Olli Nyrhilä

Direct Metal Laser Sintering – New Possibilities in Biomedical Part Manufacturing

Direct Metal Laser Sintering (DMLS) has been utilized for prototype manufacturing of functional metal components for years now. During this period the surface quality, mechanical properties, detail resolution and easiness of the process have been improved to the level suitable for direct production of complex metallic components for various applications. The paper will present the latest DMLS technology utilizing EOSINT M270 laser sintering machine and EOSTYLE support generation software for direct and rapid production of complex shaped metallic components for various purposes. The focus of the presentation will be in rapid manufacturing of customized biomedical implants and surgical devices of the latest stainless steel, titanium and cobalt-chromium-molybdenum alloys. In addition to biomedical applications, other application areas where complex metallic parts with stringent requirements are being needed will be presented.

Correlation between pyrometer monitoring and active illuminaton imaging of laser assisted additive manufacturing of stainless steel

Laser assisted additive manufacturing which can e.g. be used for manufacturing of 3-D parts from stainless steel powder layer-by-layer by assist of laser beam. Stainless steel is molten selectively with laser beam and solidified layers of material, attached to each other, form desired 3-D structure.Nowadays range of materials that can be used for laser assisted additive manufacturing is widened and high automation level of equipments has made this method more interesting process for manufacturing. This is why also methods to control the process have started to gain an essential role in laser assisted additive manufacturing processes. Control of process parameters is also essential to get good appearance, good quality and good strength properties of work piece still maintaining the optimum processing speed. Control of temperature in of process is most important of all numerous process factors.The objective of this study was to monitor selective laser melting process simultaneously with pyrometer and video camera system with active illumination. Aim of this study was also to find out correlation between phenomena captured with imaging system and pyrometer measurement data.All tests in this study were carried out at Lappeenranta University of Technology with trial set-up of IPG 200 W SM CW fiber laser and a layer of metal powder. An inert atmosphere was simulated by nitrogen gas flow during process. Material used in this study was EOS StainlessSteel PH1.Results indicate that several phenomena observed from video imaging system had correlation to pyrometer measurements. This makes pyrometer monitoring suitable method for controlling laser sintering process.Laser assisted additive manufacturing which can e.g. be used for manufacturing of 3-D parts from stainless steel powder layer-by-layer by assist of laser beam. Stainless steel is molten selectively with laser beam and solidified layers of material, attached to each other, form desired 3-D structure.Nowadays range of materials that can be used for laser assisted additive manufacturing is widened and high automation level of equipments has made this method more interesting process for manufacturing. This is why also methods to control the process have started to gain an essential role in laser assisted additive manufacturing processes. Control of process parameters is also essential to get good appearance, good quality and good strength properties of work piece still maintaining the optimum processing speed. Control of temperature in of process is most important of all numerous process factors.The objective of this study was to monitor selective laser melting process simultaneously with pyrometer and video ...

Dimensionally Accurate Mold Inserts and Metal Components by Direct Metal Laser Sintering

One of the main deficiencies in today‘s rapid tooling techniques is the capability of producing only near net-shape parts. Direct Metal Laser Sintering (DMLS) is a technique that enables the fabrication of true net-shape parts in just a few hours with only minimum postprocessing. The DMLS is a laser-based rapid tooling process developed in Europe by Rapid Product Innovations (formerly Electrolux Rapid Development Finland) and EOS GmbH Germany. Rapid Product Innovations was also the first to implement this technology to functional prototyping by using two proprietary bronze-based powders and a new steel-based powder. The technique enables the fabrication of tailored microstructures from porous matrix to near full density. Thus, functionally gradient structures can be fabricated, i.e. material is sintered to full density only where it is needed. This paper describes the philosophy of fabricating true net-shape mold inserts and metal components, but also concentrates on how to maintain the dimensional accuracy even after the post-processing. The study shows that even +/− 0.05 mm accuracy can be obtained. The results of the study also illustrate the beneficial effects of reduced layer thickness and post-processing on the surface roughness and mechanical properties as well as the suitability of various conventional and non-conventional coatings. With reduced layer thickness, the step-shaped effect of the layers was no longer visible. The surface was even further improved by shot peening and coating. In addition, case studies from injection molding, pressure die-casting and direct metal component fabrication are presented.

Preliminary characterization of phenomena occurring during single track fabrication in laser additive manufacturing of stainless steel

Laser additive manufacturing (LAM) is a layer wise fabrication technology which enables the production of complex shaped, individually designed parts with mechanical properties comparable to conventionally manufactured parts. However, the part manufacturing is relatively slow and via this whole production feasibility is not yet totally studied for real series production, as findings from literature shows. It is obvious that many of those studies are carried out in companies “behind locked doors” and because of this whole era of research is suffering of this lack of information.Even though the throughput time from idea to real metal product is short, the throughput time of the actual LAM phase could still be improved to gain more feasible fabrication method. Due to this, it is necessary to increase the build rate in order to improve the process efficiency and also improve whole production feasibility of LAM. It was observed that there are only few public studies about process efficiency of laser additive m...

Effect of process parameters to monitoring of laser assisted additive manufacturing of alumina ceramics

Nowadays the widening range of materials suitable for laser assisted additive manufacturing (laser sintering and laser direct melting) and high automation level of equipments has made this method more interesting process for rapid manufacturing. Also use of alumina (Al2O3) as a raw material in these cases has raising interest among different industries, since has very favorable properties like high hardness and high melting point. Alumina is used industrially for example as abrasive, filler, isolator, catalyst and catalyst support.Laser assisted additive manufacturing of alumina has been very difficult according to literature. There exist a lot of methods to build-up 3-D structure of work piece with the assist of laser beam. In those cases, typically a binder is mixed to alumina and laser melts/evaporates this binder which is joining the particles together thus giving the shape to work piece, such that in final construction alumina particles are very close to each others. This is followed with post-heating during which the closely packed alumina particles are actually sintered/melted together. There are only a few articles of direct laser beam sintering of alumina. In this case laser beam directly melts material and a 3-D structure is formed from alumina powder layer-by-layer as solidified layers of material build on top of each others.The aim of this study was to examine effect of heat profiles by changing laser power and scanning speed to monitoring of additive manufacturing with direct laser melting /sintering of alumina ceramics. The monitoring was done by using spectrometer, pyrometer and video camera system with active illumination. All tests in this study were carried out with a commercial laser sintering facility EOS M270 installed at Stockholm University (Sweden) consisting of IPG 200W fiber laser and inert atmosphere. The pure alumina powder was used as precursor material.Process was examined with fixed monitoring devices previously mentioned. The obtained results were collected to be for afterwards analyzed. The microstructure of laser sintered alumina ceramics was characterized both by optical microscope and scanning electron microscope. Results indicate that as laser assisted additive manufacturing is a sensitive process; also change of the process parameters has strong effect to monitoring results. This could also be noticed from micrographs taken from sintered parts of alumina.Nowadays the widening range of materials suitable for laser assisted additive manufacturing (laser sintering and laser direct melting) and high automation level of equipments has made this method more interesting process for rapid manufacturing. Also use of alumina (Al2O3) as a raw material in these cases has raising interest among different industries, since has very favorable properties like high hardness and high melting point. Alumina is used industrially for example as abrasive, filler, isolator, catalyst and catalyst support.Laser assisted additive manufacturing of alumina has been very difficult according to literature. There exist a lot of methods to build-up 3-D structure of work piece with the assist of laser beam. In those cases, typically a binder is mixed to alumina and laser melts/evaporates this binder which is joining the particles together thus giving the shape to work piece, such that in final construction alumina particles are very close to each others. This is followed with post-heatin...