Computerised sewing machines

Computerised sewing machines generally are a lockstitch (301 stitch type) sewing machine. An operator terminates a typical lockstitch sewing operation as following ... 

The above non-sewing activities are non-value adding and involve wasteful motions. Computerised lockstitch machines are developed to reduce and/or eliminate these non-sewing wasteful motions. There were four different generations of development of computerised sewing machines, and every generation offered incremental benefits in features. 

The fundamental principle behind a computerised sewing machine is the synchroniser, a device that monitors and counts the rotation of a hand wheel. While the synchroniser acts as the logic provider to the electronic circuit, the solenoids or pneumatic cylinders move the machine parts. With one complete rotation of the hand wheel, the needle bar completes one cycle of needle up/down movement. For example, when the needle is at topmost position, and the electronic marker is set at 90° position on the hand wheel, every time the electronic marker come to 90° position on the hand wheel the needle will be at topmost position. Using this logic, the synchroniser can... 

Figure 11.16 Control panel in a computerised sewing machine. From Typical Corporation product catalogue.

As the synchroniser can monitor the rotation of the hand wheel, it can also count the number of rotations of the hand wheel. One complete rotation of the hand wheel equates to one stitch formation. To ensure that thread is not slipped out of the needle hole while starting the next sewing cycle, all generations of computerised machines have one thread catcher and thread wiper fitted near the needle point. While the thread wiper swipes away the thread tail towards the right side of the stitch line, the thread catcher holds the thread end by suction or pinch force to ensure that the thread is not shpped out of the needle hole while starting the next sewing cycle. 

The first generation of computerised machine featured a needle positioner (NP) and UBT. The NP can definitively take/move the needle either up or down based on settings, when the machine stops and the UBT automatically cuts the threads whenever the machine gets a signal to complete/terminate sewing. While using this first generation of the machine, only activities (3), (5) and (6) in the list in Section 11.5 are eliminated, but the operator still needs to perform the rest of the wasteful motions. 

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