1 Foreword In 1996, when our company introduced the Japanese Toyota JAT600-280 air-jet loom, it also introduced the Japanese Toyota JAT600-280 air-jet electronic dobby loom. The dobby box is composed of the STAUBLI1258RS type dobby box produced in France. The weaving patterns and weaving steps of this electronic dobby box loom are directly input by the computer, which is very convenient when weaving new varieties. Whether the selection of weaving process parameters is appropriate has a great impact on the production efficiency of the dobby loom. In the early days, due to insufficient understanding of the machine, the weaving process parameters in the machine manual were copied rigidly, and the machine's production efficiency could only reach about 30%. After nearly five or six years of production practice, the process configuration was continuously optimized, and the machine's production efficiency was improved. We have made some improvements in the selection and selection methods of weaving process parameters, and have mastered the basic rules for selecting weaving process parameters for this machine. So far, the production efficiency has gradually improved. The production efficiency of some machines has reached more than 90%, and the average efficiency is also More than 83%. 2 Selection and determination of weaving process parameters The weaving process parameters of the dobby loom mainly include the following aspects: back beam height, drop frame height, heald frame height, cloth fell height, warp tension, opening angle, heald leveling time and lead The weft parameters, etc. are now described as follows: 2.1 Selection and determination of the height of the back beam. Since the air-jet loom relies on air flow to insert the weft, compared with other shuttleless looms (such as rapier looms, projectile looms) , shed clarity has a greater impact on weft insertion of air-jet looms. For the upper and lower warp yarns, it is mainly the upper warp yarn that affects the clarity of the shed, because the upper and lower warp yarns have a drooping effect, which requires the upper warp yarn to have a higher tension, and adopt an unequal tension shed with upper tightness and lower looseness. To form this shed form, the height of the back beam must be chosen lower. It is introduced in the manual of the machine that on the dobby machine, the height of the back beam is zero, that is, the equal tension shed is used. In this case, the number of weft stops is large, and the production efficiency of the machine is low. The main reason for the weft stops is the upper layer. The warp yarns block the weft yarns. In order to increase the tension of the upper warp yarn, an unequal tension shed with upper and lower tension is used, and the height of the back beam is adjusted from zero to -3 or -4 (the lowest scale of the back beam is -5), that is, the low back beam process is adopted, which reduces the weft of the machine. The number of stops increases the production efficiency of the loom and the weaving effect is better. 2.2 Selection and measurement method of heald frame height Heald frame height has a certain impact on the production efficiency of the loom and the quality of the fabric. First of all, it affects the clarity of the shed. The effect of increasing the height of the heald frame and reducing the height of the back beam is the same. They can form an unequal tension shed that is tight and loose. Similarly, the effect of lowering the height of the heald frame and raising the height of the back beam is the same. They can form an unequal tension shed with upper and lower tension, which requires us to choose a reasonable heald frame height according to the different types of fabrics we are weaving. The height of the heald frame also affects the height of the cloth fell, and the height of the cloth fell has a great influence on beating up. In addition, the determination of the heald frame height is also related to the height of the lower yarn when the shed is opened and the cooperation between the shed and the special-shaped reed groove. Regarding the method of measuring the height of the heald frame, in the manual of the machine, the method of measuring the height of the heald frame is to measure the height of each heald frame separately when the heald frame is in the upper opening position, because the height of each heald frame is from front to back. It gradually increases and the measuring steps are more troublesome. After a period of practice and exploration, the method of measuring the height of the heald frame was changed to measuring the height of the heald frame when the heald is healed. At this time, the height of each heald frame is the same, and it is more convenient to measure the height of the heald frame. According to our production practice, the height of the heald frame is generally between 175 and 180mm, which is selected according to different types of fabrics. 2.3 Determination of the height of the drop frame. The height of the back beam and the height of the heald frame have been determined. It is very easy to determine the height of the drop frame. You just need to raise or lower them in conjunction with them. 2.4 Selection of cloth fall height The cloth fall height is very important to the beat-up movement, especially for air-jet looms with special-shaped reeds. The height of the cloth fall is even more important to the beat-up movement. Improper selection of fabric fell height may result in insufficient or excessive beat-up force, resulting in sparse or dense wefts, or even holes in the cloth. The principle for determining the height of the cloth fell is to ensure that the cloth fell must be within the beat-up point of the special-shaped steel reed so that normal beat-up can be achieved. The main factors that determine the opening height are the height of the fabric flap and the thickness of the side brace foot pads. On this dobby machine, we choose the height of the cloth fell board to be 3mm, which has better effect. In addition, the height of the heald frame also has a certain impact on the height of the cloth fell, and sometimes it must be considered.
2.5 The selection and determination of the opening angle have a great impact on weft insertion and the production efficiency of the loom. When the opening angle is large, the shed has high definition and is convenient for weft insertion, but the opening angle is too large , the warp elongates greatly when shedding, and the warp breakage rate is high, which affects the production efficiency of the loom. Under the condition of ensuring normal weft insertion, it is better to use a small opening angle. The machine manual states that the opening angle of the dobby machine is 30 degrees, but in actual production, an opening angle of 28 or 26 degrees is selected according to different fabric types, sometimes even 24 degrees, and the weaving effect is good. In addition, according to different types of fabrics, each heald frame can also adopt different opening angles. For fabrics with poor edges, we use ground fabric and edge weave to choose different opening angles to solve the problem. 2.6 Determination of warp tension The size of the warp tension not only affects the shedding clarity, but also affects the warp breakage rate, which in turn affects the production efficiency of the loom. The warp tension is large and the shed clarity is high, which is beneficial to weft insertion. However, the warp tension is too high and the warp breakage rate is high, resulting in low production efficiency of the loom. The warp tension is too small, the shed clarity is poor, and the number of weft stops increases, which also affects the production efficiency of the loom. In the early stage, the selected warp tension is the warp tension directly transmitted by Toyota software. The warp tension of general varieties is between 250 and 350kg. At this time, the main reason that affects the efficiency of the loom is too many weft stops. In order to improve shed clarity and reduce the number of weft stops, the warp tension was increased to between 400 and 450kg, which greatly reduced the number of weft stops. However, due to the small opening angle process, the warp breakage rate did not increase, which improved the weaving efficiency. machine production efficiency. 2.7 Selection of Healing Time The instruction manual introduces the selection of the Healing Time as 300 degrees. However, in actual production, the best parameters are selected between 290 and 310 according to the different varieties of fabrics and closely coordinated with the weft insertion parameters to make the weaving The machine is in optimal condition. 2.8 Selection of weft insertion parameters The weft insertion parameters mainly include the opening time of the electromagnetic needle, the injection time of the main and auxiliary nozzles, the start time of weft insertion and the arrival time of the weft yarn. The selection of these process parameters should be reasonably coordinated with the leveling time to facilitate the weft insertion. The weft is normal, the number of weft stops is reduced, and the production efficiency of the loom is improved. 3 Key Selection of Weaving Process Parameters The following is a detailed explanation of the key selection of weaving process parameters for this dobby loom, taking several varieties of dobby fabrics produced by our factory as examples. 3.1 Vertical strip fabric When weaving vertical strip fabric (for example, the pattern diagram is shown in Figure 1), the determination of the heald frame height has a great influence on the production efficiency of the loom. It can be seen from the pattern diagram that when the loom is opening, four-fifths of the warp yarns on the first to fifth heald frames are on the upper layer of the opening, and one-fifth of the warp yarns are on the lower layer of the opening. Under the action of the warp tension, Pull the fabric fell upwards, and of the warp yarns on the 6th to 10th heald frames, one-fifth of the warp yarns are on the upper layer of the opening, and four-fifths of the vertical striped fabric pattern in Figure 1 is on the lower layer of the opening. The effect of warp tension Then, pull the fabric fell down, thus forming a wavy fabric fell on the entire fabric fell, which is not good for beating up, but also affects the clarity of the shed, and is also bad for weft insertion. In order to solve this problem, the height of the heald frame is usually adjusted so that the 1st to 5th heald frames are flush and the 6th to 10th heald frames are flush, but the height of the 6th to 10th heald frames is higher than that of the 1st to 5th heald frames. A higher height can ensure that the entire fabric fell in a straight line, which improves the beat-up and weft insertion conditions, facilitates weft insertion and beat-up, and also improves the quality of the cloth to a certain extent. Figure 1 Vertical stripe fabric pattern diagram 3.2 Horizontal stripe fabric When weaving horizontal stripe fabric (the pattern pattern of weaving sample 1 and weaving sample 2 is shown in Figure 2) 5, the height of the cloth fell, the heddle height and the height of the back beam Determination is very important. Whether the choice is appropriate is directly related to whether weaving can proceed smoothly. A series of problems occurred during the mutual conversion process of fabric sample 1 and fabric sample 2, causing the weaving to not proceed smoothly. Figure 2 Horizontal stripe fabric pattern (weaving sample 1) The specific analysis is as follows: First, when weaving the loom opening in weaving sample 1, four-fifths of the warp yarns are on the upper layer of the opening, and one-fifth of the warp yarns are on the lower layer of the opening. , under the action of warp tension, the cloth fell is at a higher position. When weaving the loom in sample 2, four-fifths of the warp yarns are in the lower layer of the opening, and one-fifth of the warp yarns are in the upper layer of the opening. The cloth fell is at a low position under the action of warp tension.
During the mutual conversion process between weaving sample 1 and weaving sample 2, the cloth fell moves up and down, which is detrimental to beat-up and weft insertion, and even normal weft insertion and beat-up cannot be achieved. In order to enable normal weft insertion and beat-up, the thickness of the side support foot pad, the height of the fabric fell plate and the height of the heald frame must be reasonably selected to ensure the appropriate height of the fabric fell and ensure that the fabric fell is still in place even if the fabric fell moves up and down. Within the beat-up point of the different steel reed, so that the weft can be beaten normally. According to the instruction manual of the machine, when weaving 4/1 fabric, the thickness of the side support rod foot pads should be 2mm. When weaving 1/4 fabric, the thickness of the side scale rod foot pads should be 4mm. The mechanism of this selection is : When weaving 4/1 fabric, four-fifths of the warp yarns are on the upper layer of the opening, and one-fifth of the warp yarns are on the lower layer of the opening. Under the action of the warp tension, the cloth fell is pulled upward, in order to ensure that the cloth fell is in the correct position. , so choose a thinner side support rod pad (2mm). When weaving 1/4 of the fabric, four-fifths of the warp yarns are in the lower layer of the opening, and one-fifth of the warp yarns are in the upper layer of the opening. The effect of warp tension down, the fabric fell is pulled downwards. In order to ensure that the fabric fell is in the correct position, the thickness of the side support foot pad is selected to be thicker (4mm). This horizontal stripe fabric is a joint weave. According to the above mechanism, in order to ensure that the cloth fell is in the correct position when weaving the two weaves, select the side support bar<