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Laser-sintering shifts DFM paradigm

Apr 7, 2010 10:36 AM, Martin Bullemer Key Account Manager Medical EOS GmbH Munich, Germany
www.eos.info/

Gold medal winner Michael Teuber wears an orthesis laser-sintered from polyamide.

While surgical instrument makers are currently prototyping with plastic and metals, stainless steel PH1 (precipitation hardening), is now available. This material is characterized by high hardness, strength, and corrosion resistance and can be machined, sparkeroded, welded, micro shot-peened, polished, and coated.

Of great interest to the medical implant community is the devlopment of PEEK (polyether ether ketone) plastic for additive manufacturing. Both biocompatible and neutral in terms of interaction with the body, PEEK is less prone to cellular adhesions as some metals can be and has the added advantage of being permeable to X-rays.

Research on custom-made laser-sintered PEEK, as well as titanium, spine implants is currently underway. Future efforts may lead to the development of PEEK “bones” designed with an internal honeycomb structure to be lightweight, strong, and as bionic in behavior as real bones. Then, the stress shielding and bone deterioration caused by some of the current implants could be eliminated.

How laser-sintering works

Laser-sintering builds a plastic or metal product layer-by-layer, in three dimensions, turning the designer’s 3D CAD model into streamlined reality. The system cuts the CAD data into thin cross-sections (.004 to .006 inch for plastic, for example) and projects a plot file for each layer onto a build platform covered with a powdered form of the material to be sintered.


Direct metal lasersintering (left) of cobalt-chrome dental bridges and copings (right).
Photos: EOS

A laser traces the plot file, melting the material, which then solidifies. The platform is lowered by one layer, a new cross-section is sintered onto the previous one and the process repeats automatically to produce whatever geometry the designer has envisioned.

Applications for laser-sintering range from prototyping to manufactured series products and end parts. Particularly well-suited for smaller volume, custom-designed parts, laser-sintering’s precision and design flexibility are increasingly popular for use in the medical device, dental, surgical instrument and orthopedics industries—as well as aerospace and toolmaking.