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May/June 2009
Feature

Manufacturing Goes Digital

New ASTM International Committee Tackles 3D Fabrication Technologies

Do you need a hearing aid that matches the exact shape of your ear canal? What about a full-color model of your favorite mountain range? Have you ever wanted a PEZ dispenser that looks like your third-grade teacher?

If you’ve answered “yes” to any of these questions — or even if you haven’t — all of these items can be yours thanks to any one of a number of different technologies that fall under the heading of additive manufacturing, also referred to as direct digital manufacturing.

“AM processes are a fundamentally different way of working,” says Professor Richard Hague, Ph.D., Loughborough University, Leicestershire, U.K., an industry veteran. “Each process has its strengths and weaknesses, and some are more suited to making specific types of parts than others.”

Partnering for a Common Goal

In response to the need for standardization in additive manufacturing, ASTM International has joined forces with the Society of Manufacturing Engineers to create a new committee covering the multiple technologies that comprise
additive manufacturing.

The mandate of the new group, Committee F42 on Additive Manufacturing Technologies, is to promote knowledge of the industry, help stimulate research and encourage the implementation of technology by developing a comprehensive set of standards. The request for the formation of Committee F42 was initiated by the SME rapid technologies and additive manufacturing technical community. Professor Brent Stucker, Ph.D., RTAM Steering Committee member from Utah State University, Logan, Utah, led the effort. Stucker, who has been researching AM technologies for more than 15 years, will serve as chair for the new committee.

“We have discussed the need for standards for many years now, but SME isn’t a standards-making body,” says Stucker. “We did not have the infrastructure in place to follow through on that need, but ASTM’s proven process and standards development infrastructure made it the logical choice for our needs.”

The partnership between ASTM and SME is an important milestone for the industry, notes Terry Wohlers, president, Wohlers Associates Inc., Fort Collins, Colo., SME fellow and a 20-year industry veteran. He sees the collaboration as a natural next step in the industry’s development. “Consensus standards developed by ASTM will influence the application and adoption of additive technologies in the manufacturing of products across a wide range of global industries.”

What is Additive Manufacturing?

Many conventional production processes such as milling, turning and grinding fall under the heading of subtractive manufacturing because material is removed to create the final part: Manufacturers start with a block of metal or wood and cut away the excess until the desired object is produced.

AM processes are exactly the opposite. Objects are created by adding material — layer by layer — until the part is formed.

There are a number of production methods that fall under the heading of additive manufacturing, but they all start the same way, with a CAD (computer-aided design) file — a computer generated, three-dimensional image of the part to be made. A computer analyzes the CAD file and digitally slices the object into multiple cross sections or layers — much like a deck of cards. The fabrication machine reads the CAD file and recreates the object layer by layer until the intended part is formed.

Some of the processes commonly used in AM include electron beam melting, stereolithography, fused deposition modeling, three-dimensional printing, PolyJet and laser sintering.

  • Electron beam melting is a process designed for the creation of metal parts. Powdered metal is fed into a vacuum-sealed fabrication chamber where it is heated and solidified by a beam of electrons. The machine lays down additional layers of material that are fused together, building on each other until the intended object is completed.
  • Stereolithography creates objects by moving a laser beam across the surface of a container of liquid polymer or plastic, causing it to harden and solidify. When the first layer of the object is completed, the container is lowered slightly, and the laser makes a second pass across the surface of the liquid to form another layer of the object. The layers bond to each other as they are created, building up on each other so that when the final layer has been completed and the remaining liquid is drained away, only the completed object remains.
  • Fused deposition modeling uses a heated tip to extrude thermoplastic materials such as acrylonitrile butadiene styrene and polycarbonate onto a build platform. After the first layer is formed, the platform lowers and the next layer is formed. The process repeats until the desired part is formed. A second material used to support the structure is deposited through another extrusion tip and is removed at the end of the process.
  • 3DP is a 3D printing process that uses an inkjet print head to deposit a liquid binder onto the surface of a powder such as a plaster-based composite material. The process is capable of depositing color ink, resulting in multi-colored parts.
  • PolyJet technology uses an inkjet print head to deposit photopolymer layer by layer. An ultraviolet lamp source cures and solidifies layers as they are produced. A second material, used for supporting the part(s) as they are being built, is also deposited and later washed away.
  • Laser sintering uses two chambers, a fabrication chamber and a supply chamber containing powdered material. The powdered material is dispensed from the supply chamber, and a roller moves it into the fabrication chamber. A laser melts and bonds the powder creating the first layer of the part. The fabrication chamber is lowered slightly and more powder is dispensed on top of the existing layer. This process is repeated until the part is complete. The fabrication chamber is raised and the excess powder is brushed or washed away.

Overall, AM production techniques provide manufacturers and designers with a number of benefits when compared to conventional techniques. Often, less material is used in the production process so that manufacturers benefit from lower production and materials storage costs. Also, because products are made directly from computer files, designers have more flexibility resulting in more refined and, in some cases, more ergonomically sound designs.

The Technology Applied

Even without a comprehensive set of standards in place, many products manufactured today — cars, planes, consumer electronics, sporting goods — are impacted in some way by AM technology.

“Many of the parts that go into these products are modeled or prototyped using the technology,” says Wohlers. “A growing number of custom, limited edition, and short-run production parts are also being manufactured using AM technology.”

To find examples of AM technologies in use, look no further than international aviation giant Boeing, which uses AM processes to make parts for such military and commercial aircraft as the F-18 fighter jet and the new Boeing 787 airliner. Sony Ericsson, the mobile phone company, uses the technology to model and prototype new designs, as does power tool producer Black and Decker. Two European companies, Arcam AB in Sweden and the Materialise Group in Belgium, both use AM technology to make artificial knees and other medical implants.

More artistic uses of the technology come from companies like Freedom of Creation Inc., Amsterdam, the Netherlands, which makes unique lighting fixtures and home furnishings. On the fun side, players of World of Warcraft, the popular online role-playing game, can have customized models of their characters made for them by Figure Prints Inc., in Vancouver, British Columbia, Canada.

AM technology has even crossed into the “sweet tooth” sector with the CandyFab Project. Using the Internet to share pictures and information, a group of intrepid do-it-yourselfers uses a modified version of the technology — with hot air and powdered sugar — to create sweet-tasting treats shaped like trefoils, chain links and giant screws.

Standards Will Set the Tone

The development of standards will help advance the AM industry in a number of ways. Manufacturers will gain an accurate way to measure the performance of different production processes as well as help ensure the quality of the end products. Purchasers and suppliers will gain a common set of parameters for specifying parts and equipment. A set of comprehensive standards will also provide researchers and developers with uniform procedures for the calibration of AM machines and testing the performance of new and existing technologies.

“Having comparable standards will make my job easier,” notes Richard Bryson, lead wind tunnel designer for Denel Dynamics, Centurion, South Africa, a manufacturer of missile and unmanned aerial vehicle systems. “The lack of standards has meant that before I can use model parts in the wind tunnel I have to manufacture test pieces and have those pieces tested. Next I have to present the test results to the facility managers and wait for their approval before I can actually manufacture the part, thus negating one of the big attractions of the technology — reduced lead times and cost.”

Comprehensive standards will mean that material producers in the U.S., Europe and throughout the world will be able to present the mechanical properties of their materials using common procedures. Says Bryson, “No longer will I have to try and correlate ASTM, ISO, DTI, BSI or other standards to decide what material or process I need to use to meet the requirements for a particular job.”1

Looking Ahead

“The industry is on the threshold of becoming something really big,” notes Hague, an officer in Committee F42. “This ASTM/SME initiative will lift the industry to the next level.”

Stucker agrees. “We believe that five years from now we’ll look back and see the formation of this committee as a turning point in the industry,” he says. “The development of standards will have laid the foundation for the widespread implementation of these technologies. It will be clear that this initiative was a catalyzing force.”

Want To Know More?

For more information, click here, or contact Pat Picariello, director of developmental operations, ASTM International (phone: 610-832-9720).

Reference
1. ISO: International Organization for Standardization; DTI: Department of Trade and Industry, U.K.; BSI: British Standards Institution.

 

Kessel Nelson is a freelance writer whose work has appeared in national and international publications, covering subjects ranging from art to energy to schizophrenia. He has a B.A. in history from the University of Pennsylvania, and he spends his time between Philadelphia and New York City.