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Research on the electronic thread clamp in the computerized lockstitch sewing machine

                       
Update:2021.12.2021-12-06T15:36:41+00:00
Summary:

1. Current status of the use of electronic thread clamp […]

1. Current status of the use of electronic thread clamps
As far as the current state of technological innovation in the industry is concerned, my country's sewing equipment still remains at the expansion of A, mainly based on the technology and products of advanced countries, introducing digestion, absorption and imitating surveying and mapping. Domestic sewing equipment generally has serious deficiencies in product R&D and scientific research projects. The industry’s technological foundation is relatively weak, and there is a lack of effective research and analysis of basic theories and typical product institutions. Product R&D capabilities can no longer meet the growing social needs . In recent years, various sewing equipment manufacturers have launched computerized lockstitch sewing machines with thread clamping function, but their sales performance is not satisfactory. After a long period of visits and investigations to clothing manufacturing companies, the main problems reflected in the use of electronic thread clamps are mainly concentrated in the following two points:
(1) The thread is often broken when starting the seam, and the applicability to the suture is poor;
(2) The sewing cannot be completely pulled under the sewing material, the thread ends cannot be completely eliminated, and the excess thread ends must be manually cut off.
2. The structure and principle of the electronic clamp
(1) Electronic clamp structure
The electronic wire clamp adopts a straight-pull electromagnet structure, and one end of the iron core is made into an end cap type. The electronic thread clamp is installed on the machine head, located in the middle position between the thread rod and the needle. After the electronic thread clamp is sucked in, the sewing is clamped by the electromagnet end cover surface. When the action is completed, the electronic thread clamp comes with The spring resets the iron core.
(2) After the needle of the working sewing machine moves from the high limit position to the low limit position, when the needle is raised a certain distance, it enters the hook thread hooking process, and the hook thread starts to hook the thread. At this time, the electronic thread clamp is required to move and start to hold the upper thread. At this time, the hook cannot use the thread rod to provide the thread amount. After the thread, the part where the suture remains at the end of the needle) is pulled out, and the end of the suture left before is pulled under the sewing material. Before the hook thread hooking process is over, the electronic thread clamp is released in advance to loosen the thread. At this time, the thread take-up lever has entered the thread take-up process, and then it enters the normal sewing stage.
3. Analysis of problems in the actual use of electronic clamps
(1) Causes and solutions for the thread breakage of the sewing machine when sewing starts
Analysis: From the principle of the electronic thread gripper mechanism, it can be seen that when the hook is in the thread hooking process, the electronic thread gripper is in a clamped state, and the suture thread head is placed at the bottom of the presser foot, the suture will be greatly affected. The tensile force, it is easy to break the suture. At the same time, during the hook thread hooking process of the whole machine, the needle is in the ascending stage, and the suture passes through the needle hole in the stretched state. If the needle hole is not smooth enough, it will easily cause the thread to break.
Solution:
A. Choose better quality sutures to ensure the strength of the sutures
B. Appropriately reduce the pressure of the presser foot on the sewing material to ensure that the suture can be pulled out from the bottom of the presser foot smoothly
C. Choose a needle with a smoother pinhole or a polisher pinhole to ensure that the suture is not cut by the rough pinhole.
(2) The cause and solution of the seam that cannot be completely pulled under the sewing material
Analysis: From the principle of the electronic thread clamp mechanism, it can be seen that when the suture strength is sufficient and the clamping effect of the presser foot on the suture is greater than that of the electronic thread clamp, the rotary hook can obtain the required suture from the thread take-up lever. The sewing thread under the presser foot cannot be pulled completely under the sewing material.
Solution:
A. Appropriately reduce the pressure of the presser foot on the sewing material to ensure that the suture can be pulled out from the bottom of the presser foot smoothly
B. Through system adjustment, appropriately delay the release time of the electronic thread clamp to ensure that the electronic thread clamp has enough time to clamp the suture.
Irregular placement of the suture under the presser foot when sewing starts will not cause the above two problems. When sewing starts, the sewing material is clamped between the presser foot and the needle plate. The test experiment proves that when the suture is pressed in the lower part of the presser foot A and C, the pressure on the suture is also the largest, and the above is easy to occur when the sewing starts. The problem mentioned; when the suture is pressed in the B area of ​​the lower part of the presser foot, the pressure on the suture is also the smallest. Therefore, to solve the two problems mentioned above, it is necessary to standardize the habits of the operators and ensure that every time The suture can be pressed in the B area at the bottom of the presser foot. Except for the three areas, when the suture is placed in the remaining areas, the suture is basically free of any resistance, and the two problems mentioned above will not occur.
4. The scheme optimization of the electronic clamp
In order to make the electronic thread clamp better be used in actual production, the electronic thread clamp should be further optimized. Before the electronic thread clamp clamps the suture, the sewing machine control system will cooperate with the timing of the thread to execute the automatic presser foot electromagnet synchronization action, so that the presser foot electromagnetic money will give the presser foot a reaction force (according to the given solenoid voltage Size to adjust the size of the force).
The suture should be pulled out smoothly from the bottom of the presser foot. The resistance is the friction force given to the suture by the sewing material and the presser foot at the same time. From the friction force F=5N, it can be seen that the main friction force on the suture: f=f1+ f2(u1+u2)(N1-N2)
Among them: fl--the suture is blocked by the sewing material, f2--the suture is subjected to the friction force of the presser foot, u1--the friction factor of the sewing material to the suture, u2--the friction factor of the presser foot to the suture , N1--the suture receives the positive pressure from the presser foot, N2--the force from the electromagnet for lifting the presser foot to the presser foot.
Note: When the needle penetrates the sewing material, the suture is in the groove of the needle, and the friction force on the suture is not the main factor, so it will not be considered for the time being.
When the machine and sewing material are selected, u1, u2, and N1 are fixed values. Therefore, only by increasing the value of N2, can the friction on the suture be better reduced. In actual use, in order to ensure the sewing quality, the presser foot can not be lifted away from the sewing material under normal circumstances, only to reduce the pressure of the presser foot, because the thread end can be smoothly received under the sewing material. If N2>N1, the presser foot will be lifted when sewing starts, which will directly affect the sewing material. Lack of the pressure of the presser foot causes the sewing material to spread out or misalignment during the sewing of the above sewing modes, which affects the sewing quality; for example, when the upper and lower sewing materials require more than the most sewing, it is required to pull a layer (upper layer or Lower layer) sewing material. When the presser foot starts to sew, the tightened layer of sewing material will be pulled out from the bottom of the presser foot, which will affect the sewing material basin, so the value of N2 should be: N2<N1 to be effective The sewing quality is guaranteed, and the application range of the electronic thread clamp is completely improved.
5. Comparison of the effect of the electronic thread clamp and the thread blocking electromagnet
The automatic thread blocking of the automatic machine of the computerized lockstitch sewing machine. The sewing machine is equipped with automatic thread blocking (thread sweeping). After the thread is trimmed, the thread blocking (thread sweeping) function is used to pick the end of the thread out of the sewing material, and the sewing bowl is placed on the presser foot The upper part, so that when sewing underneath, the thread ends will be brought to the lower surface of the fabric to hide. The following problems may occur when using automatic thread (thread sweeping):
(1) If the sewing thread is pressed by the presser foot, the upper thread end cannot be received under the sewing material due to greater pressure, resulting in the thread end remaining on the sewing material, which requires manual trimming.
(2) The structure of the automatic gear itself is complicated, and the transmission is cumbersome. If the adjustment is not in place, the needle may be interrupted, which poses a safety hazard.
(3) After the thread is trimmed, the needle must stop moving and start to move. The entire movement time takes about 100 milliseconds. Many sewing workers turn off this function in order to achieve higher personal efficiency, which also causes the thread to remain on the sewing material. Need manual trimming.
(4) When the thread is automatically blocked, the thread hooking process is realized by a spring, which has a strong impact. When many sewing workers are pursuing speed, they do not wait for the end of the thread to perform the next operation. have an accident.
The use of the electronic thread clamp solves the above-mentioned problems. When sewing the first stitch, the electronic thread clamp has the following advantages compared with the realization of the thread clamping action.
(1) It does not affect the original acceleration time of the sewing machine and saves the time occupied by the automatic thread;
(2) At the same time, the mechanical parts of the wire (line sweep) are simplified, and the cost is reduced reasonably.
(3) When the sewing machine is working, even if the end of the thread is pressed under the presser foot after the thread is cut, the sewing thread will be easily pulled under the sewing material during sewing, and the operator does not have to worry about the position of the sewing thread.
(4) The electromagnet of the wire clamp is simple in structure, low in cost and easy to install;
(5) When the thread clamp solenoid clamps the suture, the needle starts to pierce the cloth, and the thread remaining at the needle will become shorter due to the downward movement of the needle. At this time, the thread clamp solenoid loosens the thread. The sewing machine works normally to reduce the "bird's nest" and achieve the purpose of "clean sewing". Especially after the thread clamp solenoid is optimized, the synchronization action of the automatic presser foot solenoid is greatly improved, which greatly improves the stability of the passive thread pulling back. It reduces the requirements for the stability of the machine itself.
6 Conclusion
Electronic thread clamps have attracted more and more attention from various sewing equipment manufacturers. Through the analysis and research of electronic thread clamps, the scope of application of electronic thread clamps has been improved. Electronic thread clamps have been used in the market. , While simplifying the mechanical parts of the line (line sweeping).

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