A sewing machine consists of four basic mechanisms: a take-up mechanism, a needle-motion mechanism, a material-feeding mechanism, and a bobbin. Its proper operation requires a delicate balance of these mechanisms. This paper introduces a computer-simulation model that represents these mechanisms and uses the model to predict the kinetic behavior of sewing machines. Based on the simulation. a quantitative understanding of the sewing machine can be achieved that leads to improved sewing-machine design and better sewing-process control. In particular, the balance of thread supply and thread requirement is studied. the thread supply is defined as the amount of thread supplied by the take-up mechanism within one stitch. The thread requirement is defined as the amount of thread required in one stitch and is controlled primarily by the bobbin mechanism. Both properties change instantaneously. From a practical point of view, if the thread requirement were much larger than the thread supply, then there would be skip stitches (when the loop cannot be formed properly) or even thread breakage. On the other hand, if the thread requirement were much less than the thread supply, then there might be poor stitches (with too much thread in the loop) or even needle-jamming. By using the simulation model, the instantaneous balance of the thread supply and the thread requirement is quantitatively studied. It is shown that the balance of thread supply and thread requirement can be changed and optimized by changing the design parameters of the take-up mechanism. The model is validated experimentally by using a Pfaff lockstitch industrial sewing machine.
Industrial sewing machines differ from traditional consumer sewing machines in many ways. An industrial sewing machine is specifically built for long term, professional sewing tasks and is therefore constructed with superior durability, parts, and motors. Whereas traditional sewing machines might include nylon or plastic gears, an industrial sewing machine's gears, connecting rods, housings, and body are typically constructed from high-quality metals, such as cast iron or aluminum. Beyond that, industrial sewing machines are made to handle thick materials such as leather, produce faster stitch rates, and incorporate stouter, more positive feed components than do their consumer equivalents.
Sewing Machine Feeds
Different industrial sewing machines offer several ways to feed the material. Typically, industrial mini sewing machines that deliver numerous feed capabilities are more expensive. The main types of feed mechanisms are:
Drop feed: The feed mechanism lies below the machine's sewing surface. This is probably the most common feed type. Toothed segments called feed dogs lift and advance the fabric between each stitch, with the teeth pressing upwards and sandwiching the material against a presser foot.
Needle feed: The needle itself acts as the feed mechanism, which minimizes slippage and allows workers to sew multiple layers of fabric.
Walking foot: The immobile presser foot is replaced with a foot that moves with the feed, which allows easier performance on thick, spongy or cushioned materials.
Puller feed: The machine grips and pulls straight-seamed material as it is sewn and can perform on large, heavy-duty items such as canvas tents.
Manual feed: The feed is controlled entirely by the worker, who can do delicate, personal work such as shoe repair, embroidering, and quilting. On industrial overlock sewing machines, it is sometimes necessary to remove the feed dogs to obtain a manual feed.
