Selection and Adjustment of Air Jetting Weft
The weft process mainly refers to the reasonable selection of the weft parameters, the weft insertion parameters and other parameters of the loom with the best, in order to achieve high yield, high quality, low consumption purposes. This paper analyzes the selection of weft insertion parameters of PAT air-jet looms (collective air supply, solenoid valve control, electronic or mechanical weft insertion) and discusses the technological principles involved in the air-jet loom. The air-jet weft insertion parameters of different types of air- (Or weft flying angle), weft clip folder opening and closing time, the main nozzle valve opening and closing time, auxiliary nozzle valve opening and closing time, tension (or weft flying angle) Nozzle valve opening and closing time, air pressure, weft cutting time.
7628 and other glass fiber fabrics used in the PAT type air jet loom main have the nozzle features: loom main nozzle is a “gradual reduction chamber + round nozzle” combination of the nozzle, to improve the weft insertion speed and good weft quality . The diameter of the main nozzle is 3 mm, which is smaller than the diameter of the main nozzle of the air jet loom. According to the fluid continuity equation, the gas flow is proportional to the nozzle cross-sectional area under the same gas pressure, temperature and flow rate. Therefore, the nozzle hole diameter is small, to reduce gas consumption is good. However, the diameter of the nozzle hole is small, and the injection capability of the jet (the capability of maintaining a large jet velocity after leaving the nozzle) is weak. For the axisymmetric jet with circular cross section, the ratio of the axial flow velocity μm of the jet centerline to the flow velocity μ0 at the outlet cross section is
here : α is the nozzle form factor; S is the distance from the jet to the exit section; R0 is for the nozzle radius.(Formula 6) shows the injection capacity and nozzle radius is proportional . That is, the diameter of the nozzle hole is small, the jet will send the weft yarn close to the distance (μ0 is a fixed value), but for the relay weft, how far the main nozzle can send the weft is not important.
According to the information that, from the nozzle exit of about 200 mm, the increase in jet airflow, the friction of the yarn will not significantly increase the force, so the main nozzle jet to increase the yarn speed, the effect is not obvious. A fine nozzle, a small flow rate, a high flow rate of air flow, the weft yarn to obtain a higher initial speed, and then rely on inertia and auxiliary nozzle airflow will be cited weft through the shed. So often used in the process
Main nozzle low pressure & in ensuring that the weft can easily pass through the main nozzle, and in the loom parking for at least 2 min within the weft is not due to jet damage and breakage under the premise, the air pressure is as low as possible.
Main nozzle and auxiliary nozzle weft insert pressure. In ensuring the weft on time under the premise of the cloth fell, the auxiliary nozzle pressure is low as well. Since increasing the main nozzle pressure does not have a large effect on gas consumption, any change in the auxiliary nozzle pressure will have a significant effect on gas consumption. Generally take the lower auxiliary nozzle pressure and higher main nozzle pressure.
Weft flying time. The longer the weft flying time, the better. Because the longer weft flight time, the lower the speed, the smaller the air consumption. The necessary flying speed of the weft yarn is directly proportional to the loom speed, inversely proportional to the allowable weft flight angle.
Weft storage device off the yarn and magnetic needle opening time is t. Weft storage device off the yarn and magnetic needle opening time is t ,in order to ensure the principle of weft into the shed on time, T in the PAT air-jet loom always take 15ms.
Main nozzle opening time t9. As with the needle opening time of the weft picker, the main nozzle opening time must be at a point in time, to ensure that the weft into the shed before the straight, and into the shed for the principle on time.
Main nozzle closing time T. In the multi-nozzle relay air-jet loom, The main nozzle acts as a first biasing member for the weft yarn, and is responsible for removing the weft yarn from the weft feeder during weft flying, and fed into the shed at a rate to be delivered to the air stream injected by the auxiliary nozzle.
Nozzle tension open time t1. The role of the nozzle tension is the end of the flight from the weft (t1 + t-10) played by the upper and lower warp yarn is reliable only when the period of time to tighten the weft within the shed, to prevent the auxiliary nozzle slack after the closure of the weft and make sure that the weft yarn and weaving yarn good intertwined.
Since air-jet looms are developed from shuttle looms, its process principle change is not big, but the form of weft insertion has changed. Therefore, the fixed process parameters also changed little, variable process parameters vary greatly. Normally opening time, flat height, opening amount, rear beam high and low position, before and after the halt of the frame up and down position, the tensile length of the tension spring, damping buffer, winding weft teeth and so on,all above need to be based on different product varieties of scientific and rational process parameter configuration so as to ensure the quality of weaving products and production of the best to meet production needs.
In the glass fiber cloth with electronic grade, such as 7628, 1080, 7629, these kinds of fabrics are generally more closely to plain fabric, The fabric style is mainly that the counts of glass fiber warp / weft yarn is close to the weft / Warp yarn density, therefore, the tightness of the latitude and longitude is about 1: 1, And the tightness of the fabric are around 50%. The appearance of the plain fabric which used in the copper-clad laminate manufacturing process requires smooth, uniform The surface of the impurities and should should be less and the strength of the latitude and longitude should also small, therefore, 7628 fabric is a high technology product in the world’s glass fiber industry. And the supporting production line Is more, the equipment also has more complex factors, the process technology is difficult, we have more seriously researchs to study on the subject,In view of the above situation that the main problem is:(1)the quality of the glass ball product which affect the crucible wire drawing operation and the quality of the original wire is the main problem;(2)It is necessary to strictly control the glass fiber pass rate which is the first conditions to improve the quality of glass fiber gray appearance (3)To carry out the introduction of glass yarn 7628 series of weaving fabric technology research, strictly control the number of defects per hundred meters of glass fiber cloth to improve the inherent quality of cloth;(4)Study on the weaving technology of E – glass Fiber Yarn 7628 fabric and so on.
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