Poor drainage in the drying drum
Phenomenon: Whether it is a new sizing machine or a traditional sizing machine, whether it is an elevated drying room or a floor-standing parallel drying room, the drying cylinder drainage system is prone to failure, and such failures are not easy to find. Models with the drying drum positioned close to the ground are more likely to suffer from poor drainage.
Troubleshooting: This type of fault can be assessed using the temperature display on the temperature controller. For example, after a temperature is set, if other drying cylinders quickly reach it but one cylinder reaches it very slowly or cannot reach it, poor condensate drainage may be suspected. Open the drying cylinder's direct condensate drain valve and observe the discharge. With the sizing machine operating normally, condensate containing a small amount of steam should drain completely within 1–2 minutes after the valve is opened. If drainage takes much longer, a fault may already be present.
To reduce dryer-cylinder drainage-system failures, install the siphon correctly, as close as possible to the lowest point of the cylinder's inner wall without rubbing against it. Condensate drain piping must not be too small: each cylinder's drain pipe must be at least 20 millimeters in diameter, a combined drain for 4 cylinders at least 40 millimeters, and the main dryer-cylinder drain at least 65 millimeters. Steam-trap quality is crucial. Inspect and clean traps regularly to keep them in good condition. During operation, drain all condensate from the cylinders before starting the machine from cold.
If a boiler is used to supply steam, the steam supply pipeline should be shortened as much as possible, and attention should be paid to thermal insulation and water drainage along the way. The water level of the boiler should be well controlled, and the steam pressure should meet the standard to reduce steam carrying water.
Automatic speed increase failure of sizing machine
Phenomenon: During production, the normal sizing machine suddenly increases its speed automatically, and the speed is getting higher and higher, exceeding the normal process setting range. The operator on duty presses the speed-down button, and the vehicle speed gradually drops to the normal process setting range. Release the speed reduction button, and the machine will automatically increase speed. The vehicle speed will get higher and higher, exceeding the normal range and unable to operate normally.
Troubleshooting: Open the setting interface of the touch screen and check the function items. It is found that the "automatic moisture regain control" function item is "on". After turning it to "off", the automatic speed-up phenomenon of the machine disappears. Only when the speed-up button is pressed, the speed is gradually increased. The fault is eliminated.
There is an automatic tension adjuster, but the yarn was broken
Phenomenon: After using a UA308 type sizing machine with a box width of 3.6 meters for several years, it was found that the middle part of the drag roller could not hold the yarn. When the lower shaft yarn was cut, the yarn in the middle of the drag roller obviously retracted to the dry area, causing the yarn in the dry area to relax and intertwine. For this reason, the company purchased a new tractor roller for replacement. Unexpectedly, after the new tractor roller was put on the truck and started running, a large amount of yarn in the dry area was pulled apart, making it impossible to drive.
Troubleshooting: The sizing machine has a tension roller in its dry zone, with an angular displacement potentiometer installed at the roller. Yarn tension in the dry zone is measured indirectly by detecting the tension roller's vertical position. The result is fed back to the PLC, which adjusts the speed ratio of the variable-frequency motor to maintain dry-zone tension within a set range automatically. A fault in the dry-zone automatic adjustment system was initially suspected, but inspection found no problems with the angular displacement potentiometer or wiring. Because the problem had appeared after replacement of the draw roller, the draw roller was examined. Its diameter was found to be much larger than that of the original roller. After the new draw roller diameter was entered on the touchscreen, the machine operated normally, dry-zone yarn tension stabilized, and yarn breakage stopped. The fault was resolved.
The drag roller cannot press the yarn. The greater the pressure, the looser the yarn.
Phenomenon: During operation, the middle part of the pressure roller on the drag roller of a sizing machine cannot press the yarn. When the yarn is cut on the lower shaft, the middle part of the yarn retracts seriously toward the dry area. The lathe on duty increased the pressure. As a result, the greater the pressure, the more serious the yarn shrinkage.
Troubleshooting: Check on the machine and find that when the pressure value is small, increase the pressure and the yarn will be pressed tighter; but when the pressure reaches a certain value, if the pressure is adjusted higher, the yarn in the middle of the drag roller will become less compressed; after adjusting the pressure to a smaller value, the yarn in the middle will no longer relax, but will be compressed.
Improper power matching of the tension adjustment mechanism
Phenomenon: At normal vehicle speed, the tension (elongation) varies significantly due to changes in vehicle speed. After the vehicle speed is reduced (most obvious when crawling), the output power of the tension adjustment mechanism is significantly reduced. Some sizing machine tension adjustment mechanisms often malfunction under normal maintenance.
Troubleshooting: The power capacity of the sizing machine's transmission components (adjustment device) is mismatched; in other words, the power these components can transmit at low machine speeds is insufficient. The simplest solution is to increase the adjustment device's input shaft speed and reduce its output shaft speed by the same ratio. A larger tension (elongation) adjustment device is unnecessary. At the sizing machine's maximum design speed, the device's maximum permissible rotational speed must not be exceeded. This greatly increases the power transmission capacity of the sizing drive components at low speed, resolving the power mismatch, reducing mechanical failures, and stabilizing sizing tension.
Source: China Textile Machinery Network
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