Transparentization of SLS Processed SMMA Copolymer Parts by Infiltrating a Thermosetting Epoxy Resin with Tuned Refractive Index

Selective laser sintering is quite advantageous to build complicated tubular structures such as intake manifolds of automotive engines because of its ability of building undercut structures without using support ribs. On the other hands, inevitable opacity of the parts obtained from the process is lowering its advantage when we need to observe inside of the parts. A technology that can transparentize SLS processed parts by infiltrating curable resin with tuned refractive index was introduced by the authors in 2004, and in this paper, several modifications are added on material, process parameters and their control accuracies to improve clarity of obtained parts. As a result of these modifications, haze of the processed part was reduced by a factor of 40% reaching the lowest value of 20% through a plate with thickness of 5mm.Mechanical Engineerin

Effective Mechanisms of Multiple LED Photographic Curing

Multiple LED Photographic Curing (MPC) has proven capable of drawing cross sections of three-dimensional objects like printing a sheet of paper. Using raster scanning, however, simultaneously exposing a photopolymer with 1,024 beams of light involves various unknown issues. The aim of this research work was to examine the formation of individual strings and the connecting mechanisms between strings and layers. At light power ranging from 19.0 to 30.3flW and at various scan speeds, string formation perpendicular to scan direction differs greatly from that in scan direction. Curing of plane layers happens by curing strings side-by-side with a constant spacing of 62.5flm.Mechanical Engineerin

Laser Sintering Fabrication of Highly Porous Models Utilizing Water Leachable Filler-Experimental Investigation into Process Parameters

The authors are developing a laser sintering process to fabricate highly porous models with such high porosities as 90% and more. In the process, water-soluble filler is mixed with designated plastic powder and leached out after laser sintering process is finished to generate pores where the grains used to exist. Previously, the authors reported successful application of this technology on a tissue engineering scaffold. However, relationship between process parameters and obtained results has not been clarified. This paper reports experimental investigation into effects of optimizing process parameters such as mixture, grain size of the filler on resultant porosity, pore size and process resolutionMechanical Engineerin

Effect of Powder Compaction in Plastic Laser Sintering Fabrication

Powder compaction is introduced into plastic laser sintering fabrication. Compaction was carried out by using a roller of which rotation speed is independently controlled of its traversing speed. This additional process improved packing density of powder bed by a factor of 20% and reduced residual porosity of obtained parts by a factor of 30%. As an advantage, powder compaction can improve mechanical strength of parts of semi-crystalline powder, but increases excessive sinter to reduce fabrication accuracy especially in fabrication of amorphous plastic. This paper presents characteristics of the powder compaction process itself and its effects on performance of obtained parts.Mechanical Engineerin

Low Temperature Selective Laser Melting of High Temperature Plastic Powder

In a typical plastic laser sintering or melting system, powder bed temperature is maintained above the recrystallization temperature of the powder material to prevent the parts under process from warping until the whole layers are processed. Although this countermeasure can elegantly suppress the part warpage, heating the powder bed to such a high temperature causes many problems. In case of high temperature plastic such as polyetheretherketone (PEEK), bed temperature should be more than 300°C. Due to this requirement, machine cost is extremely high and powder recyclability is very low. The authors had introduced another countermeasure for the part warpage that anchors the in-process parts to a rigid base plate instead of heating the powder bed above the recrystallization temperature. In the current research, application of this method to PEEK powder is tested, and a simple test piece of which relative density is more than 90% was successfully obtained with preheating temperature of 200°C. In this paper, mechanical performances of obtained parts are presented, and several problems with the process of PEEK powder are discussed as well.Mechanical Engineerin

SLS Fabrication of Highly Porous Model Including Fine Flow Channel Network Aiming at Regeneration of Highly Metabolic Organs

Fabrication of very porous scaffold for regeneration of highly metabolic organs is reported. Polycaprolactone (PCL) powder was mixed with fine salt grains as filler and SLS processed to develop a model including fine flow channel network. The fabricated model was rinsed with water to dissolve the salt, and high porosity of 90% was successfully obtained. Additionally, residual powder in the channels was effectively removed by solution of the filler. Through micro-CT observation, it was confirmed that channels of which diameter was smaller than 1mm were successfully fabricated and repeating branching and merging. Result of culture test is also reported.Mechanical Engineerin

Process Resolution of Laser Sintering Process Using Plastic Powder Containing Inorganic Filler at a High Rate

Research is being performed on a laser sintering process in which inorganic filler is employed as porogen at a high content to fabricate highly porous three dimensional tissue engineering scaffold. Previously, the scaffold, which included capillary like flow channel network, was used in cell culture test, but obtained cell density was limited due to insufficient fineness of the network structure. In the scaffold fabrication the author experienced degradation of process resolution when inorganic filler was introduced at a high content, but reasons for the low resolution has not been cleared. This paper investigates the dominating cause of the low resolution. Discussion is focused on effect of optical and thermal properties of filler. Experiments using transparent and opaque fillers are performed, and existence of dominating effect of difference in the optical property is denied. Experiments using thermally conductive solid filler and insulating hollow filler is performed, and it is concluded that temperature conductivity is dominating on process resolution.Mechanical Engineerin

研究速報 : Making five atomic force microscope for 200,000yen each : A student project

特集2 日仏マイクロメカトロニクス国際共同研究組織(LIMMS

Implementation of Tophat Profile Laser into Low Temperature of Poly Phenylene Sulfide

Poly Phenylene Sulfide is a high performance plastics that is used in high-value parts. The most commercially available plastic laser sintering machines employ Gaussian profile CO2 laser. In this research, low temperature process of the material with tophat profile laser is tested. By using tophat profile, a tensile strength of 64.5 MPa was obtained. The value is equivalent to 75% of those from injection molding and 140% of standard laser sintered polyamide. Tophat profile effectively suppressed sparkling and fuming and improved surface finish decreasing surplus sintering or sticking powder.Mechanical Engineerin

Improvement in Geometrical Resolution of Plastic Laser Sintering by using Reduced Spot Sized Laser

Plastic laser sintering is one of the most promising processes for rapid manufacturing among various additive manufacturing (AM) technologies. Though the process tends to be applied to fabrication of larger parts in comparison to stereolithography, its ability of creating complex structure as an advantage of additive manufacturing technologies should be demonstrated in production of smaller parts and parts including fine and complex geometries as well. In this research, narrow CO2 laser beams with spot diameters of 130µm and 150µm were tested while the commercially available machines are equipped with those around 500µm. Relationship between resolution (available wall thickness) and spot diameter is proportional when the diameter is greater than 150µm, but effect of reducing the spot size further is not significant. The minimum wall thickness of 180µm was obtained, but this part was so fragile that skill in breakout treatment is critical. To discuss the mechanical strength of micro-plastic-laser-sintering, packing rate of obtained parts was introduced as an index of the strength. Build parameter that minimizes the wall thickness without decreasing the tensile strength below 30MPa was searched, and a set of parameters that provides minimal thickness of 0.6mm was obtained. Reducing laser spot size inevitably leads to shrinkage of scanning range of galvanometer mirrors. To overcome this problem, the whole laser scanning system was set on an X-Y positioner which are driven by stepper motors. The whole exposure area is divided into some regions each of which is smaller than range of galvanometer mirror system, and it is exposed by repeating fast scanning by galvanometer mirrors and slow sliding by the X-Y positioner. Problems occurring at the region boundary were investigated. As counter measures, overlapping of exposure areas and switching of region boundary are introduced and successfully eliminate the problem.Mechanical Engineerin