What are the elements to measure stitch quality? Stitch quality is measured with : • Stitch size. • Stitch tension. • Stitch sequence. • Elasticity. • Resilience. • Elongation. • Fabric distortion. • Yarn severance. • Abrasive strength. Principle of Lock Stitch Formation • Stitch class-300 is called lock stitch. It can be formed by the interlacing of two or more threads. • One group of thread is passed through the fabric and interlaced with the another group of thread and formed lock stitch. • One set of thread is called is needle thread and another set of thread is called bobbin thread. Lockstitch utilizing a rotating hook invented by Allen B Wilson. This is employed on many modern machines. The following are the steps referred as the principle of stitch class-301 formation : Step-1 • After finishing 2nd stitch the needle and the sewing thread are in the top position, preparing for next stitch. • In this situation thread take up lever goes to its maximum position and fabric has advanced one stitch. • Needle is entered with threads through the fabric and reached to its lowest position. • Again needle moves up a bit and stops for a while. At that time thread take up lever also moves downwards and a loop is formed due to the upward moving of needle. The formed loop is called needle loop. Fig : Step-1 Step-2 • It is informed that, the hook of bobbin holder always rotates at half circle. • Due to rotation of the half circle bobbin holder hook catches the needle loop and moves the needle loop over the bobbin case. • Interlacement takes place between the loop of bobbin thread and needle thread. Principle of Lock Stitch Formation Fig : Step-2 Step-3 • Needle start to move up wards with needle thread and take up lever also starts to move upward. As a result, needle loop pulls the bobbin thread upward. • In the mean time fabric is also moves one stitch forward due to feed dog mechanism. Principle of Lock Stitch Formation Fig : Step-3 Step-4 • Loop clears bobbin and take-up draws to loop closed. • It should be remembered that tension of bobbin thread and needle thread should be proper for correct appearance of stitch formation. So that it must be adjusted before sewing start. • Needle thread tension can be adjusted by tensioning disc and thread guide path changing. • Bobbin thread tension can be adjusted by small screw which is attached on the case through tightening and loosening. Principle of Lock Stitch Formation [...]...Fig : Step-4 Principle of Lock Stitch Formation Step-5 • In this stage, needle descends to lowest point to stroke • New loop has been formed and is passing around bobbin • Loop is pulled up to complete the stitch Fig : Step-5 Thanks to All . What are the elements to measure stitch quality? Stitch quality is measured with : • Stitch size. • Stitch tension. • Stitch sequence. • Elasticity. • Resilience. • Elongation. • Fabric. machines. The following are the steps referred as the principle of stitch class-301 formation : Step-1 • After finishing 2nd stitch the needle and the sewing thread are in the top position,. through the fabric and interlaced with the another group of thread and formed lock stitch. • One set of thread is called is needle thread and another set of thread is called bobbin thread. Lockstitch