Jumping is a phenomenon in which stitches cannot be formed continuously because the hook at the bottom of the machine cannot pick up the upper thread or the upper thread slips off after being hooked during the stitching process of the sewing machine. This is mainly caused by the mismatch between the movement time or movement position of the needle and the hook. Of course, it is also possible that the needle cannot form a loop, which leads to a jumper.
If there is a jumper, you can find the reason from the following aspects:
- Needle problem
(1) Check whether the upper thread is threaded wrongly or missed a certain thread position.
(2) Check whether the needle is installed correctly, such as the long groove of the needle is installed backwards or skewed.
(3) Check whether the needle model is applicable, whether the height of the needle bar adjustment is accurate, and check whether the needle is close to the top of the needle bar. If the needle is installed too high or too low, it will affect the hook thread.
(4) Check whether the needle is distorted. When sewing with a distorted needle, the hook cannot pick up the suture because the loop formed is far away from the hook. Slightly bent needles are difficult to identify directly with the naked eye, and can be identified by turning the needle on the platform.
(5) Check whether the movement time of the needle and the hook coincide. The movement time of the needle and the hook is fully matched, so that the hook can accurately hook the suture.
(6) Check whether the thickness of the needle and sewing thread are appropriate. The use of a large needle with a thin sewing thread can also cause jumpers. This is because the needle eye of the large machine needle is longer and wider, and the hole position for piercing the fabric is larger, so that the thin sewing thread has a larger space to move. If it exceeds the range of the hook and hook thread, a jumper will appear.
(7) Check whether the needle eye of the machine needle is blocked due to the melting of chemical fiber sewing thread scraps, so that the suture cannot be conveyed normally and cannot form a loop.
- Presser foot problem
Check whether the presser foot is installed too high and the feeding speed is too fast. If the presser foot is installed too high, the pressing force of the presser foot to feed the fabric will be insufficient. At this time, the fabric will vibrate with the presser foot, so that the upper thread cannot be pressed to form a loop. The presser foot is too fast. The upper thread is quickly taken away with the fabric, and the hook cannot catch the upper thread.
- Sewing thread problems
(1) Check whether the sewing thread is too thick, uneven in thickness or the texture of the sewing thread is too soft.
(2) Check whether the tension of the upper thread is too tight. The upper thread tension is too tight, and the needle loop formed under the machine tool is too small, and the hook cannot be hooked.
- Other issues
(1) Check whether the hook is defective. The missing hook cannot be hooked with sutures.
(2) Check whether the needle plate hole is too large. Many manufacturers did not replace the matching needle plate in time after changing to smaller needles when producing thin materials. The large needle plate hole causes the fabric to be brought into or out of the round hole position by the machine needle, and the sewing thread cannot be compressed to form a loop, and it will also cause the thread to jump.
(3) Check whether the feed dog, shuttle bed, etc. are silted with cotton dust and dust, and you should always keep it clean to avoid affecting the formation of thread steps.