Basic knowledge of sewing machine

1. Selection and installation of needles. Under normal circumstances, small (fine) needles should be used for thin, brittle and dense sewing materials, and large (thick) needles should be used for thick, soft and sparse sewing materials. )needle. Thick needles used to sew thin materials, due to the greater friction between the needle and the sewing material, the sewing material will randomly rise in the presser foot groove when the needle rises, which delays the formation of the loop and causes skipped stitches; If a thin needle is used when feeding, the needle will bend or break.
During high-speed sewing, the intense friction between the needle and the sewing material will cause the needle temperature to be too high, and severely will form a melt hole in the chemical fiber fabric or cause the chemical fiber suture to melt, increase the needle hole thread resistance, and deteriorate the upper thread forming condition It may cause skipped stitches or thread breakage, so the needles should be specially selected and cooled.
When sewing low-melting chemical fiber fabrics at high speed, double-section needles or high-speed needles can be used. The upper section of the double-section needle can increase the stiffness of the needle, and the lower section can reduce the friction between the needle and the sewing material, thereby making the needle warm. Reduced; the size of the needle tip and both sides of the needle hole of the high-speed machine needle is 5% to 7% larger than the diameter of the needle shaft, which can reduce the friction and heat generation between the needle shaft and the sewing material.
Adding silicone oil to the suture and air cooling can effectively reduce the needle temperature. The silicone oil is colorless, transparent and easy to volatilize. It can take away some of the heat of the needle during high-speed sewing.
When installing the needle, cut off the power of the motor, turn the upper wheel to raise the needle bar to the highest position, loosen the needle installation screw, turn the long thread groove of the needle toward the operator's left, and then insert the needle handle into the needle at the bottom of the needle bar. In the hole, make it touch the top of the needle bar hole, and then tighten the needle screw.
2. Sewing thread selection and threading. When selecting sewing thread, the seamability, strength and uniformity should be considered first, so as to ensure the seam fastness. The upper thread used by the high-speed sewing machine should be left-handed thread, and the twist is moderate, the bottom thread can be used for both left and right-handed thread. To distinguish the direction of thread rotation, pinch the suture with both hands and turn the suture with the right hand. If the thread strands become tighter and tighter, it is left-handed.
The relationship between stitches, stitches and sewing materials
Needle size sewing thread sewing material
9# 80～100 metric counts, very thin material, crepe, georgette, organza, etc.
11# 80～100 public thread thin material, silk, printed cloth, poplin, etc.
14# 50～60 public branch Ordinary material, cotton and wool fabric
16# 30～50 public branches, medium and heavy materials, wool fabrics, rain-proof cloth, thin leather, etc.
(1) Threading: the needle bar should be at the highest position when threading the upper thread, and then the thread end is drawn from the thread stand to thread the thread.
When drawing the bottom thread, first pinch the end of the upper thread, turn the driving wheel to move the outer rod downward, and then return to the highest position, then pull up the pinched end of the upper thread, and the bottom thread will be pulled up. Finally, put the bottom and top thread together in front of the presser foot.
(2) Winding method of the bottom thread: ①Insert the bobbin into the winding shaft, and wind the suture on the bobbin a few times; ②Press the full thread jumper to make the winding wheel contact the belt; ③Adjust the amount of winding Screw to make the winding volume about 80%, turn the adjusting screw to the right, the winding volume will increase, otherwise the winding volume will decrease; ④When the winding is off, move the spool left and right to correct the winding state; ⑤Winding At the end of the thread, the full thread jumper is released, the winding wheel automatically stops rotating, and the bobbin is removed.
(3) How to install the bobbin: ①Hold the bobbin, turn the thread to the right, and put it into the bobbin case; ②Pull the thread through the thread groove on the bobbin case, and then pass the thread clamping The thread is drawn out from the thread hole under the spring; ③When the lower thread is pulled, the bobbin rotates
Assembly and disassembly of the bobbin case: ①Open the shuttle door cover to take out the bobbin case. If you open the shuttle door cover, the bobbin should not fall out; ②When installing the bobbin case, insert it into the shaft of the hook completely And close the shuttle door cover.
3. Stitch length adjustment The length of the inverted (forward) feeding stitch length can be adjusted by turning the stitch length knob A. The number on the dial indicates the size of the stitch length (unit: mm).
4. The presser foot pressure should be adjusted according to the thickness of the fabric. First, loosen the nut. When inserting thick materials, increase the presser foot pressure, that is, turn the presser foot adjustment screw in the forward direction to increase the pressure. When sewing thin materials, the opposite is true.
5. Adjust the stitches of the stitches. To adjust the bottom thread tension, just use a small screwdriver to rotate the shuttle screw on the bobbin case.
Generally speaking, if the bottom thread is 60-gauge cotton thread, after the bobbin is loaded into the bobbin case, pull the suture through the bobbin case thread hole, pinch the straight head to lift the bobbin case, and the bobbin case can be used if it can fall slowly.
The upper thread tension is based on the lower thread tension. The adjustment of the upper thread tension is mainly realized by adjusting the thread clamping nut. After the trial sewing, observe the stitch formation.
6. Adjusting the working height of the feeding dog The working height of the feeding dog refers to the height of the needle plate surface when the feeding cloth rises to the highest position. To sew thicker or harder fabrics, the working height of the feed dog should be higher, and vice versa.
Loosen the tightening screw of the swing lever during adjustment, and tighten the screw when the swing lever is adjusted to a suitable height.
7. Adjusting the thread take-up amount of the thread take-up lever When sewing different fabrics, the position of the thread hook should be adjusted, which is related to the quality of the sewing stitches. When sewing thick materials, move the thread hook to the left to increase the thread take-up amount. When making thin material, move the thread hook to the right to reduce the thread take-up amount.
8. Sewing machine lubrication. Because the speed of high-speed industrial lockstitch sewing machine can reach about 5500r/min, and the various motion mechanisms require accurate coordination with each other, in order to enable the machine to maintain its due working accuracy and performance for a long time, it can have a long service life. In use, it has better movement stability and lower noise, which is an important part of lubrication.