One would think that after nearly three decades of additive manufacturing (AM) technology using various polymer materials, we would be further along than we are currently. In the 1990s, most of the parts obtained through the stereolithography (SLA) or selected laser sintering (SLS) process were of the touchy-feely variety. You could get a good idea of what the part would look like and if the dimensions were suitable, but that was about it.

While there have been some advances in materials, machines and processes over the past 15 years, the number of thermoplastic resins offered for 3D printing remains a problem. Compared to the number of thermoplastic resins in the mainstream plastics industry (as many as 77,000 different resins, according to some estimates), the options available for 3D printing are quite small. That is a limiting factor in the fabrication of actual end use parts in a production environment.

At RAPID 2015, a panel discussed this issue under the heading, Enabling Growth of Thermoplastic Additive Manufacturing. The panelists included Elizabeth Jordan, PhD and Director, Americas Industrial Technology & Innovation, SABIC. Jordan explained to PlasticsToday in a subsequent interview that the success rate for thermoplastic AM will be much higher if we make sure, as an industry, that there is simultaneous development in processes, materials and design. "The important thing is to understand and take advantage of the intersection of these three things," Jordan said. "Our goal is to understand and work actively with innovators in the value chain and enable the shift in additive manufacturing from prototyping to production parts that are economical to produce."

Steady progress is being made in the development of 3D printers, but one of the major obstacles to producing larger parts for industrial applications continues to be the size of the build chamber. Advances are happening, but not fast enough to meet application demand. Design is moving forward, as many of the CAD firms are including 3D printing design options in their software.

Jordan notes that collaborative efforts are beginning to pay off. She cited the collaboration with Local Motors (makers of the first 3D printed car, the Strati), Cincinnati Inc. and Oak Ridge National Laboratory. "In that case, we provided the high performance material—a carbon-fiber-filled Cycolac resin that improves strength-to-weight ratio and reduces part shrinkage—to build the Strati. We have other collaborations ongoing," she said.

One common material in aerospace applications is Ultem 9085 resin, a thermoplastic material used in Stratasys' fused deposition modeling (FDM) printers. "It provides functionality that is key and meets the flame, smoke and toxicity requirements for aerospace," notes Jordan. "As we move forward, there are some challenges we need to address in the [aerospace] industry to enable this shift from prototyping to part production. One of those is part performance. We need to match what we can do in injection molding. Ultimately we need advances in all three areas—printing processes, materials and design—to approach the performance properties of injection molded parts."

Other industries also require materials with properties and features for specific applications, said Jordan. "The flame, smoke and toxicity performance of Ultem 9085 resin is only one example. Other types of functionality for specific applications can include UV resistance or targeted electrical properties. However, these functionalities must be present in materials that result in viability and performance for the expected lifetime of the item. Our approach is to fundamentally understand how material properties, along with process and design, affect the resulting printed item with the goal of enabling thermoplastics to be an important part of production in additive manufacturing."

Additive industry must decouple the materials from the machinery

Also on the panel at RAPID 2015 was Jeff DeGrange, Chief Commercial Officer for Impossible Objects, a technology company that has developed composite-based additive manufacturing (CBAM). DeGrange has a long career in manufacturing, including in the aerospace as well as the 3D printing industry, and he understands the role that the availability of materials plays in the success of thermoplastic AM.

Impossible Objects' CBAM technology uses fabrics of carbon fiber, Kevlar, fiberglass and more. "What's really novel about the technology is the wide range of materials that can be used," said DeGrange. "Using sheets of nonwoven carbon fiber bonded with any type of semi-crystalline thermoplastic, we produce carbon-fiber-reinforced parts. You can pick whatever thermoplastic you want to use to bond these sheets together. We work with high-engineering-grade plastics from PEEK or PEKK to any commodity grade thermoplastic."

DeGrange explained that in order to get "wide-scale adoption" of 3D-printed plastic parts, two things have to happen. "First, you need to have a large number of thermoplastic materials to meet the properties required for a range of applications, and second, you have to able to buy them from anyone for production," he said. "One of the big limiting features in the 3D printing world—and a pet peeve of mine—is that you have to purchase the materials from the equipment OEMs. It would be like an injection molding machine supplier saying, if you buy our machine, then you can only buy the material from us.

"The additive industry is going to have to decouple the material and the machinery and allow third parties to sell materials and provide more material options for increased application uses. This is when you'll see the growth," DeGrange emphasized. "The larger 3D printing companies have an HP or razor blade mindset—we'll give you the razor or ink-jet printer, but you'll have to buy the blades or the ink from us. On the plastics side, you have Arburg with its freeformer machine or there's Cincinnati Inc. You can bring in 1,000-lb. gaylords of whatever pellets you need, and it doesn't matter where you're getting your pellets from as long as you know the material type for the process parameters."

Some of the applications that Impossible Objects is looking to supply are in the aerospace and automotive industries. Sheet molding composites for structural, low-cost transportation components involves putting woven materials into a matched metal tool under temperature and pressure to form the body panels or hoods. Essentially that is what Impossible Objects' technology does but minus the tool. "The goal is to replace aluminum parts in the transportation market with CBAM parts at least half the weight,"said DeGrange.

Impossible Objects is looking at motor sports, particularly the auto racing industry, as well as aftermarket opportunities. Another area is commercial drones. "A lighter structure means the battery-powered drone can operate longer," said DeGrange.

Longer term, Impossible Objects is working with Oak Ridge National Laboratory (ORNL ) to scale CBAM technology and use ORNL's low-cost carbon-fiber materials to produce high-strength, lightweight, energy-efficient structures. It will be critical for additive manufacturing systems to have open architectures capable of using third-party materials, so users do not have to wait for the 3D-printing equipment providers to come out with a wider range of materials.