Growing global environmental threats have attracted researchers and engineers toward design and manufacture of green materials. In this regard, natural filler reinforced composites are environmentally friendly, cost-effective materials with a lot of advantages over conventional carbon/glass fiber reinforced composites. Hence, in this study, the drilling performance of walnut shell powder reinforced composite material was experimentally investigated. For this purpose, the composite specimens were first fabricated by injection molding process, followed by further drilling tests, which were performed with and without ultrasonic vibration. The effect of drilling parameters and ultrasonic vibration was investigated on surface roughness, thrust force and geometrical tolerances (circularity and cylindricity), as the process performance parameters. The obtained results demonstrated that by increase of the spindle rotational speed and decrease of feed rate, the thrust force, surface roughness and geometrical tolerances were reduced. Also, it was seen that ultrasonic vibration could effectively enhance the performance parameters, which was attributed to the intermittent cutting process and impact action of ultrasonic vibration, leading to reduced friction, improved material removal, reduced cutting forces, and better surface quality.
