International Journal of Advanced Science and Technology Vol. 29, No. 6, (2020), pp. 3362 - 3371 3362 ISSN: 2005-4238 IJAST Copyright ⓒ 2020 SERSC Influence of Infill density and Orientation on the Mechanical Response of PLA+ Specimens Produced using FDM 3D Printing Mohammed W. Alhazmi 1 *, Ahmed H. Backar 1,2 1 Department of Mechanical Engineering, College of Engineering and Islamic Architecture, Umm Al-Qura University, Makkah, KSA 2 Production Engineering Department, Faculty of Engineering, Alexandria University, Egypt * Corresponding author: mwhazmi@uqu.edu.sa Abstract Fused Deposition Modeling (FDM) is one of the famous 3-D printing techniques, wherever in this technique the specimen is built as layer by layer with different orientations deposition of molten thermoplastic material from the extruded filaments. These infill layer density and angle of orientation play an important role in mechanical behavior of the sample. Present research is an attempt to evaluate the tensile strength and the 3-D printed model Young’s modulus using ASTM D638 standard raster fill process. The tensile strength and the modulus were demonstrated to differ depending on the design orientation of similar test specimens. This paper aims to present the experimental tensile characterization of 15 different specimens 3D printed from poly lactic acid (PLA+) material. Specimens were printed with five different infill densities as follows (20%, 40%, 60%, 80% and 100%). Every infill has three different flat orientations (±45°, 45°, and 0°) to determine the directional properties of the material. Dog bone tensile specimens were printed and loaded to Exceed E42 universal testing machine. Yield strength, ultimate strength, and breaking strength were gathered for each tensile orientation combination. Results yield that both raster and build orientation affect Young’s modulus, the position of fracture and angle of fracture. Keywords: Miniature; FDM; Dog Bone Specimens; Material Strength Testing; Infill density 1. Introduction Today, rapid developments of new micro-products like microelectromechanical systems (MEMS) and their tendency toward miniaturization in many modern industries, including medical, aerospace, automotive, optics, electronics and biotechnology, have resulted in the urgent need to rapidly develop micro- and nano-manufacturing technologies and incorporate them in new micro-manufacturing phases [1,2]. New development approaches, such as micro-additive manufacturing, can be considered to increase the capability of micro-production technology in the real manufacturing field of 3D micro-components. Rapid prototyping (RP) (or additive manufacturing) technologies provide an revolutionary advantage in the production of prototyping processes. With the latest developments, physical 3D models can now be produced faster and with more complex geometries, moving RP technologies from