Browsing by Subject "plastic laser sintering"

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Feasibility Study on Plastic Laser Sintering without Powder Bed Preheating
(University of Texas at Austin, 2011-08-17) Niino, Toshiki; Haraguchi, Hisashi; Itagaki, Yutaro
In a plastic laser sintering machine, the most part of power consumption is spent on heating of powder bed. The powder bed heating is essential to prevent parts from warping during the process. However metal laser melting is normally performed without such heating. During the process, warping is suppressed by fixing the parts to a base plate. In the present research, the same scheme was introduced to plastic laser sintering. A plate of 2mm was successfully obtained. Residual stress was completely relieved by annealing treatment of 30min and permanent deformation was negligible. A relative density of 90%, which is standard level of commercially available part, was obtained. Tensile and impact strength were limited to 1/2 and 2/3 of those obtained by normal process, respectively. Energy consumption of laser module in preheating free process is around 45MJ/kg, and complete robustness against power supply interruption was demonstrated.
Improvement in Geometrical Resolution of Plastic Laser Sintering by using Reduced Spot Sized Laser
(University of Texas at Austin, 2010-09-23) Niino, Toshiki; Morita, Keisuke
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.
Low Temperature Selective Laser Melting of High Temperature Plastic Powder
(University of Texas at Austin, 2015) Niino, Toshiki; Uehara, Takashi
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.