Sewing machines use similar devices, called feed dogs, to move the cloth beneath the presser foot.

Sewing machines use similar devices, called feed dogs, to move the cloth beneath the presser foot. The motion of the feed dogs can be simulated using fuctions of the type abs(sinkt)/ sinkt in place of sines and cosines. use this to design a set of parametric equations to produce a stitch that looks like "z's"