The automatic thread trimming device is a driven rod pulled by a solenoid valve; the driven rod contacts the control cam, starts the thread trimming mechanism, and the shearing type thread cutter cuts the suture neatly. When the thread needs to be trimmed, step on the pedal with the foot, and the thread trimming mechanism starts to work; the sewing machine automatically lifts the needle bar from the lower position of the needle to the upper position of the needle, and when it reaches the predetermined point, the thread puller installed under the needle plate starts to work; The machine grasps the needle thread and the bobbin thread at the same time, pulls the two threads into the fixed thread cutter, and cuts the thread like a pair of scissors.
The distance between the cutting edge of the static scissors and the center of the needle is 4 mm, and the height of the cutting edge is 0.6 mm; the distance between the moving scissors and the center of the needle is 2-2.5 mm.
When the distance between the edge of the static knife and the needle tip is 4 mm, it is in the standard position, but it can be moved a little more to the right, which is slightly larger than 4 mm; at this time, the thread trimming time of the bottom thread is delayed, but the amount of thread used is increased, because The bottom thread is left long; if the distance between the moving scissors and the center of the needle is more than 2.5 mm or less than 2.5 mm, the bottom thread will not be cut.
Turn the two selector switches to the ON position first, and the sewing head can be automatically backstitched at the beginning and end of sewing. If the start backstitch selection switch is turned to the OFF position, and the end backstitch selection switch is turned to the ON position, the sewing head can be automatically backstitched at the end of sewing; otherwise, the sewing head will be backstitched automatically at the beginning; If all the beginnings are turned to OFF position, automatic backstitching cannot be performed, but the button switch can be used to perform backstitching as required; if only plain stitch sewing is required, backstitching is not required, both switches can be fully adjusted to OFF bit.