The thread breakage and jumper of computerized sewing machine are generally caused by the incorrect installation of needle, the incorrect installation of needle, the bending of needle, the wrong threading, and the hard thread passing position. The thread breakage and jumper are caused by the unreasonable position of needle rod, the unreasonable time position and coordination between needle and rotary shuttle, and the abrasion and burr of shuttle tip, The working state of presser foot is not good or loose when sewing thin material, resulting in broken line, jumper and other problems; This is mainly due to the movement time or position of the needle and hook does not match.
The causes of jumpers can be found from the following aspects:
（1） Check whether the surface line is wrongly threaded or underthreaded at a line crossing position.
（2） Check whether the needle is installed correctly, such as the long slot of the needle is installed reversely or installed askew.
（3） Check whether the needle model is applicable, whether the height of needle rod is adjusted accurately, and whether the needle is close to the top of needle rod. If the needle is installed too high or too low, it will affect the thread taking of the hook.
（4） Check the needle for distortion. Using distorted needle suture, because the formed coil is far away from the hook, the hook cannot pick up the suture. The slightly curved needle is difficult to be identified directly by naked eyes. It can be identified by rotating the needle on the platform.
（5） Check whether the movement time of needle and hook is consistent. Only when the movement time of the needle and the hook is fully matched, can the hook accurately pick up the suture.
（6） Check whether the thickness of needle and sewing thread is suitable. Large needles with fine sewing thread can also cause jumpers. This is because the eye of the large machine needle is longer and wider, and the hole for piercing the fabric is larger, so that the fine sewing thread has a larger space to move. If it goes beyond the scope of the hook, there will be jumper.
（7） Check whether the needle eye of the machine is blocked due to dissolving and sticking the chemical fiber sewing thread, so that the sewing thread cannot be transported normally and the coil cannot be formed.