Basic knowledge of industrial sewing machines

Basic knowledge of industrial sewing machines

(1) Classification of sewing machines
Sewing is the main process of garment processing. In this process, many operations such as sewing, piecing, overlocking, sewing, sleeves, buttonholes, buttons, and zippers are completed.
Industrial sewing machines are roughly divided into general, special, decorative and special sewing machines.

1. Universal sewing machine
①Industrial lockstitch machine is a widely used equipment in garment production, mainly used for lockstitch.

In recent years, industrial lockstitch machines are developing in the direction of high speed and computerization. The speed has been increased from 3000r/min to 5000~6000r/min; in addition to general purposes, the sewing function also has automatic reverse sewing, automatic thread trimming, automatic dialing thread, automatic release of the presser foot, automatic control of the needle stop at the upper and lower needle positions, and a variety of protection functions.
②Overlock sewing machine is divided into 3-thread, 4-thread and 5-thread overlock sewing machine, among which 3-thread overlock sewing machine (overlock machine, code edge machine) and 5-thread overlock sewing machine are widely used.
③Interlock sewing machine is mainly used for splicing cotton wool, single jersey, rolling collar, piping, hemming, interlocking, etc. of knitted underwear.



2. Special sewing machine A special sewing machine is a sewing machine used to complete a certain special sewing process, such as a buttonhole machine, a buttoning machine, a sewing machine, etc.

3. Decorative sewing machine Decorative sewing machine is a sewing machine used to sew all kinds of beautiful decorative stitches and seams, such as embroidery machine, zigzag sewing machine, crescent machine, etc.

4. Special sewing machine Special sewing machine is a sewing machine that can automatically complete a strict operation cycle according to the set process procedures, such as automatic bag opening machine, automatic sleeve machine, automatic small piece sewing machine, etc.

(2) The structure and use of the lockstitch machine

How to use the industrial lockstitch machine:
1. Selection and installation of machine needles In general, small (thin) needles should be used to sew thin, brittle and dense materials, and large (coarse) needles should be used for thick, soft and sparse materials. )Needle. Thick needles used for sewing thin materials will cause the friction between the needle and the sewing material to be large. When the needle rises, the sewing material will randomly rise in the presser foot groove, delaying the formation of loops and causing skipped stitches. If a thin needle is used in the material, it will cause the needle to bend or break.
During high-speed sewing, the severe friction between the needle and the sewing material will cause the needle temperature to be too high, and in severe cases, a melt hole will be formed in the chemical fiber fabric or the chemical fiber suture will be melted. It will cause skipped needles or broken threads, so special selection and cooling of the needles should be carried out.


When sewing chemical fiber fabrics with low melting point 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, so that the needle temperature can be increased. Lower; 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 bar, which can reduce the friction and heat generation between the needle bar and the sewing material.
Applying silicone oil on the suture and air cooling can effectively reduce the needle temperature. Silicone oil is colorless, transparent and easy to volatilize, and can take away part 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 make the needle bar rise to the position, loosen the needle mounting screw, orient the long thread groove of the needle to the left of the operator, and then insert the needle handle into the needle hole at the lower part of the needle bar inside, so that it touches the top of the needle bar hole, and then tighten the needle screw.

Figure 3-9.

2. Selection and threading of sewing threads When selecting sewing threads, first consider their sewability, strength and uniformity, so as to ensure the fastness of the seam. The upper thread used by the high-speed sewing machine should be left-handed, and the twist is moderate. Both left- and right-handed bottom threads can be used.

The identification of the suture rotation can be carried out as shown in Figure 3-10. Pinch the suture with both hands, and turn the suture in the direction of the arrow with the right hand.

Table 3-1 The relationship between needle, thread and sewing material

(1) Threading: The needle bar should be in the position when threading the upper thread, and then the thread end is drawn out from the thread stand, and threading is performed in the order shown in 3-11.

When pulling the bottom thread, first pinch the end of the upper thread, turn the driving wheel to move the outer rod downward, then return to the rising position, and then pull up the pinched end of the upper thread, and the bottom thread is pulled up.

Place the bottom and top two thread ends together under the presser foot.

(2) Winding method of the bottom thread: ①Insert the bobbin into the winding shaft, and wrap the thread around the bobbin several times; ②Press the full-thread springboard to make the winding wheel contact the belt; ③Adjust the amount of winding Turn the adjusting screw to the right to increase the amount of winding, otherwise the amount of winding will decrease; ④When the winding is off, move the wire rack left and right to correct the winding state; ⑤Wound At the end of the thread, the full thread jumper is disengaged, the reel automatically stops rotating, and the bobbin is removed. (Figure 3-12)

3) How to install the bobbin: ① Hold the bobbin, turn the thread to the right, and put it into the bobbin case; ② Pull the thread out through the groove on the bobbin case, and then pass the thread tension spring Pull the thread out of the thread hole; ③When pulling the lower thread, the bobbin should rotate in the direction of the arrow (Figure 3-13)

Assembly and disassembly of the bobbin cover: ① The bobbin cover can be taken out by opening the shuttle door cover. If the shuttle door cover is opened, the bobbin should not fall out; ② When installing the bobbin cover, insert it completely on the shaft center of the rotary hook And close the shuttle door cover.

(Figure 3-14)

3. Needle distance adjustment: The length of the feeding needle distance can be adjusted by turning the needle distance knob A. The number on the dial indicates the length of the needle distance (unit is mm). (Figure 3-15)

4. The pressure of the presser foot should be adjusted according to the thickness of the fabric. First, loosen the nut, as shown in Figure 3-16. When placing thick materials, increase the pressure of the presser foot, that is, turn the presser foot adjusting screw in the forward direction to make Pressure increases. The opposite is true when sewing thin materials.

5. Adjustment of stitches To adjust the tension of the bottom thread, just use a small screwdriver to rotate the bobbin screw A on the bobbin case. As shown in Figure 3-17.

Generally speaking, if the bottom thread is made of 60-gauge cotton thread, after the bobbin is loaded into the bobbin case, pull out the stitching thread through the thread hole of the bobbin case, and pinch the straight end to lift the bobbin case. If the bobbin case can fall slowly, it can be used.

The upper thread tension is based on the lower thread tension.

The adjustment of the tension of the upper thread is mainly realized by adjusting the thread tension nut. After the trial sewing, observe the stitch formation, as shown in Figure 3-18.

① Indicates the normal stitch of the sewing thread.

②Indicates that the upper thread is tight, indicating that the tension of the upper thread is too large, and the thread clamping nut should be rotated counterclockwise to loosen the pressure of the upper thread, as shown in Figure 3-19.

The randomness of the surface and the bottom line should cooperate with each other, as shown in Figure 3-20.

③ Indicates that the lower thread is tight, indicating that the tension of the lower thread is too large, and the bobbin screw should be loosened.

④Indicates that both the surface and the bottom thread are loose, and the tension of the top and bottom thread should be adjusted at the same time to match.



⑤ Indicates that the upper and lower threads are tight, and the upper thread clamping nut and the bobbin screw should be loosened at the same time.

6. When adjusting the thread take-up spring to change the swing amount of the thread take-up spring ①, loosen the positioning screw ② of the thread take-up spring adjustment seat, and turn the thread clamping screw ③; to change the tension of the thread take-up spring, loosen the positioning screw screw ②, and take out the thread clamping screw. Then loosen the thread clamp screw ④ and adjust it.



7. Adjustment of the working height of the feeding dog The working height of the feeding dog refers to the height of the needle board surface when the feeding cloth rises to the position. When sewing thicker or harder fabrics, the working height of the feed dog should be higher, and vice versa.

When adjusting, loosen the tightening screw of the swing rod, and tighten the screw when the swing rod is adjusted to a suitable height (Figure 3-22)

6. When adjusting the thread take-up spring to change the swing amount of the thread take-up spring ①, loosen the positioning screw ② of the thread take-up spring adjustment seat, and turn the thread clamping screw ③; to change the tension of the thread take-up spring, loosen the positioning screw screw ②, and take out the thread clamping screw.

Then loosen the thread clamp screw ④ and adjust it.

7. Adjustment of the working height of the feeding dog The working height of the feeding dog refers to the height of the needle board surface when the feeding cloth rises to the position. When sewing thicker or harder fabrics, the working height of the feed dog should be higher, and vice versa.



When adjusting, loosen the tightening screw of the swing rod, and tighten the screw when the swing rod is adjusted to a suitable height (Figure 3-22)

8. The relationship between the needle and the hook adjustment needle and the hook should be coordinated as follows.

9. Adjustment of the thread take-up amount of the thread take-up lever The position of the thread hook should be adjusted when sewing different fabrics, which is related to the pros and cons of the sewing stitch. When sewing heavy materials, move the hook to the left to increase the thread take-up.

When making it thin, move the hook to the right to reduce the amount of thread take-up.

10. Lubrication of sewing machine Because the speed of high-speed industrial lockstitch sewing machine can reach about 5500r/min, and the movement mechanisms are required to cooperate with each other accurately, in order to enable the machine to maintain the proper working accuracy and performance for a long time, it can have a long service life. In use, it has better motion stability and lower noise, and is an important part of lubrication.