There are many factors that affect the broken line, so as to make the broken line less, the machine's parked must be horizontal and smooth, the jitter of the running time is small; the spindle rotation should be light; the gap between the parts should be small; the installation position of each part should be accurate (the parameters of each reference point); the crossing line and hole should be smooth; the following are some more common breakages. Reason：
A) the smoothness of the needle is not enough, the polishing of the needle slot and pinhole is not good, and the needle tip is blunt.
B) the needle is bent, or the installation is not in place;
C) the installation angle of the needle is not correct, the line is not straight, the left side or the right side is too much, or the line slot is on the back.
D) there are attachments (like glue) in the pinhole.
E) the position of the clamping screw is not right. It should be 40 degrees to the right side.
A) the quality of the line is poor, the strength is not enough, too hard and too brittle, there are too many joints on the line tower.
B) the rotation direction is incorrect, and the left-hand line is applied.
C) the tension of the line is too large;
D) line off line;
E) the line is not matched with the needle number;
3. over line system
A) there are rough or burr lines across line holes, line passing wheels, line crossing hooks, clip wires, upper, middle and lower lines, line picking rods, pick up springs, etc.
B) a needle with a needle and a burr on the foot.
C) needle plate coarse or burr hole;
A) scratches on a spin or a large gap;
B) the surface of the shuttle shell has scratches.
C) the deformation of shuttle and spindle.
D) there are scratches on the positioning rod.
E) poor lubrication;
5. parameter (installation position)
A) the position of the dead point of the needle bar (172 degrees);
B) the volume of the hook line (196 degrees);
C) needle height (172 degrees in the rotating plane of intrafusal pinhole center);
D) line picking time (286 degrees);
6. the patterns are too dense or confused.