A Study on the SMLS Process as a Industrial type Solid Freeform Fabrication System

摘要

Selective Laser Sintering (SLS) is a useful rapid prototyping technique for the manufacture of three dimensional (3D) solid objects directly from a scanning data. A new approach called a Selective Multi-Laser Sintering (SMLS) system has been developed at Korea Institute Machinery & Materials (KIMM) as a industrial type SFFS. This SMLS machine is built with a frame, heaters, nitrogen supply part, laser system. The control is performed by the homebuilt control program made using Visual C~(++). This system uses the dual laser and 3D scanner made in Solutionix? to improve the precision and speed for large objects. The 3 dimensional solid objects are made of polyamide powder. The investigation on each part of SMLS system is performed to determine the proper theirs design and the effect of experimental parameters on making the 3D objects. The temperature of the system has a great influence on sintering the polymer. Because the stability of the powder temperature prevents the deformation of each layer, the controls of the temperature in both the system and the powders are very important during the process. Therefore, we simulated the temperature distribution of build room using the temperature analysis with ANSYS program. Selected radiant heater is used to raise temperature of powder to melting point temperature. The laser parameters such as scan spacing,, scan speed, laser power and laser delay time affect the production the 3D objects too. The combination of the slow scan speed and the high laser power shows the good results without the layer curling. As a result, we find the optimum condition for our machine as 0.35 mm in scan spacing, I m/s in scan speed, 13 Watts in laser power, 165℃ in temperature of build room and 140℃ in temperature of feed room. This system can be used to make the large size industrial samples such as transmission covers, cylinders, engine blocks, chassis of automobile and duplications of object with high precision and speed. The work is under way to evaluate the effect of experimental parameters on process and to produce the various objects. We are going to experiment continuously to improve the size accuracy and surface roughness.