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    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.

    With regard to these types of industrial sewing machines, the primary differentiation between them is based on the design of the bed. These four different sewing machine bed styles and their uses are as follows:

    Flatbed: The most common type, these machines resemble traditional sewing machines in that the arm and needle extend over the flat base of the machine. Workers typically use this machine for sewing flat pieces of fabric together. Some type of fabric feed mechanism is usually housed in the bed (see below).

    Cylinder-bed: These machines feature a narrow, cylindrical bed as opposed to a flat base. This allows the fabric to pass around and under the bed.  Workers employ the cylinder-bed machine for sewing cylindrical pieces such as cuffs, but it is also useful for bulky and curved items such as saddles and shoes.

    Post-bed: These machines feature bobbins, feed dogs, and/or loopers in a vertical column that rises above the flat base of the machine. The height of this column can vary depending on the machine and its application. Applications that make access to the sewing area difficult, such as attaching emblems, or boot or glove making, utilize the post-bed machine.

    Off-the-arm: The least common group, these machines extend a cylindrical bed out from the back of the machine perpendicular to the direction taken by the bed of the cylinder-bed machine. This allows for long runs of tubular goods, such as the inseams of trousers, and is useful for sewing sleeves and shoulder seams.

    Other special-purpose sewing machines exist, as well. Portable and fixed electric units are often employed for closing large sacks of agricultural products, dog food, etc. Bookbinders use special machines in their operations. Carpet installers also use special machines for binding carpet. Embroidering and monogramming machines are used for textile customization and decorating and are often program-controlled. Special long arm machines are made for sailmakers and purpose-built machines are available for cobblers.

    Sewing Machine Feeds