Direct laser sintering (DLS) is seeing rapid uptake in the construction of unmanned aerial vehicles. DLS is an additive manufacturing (AM) technique that can produce some of the most durable high-quality products around. Aerospace manufacturers -- along with numerous users in the medical sector -- are taking advantage of AM to produce low volumes of complex products requiring high precision.
"We're seeing a growing interest in DLS for aerospace," Andy Snow, EOS regional director for North America, told us in an interview.
The process can be used to make parts as simple as basic clips that hold harnesses. Some typical applications include components of engines and turbines, as well as parts for cabin interiors. Manufacturing gas turbine engines for use on commercial aircraft -- a use of DLS that's accelerating quickly -- is one high-value application. More manufacturers are identifying many components within the engine that can be laser sintered.
A wing fuel tank for an Arcturus T-20 UAV made with EOS laser sintered plastic (PA 2201) by Northwest Rapid Manufacturing (part of the Northwest UAV Propulsion Systems family of companies).
Photo courtesy of Northwest Rapid Manufacturing
EOS DLS systems process different materials, including polymers and metals. Part of the reason for using laser sintered parts is to reduce part counts and simplify assembly procedures. Another is the speed and cost-effectiveness with which fully operative parts with complex geometries and aerodynamic properties can be made available. Other factors include material and weight savings, which can reduce fuel consumption. In addition, manufacturers get fully integrated parts faster and reduce costs. They can also produce small batches and make manufacturer-specific modifications, such as in the cabin.
But the fastest-growing demand in aerospace is from makers of UAVs for lightweight components. Northwest UAV Propulsion Systems’ Northwest Rapid Manufacturing business, for example, uses EOS laser sintering systems to produce polyamide and polystyrene UAV components. Laser sintering melts materials at high temperatures and lays them down one at a time in thin layers, making it possible to create complex and unusual shapes.
In North American automotive applications, EOS is still focused primarily on rapid prototyping. "But we have some low-volume manufacturing applications for specialty, limited-series, custom-made automotive designs and luxury vehicles using DLS," said Snow. Those production runs are around 2,000 vehicles per year. Car manufacturers and their suppliers are also using EOS processes in the Formula 1 industry for very small quantities.
Medical and dental uses for DLS are growing rapidly. The materials that have been developed for these applications, such as EOS PEEK HP3, are biocompatible and capable of being sterilized, since they withstand very high temperatures.
Laser sintered parts made of EOS PEEK HP3 have a continuous use temperature of 180°C for mechanical dynamic, 240°C for mechanical static, and 260°C for electrical. One of the highest-volume uses for making end-products is dental copings and crowns. Another is patient-matched cutting and drilling guides, such as for knee and hip replacements, which have been used in hospitals for the past three years. "In one hospital, surgeons reduced the number of operating trays per surgery from a dozen to one or two," Snow said.
Laser sintering is, in fact, being used for very small production quantities in aerospace and high-end automotive applications, such as race cars. Dave, you hit the nail on the head--one reason is for very small volumes where the cost of tooling is huge and amortizing it over a few parts make them very expensive parts, indeed. It's also being used to make the pattern for the mold in plaster cast aluminum parts, as a substitute for die-cast parts. Stay tuned--a January feature article looks at low-volume manufacturing with AM techniques, including LS.
My point was intended to assert that a means of forging without needing a forging die, strictly a noncontact forging mechanism, such as a bust of laser energy to create a shock wave equivalent to the forging impact. Probably it would not be competitive beyond relatively small production runs. My thought was that if an approximation of a hammer forging process could be developed that would be the way to get 100% density and a desireable grain pattern.
In short, it would wind up being a fundamentally different technology from anything that we have presently.
Yes, we are also using additively-manufactured (AM) patterns for investment-casting of various copper and nickel alloys, as well as stainless steel. Another point to consider is that AM is the only means of producing complex patterns effectively. Case-in-point, there are numerous articles being released on the internet discussing the "world's lightest material," produced using an AM pattern.
Doug, can you tell us what kinds of parts you're making using AM for investment casting? If they're for automotive, medical, aerospace or industrial applications, we'd like to find out more about your application. Please send me an email if you'd like to share some information.
@Doug: Actually, it might be more accurate to call the technique used by the group at UCSB to make the ultralight metallic microlattices which have recently been seen balancing on the head of a dandelion "subtractive manufacturing." First, they made a pattern out of a photocuring polymer, then they coated it with electroless nickel, then they etched away the plastic. It's a fascinating approach. I would never have thought of using electroless nickel plating as a stand-alone structural material!
I agree with you that additive manufacturing is a great way to make patterns for castings - and not just investment castings, but also sand castings.
What kind of rapid patterns are you using? When I worked in investment casting 5 - 6 years ago, we mostly used QuickCast patterns. These are epoxy patterns made using a stereolithography process. What makes them unique is that they have a cellular structure, which allows you to burn them out with a minimum of ash and without cracking your mold. A disadvantage is that they are not autoclavable, so you can't take a QuickCast pattern and put it on a wax sprue. We also used wax patterns made on a ThermoJet 3D printer. They were autoclavable, but the dimensional accuracy was not as good.
Given how quickly things have been developing, I wouldn't be surprised if there have been new developments in the past few years.
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