NSF-EPSRC A Transatlantic Institute for Volumetric Powder Bed Fusion

Additive manufacturing (AM) is revolutionizing not only modern manufacturing but also the entire product development cycle, including the types of products that are designed and the supply chains through which they are delivered. By placing material only where it is needed, in an additive, layer-wise fashion, it is possible to create very complex architectures and functionally graded features that enhance the functionality of a product. By fabricating a part directly from a digital file, with no required tooling or fixtures, it is economical to fabricate parts locally in small quantities, opening the door to personal customization and one-of-a-kind fabrication and repair. Although AM enables production of complex parts in small volumes, the slow speed and high cost of additively manufacturing a part-relative to high-throughput conventional manufacturing methods-are significant barriers to the growth of AM. The barriers are particularly acute for powder bed fusion processes. For example, laser sintering (LS), one of the most broadly utilized AM technologies for end-use parts, can require more than 24 hours to fabricate a full batch of polymer parts. Parts are built in layers-typically on the order of 100 microns thick-by sintering powders with a laser that traces successive cross-sections of the part in a raster-like pattern. Depending on the complexity of the cross-section, each layer can require 60 seconds or more to prepare and fabricate, resulting in excessive build times. Combined with post-build cooling operations, the cycle time for a full build can approach 36 hours. Although recent technological advances have improved processing speeds these improvements are still essentially fabricating objects in a layer-by-layer manner and are therefore inherently limited in terms of the speed with which they consolidate material. We propose to consolidate sintered parts volumetrically, resulting in at least a 25 time reduction in cycle time relative to commercial LS, along with the ability to sinter a wider variety of polymer materials.

Beneficiaries of this research are wide ranging, firstly the concept of volumetric printing should bring about the ability to make additive manufacturing, and powder bed fusion in particular a technique that can be applied more widely due to a step change in economics. The ability to print layers quickly without a heating step means that the slowest part of the process is overcome and can be left until the end of the build - thereby removing a sequential time penalty that occurs thousands of times per build to a single post-deposition operation. The consequent benefits of this are many fold, firstly, as the economics of all current AM machinery are dominated by build time, this will be reduced and remove one of the significant barriers to adoption for manufacturers of polymeric parts and components.
Secondly, the ability to deposit differential materials through the inkjet printing process may mean that we can begin to manipulate properties and structures on a level not seen before in AM, and coupling this with increased build speed will mean a faster route to market, with increased performance of products. This will mean that many industries and sectors that have been unable to implement AM in its current guise due to unfavourable economics will be able to re-visit this technology and gain the benefits for a range of 21st century products, which may include, aero, auto, industrial engineering, pharma, consumer and electronics manufacturers. The ability to translate to a highly efficient method of AM and to manage the economics of new product development should yield significant advantage to those taking up the process.