Powders Are Building Production Parts

Granules in an additive manufacturing powder should be 100 percent spherical.

Laser sintering, an industrial 3-D printing or additive manufacturing (AM) process, entered the manufacturing world as a technology primarily used for prototyping or proof of concept. Now it is building its own reputation as a production technology for quantities of functional parts. Equipment builders and material suppliers are keeping a laser focus on advancing the machine tools and powders used to build components a layer at a time and educating manufacturers and engineers about the high level of design flexibility that accompanies producing a part with AM.

Andrew Snow, senior vice president, EOS of North America Inc., talked with CIM about the growing AM market and the powders that form the parts.

CIM: How long has EOS been providing AM equipment and powders?

Andrew Snow: For 26 years EOS has been developing and providing the market with laser sintering technology. We continue to innovate. About one-third of our more than 700 employees and 15 to 18 percent of annual sales are dedicated to R&D. We have almost 2,000 systems installed worldwide.

CIM: Since AM has been an accepted industrial process for 26 years, why has it gained so much attention recently?

Snow: A lot of the movement and hype you see now are related to the consumer side of the business and the advent of affordable polymer printers for the home or office.

CIM: What types of metals can be used in the laser sintering process?

Snow: Laser sintering is virtually a microwelding process, so you can only process alloys that are weldable.

The powders that have been commercialized— maraging steel, stainless steels, nickel alloys, cobalt chrome, titanium, and aluminum—fit into a large variety of applications for various industries.

CIM: Are new powders being developed?

A cobalt chrome aerospace swirler has a highly polished exterior finish.

Snow: Applications drive the development of materials, and new materials drive the development of new applications. Indeed, there are materials out there that haven’t been officially processed for use in laser sintering, and these additional materials may become commercially available. But before a powder is commercialized, there has to be extensive research on its performance, and data needs to be collected to support its mechanical properties when used in an additive manufacturing build. And ultimately there needs to be enough market demand for the material.

New alloys are always being investigated by OEMs, manufacturers, and universities, but not all powders go to market. A material with a specific build parameter can be developed for a customer, but it might be proprietary or might not have a wide enough appeal to become part of the standard materials offerings.

CIM: What physical characteristics are important for an AM powder?

Snow: The shape of the granules is very important. They should be 100 percent spherical. And particle size and distribution comes into play. We work with particle size distribution of about 20 microns.

CIM: Should a manufacturer purchase powder from the OEM?

Snow: Powder can be purchased from the equipment manufacturer or an outside source. Some OEMs provide an assurance that their powders will perform with their machines. For example, our powder is offered into the marketplace as a prequalified lot of material. We add value to our powders by performing quality checks based on our specifications for material, consistent performance, and processing parameters. We design our systems around our materials and our materials around our systems so they work in sync.

CIM: What specifications make a component a good prospect to move from subtractive to AM?

Snow: In many cases we find that engineers, for example, are redesigning existing products and adapting them to additive manufacturing by lightweighting the original product. Front-end software allows for lattice structures to be implemented in the design to maintain the mechanical strength and properties and to take a significant amount of weight out of the product itself.

Also, we see part consolidation. Many customers are reducing the assembly and secondary manufacturing costs by taking an assembly of 10 or 15 parts that are brazed or welded together and consolidating them into one part. It streamlines the manufacturing process. Overall, laser sintering lifts the constraints of conventional manufacturing. Complex parts that are not achievable with traditional methods are now attainable via additive manufacturing. We look at this as being design-driven manufacturing as opposed to manufacturing-driven design.

CIM: Is there a difference between machining parts produced by AM compared to subtractive technologies?

An aluminum heat exchanger is lightweight and incorporates complex internal features.

Snow: There is really no difference in machinability. Parts produced with AM can be machined just like any other alloy. Treat additive-manufactured parts just like any conventional piece of barstock or material.

CIM: How does the material in an AM part compare to the material in a component produced by traditional technologies?

Snow: The material in an additivemanufactured part has less porosity, especially when compared to castings. There might be some surface porosity and an occlusion within the product, but the finished material will have a very high integrity and mechanical properties that are closer to the raw material than when working with other processes.

CIM: What can be done to avoid material occlusions?

Snow: If it is a really critical application, like for an aerospace component, many manufacturers will perform a secondary sintering of the component just to be sure that microporosity no longer exists.

CIM: How environmentally friendly is AM?

Snow: With laser sintering, nearly 100 percent of the powder that is not used, or in other words fused in the part, can be recycled. Unused material in the build chamber can be repossessed, reprocessed, and blended into the machine for another lot.

CIM: What else should manufacturers know about AM?

Snow: Unlike the subtractive manufacturing practices that have established design parameters taught in universities, AM has virtually no design restrictions. Very few rules have to be considered, so it offers new creative opportunities and provides design freedom.

We are beginning to see organizations, institutions, and universities developing additive manufacturing guidelines that will help engineers gain an appreciation for how things can be designed differently to gain the full advantages of metal fusion technology.

Titanium brackets withstand the high temperatures and external forces found in space.

www.eos.info