How does the three thread overlock sewing machine handle the skip needle（2）?

1. Specific treatment methods for needle thread skipping of three thread overlock sewing machine.

A pear shaped thread loop formed shortly after the needle rose at the bottom dead point. The needle skipping phenomenon caused by the lower bent needle not entering the thread loop is called "needle skipping", which is also a needle skipping fault with high probability.

The following methods are commonly used:

The gap between the needle notch and the needle tip of the lower curved needle is too large, which is the main reason for the skipped needle thread. The lower curved needle can be adjusted to the state that its needle tip is close to the needle and cannot touch the needle (the standard value is between 0mm-0.05mm).

Check whether the needle is bent or worn. If it is bent or worn, replace it with a new needle or trim the worn part.

Check whether the needle is installed in the proper position, and install the needle to the bottom according to the standard operation method.

Check whether the needle tip of the lower bending needle is worn (commonly known as "bald tip"), and the minor fault can be polished with an oilstone. Check the return amount of the lower bending needle (commonly known as "eating power"). The return amount is different for different models. Check and adjust according to the specified value in the manual; Next, check the height of the needle bar, and check and adjust it according to the standard specifications in the manual.

In addition, excessive needle thread tension is also easy to cause needle skipping. The wire clamping pressure shall be adjusted timely, and the wear condition of the wire passing parts shall be noted. At the same time, regularly check the position and clearance of the front and rear needle guards. See the specified value in the manual for details.

2. Treatment method for jumping off curved needle thread of three thread overlock sewing machine

When the upper and lower bending needles swing to the intersection point in the opposite direction, the needle tip of the upper bending needle does not enter the triangle coil formed by the lower bending needle, resulting in needle skipping, which is called "jumping off the bending needle thread". The probability of needle skipping is small.

The large gap between the upper bending needle tip and the back of the lower bending needle tip is the main reason for needle skipping. Adjust the gap to the standard value of 0.1mm-0.2mm, and check whether the lower bending needle threading system is correct.

In addition, the phenomenon that the upper bending needle tip is worn into "bending bald", and the material stagnation caused by the cutter wear (sharpening the cutter) are the main reasons that cause the overlock sewing machine to jump off the bending needle thread. It is recommended to replace or sharpen the upper bending needle and cutter.

3. Jump onto the curved needle thread of three thread overlock sewing machine

When the needle of the overlock sewing machine rises to the top dead center position and starts to fall, the needle tip does not enter the triangle coil formed by the upper curved needle, which is usually called "jumping onto the curved needle thread". The excessive clearance between the machine needle and the back of the head of the upper looper is the main reason for jumping on the looper thread, and the standard clearance should generally be controlled at about 0.05mm-0.1mm.

When the needle thread jumps up, the following points can be used to check and eliminate the fault:

Check whether the needle is bent or damaged. If yes, replace or trim the needle in time; If the threading is incorrect, re check and thread the needle according to the instructions.

When the upper bending needle swings to the left limit, if the distance (lead) from the needle centerline is lagging behind the standard requirements, please check again according to the instructions and adjust it until it is qualified.

If the cutter is too blunt and the feed dog height causes material stagnation, the feed dog height can be adjusted to 1mm (± 0.2mm).

If the tension of the stitches is too weak, adjust the tension of the clamp in time.