3D Printers in Aerospace
By Kim Robertson and Jon M Quigley
When you think of product design and development what comes first to mind? Is it an understanding of our business objectives (scope) followed by functional decomposition of requirements and allocating them to various systems and subsystems to achieve that objective? Is it design to manufacture with designers, facility and work center collaboration to assure cost savings through coordinated and producible designs? Or is it early and iterative design validation prior to manufacture? However you view it additive technologies can play a major role in not only better designs but less expensive manufacturing that is quickly gaining mainstream acceptance.
“I believe we’re on the verge of a major breakthrough in design for manufacturing in being able to take something from the concept of something from your mind and translate that into a 3D object and really intuitively on the computer and then take that virtual 3D object and to be able to make it real just by printing it. It’s going to revolutionize design for manufacturing in the 21st century.” Elon Musk.
The idea of being able to rapidly generate a prototype to validate solution through a construct of the proposed functionality, interfaces and best case design solutions was unheard of a decade ago. It is becoming the norm along with modified preliminary test to destruct (Highly Accelerated Life Testing or HALT) evaluations with a shortened test parameters based on wear parameters for differences on material properties (e.g. making a prototype of one material to validate testing parameters for another before final production and test. Additionally high quality prototyped in recyclable wax deposited in half thousandths layers using printers like the Solidscape’s R66 Plus can be made for visual evaluation and improvement prior to casting of a final product in titanium.
Once reserved to the fringes of Aerospace in small development labs the results of 3D prototyping are translating into the printing of 3D parts in aerospace applications. December 2013 saw the introduction of 3D printed components created on a BAE Tornado fighter, GE Aviation’s LEAP engine will use 3D parts, and NASA announced the successful development of a 3D printed rocket engine component. Rolls-Royce, Pratt & Whitney, and GNK aerospace are also investing in additive manufacturing of finished products.
Several obvious advantages of the 3D capability soon become obvious. With additive processes costly materials like Titanium are utilized in only the quantities required (adjusted for finish). In a production environment prototyping of designs that would not be possible, consume many hours or would be cost prohibitive using standard manufacturing methodologies can be explored. In the field product improvements can be scanned, prototyped and more rigorously tested prior to being incorporated into the product line. One of the problems with earlier prototypes is their ability to stand up to the sort of tests that the final product would experience. For example, nobody would place a stereo lithography part on a vehicle and expect it to survive vehicle durability and reliability testing. Those concerns are reduced through 3D printing.
The greatest challenge is for designers in aerospace to rethink what is possible outside of traditional manufacturing methods and available tools. In many cases the need for complex fixtures and tooling to aid complex assembly and welding operations are eliminated reducing costs and design time. Let’s put this into perspective. Rapid prototyping in 2012 was estimated as a $2.2B industry. On 10/14/2013 Chris Fox of Pddnet.com stated a business insider quoted Goldman Sachs as saying 3D printing is “one of eight technologies that are going to creatively destroy how we do business.”
Let’s see how in a single scenario of 3D capabilities play out in a few aerospace related activities. Assume that you have just received a contract to produce replacement parts for a product with faulty or non-existent design data packets. The customer can provide a copy of each part from inventory but due to concern about material fatigue wishes your company to re-evaluate the part and beef up the design to eliminate the problem. Under normal PD&D operations critical parts data is obtained in your dimensional lab and provided to the designer. Once the design is captured improvements can be explored that mitigate the customer’s concern and production and test can start.
3D scanners now exist that allow you to generate a refined cloud model of the part for export to your cad system or directly to a 3D printer. The various aspects of the model can be manipulated to increase thicknesses in higher stress portions of the design and a rapid prototype can be printed to assure critical interfaces have been maintained and the part does not interfere with other components in the airframe. Once the design is validated distributed manufacturing in the form of mobile 3D printing and finishing operations are co-located with the customer’s logistics operations allowing print on demand to meet critical inventory needs while other part replacements come on line. Once inventory has been established and retrofit operations completed the 3D model is archived and a print on demand relationship is established with the company.
If this sounds far-fetched let’s turn to another industry requiring precision 3D additive capabilities. Align Technologies was founded in 1997 and received FDA clearance in 1998 and introduced their Invisiline orthodontic process in 2000. Alignment trays are printed using an additive process. In addition Align Technologies acquired Cadent Holding, Inc. and their iTero and iOC intra-oral open architecture scanning systems allowing compatibility with laboratory based CAD/CAM milling systems as well as over 1,200 dental labs. Their more than 1.5 Million patient base was built on the existing 3D capabilities of the time.
The printing of a 285 µm model of a racecar and a 75 µm model of the St. Stephen’s cathedral using two photon technology by the Vienna University of Technology Austria in March 2012 show what may soon be possible. Printers with half-thousandth resolution in wax and 0.004 resolution in other materials are commercially available now. Yet such capabilities are in their infancy. The technology was unknown until 1984 and not readily available until the 2000’s. What remains is not so much a decision of if such technology holds promise as one of how your product design and development teams can best benefit from it. In an integrated design, test evaluation, and refinement environment multiple defined builds of moderate size and constant critique are now possible allowing for readily available reviews of the product. In addition, risks are reduced by developing superset releases wherein each subset remains relatively untouched. Most defects reside in the new portion (the previously developed part of the product is now a subset and proven defect-free). Should the previous iteration contain unresolved defects, the opportunity exists between these iterations to correct these defects. Frequent critical reviews utilized to guide design and to find faults along with frequent testing facilitates quality growth and reliability growth and data from which we can assess the product readiness level before final release to production. All of which is expedited through our 3D printer capabilities.