While it was developed to 3D print ceramic materials, the Energy research Centre of the Netherlands (ECN) says Digital Light Processing (or DLP) can shape metal materials – without melting.
Unlike the techniques used in Selective Laser Sintering (SLS) or Electron Beam Melting (EMB), the ECN says the DLP process can build metals parts which feature a well-compacted and homogeneous structure.
Originally developed in 1987 by Dr. Larry Hornbeck of Texas Instruments, DLP is a type of projector technology which employs a digital micromirror device. It's used in additive manufacturing applications to cure resins and ceramics into solid 3D objects.
The European research project PHOCAM has developed systems and materials for lithography-based additive manufacturing technologies, but until now, the technology has been used to shape advanced ceramic materials.
The technique uses a ceramic-filled photosensitive resin which is selectively exposed, layer by layer, in thicknesses of between 25 and 50μm. After the initial structuring, a solid part consisting of a ceramic filled polymer is built. The polymer is then burnt off and parts are sintered to leave a fully dense ceramic result.
The key element of the current systems is a 'light engine' which uses digital mirror devices (DMD) and light emitting diodes as a light source. The use of LEDs, in combination with a customized optical projection system, creates a spatial and temporal homogeneity of the intensity of light at the build platform, and that has proved to be a significantly better system than that used in traditional light engines.
Featuring a resolution of 40μm, such systems are capable of fabricating dense ceramic parts with excellent strength. When used with alumina, densities up to 99.6% of the theoretical density have been achieved. Aside from technical ceramics like alumina, the process is also capable of structuring bioceramics like tricalcium phosphate.
The ECN's DLP method eliminates the metallic melt pool created by laser sintering machines, and because DLP metal manufacturing avoids the melting process, parts can be made faster and every layer of the resultant components are made of the constituent material, are equally as dense and contain the same conductive properties.
Working in conjunction with InnoTech Europe, Formatec Ceramics and Admatec Europe, the DLP process is used to manufacture ceramic materials and parts.
But according to Jan Opschoor, a researcher in Materials, Testing and Analysis at ECN, the DLP process can be used in powder metallurgical shaping as well.
"We think that this technology will make a large number of new applications possible that could not be produced, or could hardly be produced, in the past," Opschoor says.
The adaptation of DLP technology for metals is expected to open new avenues for high-tech companies to produce machine parts using a new range of metals and alloys in powdered form.