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Stitch skipping when sewing on the sewing machine

                       
Update:2021.09.2021-09-30T09:20:30+00:00
Summary:

      One, first determine the cause of skipped stitche […]

      One, first determine the cause of skipped stitches
   (1) Check whether the sewing machine needle is in good condition (bent, blunt, installed correctly, etc.).
   (2) Check whether the pattern line is correct, especially whether the line is on the line block, if it is not on it, it is easy to skip stitches.
  (3) Check the quality of the wire and whether it should be lubricated with silicone oil.
   2. After the above points are eliminated, the relationship between the sewing machine needle and the looper should be checked
   (1) Check the aggressive relationship between the curved needle and the sewing machine needle. Generally speaking, when the needle bar drops to the lowest point and starts to rise, the sewing machine needle thread loop on the far right will form a little, and the curved needle can begin to penetrate. The standard power position is: the relationship between the looper and the left sewing machine needle is that when the looper swings from right to left to the leftmost sewing machine needle, its tip is just about 0.5-1mm above the threading hole behind the left sewing machine needle.
   (2) Check the interference (clearance) relationship between the looper and the sewing machine needle. Generally speaking, the sewing machine needle can be skewed appropriately, that is, there should be a gap of 0~0.05mm between the sewing machine needle on the rightmost side (the shortest inside) and the looper needle, and the sewing machine needle on the leftmost side should have a gap between the looper needle and the looper. With a gap of 0.03~1mm, there is a deflection angle of 2°~5°. When the curved needle starts to swing to the right from the leftmost (dead point), there should be a distance of 1.5~2.5mm between the left straight line and the eye of the curved needle. At this time, the left straight needle passes through the back of the curved needle, that is, the straight needle passes through The looper thread, that is, passes through the loop of the looper triangle, and has an interference size of 0 ~ 0.05mm, otherwise it will easily cause skipped stitches.
(3) Check the relationship between the front and rear guard needles and the straight needles. Because the front guard needle and the straight needles are too large, the straight needle thread loop formation is not ideal, and the formation time is slow, causing the curved needle to pass through the thread loop. , Straight needles are unstable and easily misaligned to cause skipped stitches. If the guard position is too high or too low, it is easy to cause the thread bubble to fail to be thrown out and cause skipped stitches. The front and rear position of the guard: There should be a gap of -0.01~0mm between the front guard needle and the straight needle. The height position of the front needle guard: When the curved needle passes through the back of the straight needle from right to left, the front needle guard should be about 1mm higher than the needle tip of the leftmost sewing machine; the height of the rear guard needle should be formed by a straight needle thread loop. It does not affect the threading of the looper needle. The above points can be adjusted by referring to the parts drawing in the manual.
  (4) Straight stitches skip stitches at the seam head. This is because when the curved needle passes through the straight needle thread loop, due to the thick fabric at the seam, the straight needle moves backward, causing the curved needle to pass in front of the straight needle. The general reason is mostly that the needle guard fails to protect it in place. Just stick the back guard a little closer to the back of the straight needle. The needle guard just touches the sewing machine needle a little bit. And the gap between the front guard needle and the straight needle is also smaller, as long as the sewing machine needle is not lint, keeps the needle, or breaks the thread.
   (5) Skipped stitches caused by the loose thread cam. Generally, it depends on the tension of the looper thread and whether it is caused by the premature thread feeding time. If it is caused prematurely, just slow down the thread take-up cam. When the left sewing machine needle passes through the looper triangle line, it should be checked whether the triangle line tension meets the penetration requirement. If the thread tension is loose, it means that the thread take-up cam is feeding fast; if it is too tight, it means the thread feeding is slow, so adjust accordingly.

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