累了超过1,040秒。”
Arc-based deposition has also been tested alongside this project, to produce a near net shape liner to contain water jet milled channels for nozzles.
MSFC工程局局长普雷斯顿·琼斯（Preston Jones）评论：
“NASA is committed to revitalizing and transforming its already highly advanced manufacturing technologies for rocket engines,”
“What makes this development project even more unique is there were three separate, state-of-the-art, advanced manufacturing technologies used together to build a better nozzle and prove it out through hot-fire testing — an example of why Marshall continues to be a worldwide leader in manufacturing of propulsion technologies.”
Next generation rockets
与奥本大学合作，MSFC最近被选为ASTM International的创始成员国家增材制造业卓越中心帮助推进技术，以利用美国航空航天。
NASA也是heavily applying additive manufacturingto the development of its next generationSpace Launch System（SLS），计划在2022年至2023年之间发布。
Hot-fire testing of the RS-25 SLS engine, containing a 3D printed pogo accumulator. CLip viaNASA Stennison YouTube
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Featured image shows hot-fire testing of a 3D printed nozzle at NASA’s Marshall Space Flight Center. Photo by David Olive/NASA/MSFC
