Since Automated Fiber Placement (AFP) is used to manufacture twin-aisled commercial aircraft parts, extremely large envelope machines are often required and appropriate. Additionally, for very large parts, the average AFP course length may be on the order of one to two meters, and the part may have numerous contours. With courses of this length, a high acceleration machine is necessary to achieve fast laydown rates because the machine is frequently starting and stopping. Part contour also requires high acceleration machine axes to accurately maintain the AFP tow path at high feedrates.Large machines with high accelerations result in very large loads on bearings. Large loads and the long, high speed axis travels associated with large envelope machines make achieving a long service life difficult. Designing efficient, lightweight machine structures becomes critical to provide long machine service life. This paper compares two structural configurations of large AFP machines to achieve high acceleration, high stiffness, and long service life. A single-tower and two-tower post style machine structure were compared, demonstrating the performance advantage of the two-tower structure. The two-tower machine mass was reduced 49% below an existing single-tower machine and 29% below an optimized single-tower design while maintaining required stiffness.