Harnessing The Power Of 3D Metal Printing In Manufacturing

The technical and market opportunities for 3D metal printing are growing as equipment process speeds, reliability and safety improve, applications are being vetted and commercialized, and costs gradually decline.

The commercial success of affordable, three dimensional (3D) printed plastic products and parts for science, industry and medicine has spurred similar innovations in 3D metal printing. Already, early adopters in manufacturing are using 3D metal printers to create everything from prototypes of jet engine fuel nozzles to customized medical parts, and personalized home faucets.

To be sure, the processes and materials for 3D printing will require further research and testing before we see broad commercialization. However, as manufacturers look to future opportunities for growth, it is helpful now to understand the technologies, opportunities, risks and costs associated this approach brings.

Early Technology: Metal Sintering

The first 3D metal printing technology to emerge is sintering. These printers can produce intricate shapes by melting popular metal powders like aluminum and titanium, one thin layer at a time in precise patterns, using high energy sources, such as lasers and electron beams. Many products manufactured by this 3D printing approach are for aerospace and defense applications that can undergo temperature extremes and physical stresses that require 100% purity of material and quality of structure to assure safety and mission-critical performance for these parts. These markets can deal with the high cost to produce due to the small quantities, the significant investment in the equipment, and relatively slow process required.

Metal powders used in sintering are volatile by nature, and the presence of a spark or flame in open air can result in flash fires or explosions. So, extra care needs to be taken in loading 3D metal printers with powder through the use of anti-static grounding systems, and operators and material handlers wearing safety suits. To further assure safety and product quality, 3D printers require high precision and extremely accurate control of the energy sources as layers of very fine powder are melted. Typically, the printing mechanism is in a sealed chamber at a vacuum or filled with special inert gas to prevent contamination and flashes.

The material-related factors plus the cost of precise motion control and power management for high-energy metal fusing sources currently make investment in process equipment significantly higher compared to most commercial quality plastic resin printers, which use ultra violet light and low-powered laser curing sources.

Newer Additive Approaches

Two newer printing technologies are based on 3D metal additive manufacturing processes that have applications for specialized products. These processes require less equipment investment and can produce parts at a higher speed in a relatively safe, open-air manufacturing environment.

One, called jet binding, is a hybrid of resin and metal “printing” where a liquid resin binder is deposited on metal powder by a precisely controlled print head much like in an ink jet printer. The resin needs to be cured to hold an accurate shape. Then it is sintered in a high temperature chamber to create higher metal densities. In some cases, post processing may be done to infiltrate additional materials and tune part properties. This technology eliminates the need for high-energy sources with sophisticated controls, so the printer mechanism usually requires reduced capital investment and is inherently safer than direct sintering.

The second is automatic deposition of metal from a rod or wire using an electric arc energy source that moves in a back-and-forth pattern in an open air environment to create a fairly large part. Since this approach relies on very stable welding-style wire as the base material instead of volatile powder, it requires significantly reduced process investment and is quite safe. This process makes a very strong part given that the material is created by the layering of welds in a precise pattern which deposits a large amount of metal very quickly to achieve larger structures. Since the resulting structure can look like a bumpy buildup of frosting, a modest amount of surface machining is often needed to form smooth, flat surfaces and other accurate features (holes, bevels, etc.).

The thick-layered deposition approach is an alternative to heavy machining of a large casting or metal billet to create a rough shape that requires finish machining to create a final usable product. It produces a close-to-net shape, eliminating much of the material waste associated with heavy machining of metal.

As sintering and additive approaches mature, there is continuing research and development into additional metal powders — including Inconel, stainless and other steels, nickel, cobalt and chrome — to meet the needs for robust final product performance in various commercial applications.

Applications in Transportation, Aerospace and Defense

The use of 3D metal printing is well-suited for sophisticated designs not readily produced by casting, machining, or mechanical pressing such as forging, stamping, rolling, and spinning. Where designs with intricate channels, wispy structures, and hidden passages are required, direct metal melting or sintering 3D printing can produce these parts from 3D computer-aided design (CAD) models.

Though most current printing technologies using lasers or electron beams are slower than tooled processes, they yield almost no waste and are very suitable for prototypes or small quantities, making these processes extremely useful for aerospace. GE Jet Engine group now designs and builds jet fuel nozzles using 3D metal printing. Other aerospace companies are creating lightweight structures and valves for space satellites.

In the transportation, aerospace and defense industries, sourcing service parts for vehicle repairs is a major challenge, particularly for vehicles last produced 10 to 20 years ago. So, large manufacturers and top-tier suppliers are investing in 3D metal printing solutions that can produce a few parts from CAD 3D models within days instead of the weeks or months typically required to negotiate re-supply.

Emerging Medical Applications

Medical manufacturers also can respond quickly to requests for custom-made parts, using 3D metal printing to produce tailored implantable devices, such as artificial joint parts based on high-resolution medical patient scans. These patient-matched devices can be made in a specific size and shape, with very tight tolerances to assure optimum fit in the patient. The latest implants have surface features and porosity designed to let bone and tissue to grow “into” the implant to improve the bonding and strength of the artificial joint, enhancing patient outcomes.

Even metal surgical instruments can be custom printed to help make surgeries more efficient with less tissue damage. Not to be outdone, dental device manufacturers are printing forms (a kind of tooling) and dental restorative products, such as bridges and crowns.

3D Metal Printing Work Centers

The technical and market opportunities for 3D metal printing are growing as equipment process speeds, reliability and safety improve, applications are being vetted and commercialized, and costs gradually decline. As manufacturers add 3D metal printing work centers to their facilities, it is important to integrate them into a production monitoring scheme, particularly in industries where product safety is heavily regulated, and managing the traceability of materials and process parameters is critical.

Specialists and manufacturers should be able to plan, schedule, monitor, and ultimately trace production quality using modern enterprise resource planning (ERP) and smart manufacturing systems. In doing so, manufacturers will be well positioned to drive growth with a new generation of innovative, high-value printed metal products.

Ed Potoczak is director of industry relations at IQMS.

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