جستجوی مقالات مرتبط با کلیدواژه « selective laser sintering » در نشریات گروه « مکانیک »

Selective laser sintering is one of the methods of additive manufacturing based on powder bed which is widely used in various industries today. In this process, the amount of laminated mass has a high impact on reducing the porosity and quality of the final parts produced. For this purpose, in this study, a mechanism was designed and developed to investigate and achieve the maximum amount of laminated mass in a laminating process. The optimal state was obtained using the central composite design method. The results show that the parameters of blade velocity, angle under blade, and excess powder percentage have a greater effect on the amount of laminated mass, respectively. The optimized laminated mass was predicted by the experimental model to be 0.811 g, in which case the velocity is 2.78 cm / s, the blade angle is 3.1 ° and the initial powder content is 159%. To validate the model, the experimental experiment was performed based on the parameters of the optimal state, in which the laminated mass was measured 0.83 g, which shows that the error of the obtained model is 2.2%.

With the development of additive manufacturing technology, the quantity of devices that can be used in small office with the commercial or educational purposes increases. In this research, the goal is to build a desktop 3D printer with selective laser sintering technology, which can be used for research purposes. The main concentration is focused on fabrication with parts that can be manufactured in the country or can be procured from the domestic market. It is also tried to make the 3D printer compatible with the common open-source additive manufacturing softwares. The fabricated 3D printer has the ability to work with all kinds of common polymer powders. In addition, it is easy to update the device's firmware according to the researcher's needs. The capabilities of the device was tested with Glucose powder, paraffin wax powder, and thermoplastic-ceramic material combinations. It is currently used for research on fabricating ceramic parts with indirect laser sintering.

Selective laser sintering is one of the most popular additive manufacturing techniques used in recent years, due to its capability to build complicated geometries without the support structure. Thermal history plays a major role in the mechanical properties of the final product. In this research, the effects of different cooling down processes on mechanical properties of PA12 parts produced by selective laser sintering have been investigated. For this purpose, temperature changes of different points inside the powder bed during the built and cool down process have been monitored and recorded. Crystallization kinetics for the produced parts has been investigated by the non-isothermal crystallization model to help the interpreting of the results. Differential scanning calorimetry and X-ray powder diffraction (XRD) analysis were performed to find the degree of crystallinity and its possible correlation with mechanical properties. The results indicated that the parts cooled with the lower cooling rate showed 5% higher tensile strength and 10% more crystalline structure fraction comparing with the other two cool down methods. The results of crystallization kinetics for the produced parts by non-isothermal crystallization model showed that a lower cooling down rate led to slower crystallization in the component. The degree of crystallinity of the slow cooling down parts was about 10 percent more than the other samples. Based on the XRD results, the crystalline structure of the parts in all cooling down processes was the same (γ form crystal).