I. Locating the Problem by Identifying Fabric Defects
Observing the appearance defects of the dyed fabric is the most direct way to determine the source of the malfunction:
If there are darker areas at both ends (overlap marks), first check if the seam allowance is too wide, if the guide yarn is inconsistent with the fabric material, or if the tension setting is too high.
If the fabric has inconsistent colors at the beginning and end (light and dark ends), focus on checking if the guide yarn is contaminated, if the dye was not added in the correct order (active/disperse/direct), or if there are temperature fluctuations in the initial dyeing stage.
If the fabric edge and center are different colors (light and dark edges), check if the fabric width is neat when it is loaded onto the roll, if the curvature of the tensioner is too large (it is recommended to control it within 4~8mm), and if there are temperature or pH differences between the edges and the center.
If there are longitudinal wrinkles (creases), it may be caused by uneven seam allowances, excessive tension, yarn wrapping on the roller, or excessive steam impact; these need to be checked one by one.
If weft yarn skew is found, it is usually related to uneven operator input into the dyeing vat or excessively high steam pressure during boiling dyeing.
If ring-like patterns (loose board marks) are present, it is often due to hot fabric winding or excessive initial tension. It is recommended to use cold water for pre-winding.
If the fabric surface has uneven color (color spots), it is commonly due to excessively rapid heating (especially after 80℃ > 1.5℃/min), one-time addition of dyeing accelerator, or insufficient alkali sulfide.
If transverse color difference stripes (color streaks) appear, it can generally be determined that the machine stopped during the dyeing process, and the equipment operation log needs to be checked.
If the colors are inconsistent between different batches (color difference), the process parameters should be checked for uniformity, whether the floating dye has been washed away, and whether the sampling procedure has been strictly followed.
II. Troubleshooting by System Module
Electrical Control System: If the frequency converter alarms (e.g., ENF self-tuning failure), check if the encoder AB phase signal lines are reversed; if tension is out of control, check if the PLC parameters and sensor feedback are normal.
Hydraulic System: If the drum speed is unstable or the drive is weak, focus on checking the cleanliness of the hydraulic oil, the wear of the hydraulic pump, and whether the pressure valve is stuck.
Dye liquor circulation system: If color spots or uneven color distribution occur, check whether the circulation pump is working properly, whether the filter is clogged, and whether the dye liquor flow rate is uniform.
Temperature control system: If the temperature fluctuates greatly, check whether the steam valve, temperature sensor, and insulation cover are intact.
III. Implement the rapid troubleshooting method
Step 1: Inspect the fabric surface → Initially identify the type of fault based on the defect morphology.
Step 2: Check records → Retrieve the equipment operation log to check for any abnormal shutdowns, temperature jumps, or tension fluctuations.
Step 3: Question the operators → Confirm whether the personnel on duty have followed the procedures for adding material, changing direction, and verifying samples.
Step 4: Trial run → Test the tension, speed, and changing direction response under no-load conditions to ensure they are normal.
