Correct maintenance method for needle skipping of overlock sewing machine

The correct repair method for skipped stitches of the stretch sewing machine is to follow the principle of "check before adjustment", and systematically check and adjust the key links such as threading, machine needle, crochet (looping needle) synchronization, needle protection, and suture tension one by one. ‌‌
General inspection and basic adjustment
Before adjusting complex mechanisms, the following basic checks should be completed, which are often the simple reasons for needle skipping. ‌‌
Check and thread correctly: Ensure that all stitches (face and bottom) are correctly threaded according to the machine's standard "threading diagram". Incorrect threading paths will directly affect the formation of the thread loop. ‌‌
Check and replace the needle: Confirm that the needle is securely installed and oriented correctly (usually with the needle slot facing the operator), check if the needle tip is worn, bent, or hairy, and promptly replace it with a new needle of the appropriate model. At the same time, ensure that the needle model matches the thickness of the stitching and fabric. ‌‌
Cleaning and basic maintenance: Clean the wire hair and cloth debris inside the machine head to keep the interior of the machine clean; Check and ensure that the needle plate holes are clean and unobstructed. ‌‌
Synchronization and gap adjustment of core institutions
If the basic inspection is correct, the problem of needle skipping usually stems from the misalignment of core mechanisms such as crochet hooks (bent needles), machine needles, and needle guards. Adjustments need to be detailed and carried out in order. ‌‌
Adjusting the synchronization and gap between the crochet hook and the machine needle: This is the key to solving needle skipping, especially "bent needle skipping". ‌‌
Synchronization relationship check: manually rotate the wheel to retract the crochet hook to the far right. Check the distance between the hook tip and the center of the rightmost needle, which should be maintained between 3.5 millimeters and 5 millimeters. If the distance does not match, the synchronization relationship is incorrect. ‌‌
Gap adjustment: Remove the needle board and observe. When the crochet hook swings from left to right and meets the left needle (long straight needle), the gap should be controlled between -0.03 millimeters and 0.5 millimeters (i.e. slight contact to small gaps); When the crochet hook moves from right to left until its lower edge is parallel to the left needle tip, the gap should be around 1 millimeter to 1.5 millimeters. At the same time, ensure that the tip of the crochet hook is about 1 millimeter higher than the upper edge of the needle hole when hooking. ‌‌
Check and adjust the needle guard: The function of the needle guard (front and rear) is to stabilize the needle and assist in the formation of the thread loop. The rear guard needle should be slightly attached to the back of the needle, and the gap between the front guard needle and the needle should be as small as possible, but it should not cause the needle to become rough or break. Excessive or insufficient position of the needle guard can cause the wire loop to throw out smoothly, resulting in needle skipping. ‌‌
Adjusting the height of the needle bar: The height of the needle bar directly affects the size of the wire loop. The standard height should refer to the specific model manual, usually based on when the needle is lowered to the lowest point. The incorrect height of the needle bar needs to be readjusted. ‌‌