ISSN: 2277-9655 [Wicaksono* et al., 6(8): August, 2017] Impact Factor: 4.116 IC™ Value: 3.00 CODEN: IJESS7 http: // www.ijesrt.com © International Journal of Engineering Sciences & Research Technology [230] IJESRT INTERNATIONAL JOURNAL OF ENGINEERING SCIENCES & RESEARCH TECHNOLOGY INFLUENCE OF INTERNAL GEOMETRI ON MECHANICAL PROPERTIES OF 3D PRINTED POLYLACTIC ACID (PLA) MATERIAL Sigit Tri Wicaksono*, Hosta Ardhyananta, Arif Imbang Pambudi *Materials and Metallurgical Engineering, Faculty of Industrial Technology, Institut Teknologi Sepuluh Nopember Surabaya (ITS) Jl. Teknik Industri, Kampus ITS Sukolilo Surabaya 60111 Indonesia DOI: 10.5281/zenodo.843886 ABSTRACT Three dimensional (3D) printing technologies have been developed within recent decades and have been demanding for today practical application because of its advantages such as low cost production and easy and simple to use. However, there are still weaknesses in the printing result and processing, including the process efficiency, limited resolution especially for complex design of resulted product, and optimization of the mechanical properties of the filaments used. This study aimed to analyze the effect of variations in the internal geometry on the mechanical properties of 3D printed object using PLA materials. The printed object varied by geometrical shapes and thickness of each geometry. Internal shape geometry used is a triangle and honeycomb, with variations in the size of each symmetry axis of the goemetry are 4.5 mm and 9 mm, and the thickness variation between objects are 1 mm and 2 mm. Test results show that the best performance obtained by measuring its tensile and flexural strength is the sampel with triangle geometry of 9 mm geometrical size and 2 mm of thickness. The tensile strength and flexural strength values of the object are 59.2996 MPa and 123 MPa respectively. KEYWORDS: 3D Printing, internal geometry, Polylactic Acid, mechanical properties INTRODUCTION Generally, there are two types of prototyping method base on the steps of processing methods, bottom-up and top-down prototyping. The bottom-up method mean the printing process started from nothing to become a bulk product of printed prototype. The top-down method use a reverse method at which a printed prototype resulted from a bulk precursor materials. Both of prototyping method have been developed widely [1,2]. Three- dimensional (3D) printing is one of the most versatile and revolutionary additive manufacturing (AM) techniques to create 3D objects with unique structure and diverse properties. 3DP is possibly categorized as bottom-up or top-down prototyping methods depend on the precursor materials used. Presently, there are various techniques or method of printing such as fused deposition modeling (FDM), stereo lithography apparatus (SLA), continuous liquid interface production (CLIP), digital light processing (DLP) and selective laser sintering (SLS) have been developed to form stereoscopic objects with complex architecture. In the late 1980s, S. Scott Crump developed FDM 3D printer and it was commercialized by Stratasys in 1990 [3]. Now, FDM become the most applicable 3D printing method, because of the ease of use, low operational costs, and environmentally friendly. These advantages enhance the development of a wide range of prototype products and manufacturing processes in various industries for various applications. The development of printing three dimensional objects cannot be separated from the development of various software designs that allows creating three dimensional objects and printing them using a 3D printer machine. Commonly design software used before printing three dimensional objects are Solid work and Inventor. The application of the design allows users to create three dimensional objects with a specific format and then convert it in stereo lithography format that can be applied to three dimensional object printing software. On the other hand, results products using FDM 3D printing typically has mechanical properties that are not better than the injection molding process because there is a weak point between the layers. As well as the depreciation happened by the thermoplastic material when the cooling process [3, 4]. In research process and refinement of FDM, of course there are many variables and parameters with the aim of producing three dimensional objects with good results and the level of accuracy approaching its original design and can be applied as the design expected. These variables include the type of printer used, printer dimensional