Norsk Titanium AS公司凭借在快速等离子沉积工艺（Rapid Plasma Deposition，RPD）方面超过10年的研发经验，声称有能力以25%-50%的成本，提供同类钛材料组件。具体来说，Norsk公司会将室温状态下的6-4钛丝送入在氩气环境中由一对等离子发生器产生的等离子弧。此后，钛丝原料的温度将快速上升至上千摄氏度，然后作为一种液体材料，供机械沉淀臂打印使用。沉积后的液体钛材料将立即凝固。总体来说，组件将在这样的闭环工艺过程中快速层叠成型，可以最大程度降低精加工需求。
事实上，MERKE IV RPD设备与标准的计算机数控加工中心(CNC)很类似，只不过使用的是等离子弧，而不是轴而已。Norsk公司总裁兼CEO Warren Boley表示，MERKE IV RPD设备“每年可以打印20吨钛材料”，而且“将真正改变航空器级钛材料零部件的生产现状。”
今年4月，总部位于奥斯陆的Norsk公司宣布，公司将为波音787 Dreamliner梦幻客机提供3D打印RPD工艺结构性钛材料组件。波音公司在组件的整个开发设计过程中一直与Norsk保持密切合作。此外，为了验证这些原始结构性组件在Dreamliner梦幻飞机上的表现，波音公司还与Norsk一起联合美国联邦航空管理局(FAA)进行了一系列严格的测试，并在今年2月完成了认证。Norsk公司是首家为波音提供RPD工艺组件的供应商。
波音公司飞机材料与结构、供应商管理副总裁John Byrne表示，“我们总是在探索最新的技术，从而降低成本、提升性能并给我们的客户创造更多价值，Norsk的RPD工艺完全符合我们的要求。”
Norsk公司声称，RPD工艺的生产成本低于传统的锻造和制造工艺技术，而后者需要使用钛坯料作为加工原材料。
“你可以找一块200磅的材料进行锻造，然后生产一个20磅的部件，”Boley表示，“而我们可以直接用30磅的材料打印一个20磅的部件。”通常来说，采用传统加工工艺的组件交货期在55到75周左右，而如果采用我们的RPD工艺，这些组件的打印和加工完全可以在2到3小时内完成。
Norsk表示，由于这种增材工艺本身可以在生产过程中节省大量能耗，因此能够节省75%的成本，并显著节省工时。
Boley认为，波音787中大约有1,000个组件均可采用RPD工艺，“每个部件大约可以节省2,500美元，那么整部飞机则可以节省接近250万美元的成本。如果按照每年生产144架飞机计算，波音每年可以节省3.6亿美元。这可是革命性的进展！”
Norsk公司也非常注意RPD工艺对环境的影响。通过减少浪费的废钛（传统工艺钛材料组件的成品与原材料之间的重量比大约为1:40），RPD工艺还可以减少矿石的开采加工需求。
Dreamliner的RPD组件以及生产这些组件的NorskTitanium MERKE IV RDP加工设备均参加了今年6月在法国Le Bourget举办的巴黎国际航展。
Norsk Titanium AS—which has been researching and developing its RPD (rapid plasma deposition) process for over 10 years—says it can produce titanium components that can cost from 50 to 75% less than other equivalent components. Its process involves feeding room-temperature titanium 6-4 wire into a plasma arc created by a pair of torches in argon gas environment. The titanium temperature is raised by thousands of degrees and then is robotically printed as a liquid by a robotic depositing arm. The titanium solidifies instantly after being deposited. The component is rapidly built up in layers in a closed-loop process and requires very little finish machining.
The system itself, a MERKE IV RPD machine, bears a resemblance to a standard computer numerical control (CNC) machining center—with a plasma arc instead of a spindle. Norsk President and CEO, Warren Boley stated that the MERKE IV RPD machine “can print 20 tons of titanium per year,” and that it’s “a game changer in terms of being able to produce aircraft quality titanium parts.”
This past April, Oslo-based Norsk announced that it will be producing via RPD 3D-printed structural titanium components for the Boeing 787 Dreamliner. Boeing designed the components and collaborated closely with Norsk throughout the development process. To certify these initial structural components on the Dreamliner, Boeing and Norsk undertook a rigorous testing program with Federal Aviation Administration (FAA) certification deliverables completed in February. Norsk is the first supplier for Boeing’s high deposition rate material specification.
“We are always looking at the latest technologies to drive cost reduction, performance, and value to our customers and Norsk’s RPD capability fits the bill in a new and creative way,” said John Byrne, Vice President, Airplane Materials and Structures, Supplier Management, Boeing Commercial Airplanes.
Norsk claims that the production cost is less than that of legacy forging and manufacturing techniques where billets of titanium are machined into components.
“You can take a 200-lb forging and produce a 20-lb part,” said Boley. “We can print 30 lb of material to produce a 20-lb part.” Producing a 200-lb billet and machining it down to a 20-lb component typically requires a lead time of 55 to 75 weeks. These same components can be created via RPD and machine finished within 2 to 3 hours.
Because of the significant reduction of waste and machining energy inherent in their additive process, Norsk claims up to 75% cost and time savings.
With an estimated 1000 titanium components in a Boeing 787 that can be manufactured using the RPD process, Boley stated that, “We think we can save $2500 per part; that’s $2.5 million per aircraft. At 144 aircraft a year, that’s $360 million. That kind of saving is revolutionary.”
Norsk also takes note of the environmental impacts that its RPD process brings as well. By reducing the amount of scrap titanium (approximately 40 lb of scrap to 1 lb that sees flight), the process also reduces the amount of ore that must be mined and processed.
The Dreamliner RPD components—as well as Norsk Titanium’s MERKE IV RDP machine that produced them—will be on display at the International Paris Airshow, Le Bourget in June.
Author: William Kucinski
Source: SAE Aerospace Engineering Magazine
