Due to the Spring Festival holiday, the water jet loom is still in operation and the warp beams are not yet finished, but it needs to be shut down for a relatively long period of time (more than a week). In order to ensure that everything is normal and that the machine can be restarted smoothly, the following main tasks need to be done and the following precautions should be taken:
Main tasks and key points of operation when the loom is stopped
① When stopping the machine, first remove the raw silk fabric woven on the machine to prevent it from getting damp and moldy if left on the machine for a long time.
② Rinse the reed and heddle wires with water to remove the slurry accumulated on them, cleaning them as thoroughly as possible to prepare for future machine restarts.
③Relax the tension of the warp threads, remove the weight, and shake the heald frame to a level position to prevent the warp threads from being stretched due to prolonged opening.
④ Lower and cover the water baffle and waterproof cover on the loom.
⑤ Raise the weft pressing wheel lifting rod to prevent the weft pressing wheel from deforming.
⑥ Disconnect the power supply to the machine and turn off the water supply. Pay attention to safety and conserve energy.
⑦ Remove the circuit control board from the electrical box and store it in a well-ventilated and dry place to prevent it from getting damp and affecting its performance.
⑧ If all the looms in a workshop need to be stopped, the main power supply and main water supply should be cut off, and the workshop should be ventilated and dehumidified regularly to check the situation and keep the workshop ventilated and dry.
Main tasks and precautions when starting up a loom
① Before starting the machine, open the main water supply pipe and drain the water to prevent residual sewage in the pipe from entering the water tank, pump body and nozzle.
② Then, use water to moisten the warp threads at the weft end, reed, and heddle wires to soften any remaining sizing material and prevent the hardened sizing material from causing the warp threads to fray or break when starting the machine directly.
③ Connect the power supply, plug in the circuit control board, turn on the water supply valve of the water tank, test the power and water supply, and observe whether the water and electricity are normal.
④ Adjust the warp tension and manually rotate the main shaft dial to check if the jetting, weft insertion, and heddle raising are normal.
⑤ If it is necessary to change the type and specifications of the raw silk, the weft yarn and the appropriate warp feed and take-up gears can be replaced to change the weft density.
⑥ If the sizing at the reed heddle wire is severely sizing, causing the warp wires to fray, you can manually shake the warp wires a few centimeters to more than ten centimeters past the weaving edge, and then test drive the machine again depending on the specific situation.
⑦ If the above main tasks are completed and everything is normal, you can start the machine and operate it according to the normal procedure.
Common problems in water jet weaving
Synthetic filaments are thermoplastic fibers. When the weft yarn is cut by a high-temperature electric hot knife, a sintering point is formed at the end, preventing the fiber from becoming fluffy, which is beneficial for weft insertion. In addition, synthetic fibers have extremely low moisture regain. When using water jets for weft insertion, as long as the sizing quality is good, there will be no difficulties in weaving. Moreover, because the extremely fine water droplets are sprayed on the loom, static electricity can be prevented from being generated by repeated friction between the warp yarns and the reed and heddles during weaving, making weaving easier.
Therefore, water jet looms are particularly suitable for weaving synthetic filaments, and thus water jet looms have become the main type of loom for weaving synthetic silk in the silk industry. They account for more than 70% of the new looms in the silk industry, and Shengze in Wujiang and Shaoxing Textile City have become the concentration of water jet looms in my country.
However, during the water-jet weaving process in the silk industry, phenomena such as silk entanglement and breakage, sizing, abnormal weaving vibration, and shaft cracking are prone to occur. Many companies have encountered similar problems. Below, we will discuss the causes and propose corresponding solutions.
Hair strands tangled and broken ▲▲▲
During the weaving process, synthetic fibers such as nylon and polyester can easily form a fuzzy layer near the heald frame and reed. Often, only a few of the dozens of single fibers in a multifilament are not broken, while the other fibers are broken as if by a knife or shears. In severe cases, several multifilaments are "cut off" together, forming a fuzzy layer and causing tangled ends.
The main reason for this phenomenon is that synthetic fibers have high tensile strength but very low shear strength. When fuzz produced on one filament gets tangled on another filament, the two filaments separate during the opening process. The fuzz is not easily broken due to its high tensile strength, but the tangled fibers are "cut" due to their low shear strength. This is especially true for untwisted or low-twisted filaments, where the cohesion between fibers is poor. The cut fibers then tangle with other fibers, thus "cutting" more individual fibers. If not dealt with in time, this will accumulate into a fuzzy mass.
To prevent tangling and breakage of the fibers, it is essential to minimize the generation of fibers during preparation and weaving. This involves the following:
(1) Strictly control the processing tension of the silk thread during the preparation process.
Provided the forming is good, the processing tension of the yarn should be slightly lower. If the tension is too high, the yarn will shrink back after processing due to the loss of tension, and the bobbin wall will prevent it from shrinking back, resulting in a single fiber "breakage" phenomenon that is difficult to detect visually. In addition to processing according to the controlled tension of the yarn, the simplest way is to gently press the bobbin with your thumb and middle finger until the yarn is slightly indented. Avoid hard bobbins.
(2) The wire guide should be smooth and wear-resistant.
High-performance ceramic materials that are not prone to generating static electricity should be selected to prevent the fibers from being worn down during processing. In particular, the use of magnetic materials should be avoided, as although they are smooth, they are relatively soft and cannot withstand the friction of synthetic fibers, causing them to fuzz and wear down.
(3) The film formation and penetration of the pulp fibers should be good without sticking together.
A well-formed film-resistant filament can withstand the friction of heddles and reed teeth, while a well-permeable filament has good binding properties. Even if a few filaments break, it can bind together multiple fiber filaments, thus preventing fuzz formation.
(4) The density of heddle wires at the heddle frame should not be too high.
Based on practical production experience, if the heddle density exceeds 8 threads/cm during weaving, fuzz is likely to form due to repeated opening and friction between the warp and heddle threads, and between the warp threads themselves. Therefore, the number of heddle frames should be increased appropriately. The simplest solution is to use double steel bars, that is, to install two steel bars on one heddle frame, and to separate the warp threads into each steel bar. This reduces the heddle density and prevents fuzz formation. Furthermore, the heddle frames should be replaced regularly to prevent the warp threads from being "cut" due to rough heddle threads.
(5) The weaving workshop should maintain a certain temperature and humidity.
To prevent increased lint due to static electricity generated by dry workshop conditions, a high relative humidity is preferable, ideally controlled at 70%–80%.
Laying ▲▲▲
When weaving on a water jet loom, white, pasty or granular, sticky condensates often appear at the heddles and reeds, which is called sizing. This sizing causes the warp threads to move up and down unimpeded when the shed is opened, resulting in unclear sheds, broken warp and weft threads, and in severe cases, weaving defects, affecting product quality and weaving efficiency.
Measures to prevent grout leakage:
(1) The quality of the slurry must meet the standards.
All test indicators must be qualified; the slurry must not deteriorate; when preparing the slurry, the general slurry dosage is 7%, and water is added to make 100%. The viscosity and other indicators of the prepared slurry must meet the requirements, and there must be no impurities in the slurry and additives.
(2) The preparation of the slurry must meet the requirements.
The water used for preparing the slurry should be softened first, and the water hardness should be kept below 30 mg/kg. The boiling tank and the slurry preparation tank should be cleaned. The basic steps for preparing the slurry are as follows: put 75% water into the boiling tank, start the agitator at a speed of 80-120 r/min, heat the water to 50-60℃, add the slurry, stir for 15-20 minutes, add the additives, stir for another 15 minutes, and add water to 100% to prepare the slurry for use.
(3) The sizing process should be appropriate.
Special attention must be paid to strictly controlling the viscosity and concentration of the slurry. During the slurry application process, the viscosity of the slurry will increase due to water evaporation. Water should be added to prevent this increase, or circulating slurry should be used to prevent the viscosity from rising rapidly. If the slurry supply time in the slurry supply tank and the slurry preparation tank is too long, low-speed stirring should be carried out to prevent the slurry from settling in the lower layer, which would result in the slurry viscosity in the working layer being too low. The slurry viscosity that is suitable for the process requirements is the main measure to prevent slurry from falling off the plate.
The main reference process is as follows: the sizing solution pH value is 7-8, the solid content is 24%-25%, the sizing rate is 7%-8%, the yarn speed for sizing 77.7dtex/24f nylon yarn is 100-120m/min, and the sizing speed for 166dtex/36f polyester processed yarn is 80-90m/min. The principle of elongation control is to allow a slightly larger elongation without affecting yarn performance and causing breakage. This forms a sizing film that prevents the warp yarns from tearing due to slight elongation during weaving. The elongation control is -0.9% to 1.2% for 77.7dtex/24f nylon yarn and 0.6% to 1.2% for 166dtex/36f polyester processed yarn.
(4) During weaving, appropriately reduce the tension of the warp yarns on the loom.
To prevent the slurry film from being torn, the density of the warp threads should not be too high. The density of the warp threads on each heddle should not exceed 8 threads/cm. If it is too dense, measures should be taken to separate the heddles, such as using double steel bars. The relative humidity of the workshop should be 70% to 80%, and the temperature should be 24 to 28℃.
Abnormal shaking of the warp beam ▲▲▲
After several years of use, some water-jet looms develop abnormal warp beam vibrations during operation, especially on domestically produced looms. This can lead to warp yarn pilling and breakage, irregular horizontal stripes on the fabric surface, and a decrease in production efficiency and product quality. The main causes and prevention methods for abnormal warp beam vibration are as follows:
(1) Improper determination of tension on the warp yarn machine
In particular, excessive tension on the machine can easily cause abnormal vibration of the warp beam. Therefore, before production, the required total warp tension must be correctly calculated based on the type of warp yarn, the total number of warp threads, and the thickness of the yarn, so as to determine the mass of the counterweight. At the same time, the tension lever of the continuously variable transmission and the tension of the relaxation spring should be adjusted to keep the counterweight arm in a horizontal position.
(2) Improper tension of the delivery belt
When using a tension meter to measure the tension of the V-belt, the position of the V-belt should be adjusted to meet the theoretical requirements.
(3) Wear of the main shaft bearing of the weaving beam
Improper stress can cause abnormal vibration of the warp beam. The main shaft bearing and bearing sleeve should be carefully inspected for wear. If wear is found, they should be replaced promptly, and sufficient grease should be added during replacement.
(4) Wear of the warp beam bracket and warp beam bracket cover
Efforts should be made to repair or replace it promptly, and adjustments should be made to meet installation requirements.
(5) Improper assembly of the feed gears
Improper meshing and poor transmission can cause vibration; the appropriate number of gear teeth should be calculated according to the weft density of the fabric, and the correct module should be selected.
(6) Gearbox is short of oil, damaged, or corroded
Vibration is caused by improper transmission. It should be corrected promptly to ensure that there is no lack of lubrication, no damage, and no rust.
(7) The head of the warp beam is loose and moves outward.
If it can be repaired in time, it should be inspected and repaired immediately. If it cannot be repaired in time, it should be repaired as soon as the machine is out of service.
(8) If the bolts of the warp beam bracket cover are not fully tightened, they should be tightened in time.
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