Thread milling an additively manufactured component at Imperial Machine Co.
When we talk about additive manufacturing (AM) competing with traditional means of manufacturing, the common comparison is with CNC machining. The technology may have a few decades on AM, having been born out of an MIT lab back in the 1940s before stereolithography was even a twinkle in Chuck Hull’s eye, but it’s important not to overlook how both can offer their own unique benefits to the modern manufacturer.
Despite the alleged gripe between the two, these recent forms of manufacturing technology are by no means running in parallel. A number of technologies have emerged onto the market offering hybrid solutions such as Hybrid Manufacturing Technologies and a lot of machining OEMs now have some form of additive capability including DMG Mori, Hermle and Mazak.
Established manufacturers like Imperial Machine & Tool Co. in the U.S. have, as the name suggests, been using machining technologies for decades and in the last five years have invested in metal AM, recognising the benefits of combining the two and treating AM “as if it were any other “traditional” technology”.
Christian Joest, VP of Sales & Business Development at Imperial explained: “When commencing new projects, we discuss our manufacturing approach, and every department involved has a seat at the table – whether it be multi-axis CNC machining, precision turning, precision welding, or additive manufacturing. This approach allows us to account for any concessions that must be made to ensure overall manufacturability. For example, we might add additional material to an AM design to enable further machining or fixturing.”
Imperial’s New Jersey-based machine shop houses two SLM 280 HL powder bed fusion systems which are used to fabricate complex structures that are then finished using machining centres to achieve critical tolerances and features.
“Precision threads, flatness call-outs, mating surfaces, critical diameters, O-Ring grooves... these are all handled using CNC machines,” Joest continued. “It’s only by using additive and subtractive technologies together that we’re able to realise the most innovative designs.”
Generatively designed motorcycle upright finished with CNC machining.
It’s not only end-use customer parts where AM is giving Imperial the edge, the technology has been applied across its entire operation to improve efficiencies meaning every machinist is trained on polymer AM which can be used to create manufacturing aids such as machining fixtures.
“Making proper fixtures is traditionally a time-consuming process; especially for intricate 5-axis work pieces,” Joest added. “Utilising AM technology to print the fi xtures frees up our skilled machinists to spend time on actual work pieces. More efficient work force utilisation drives increased profitability.”
Even generative design, often promoted as a software which produces designs that could only be made with AM, is in fact enabling some pretty interesting solutions with subtractive manufacturing. At Autodesk’s Advanced Manufacturing Facility in Birmingham, UK, the majority of machines in tow are advanced multi-axis CNC systems - 3D printing is primarily left to the design workshop. That’s largely down to its origin as a Delcam cutting lab but one notable exception is its Wire Arc Additive Manufacturing technology, otherwise known as WAAM, which uses standard metal feedstock to rapidly manufacture large-scale structures which are then machined to exact specifications. The most well-known example of this is the manufacture and installation of a large ship propeller which was unveiled on a Damen shipyard vessel last year.
“AM is not a silver bullet and certainly should not be seen as replacing proven, mature processes for making things,” Kelvin Hamilton, Technical Consultant working in R&D projects at Autodesk commented. “It’s another tool in the toolbox to be called upon where appropriate and where there is a clear value addition for using it.”
During a recent visit to the facility, Autodesk’s CEO Andrew Anagnost spoke about the need to reach a middle ground between hyper efficient generatively designed parts and traditional ways of manufacturing by adding material and manufacturability constraints to create designs for a specific process. This will enable more people to benefit from the technology without having to drastically disrupt their workflows.
“Total production time, cost and lot size have a massive impact that require serious thought and trade-off s to be made depending on the production scenario,” Hamilton continues. “The chosen production method whether its casting, forging, additive, fabrication, subtractive or their hybrid combination, is a part of the production conversation and one that needs holistic almost systems-level thought to maximise flexibility and value addition.”
3D-Hybrid to bring three metal 3D printing technologies to CNC machines.
A start-up in the U.S. is tackling this head-on, literally, with a trio of tool-heads that claim to give AM capabilities to any CNC machine. The technologies on offer from 3D-Hybrid follow a recent trend for rapid deposition processes, such as wire arc, which use standard materials to build near net parts which are then machined. Manufacturers can leverage the benefits of Wire-Arc Additive Manufacturing, Laser Metal Deposition, and Cold Spray without having to invest in a costly new machine. Wire Arc is its most popular tool offering low entry costs to metal AM, 5-axis printing and 100% material utilisation. But Hybrid-3D founder, Karl F. Hranka says it’s not all about the cost.
“They [manufacturers] chose our approach because they need to work with application specific CNC machines, which are ideal for specific materials/applications,” Hranka told TCT. “We are even seeing CNC machine manufacturers embracing our technology to gain access into the metal AM equipment supply industry.”
Every generation has its rivalries. Blur vs. Oasis, Joan Crawford vs. Bette Davis and so on. For this generation of manufacturing, it’s not about this or that, it’s about finding the right solution for the application and leveraging the benefits of both.
“One big take away about AM (specifically metal AM) is that the technology is incapable of producing final net shape geometries due to process resolution and thermal effects such as distortion,” Hamilton concludes. “That dependency in effect means that we can hardly expect AM to take away some of the subtractive market. You might be doing slightly less cutting than say starting from a billet of material or some more targeted cutting on critical areas like mating faces but subtractive processes are essential. It’s the marriage of these technologies that make the added value benefits of AM shine.”
