1. When the sewing is thick and thick, the needle is too thin, so that when the needle moves up and down, the vertical position of the needle is shifted to the left and right; the needle suitable for the sewing material is selected.

2. The needle is bent, the needle tip is hairy, and the needle screw is not tightened; the screw of the needle is tightened and the new needle is replaced.

3. When the sewing material is thick and thin, the machine speed is too fast, the needle is displaced, and the hook is broken and collided; the sewing speed should be slowed down.

4. During the sewing process, the sewing material is pushed and pulled by force, the needle is broken and the needle is broken, and the movement of the hands and feet is uncoordinated; the machine is correctly used according to the operating procedures.