(II) The Stitching Robot

The robot-supported three-dimensional stitching system described here is based on the principle of a continuous relative motion between the stitching head fastened to a robotic arm and the stationary work piece held by a work piece fixation device. This system (see fig. 1) can be applied to all stitching types which are used for the processing of FRP preforms. A major advantage is that the stitching machine does not need work piece feed items known from conventional stitching machines. Thus, careful handling of the work piece is ensured and structural damage caused by the transport system can be prevented. A precondition for the continuous relative motion between the stitching head and the work piece is that the needles have no sideward movement in seam direction while they are in contact with the material to be stitched.

This is guaranteed by a mechanical differential gear, the so called transverse slide drive. The vertical upward and downward movements of needles occur concurrently to a back and forth movement in seam direction. For this purpose the moving axles of both stitching tools are integrated in a common framework. This framework is moved against the positive seam direction as long as at least one needle is in contact with the work piece. The velocity of this movement corresponds to the seam building velocity. When neither of the two stitching tools is in contact with the work piece, the transverse slide movement in seam direction takes place.
Fig1Robotics A Hi-Tech_decrypted
Figure 1 : Robotic Stitching System (iii) Double lock stitch