Antarctic Bear Introduction: Compared with traditional casting processing modes, electric arc additive manufacturing (WAAM, also known as arc metal 3D printing) can greatly shorten the delivery time of workpieces and provide more design possibilities. With its just-in-time production capabilities, it can perfectly realize the new manufacturing model of "design today, put into production tomorrow".
Little knowledge: Arc additive manufacturing uses arc as a heat source to melt metal wire or powder, and continuously transfers the molten metal in the form of droplets according to a predetermined path to form metal components. Compared with laser, electron beam, etc., arc additive has high forming efficiency and low material requirements, and has obvious advantages in forming large-size multi-dimensional heterogeneous components.
Mark Douglass, business development manager at Lincoln Electric Additive Solutions, said: "The production of castings is a complex and lengthy process because it is limited by the multiple steps of traditional manufacturing models. Today, one of our partners - located in Ohio The state-based Euclid company has used 18 WAAM robots to 3D print through metal deposition to provide production capabilities for large metal parts, thereby achieving the effect of replacing cast workpieces. The advantages of this technology during the covid-19 pandemic This became apparent as supply chains were broken and stretched. Additive manufacturing can deliver large metal parts in three or four weeks, whereas the lead time to obtain the same part through casting can easily be five times that, which in times of the pandemic could will be longer.
Produce large parts via WAAM
The picture above is a part being produced at the Lincoln Electric Company's additive manufacturing facility in Euclid, Ohio. It is a sculptural part created by artist Jenny Sabin for the University of Nebraska Medical Center. It looks about two meters long. But it also illustrates the freedom WAAM has in producing very large structures. Large parts like this can be welded together to create very large shapes because, as Douglass (right) explains, the fundamental principle behind the wire-arc additive manufacturing process is welding anyway.
The value of arc additive manufacturing
But what is the value of arc additive manufacturing technology? Douglass explained: “The lack of an accurate answer to this question may be due to seeing WAAM as a new production model that can partially replace casting.
In fact, additive manufacturing offers a large degree of design freedom, with the carefully designed part geometries and material combinations it can enable, as well as the opportunity to change the design at will during the production process. In the choice of rationalizing the production process, the degree of freedom of additive manufacturing is much greater than that of traditional processes, and the delivery time may also be much shorter, but the industry generally does not have standard measures or methods to evaluate these advantages.
Limitations of arc additive manufacturing
Of course, arc metal 3D printing has other limitations. Material cost is one of them, as the wire in arc additive must be delivered in a manner suitable for this process. Douglass said: "We are not cost-competitive when it comes to orders of hundreds or thousands of parts. There is no doubt that casting will win based on quantity. But if the quantity is around 10, additive will win, but currently through casting Many of the production parts produced are also produced in small batches. The freedom brought by additive manufacturing allows it to easily change geometries, resulting in a more diverse range of parts, which will hopefully lead to more over time. work falls within this scope."
Cleveland-area Additive Solutions factory uses machine automation WAAM.
As the image above demonstrates, robots offer greater freedom than enclosed machines when it comes to depositing material at different angles around the workspace. At the same time, the internal quality of welded parts produced through metal deposition is more stable, and its performance is closer to that of forged materials, which also confirms the strong manufacturing capabilities of WAAM technology.
Application prospects
WAAM has taken a leap forward in manufacturing tools. Currently, aerospace and other manufacturers mostly use WAAM systems to make metal and composite tooling, which can shorten lead times and speed up part manufacturing. Cleveland's large-format robot WAAM takes the same route as other 3D printing processes. What is different about WAAM is that it has been widely accepted and understood because its principles are based on welding processes that have been used for more than a century, although it is still essentially different from traditional welding techniques.
The main application targets of today's WAAM technology are large tools in the aerospace industry. What you can see in the picture above is a composite material layup tool in which the working surface is 3D printed by Invar.
Lincoln Electric has been specializing in welding for 125 years, and the company has large customers who rely on its welding systems, including well-known heavy industry OEMs who are also interested in realizing the flexibility and cost-saving potential of additive. In addition, Lincoln Electric is noted for developing and producing within its own organization all components of a welding system, including power sources, welding guns and materials.
Multiple interfaces made by WAAM
The picture above is a demonstration work of a pipe joint by WAAM. Please note that the construction layer lines are not all parallel. This is because robotic deposition allows different features to be built at different angles in the same cycle. This work is to explore the process of construction. Feasibility of additively manufactured multi-channel joint alternatives when used on offshore oil platforms.
WAAM is welding, but it is continuous welding and involves fine build-up of solder joints, which also poses challenges to every process involved in the process, including deposition, metallurgy, machine automation, and even finishing. In addition, software is also a key factor that determines the quality of WAAM. Deposition by welding is not just a matter of tool path (or welding gun channel), but is also affected by the frequency and amplitude of the current waveform. "It's unlikely that a traditional CAM software company would develop software specifically designed to match the WAAM process, but Lincoln did," Douglass said.
The welding material is another important factor. Standard wire can be used in WAAM, but how to correct the twist in pulling the wire from the spool and feed it well enough for controlled deposition is a question. This is a problem that needs to be solved to optimize WAAM.
Another promising application case for WAAM technology is replacement parts for large machines, and Lincoln Electric is currently conducting research in related areas. Douglass said: “Judging from the current acceptance and application status of additive technology by manufacturers, we must further promote the use of this technology in order to continuously improve it and open up the market.”
Manufacturing parts through WAAM has a very short supply chain. Compared with large castings shipped from overseas foundries, metal 3D printing can completely manufacture and process the same parts locally and then ship them to customers in the same region. For details, please go to [Global 3D Printing Research Report Column https://www.nanjixiong.com/forum-234-1.html].
To give the robot enough height to reach the top of the parts in the background and print them all in one cycle, Lincoln Electric first 3D printed the base on which the robot is mounted in the foreground.
For those buyers who require large, relatively low-volume castings, WAAM is an absolutely logical choice. For example, pressure vessels were previously completed by casting. This process had a delay of up to 16 to 18 weeks, but WAAM can shorten this time to 4 to 5 weeks. The completion of the container blank through WAAM, followed by finishing processing, coupled with superior metallurgical properties, allows complete delivery of the component. However, there are still certain obstacles to practical application of WAAM components. These vessels manufactured according to ASME standards must use welding procedures that comply with specific specifications. The problem is that there has never been a normative and standardized identification method for WAAM welding procedures.
WAAM’s path to standardization
The WAAM standard is very important, it is the law that pressure vessel manufacturers need to abide by. The important role of industry standards is to set a common industry baseline that defines expected part performance and quality. To use WAAM, it must adhere to these standards in some way.
WAAM is similar to welding, but it is not welding. The main difference is that welding does not require continuous deposition, while additive manufacturing does. The test setup shown here explores this difference, 3D printing on the pipe as part of a nozzle life assessment.
At the end of October 2021, Lincoln Electric Company has announced that it has made certain progress in the formulation of WAAM standardization. Thanks to discussions involving members of the Lincoln Electric Additive Solutions team, the relevant ASME code has now added a method to qualify gas metal arc additive manufacturing. WAAM procedures using mild steel alloys have been qualified according to this system.
Douglass said that advancing arc additive manufacturing now requires integration with relevant industry systems and standards, which is no longer a matter of technological development. Technical development is still ongoing, but the technology is mature enough that it has even been produced in small batches. The bigger challenge now is: does everyone still have confidence in WAAM? How to make WAAM profitable? What is the future production model of the WAAM industry? Antarctic Bear also wants to know the answers to these questions, but what is certain is that WAAM, as the main research direction in the field of additive manufacturing, will definitely move towards a more mature and standardized path in the future.
