Search

The accuracy of the products of 3D printers is a very important parameter. Many parameters that affect this accuracy, such as staircase effects, support effects, radius effects, offset and curved boundary effects, slicing and swelling effects, properties and dynamic behavior of machine drives. This study looks for the relationship between the radius effect and dynamic characteristics of 3D printer machines with Selective Laser Melting technology on the accuracy of corner formation. As the research material, PLA powder was spread and leveled on a glass substrate to form a single layer of PLA powder with a thickness of 0.9 mm. In the process of forming objects that have an angle of 90°, theoretically, the tip will have a curvature radius equal to the radius of the laser beam. However, due to the occurrence of a melt that is wider than the laser beam, the fillet radius that occurs will be greater. In right-angle formation, 2 motion mechanisms are needed, the first motion mechanism towards the x-axis then stops in one position and the second motion mechanism towards the y-axis. This is the process of acceleration and deceleration of the two mechanisms. As a result of the start and stop process, this will also affect the shape of the formed fillet. To find out the shape that occurs when the laser position stops, four specimens are made by giving a laser power of 8, 12, 16 and 20 Watt respectively with a very short time. From the measurement of the results of melt in the form of dots, it turns out that the point diameter that occurs is an average of 2.05 mm and is not affected by the amount of laser power. Furthermore, specimens were made in the form of four 50 mm lines with a speed of 16 mm/s and laser power of 8, 12, 16 and 16 Watt respectively. The tip curvature radius at start and stop is almost the same as 1.1 mm. The size of the curvature radius at start process and stop process turns out to be the same as the point radius that occurs in the point formation experiment, so the curvature radius when forming the right angle is predicted to be 1.1 mm and not affected by the magnitude of the laser power. This is evident from the formation of a 90° angle specimen, i.e. the fillet radius that occurs is 1.1 mm. [ABSTRACT FROM AUTHOR]

This study aimed to provide a noise reduction technique for the radiator fan of vehicle engine cooling system. The study utilized a seven-blades fan radiator. The test deployed a TENMARS TM-102 installed in front of the radiator as a sound level parameter with a 7-point of semi-circle dBA units. A number of data variations were utilized in the experiment, which regarded to the width of damping, angular orientation and space between damping, as well as space between the damping and radiator. The width of damping varied in measures, including 4 cm, 6 cm, and 8 cm. The angular orientations ranged from 0° to 60° with a 15° interval. The space between damping varied from 2 cm to 4 cm with a 1-cm interval. Meanwhile, the space between the damping and radiator ranged from 8 cm to 12 cm with a 2-cm interval. The study implied that the installation of damping in front of the radiator could offer a noise reduction function of the radiator fan. The different data variations that were adopted in this study signified different results in the values of noise reduction of the radiator fan. The investigation obtained the best performance of noise reduction value by 6.9 dBA. [ABSTRACT FROM AUTHOR]

A new design of automotive refrigeration system for a passenger car was proposed. To ensure less energy consumption and optimal thermal comfort, the performance of the system were evaluated. This current research was aimed to evaluate the refrigeration characteristics of the system for several types of cooling load. In this present study, a four-passenger wagon car with 1500 cc gasoline engine that equipped by a belt driven compressor (BDC) was used as the tested vehicle. To represent the tropical condition, a set of lamps and wind sources are installed around the vehicle. The blower capacity inside a car is varied from 0.015 m/s to 0.027 m/s and the compressor speed is varied at variable 820, 1400, and 2100 rpm at a set temperature of 22°C. A set of thermocouples that combined by data logger were used to measure the temperature distribution. The system uses R-134a as the refrigerant. In order to determine the cooling capacity of the vehicle, two conditions were presented: without passengers and full load conditions. As the results, cooling capacity from any possible heating sources and transient characteristics of temperature in both systems for the cabin, engine, compressor, and condenser are presented in this work. As the load increases, the outlet temperature of evaporator also increases due to the increase of condensed air. This phenomenon also causes the increase of compressor work and compression ratio which associated to the addition of specific volume in compressor inlet. [ABSTRACT FROM AUTHOR]