Direct Metal Laser Sintering (DMLS) produces high strength and finished metal parts

10 March 2012: A few weeks ago I received a press release about EOS, the laser sintering company based in Germany, that got me thinking about their process. They claimed to directly produce parts, specifically knee joints, from an additive machining process that could be used in orthopedic surgery. Nick O’Donohoe, of the PR firm, the Parker Group, stated that “A sea change in medical treatment—mass customized, patient-specific care devices—will be evident at this years’ American Academy of Orthopedic Surgeons (AAOS) meeting. There, EOS and its customers are displaying all types of innovative, high-quality orthopedic products that excel in effectiveness, fit, and comfort.”

Of course, from my years in the industry I knew quite a lot about additive manufacturing, but naively assumed it only produced low temperature and low stress capable plastic type parts.

After a little research into the background of laser sintering I was surprised to learn EOS’ laser sintering can produce parts made from chromium steel and even titanium! The difference between the melting points between plastic and these metals was several thousand degrees. I was determined to find out how this was done.

I scheduled a call with Andy Snow, Regional Director at EOS of North America. I have attached a summary of call below. But first, I had to learn a bit about powder metallurgy and high power lasers.

How it works

Basically it works similar to an SLS (stereo-lithography) additive machining process. A laser is directed to the material and it solidifies the material. In this case the material is powdered metal and the laser is high powered enough to fuse the metal in its beam area to a depth of 20 microns (typically SLS systems solidify plastics at an 120 to 200 micron depth). The elevator is lowered 20 microns, powdered metal is swept over the previous layer and the process repeats, of course with the laser beam directed to the precise locations based on an original CAD converted model.

Other similar technologies include laser sintering and electron beam welding. It is left to the reader to examine these alternatives for their particular requirements.

Conclusion

While EOS DMLS systems are pricey ($600K+) compared to plastics additive manufacturing, the choice using of high strength metals directly in this process offers the users a final product ready  for use, possibly after some clean-up such as polishing. In addition, certain geometries possible with additive manufacturing, such as internal channels, can be machined no other way. See the references below for additional links.

Disclosure:

No compensation of any sort was provided for this article.

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An interview with Andy Snow, Regional Director at EOS of North America

RAY: EOS has a unique approach with its direct metal laser sintering (DMLS). I am interested in the strength of the materials and finishing process and what’s required to produce a finished product? Can with start with a discussion of orthopedic knee replacements?

ANDY: Traditional knee replacement devices are made using a casting process. Our EOS produced parts are far better than cast materials, which need secondary machining and polishing.

RAY:  Does your final product also need additional machining operations?

ANDY: Yes, for orthopedic devices intended for implants, which need porous surface for orthopedic implants.

RAY: Porosity; does powdered metallurgy need binders?

ANDY:  Not in DMLS (direct metal laser sintering), as opposed to traditional sintering process.

RAY: I read that EOS systems melt Titanium. Is this true?

ANDY: Yes pure Titanium.

RAY:  What does a system cost?

ANDY:  $600k to 750K USD, depending on what materials you need to process.

RAY: Does titanium-sintering cost more?

ANDY: Not necessarily. It depends mostly on if there is a need to process multiple metals.

RAY:  Does the operator just dump a pail of powdered metal in the hopper and go?

ANDY: The input is powdered metal. It works similar to a stereolithography process – growing geometry layer by layer by heat from laser. Layers for our metal process can be 20-80 Microns depending on alloy. Plastics typically are thicker and 100 to 150 microns per layer.

RAY: EOS machines are slower?

ANDY: Yes

RAY: How slow? What are some example build times?

ANDY: It is geometry dependent. For example, a quantity of 16 54 mm acetabular knee cups take about 16hrs to build. The same builds in plastics might be six times faster. Of course plastic cannot directly be used for knee cups. However, patient specific drilling guides are often built in plastics. VisionAire is one trade name. [You can find out more at http://global.smith-nephew.com/us/patients/ABOUT_VISIONAIRE.htm%5D

RAY: How is this better than selecting from a suite of fixed knee cup sizes, as is most often done today?

ANDY: A custom product matches the bone geometry exactly. Thus there is a better fit.

RAY: What are the cost aspects as compared to mass-produced parts?

ANDY: The patient match is better because operating room expense is less because easier to install.

RAY: Are there any special environmental requirements?

ANDY: Nothing special is required, except within the EOS machine for specific metals. The EOS machines are typically in a machine shop at the OEM.

RAY: Does the metal sintering use a co2 laser?

ANDY: Plastics additive manufacturing uses CO2. DMLS uses Diode pumped fiber optic laser, 200W or 400W

RAY: what about finishing?

ANDY: Detail finish out of metal is better due to laser spot size; layer difference, and material particle size. Plastic 60 microns, metal 20 microns. Metal can use even smaller particle size because it’s heavier. Company is exploring micro laser sintering of 1-5 microns.

RAY: what other industries use this DMLS technology?

ANDY: Aerospace, especially in turbine designs.

RAY: Who is the competition in MLS (Metal laser sintering)?

ANDY: The competition is mostly German companies. These include SLM Solutions, Phenix Systems, and ARCAM with electronic beam technology. The DMLS acronym is only used by EOS.

RAY: What makes you better than the competition?

ANDY: Our finished part quality. We are the industry leader with 60-65% of the market share. We have a strong technical base. EOS has about 400 employees with 1/3 dedicated to R&D.

Here are some images supplied by EOS:

A laser-sintered drill guide designed to conform to the patient’s bone geometry. (Courtesy Materialise)

A DMLS-made gas turbine prototype swirler in cobalt chrome. (Courtesy Morris Technologies)

An EOSINT DMLS system laser-sintering cobalt-chrome dental copings and bridges in a batch. Each bridge can be a different custom design, based on dental data from an individual patient (Courtesy EOS)

An EOSINT M 280 direct metal laser-sintering (DMLS) system. (Courtesy EOS)

References:

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 Below is the press release that I quoted earlier:

EOS DEMOS LATEST ADVANCES IN LASERAY: SINTERED ORTHOPEDIC PRODUCTS AT AAOS 

Customization of implants and drill guides provides significant advantages to surgical teams

Novi, MI, February 2, 2012—For proof positive that laseRay: sintering is changing the face of medical design and manufacturing, attendees of this year’s American Academy of Orthopedic Surgeons (AAOS) meeting can stop by the EOS booth (#259). The world leader in laseRay: sintering systems is showcasing a working EOSINT M 280 direct metal laseRay: sintering (DMLS) system to demonstrate the extraordinary benefits the technology offers for orthopedic applications. The evidence includes a wide range of innovative medical products and prototypes used for instrumentation as well as spinal, joint, and cranial surgeries. The show is being held February 8-10 at the Moscone Center in San Francisco (California).

“An entire new world of orthopedic treatment and procedures has opened up,” says Martin Bullemer, EOS manager for medical business development. “Because our laseRay: sintering systems can cost-effectively manufacture any imaginable geometry, and any variation on it, they are changing the way we think about medical products.”

Laser sintering is an additive manufacturing process involving next-to-no tooling, molding or machining costs. As a result, devices can be economically mass-customized to conform to the requirements of individual doctors or patients. Orthopedic suppliers use DMLS and plastics laser sintering to create a diverse array of drill guides, clamps, implants, and surgical instruments.

EOS-related activities at the AAOS meeting include:

  • EOS customers C&A Tool (booth 4017), Morris Technologies (booth 359), and Oxford Performance Materials (booth 2821) are exhibiting laseRay: sintered products and prototypes. C&A and Morris both focus on DMLS, while Oxford Performance Materials uses the EOSINT P 800 with high-performance polymers to manufacture customized medical implants.
  • Highlights from WITHIN Technologies Ltd include their FEA/CAD optimization software that works with EOS’ plastic and metal laseRay: sintering systems to create strong, lightweight parts including innovative lattice structures.
  • FHC is exhibiting its new line of patient-customized stereotactic fixtures for cranial targeting. The new fixtures are more accurate and comfortable for the patient than standard stereotactic frames and are suitable for a broad range of head types, and for targets not easily reached with a traditional frame. They also reduce operating room times for the procedure by as much as two hours.

“Many surgeons and medical designers are only just now becoming aware of the breadth of applications made possible by this manufacturing technology,” says Fred Haer, CEO of FHC. “The laseRay: sintered products on display at this meeting are at the forefront of a revolution in personalized patient care.”

About EOS

EOS was founded in 1989 and is today the world-leading manufacturer of laseRay: sintering systems. Laser sintering is the key technology for e-Manufacturing, the fast, flexible and cost-effective production of products, patterns and tools. The technology manufactures parts for every phase of the product life cycle, directly from electronic data. Laser sintering accelerates product development and optimizes production processes. For more information visit www.eos.info

2 responses

  1. Another medical AM application worth mentioning is acetabular cups, where the EBM (Electron Beam Melting) technology is used for series production of CE-certified and FDA-cleared orthopedic implants, with more than 20.000 EBM-manufactured acetabular cups with integrated trabecular structures implanted to date.

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