Fused deposition modelling is an efficient rapid prototyping process used to rapidly fabricate three-dimensional solid objects with complicated geometries. Many process parameters affect the fused deposition modelling process and their settings influence the quality of the specimen. This article investigates the effect of raster angle on surface roughness (along and across the length direction) and mechanical properties (tensile and flexural strength) of fused deposition modelling parts built at 10 different raster angles (0°–90° at 10° interval). All parts are built using acrylonitrile butadiene styrene P430 material. Surface roughness for circular and parabolic curved surfaces is also measured when specimens are built at different raster angles. Fracture surfaces are inspected with scanning electron microscope to study the modes of failure under different loading conditions. The samples where raster angle is 0° and layers are deposited along the length of the specimen exhibited optimal mechanical strength and good surface finish (when measured along the length). Scanning electron microscope results reveal that for 0° raster angle, failures are mainly due to pulling and rupture of fibres and for 30° and 60° raster angle, failure is due to brittle shear in a direction parallel to raster orientation. Due to the presence of number of heating and cooling cycle in 90° raster orientation, interlayer cracking and distortion of raster take place leading to lower strength.