1. Can't draw the bottom line
Reason: The shuttle thread is too short, the shuttle thread is clamped in the shuttle door, the needle is too high, and the shuttle cannot hook the thread loop.
Solution: Stretch the shuttle thread, check whether the bottom thread is jammed, and eliminate it. Needle bar connecting shaft firm screw loosen and move the needle bar up, adjust the needle bar down, re-align the needle, and tighten the fastening screw.
2. The needle bar moves
Reason: Needle bar hole, needle bar wear, needle bar connecting screw loose, needle bar displacement.
Treatment method: change the needle bar cover, or select a new needle bar, re-align the needle; and tighten the set screw.
3. Jump over a few stitches
Treatment reasons: the shuttle is worn, the tip of the shuttle is too blunt, and the needle of the sewing machine is too high or too low.
Method: Change the shuttle, adjust the height of the needle bar or the height of the needle, and re-align the needle.
4. Continuous jumper or stitch cannot be sewn
Reason: The quality of the needle is poor or the needle is bent and the thread loop cannot be produced normally. The sewing machine needle is too high, the thread loop cannot be caught, and the sewing material and sewing machine needles are not properly matched. Long-term use of shuttle, swing bed and other parts are severely worn or broken.
Treatment method: replace the qualified needle or straighten the needle. Adjust the height of the needle bar or sewing machine needle. Under normal circumstances, the shuttle or shuttle bed can be replaced, and overhaul if necessary.
5. Thin stitch without jumper, thick stitch
Reason: Insufficient presser foot pressure, sewing machine needle is too thin, thread hook mechanism and other parts are severely worn.
Treatment method: adjust the presser foot pressure, change the needle, replace the parts, and repair.
6. Sewing thick jumpers and thin jumpers
Cause: The needle-containing hole of the needle plate is too worn, the needle of the sewing machine is too thick, the bottom of the presser foot is worn, or the presser foot pressure is too small.
Treatment method: change the needle plate, change the fine needle, change the presser foot, change the presser foot, or adjust the presser foot pressure.
7. Other reasons
(1) The threading method is incorrect. Re-thread the thread according to the "Threading Diagram".
(2) The straight needle is not installed correctly. Check the height and facing position of the needle, and move the needle down slightly in front of the needle plate hole.
(3) The needle point of the straight needle is broken or bent. Replace with a new needle.
(4) The tip of the looper needle becomes blunt. Polish it with oilstone or fine sandpaper, or replace the looper needle.
(5) Suture tension is too large or too small. Adjust the suture tension appropriately.
(6) The looper can't cover the loop of the straight needle on the right, and the right stitch of the lower decorative thread is skipped. The loop of the straight needle is too small. Increase the amount of jumper appropriately.
(7) The looper cannot cover the loop of the straight needle on the left, and the left stitch of the lower decorative thread is skipped. The loop of the straight needle is too large, so reduce the amount of jumper appropriately.
(8) The looper cannot hook the middle and left straight needle thread loops at the same time, and the middle and left stitches of the lower decorative thread have skipped stitches. Reduce the amount of skipping appropriately.
(9) The middle and left needle thread on the back of the looper cannot pass into the triangle of the knitting needle thread and looper thread. The middle of the back of the left stitch skips stitches. Check whether the suture passes through the thread clamp. Standard adjustment. (10) The needle and the looper are not matched properly. Check the height of the needle bar and the synchronization between the needle and the looper. If there is any problem, adjust it according to the standard.
(11) The needle and the needle guard are not matched properly. Check the position of the needle and the needle guard.
(12) Improper matching of the needle and the stretched needle or the wrong position of the stretched needle, causing the upper decorative thread to skip stitches. Check the matching size of the needle and the stretched needle, and check the amount of thread stretched out.
(13) If the tension of the thread take-up spring is too large or there is no thread take-up spring, it can be solved by loosening the thread take-up spring and installing it.
(14) If the tip of the rotary hook has a burr, you can use fine sandpaper to gently grind off the burr.
(15) If the position error between the rotary hook and the needle is too large, the problem can be solved by adjusting the position of the rotary hook and the needle.
The specific operations are as follows:
①Adjust the up and down position of the needle and the rotary hook. First, turn the needle to the bottom, and then slowly continue to rotate until the needle moves up slowly. At this time, the tip of the rotary hook should move to the middle position of the needle plane. Just adjust.
②After completing the first adjustment, you can adjust the position between the needle and the tip of the hook. Adjust the distance between the tip of the hook and the needle to 0~0.1mm and then tighten the fixing bolt of the hook.
