Laser-Sintering 3D Manufacturing Made Simple
- Monday, 28 December 2009
Laser-sintering has evolved significantly since its commercial introduction in the 1980s. Born out of the rise of rapid prototyping technology, laser-sintering is now the design-driven catalyst for global innovation in such industries as aerospace, medical device design, automotive and consumer.
Simply said, laser-sintering removes the constraints of traditional manufacturing methods, such as machining, molding or casting, and concurrently allows for conceptualizing, designing and manufacturing certified, threedimensional parts directly from CAD data. The process is no longer onedirectional where, for so long, manufacturing requirements dictated, and thus restricted and controlled, design. Equipment and Process Laser-sintering builds parts additively and automatically from plastic or metal powder. A 3D CAD file is divided into cross sections by control software, which causes the laser-sintering system to deposit a layer of finely powdered plastic or metal onto a build platform. A focused laser then moves across the powder, sintering it into a cross section of the part. The platform lowers itself exactly the thickness of the first layer and the process repeats layer-by-layer until a three-dimensional part emerges. This production method creates parts with complex geometries, and sometimes integrates into a single part what would have been several if manufactured by traditional means.
Plastics laser-sintering equipment employs:
- 30-50-Watt CO2 laser with two 50-Watt lasers in larger P 730 and P 800 series machines.
- build size range from 200 mm x 250 mm x 330 mm (7.9 × 9.8 × 13 in) in the FORMIGA to 700 mm × 380 mm × 580 mm (27.6 × 15 × 22.9 in) in the P 730.
- laser scan speed of up to 5-6 meters/second (twice that in models with twin lasers).
- variable build layer thickness, depending on the material, from 0.1 mm to 0.15 mm (0.004 - 0.006 in.).
- nitrogen-filled build chamber, typically.
Direct metal laser-sintering (DMLS) equipment employs:
- 200-Watt ytterbium-fiber laser.
- effective build platform of 250 mm x 250 mm × 215 mm (9.85 × 9.85 × 8.5 in.).
- scan speed of up to 7 meters/second.
- variable laser focus diameter of 100 - 500 m (0.004 - 0.02 in.), controlled by the software as it moves across the powder.
- build-layer thickness from 20 - 40 m (0.0008 - 0.0015 in.), depending on the material and the application.
- nitrogen-filled chamber except when building in titanium, which requires argon to ensure an impurity-free final part.
The variety of available plastic and metal materials has expanded considerably in the past few years, with an emphasis on materials for manufacturing rather than prototyping.
With few exceptions, available plastic material for laser-sintering is based on PA 12 or PA 11 polyamide. The fine powder is resistant to most chemicals and, when laser-sintered, produces functional prototypes and manufactured parts with a highend finish easily capable of withstanding high mechanical and thermal loads.
Particular requirements of different applications call for variants of this material, such as filling the polyamide with aluminum, glass or carbon fiber. Another polyamide variant is PA 2210 FR, containing a chemical flame retardant that produces a UL 94 V-0 flammability rating and is free of halogens. Also, PrimePart DC, a new high-impact polyamide, offers an elongation at break of 50 percent, about twice as high as that of previously available materials. PrimePart DC has a tensile strength of 48 MPa and a Young’s modulus of 1550 MPa, with its other mechanical properties similar to those of PA 2200 series polyamides.