1. The upper thread is floating

        Analysis: The tensioner pressure is too small.

        Treatment method: tighten the wire and increase the tension of the cotton thread.

        2. The bottom line is floating

        Analysis: The shuttle spring is too loose.

        Treatment: Tighten the bobbin screw to increase the tension of the bottom thread.

        3. The length of the stitch is short and long.

        Analysis: The presser foot pressure is too small.

        Solution: Tighten the pressure screw.

        4. Each needle under the sewing material has a thread sleeve, which is in the form of a towel line.

        Analysis: The feeding and picking actions do not match.

        Treatment method: Adjust the feeding cam screw to make the feeding and the thread take-up action match.