AIAA Tech Talk

The San Gabriel Valley Section of the AIAA presented a Weekend Tech Talk on October 20th, 2013 on Additive Manufacturing Techniques (Present and Future). The following guest speakers shared their experiences and challenges and their thoughts on the future of additive manufacturing:

  • Joan Horvath, Vice President of Business Development, Deezmaker 3D Printers
  • Mark Curran, Senior Aerospace Design Engineer, Structural Integrity Engineering
  • Behrokh Khoshnevis, professor of Industrial & Systems Engineering and Civil & Environmental Engineering, Director of the Center for Rapid Automated Fabrication Technologies (CRAFT) Director of the Manufacturing Engineering Graduate Program at USC.

Horvath brought two Deezmaker printers – a Bukobot and the smaller Bukito – to demonstrate before and between the presentations. The Bukobots printed plastic 3D copies of their logo as attendees watched and asked questions.

Horvath introduced 3D printing as additive manufacturing, in which the piece becomes bigger during the process through controlled adding of a material such as liquid resin, plastic, or powdered metal. This contrasts with subtractive manufacturing, in which part of the starting material is cut and smoothed away to form the final product. There have been far more examples of the latter in manufacturing, such as cutting, drilling, and milling.

She took the audience through a brief list of the first patents, beginning with the first working 3D printer, created in 1984 by Charles Hull (who later founded 3D Systems Corporation). He named his technique “stereolithography” and obtained a patent in 1986. Fused deposition modeling (FDM) was next in 1988, invented by Scott Crump. FDM involves melting thermoplastics and extruding them through a printing head into a filament, which forms the product according to computer program specifications. Crump went on to found Stratasys—whose products are expensive and aimed only at commercial use! However, in 2006, Dr. Adrian Bowyer at the University of Bath in the United Kingdom founded RepRap, an open source initiative to build a self-replicating 3D printer. RepRap units would be cheaply distributed to people everywhere, enabling widespread use of the technology.  In addition, many patents involved in FDM have expired or are going to in 2014, which has been opening the market for the development of cheaper FDM printers that even hobbyists can afford.

Horvath then described the various 3D printing processes. Stereolithography uses curable liquid resin extruded onto an elevator platform to build each layer of the product. The material is cured and solidified by an ultraviolet laser, and held together during the process by supports. Selective laser sintering (SLS) uses powder that is deposited onto a platform, with a laser tracing a cross-section and melting the powder in a specified pattern. Repeating this process forms the layers of the product, and no supports are necessary to hold the product together.  Fused filament fabrication (FFF) is the equivalent to FDM.  Deezmaker’s printers use the last of those technologies: FFF’s advantages are that it is cheaper (a commercial FFF printer costs $10K-$400K vs $100K-$500K for a commercial stereolithography printer or even as much as $1 million for SLS; and FFF printer kits are available for hobbyists for as little as $800), cleaner and safer (the powder used in SLS can be messy and the laser is expensive and too dangerous for home use, and the resin used in stereolithography is toxic), has less need for support, and can be used to print useful parts in several colors and types of plastics.

Diego Porqueras, president and founder of Deezmaker, first became interested in 3D printing while working as a camera tech in the film industry, as he wanted to make better and cheaper camera mount parts.  After using other companies’ printers, he grew interested in creating and improving his own, and ultimately went into business.  Deezmaker itself is a physical store as opposed to just an online presence. Anyone can come in, ask questions, and examine and purchase the printers. The store even has an open house on the first Sunday of each month from 12-5 pm, and is open 7 days a week from 11 am-7 pm (although that may change to 5 or 6 days a week).

3D printing is not just hitting a Print button. The process starts with a digital model generated either from 3D modeling software or from scanning an object with the desired shape. Slic3r then slices the model using G code generation, similar to Computer Numerically Controlled open source software, to generate the instructions for the 3D printer.  Arduino boards can enable cheap 3D printing.
What is the use of 3D printing? A 3D printed prototype can be produced more cheaply and quickly compared to a traditionally manufactured prototype. Within days, the prototype can be made and the design can then be tested and sent to the manufacturer.  In addition, FFF can be used to make products usually crafted with the more difficult SLS.  Horvath showed a bronze piece that had been cast from a mold created using a PLA model similarly to the lost wax process.  This involves printing the PLA model, pouring ceramic around it to create the mold, and then melting out the PLA to leave an empty mold behind. Deezmaker will be working with a sculptor who will create the final metal products.

Structural Integrity Engineering (SIE) is a company that redesigns, rebuilds, and reclaims old and unused aircraft. Curran described how SIE uses airplanes retired from service as test beds for new components. He briefly described examples, which included an engine for an old Honeywell 757 plane; installing a Row-44 broadband satellite antenna in an old Southwest Airlines plane; and testing new airplane engines for General Electric Aviation. The rest of Curran’s talk described SIE’s work for ORBIS International, a nonprofit organization fighting blindness in developing countries.

ORBIS’ Flying Eye Hospital is the world’s only airborne ophthalmologic training facility, not only providing care to patients worldwide but also training local physicians. The plane’s treatment facilities include an operating room, laser eye treatment room, and recovery room. A classroom hosts lectures, discussions, and live broadcasts of surgeries, during which trainees can ask question; videos are also made available to local institutions.  The current facility is housed in a converted DC-10 aircraft, but ORBIS is now partnered with SIE in building a new airborne hospital housed in an MD-10.

One particular challenge in designing the new facility was in producing an air duct with integrated mounted features. The part had to be designed to meet all FAA certification requirements for airflow.  The geometry was determined by the cost, shape stability, and the shape and size of the supports in the airplane.  Initially, the piece was to be 6 feet long, but this proved too expensive ($20-$30,000), whereas a 30” part would cost $7,000.  Curran and his team found that the air duct could be designed and fitted more cheaply and easily with a 3D printing process—FDM—than with traditional machining.  ULTEM 9085, a flame retardant high performance thermoplastic used for Fortus 3D Production Systems FDM, was chosen for the part.  ULTEM 9085 is engineered for harsh environments, with a high strength-to-weight ratio and is FAA compliant for smoke and toxicity regulations. The material has become widely used in the production of automotives, industrial equipment, and aircraft.  Solid Concepts built the air duct; they are experienced in additive manufacturing technologies as a provider of rapid prototyping, digital manufacturing, tooling and injection molding to the aerospace, automotive, industrial design and medical industries. Curran showed the results of a finite element analysis of the model to check stresses, and then showed the design drawing. A laser scan of the part was used to generate a point cloud image upon which the model was superimposed to reveal discrepancies. Then, the part’s fit was checked on the airplane.  Had they manufactured the duct using fiberglass—a more traditional approach—it would have taken much longer to receive the part from the manufacturer. With FDM, the team received multiple parts in a matter of days.  Also, more components could be incorporated into the part, minimizing the possibility of error otherwise resulting from splicing together multiple parts.

The air duct received an FAA Form 8130 airworthiness approval tag. It is the first 3D printed unit to be used in an ORBIS Flying Eye Hospital.

Khoshnevis is the Director of the Center for Rapid Automated Fabrication Technologies, or CRAFT. Its vision is to develop the science and engineering needed for rapid automated fabrication of objects of various sizes up to mega-scale structures such as boats, industrial objects, public art and whole building structures.

Contour crafting scales up the 3D printing processes described by Horvath and Curran. A computer-controlled gantry system moves a nozzle back and forth that extrudes concrete into thick successive layers, forming structures such as walls as large as 6 feet high and 6” thick. The nozzle has a trowel attached to smooth (ridges down to 2 microns) the sides of the extruded material, which otherwise would form ridges due to the layers’ thickness.  Concrete is difficult to work with, because unless it has the right viscosity, it will clog up the extruder as more is pressed into it.  Khoshnevis had patents for methods to address this problem, and partnered with the German company Degussa to develop the formulations. They ultimately created a concrete-composite fiber mixture that did not clog the extrusion nozzles nor leave sand behind.

Current construction methods have several disadvantages. They are slow, labor intensive, and wasteful, as well as harmful to the environment because of emissions from the vehicles transporting materials to the construction sites. Accidents account for 400,000 injuries per day, leading to increasing medical and legal costs—and construction projects are already costly and tend to run over budget.  Much material is wasted in current construction methods – roughly 3-7 tons per house. In addition, construction jobs may go to the construction company placing the lowest bid rather than to the best qualified.

Through contour crafting, entire neighborhoods can be built more cheaply, quickly, and safely compared with current, more conventional methods.  A 2,400 square foot home could be built in less than 20 hours.  Extrusion building of hollow walls takes a fraction of the time spent in making the forms currently used for concrete pouring. Khoshnevis showed pictures of hollow concrete walls, both straight and curved, made through contour crafting: these consisted of two outer smooth layers with a layer curving back and forth inside that left gaps.  A concrete metering system controlled the flow, while the nozzle extruded the material for the inside and outside parts of the wall at the same time.  Plumbing, rebar reinforcement, and electric components could be embedded into the material as it falls into place, as he showed in several animations.  LED lighting could be embedded into translucent concrete.  In addition, contour crafting is more environmentally friendly in that the machinery is electric and there is no need for exhaust-emitting vehicles to transport materials to the construction site.  Also, fewer people performing manual labor means fewer injuries.

At the same time, the contour crafting process is not new: Khoshnevis compared the layering of extruded material to the ancient practice of bricklaying.  He showed a picture of one of many old adobe houses in Iran, showing their beauty and how their curves gave them stability even though clay mixed with straw is not a strong material.

What are the ramifications of such improvements in construction? Khoshnevis answered with a slide of Maslow’s hierarchy of human needs, proposed in the 1943 paper “A Theory of Human Motivation”. Before people can even think about ascending to the hierarchy’s higher levels—safety, belonging, esteem, and ultimately self-actualization—they must meet their most basic needs, such as food and shelter. Many people in the developing world do not even have those.  Contour crafting could be used to build housing for low-income families, and also to build emergency housing, both quickly and cheaply.

Automated building would be especially valuable in the exploration and settlement of the moon and Mars.  Khoshnevis showed images of a landing pad design, apron and blast wall, with a far smoother and more heat-resistant surface than the rocky, hazardous lunar surface. Robots such as ATHLETE could be used in hangar construction. He showed mock-ups of lunar structures being designed in conjunction with NASA.  He also showed an image of a Collective Protection Shelter (CBRNE: Chemical, Biological, Radiological, and Nuclear Defense), created for the US Army; similar structures can resist harsh extraterrestrial environments.  Concrete for the lunar structures would be made from in situ materials. One problem is that lunar dust is notoriously difficult to work with because of the sharp bits, since no erosion has occurred on the Moon to smooth them.  Khoshnevis proposed using sulfur as a binder, heating a sulfur-lunar dust mixture to 250-300F in a heated nozzle.

Contour crafting will have considerable impact in many areas: economic, employment, social, regulatory, environmental, and architectural. Further research will be necessary to understand and address such ramifications.  Currently, national construction-related expenditures total approximately $1 trillion. Contour crafting can lower these costs considerably through being faster, cheaper, and far less wasteful or hazardous.  Construction costs due to financing (20-25% of total construction cost) would be greatly reduced by shorter project length and better control of time to market. Material (25-30%) costs would decrease because of lack of waste. Labor, the greatest portion of the cost (45-55%), will be significantly reduced.  Affordable housing could become available for many, especially for an emerging middle class in developing countries. At the same time, the reduction in labor would lead to the loss of employment in construction.  Further research is necessary to further understand how the new technology would change the need for construction-related employment: the decrease in unskilled labor and the increase in the need for new skill sets.  In addition, new building codes would have to be developed to address the methods and materials used incontour crafting.

CRAFT is addressing all of the above issues via an academic environment blending fundamental research with the development of large-scale engineered systems, incorporating environmental, regulatory, labor and economic expertise; partnerships with materials, equipment, construction, architecture, real estate, software and  manufacturing industries; and interdisciplinary graduate and undergraduate education.

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