Used on the world’s largest metal 3D printer and standard machine lines, MELD Manufacturing’s unique additive process for solid-state metals builds upon flexible automation, motion control and EtherCAT technologies from Beckhoff
MELD Manufacturing has pioneered an innovative solid-state metal additive process that can print with any metal. The MELD process, along with the company’s production equipment, has proven critical in many applications, including the world’s largest metal 3D printer. Developed by MELD in collaboration with others, this additive manufacturing system for the U.S. Army’s Jointless Hull project is capable of printing large vehicle parts up to 30 feet long, 20 feet wide and 12 feet high – or repairing existing parts. MELD makes this possible because its unique additive process does not melt the metals during deposition. For optimal control of its systems, MELD relies on flexible EtherCAT and PC-based automation from Beckhoff.
While the scope of the Jointless Hull project is impressive, MELD offers the same capabilities to a wide range of customers in defense, research and manufacturing. The Christiansburg, Virginia-based company is a woman-owned small business led by CEO Nanci Hardwick. MELD spun off from its parent company, Aeroprobe, in 2018 to apply its additive friction stir deposition to additive manufacturing technologies, according to Dr. Chase Cox, Director of Technology at MELD. “Since then, we have grown exponentially by focusing exclusively on delivering machines and hardware to enable the MELD process,” Cox says. “We invented this process and have more than a dozen domestic and international patents on it.”
What is the MELD process?
Friction stir welding is a method for welding metals without melting them that gained traction among aerospace companies in the 1990s. MELD developed a similar, but unique additive process to enable deposition of multiple layers for 3D printing applications. The process entails rotating a bar of solid metal while applying a specified force at the point of deposition. Friction causes the metal to plasticly deform and be deposited in a layer. Through adiabatic heating, the metal feedstock will continue to flow if spun continuously at the correct speed.
The MELD process allows equipment end users to print parts using any metal, including aluminum alloys and others that have typically posed problems for other additive manufacturing systems. It also doesn’t require melting like most other methods and thus doesn’t affect the metals’ properties. As a result, the product remains stronger than parts made through other metal 3D printing or even traditional forging processes.
Unlike melt-based metal additive processes, MELD-made parts are not susceptible to porosity, hot-cracking or other typical issues. The process is also at least 10 times faster than fusion-based metal additive processes and requires less energy.
Layer upon layer: choosing the right automation solution
Just like the additive process itself, MELD’s machines and technologies evolve constantly, adding new layers of possibility. MELD currently offers several standard machines – L3, K2, and 3PO – for various part sizes ranging from 3 feet long and 1 foot tall to roughly 13 feet long and 3.5 feet tall. It also offers the CD-14 package of a spindle with rotating deposition tool, electrical enclosure and HMI, which machine builders can implement in large, custom systems, including the Jointless Hull machine. Open, scalable industrial control technologies have proven critical to enabling continued development.
“Every time we learn something new in our engineering, we need to adapt the machines,” says Dr. Fred Lalande, Sr. Automation Engineer at MELD. “So the automation technologies we use must be very flexible.”
After the company launched in 2018, its original controls platform could not keep pace. First, Lalande had difficulty getting the controller to use G-code for printing; he had to write a G-code interpreter for that vendor’s platform. Also, a separate PC using a separate software package was necessary to run the HMI and communicate performance data. Finally, the platform had difficulty connecting field devices. As Lalande worked to make the platform communicate to a Beckhoff stepper motor terminal, he got in touch with members of the local Beckhoff team, Regional Sales Engineer Chuck Padvorac and Application Engineer Jack Plyler.
The Beckhoff engineers visited MELD to assist Lalande with the integration. As he learned about fully integrated PC-based control from Beckhoff, Lalande believed he had found the ideal platform for MELD’s developments. “Our technology evolves so quickly that it can be challenging to anticipate all future needs, but it was clear that Beckhoff and its TwinCAT software offered a platform that would not constrain us,” he explains. “It was also important for us to have a very open system with a wide range of available hardware. With EtherCAT, we can select from countless I/O terminals and field devices – from Beckhoff or third parties – to cover the gamut of functions we might need.”
PC-based automation adds a new dimension to the printing process
What pushed Lalande toward Beckhoff was TwinCAT 3 automation software. TwinCAT provides an end-to-end engineering and runtime platform for everything from PLC, CNC and motion control to HMI, machine vision, IoT and more. The software enables programming in any of the available IEC 61131-3 languages including object-oriented extensions, function blocks and computer science standards in Microsoft Visual Studio.
Since Lalande had programmed the first machine’s code in structured text using CODESYS, he found it relatively easy to convert the code in less a relatively short timeframe. In that period, he not only implemented a program that can execute G-code files within the PLC using the TwinCAT NCI package, but he also designed a new HTML5-based operator interface in TwinCAT HMI. “Previously, I had to use two or three different software packages. That was a pain,” he says. “With TwinCAT, I open one program and everything I need is there.”
As the MELD solutions have developed, the code has grown more sophisticated over time. The portability of code in TwinCAT made it easy to adapt one machine’s program when designing the next. In addition, IP protection is critical in additive manufacturing and especially so with the unique MELD process. TwinCAT provided advantages in this area, as Padvorac points out: “The Beckhoff software platform gave MELD the ability, using our OEM Certificate feature, to lock down its valuable code. Everything is password protected and encrypted, so no one can copy MELD’s developments.”
For each MELD machine, the TwinCAT program runs on a single Beckhoff C6920 control cabinet Industrial PC (IPC). This allowed the engineering team to eliminate the other PC, saving cost and space in the machines. A CP2924 multi-touch Control Panel from Beckhoff provides the operator interface with custom push-button extensions. The K2 machine features a customized version of the touchscreen in a vertical orientation. “In terms of branding, the HMIs look sleek and modern as opposed to other vendors’ options,” Lalande says. “The nicer appearance and intuitive operation create better first impressions and user experience for customers, which goes a long way.”
Flexibility and safety with EtherCAT and servo technologies
The L3, K2 and 3PO machines rely on Beckhoff servo solutions for motion control. A variety of AX5000 servo drives and AM8000 servomotors with appropriate gearboxes handle movement in X, Y and Z coordinates. DIN-rail-mounted EL72xx servo drive terminals power a continuous feeding system, Lalande explains: “The feeding system allows operators to load eight hours’ worth of material at once. The material automatically moves to the turret as needed using Beckhoff compact motion solutions.” The Beckhoff components also offer One Cable Technology (OCT), which combines power and feedback in one cable to simplify commissioning.
A VFD and spindle motor from a third party spin each machine’s rotating deposition tool, and since the VFD is EtherCAT-based, Lalande found integration to be simple. This was a major benefit of the EtherCAT industrial Ethernet system in designing the MELD machines. Beyond real-time communication, flexible topology and simple interfacing to other common protocols, EtherCAT provided plug-and-play ease, according to Lalande, when using devices from Beckhoff as well as from third parties.
MELD also leverages TwinSAFE, the integrated functional safety solution from Beckhoff. With its black channel approach, TwinSAFE uses the Safety over EtherCAT (FSoE) protocol to send safety data over the same Ethernet cables as standard communication. This allows Lalande to implement E-stops, safety doors and TwinSAFE motion functions for the drives with programming in the same TwinCAT engineering environment. “TwinSAFE is straightforward to use,” Lalande says. “By implementing this solution, we elevated the level of safety that our machines provide to PLe, the highest level.”
3D printing grows with futureproof technologies
As MELD continues to make advances in additive manufacturing, PC-based control provides a solid foundation to build upon. EtherCAT and OCT shorten commissioning times, while TwinCAT consolidates HMI, motion control, PLC and other machine control functions into one universal software. The automation platform also simplifies the implementation of OPC UA, LabVIEW™, MATLAB®/Simulink® or other software tools as needed in the future, depending on customer specifications or developments.
To keep pace with MELD’s innovation, TwinCAT provides development tools that help maintain a uniform code base across the machines. Seamless integration of source control tools, such as Git, into TwinCAT engineering and the TwinCAT Project Compare Tool are just two advantages. “Managing our beta testing is made easier with these tools,” Lalande says.
The spindle speed must be modulated for each specific material to maintain the desired temperature for continuous printing, Cox explains: “Given how far the tool has moved, we know from our development how much material should also be delivered. We ensure the incoming material deposition rate is correct using Beckhoff systems to control that velocity profile.” To accomplish this, the PID controller in the TwinCAT Controller Toolbox provides dual-loop closure on the axis, ensuring successful implementation of MELD’s unrivaled technology.
“There are other metal 3D printers in the world, but we are the only company to offer this patented technology. The MELD process is unique amongst any of the metal additive offerings in the world, which enables us to print any metal and scale the process to make very large parts,” Cox says. “With reliable automation technologies as a base, we continue to refine our capabilities and add exciting new solutions. For example, the Jointless Hull project machine is very big – the largest of its kind so far – but it's not the biggest machine we are working on with customers right now.”
Want to boost performance of your digital manufacturing equipment with scalable, secure PC-based automation? Contact your local Beckhoff sales engineer today.
James Figy is the Senior Content Specialist at Beckhoff Automation LLC.
A version of this article appeared in Additive Manufacturing.