Powder Bed Fusion
Sintavia uses a Powder Bed Fusion (PBF) AM process to produce production quality metal parts with three SLM Solutions 280HL 400W twin laser machines, an EOS M290 400W laser machine, a Concept Laser M2 400W laser machine, and an Arcam Q20+ electron beam machine. PBF has the ability to produce precise and intricate geometries in a layer-by-layer fashion without the typical tooling needed in conventional subtractive machining processes. A laser is used to accurately melt a bed of very fine powder particles, into shapes and geometries that lead to state-of-the-art fully optimized designs.
These designs can offer substantial weight savings and performance in modern aerospace advanced component and assembly design. Each design is manufactured from electronic data generated from CAD files making it a fully direct digital manufacturing process. Since the design is controlled directly from a CAD file, PBF can produce parts that were at one time impossible to manufacture by conventional processes such as cutting, grinding and drilling. The design is only limited by a designer’s creative abilities. Features such as conformal cooling inserts, functional integration, complex geometries, lattice networks and hollow members are now produced with considerable ease via the PBF process.
Since it is all accomplished in an additive fashion instead of a subtractive fashion, AM offers reduced material waste and lower lifecycle energy use while offering highly sustainable designs.
On its six high speed machines, Sintavia is currently manufacturing with Inconel 718, Inconel 625, Aluminum, Titanium, Cobalt Chrome, Stainless Steel, and other proprietary powders.
Although PBF parts come out of the machines with a remarkable near net shape, post processing is often involved to meet critical dimensions and/or surface finishes. Sintavia utilizes a wide array of finishing methods to meet or exceed customer’s expectations.
Electrical Discharge Machining (EDM)
Sintavia uses a Computer Numerical Controlled (CNC) wire EDM for post processing, material specimen manufacture, and precision machining of critical features per each customer’s specifications. The EDM features a large travel (23.6” x 15.7” x 12.2”), glass scale feedback, and auto threading capabilities. The precision and intricacy that the EDM can machine to offers a large advantage over traditional post-processing, which involved sawing and/or conventional machining. The EDM can efficiently post-process all types of alloys and is largely unaffected by material hardness.
CNC Multi Axis Milling and Manual Lathe Machining
Critical tolerances are achieved by using in-house manual and CNC machine tools.
Depending on manufactured surface and criticality, various techniques are used to finish each manufactured part. A typical surface finish as removed from the PBF process averages around 250 – 300 Ra. The finish can be greatly improved by a variety of techniques. Surface finish is more than purely aesthetic. In highly stressed parts, a fine surface finish can greatly improve part performance. Depending on the type of post processing, a PBF part can be finished to better than 1 Ra. To achieve the desired surface finish, media blasting (abrasive and shot peen), tumbling, hand polishing or secondary operations are typically used.
Hand finishing involves support removal, layer line removal, and general part cleanup which will give the end user a cleaner and more aesthetically pleasing part. As with any rough surface, it can be improved up to 1 Ra, which qualifies as a near mirror finish. Much of the hand finishing work involves small hand grinders and polishers operated by highly skilled finishers. Generally, hand finishing is used on features that do not require a tight tolerance.
Abrasive blasting works on the principle of using high pressure compressed air to propel an abrasive media through a nozzle. The abrasive media can be grit or ceramic to produce a surface finish of 125 Ra.
Stress relief is a crucial step on metal products in order to minimize residual stresses in the structure. PBF parts are subject to considerable thermal stress during build. Stress relieving can thereby reduce the risk of dimensional changes during further manufacturing or final use of the component. Stress relief of PBF parts is done after buildup while the part is still attached to the build plate.
Vacuum Heat Treatment
Sintavia uses an in-house vacuum heat furnace to achieve aerospace grade additively manufactured components. This furnace is capable of annealing, hardening, precipitation strengthening, tempering and quenching to refine the mechanical properties of the additively manufactured parts.
Hot Isostatic Press (HIP)
Hot Isostatic Press (HIP) processing of PBF parts is a pivotal process to reduce porosity and improve density. Sintavia uses an on-site hot isostatic press. Metal alloys are typically soaked at a temperature just under the melting point and subjected to a considerable pressure of 14.5ksi for 2 to 4 hours. The application of extreme heat and pressure eliminates porosity, improves density, and greatly contributes to improved fatigue life of the component.