A seat assembly machine includes a plurality of grippers useful for securing a piece of trim to a seat cushion. In a disclosed example, each gripper includes a plurality of prongs that are moved between neutral, closed and released positions that each facilitate a different portion of the assembly process. In one example, each gripper includes a sleeve within which the prongs are moveable so that the prongs are manipulated between the neutral, closed and released positions. A disclosed example sleeve includes an interior channel having a contour that manipulates the prongs between the different positions based on the location of the prongs within the sleeve.