Common Defects of Plastic Profile Products (Warping, Bubbles, Color Difference): Troubleshooting And Solutions

Core Conclusion: Warping, bubbles, and color difference in plastic profiles mainly stem from three core links: raw material characteristics, equipment parameters, and process control. These defects can be efficiently resolved through "root cause localization + targeted adjustments". Below is the detailed practical solution:

I. Defect 1: Warping (Products bend or deform, failing to fit installation requirements)

Root Cause Analysis

    1、Uneven cooling:      Significant temperature differences in different areas of the calibration      mold and water tank lead to inconsistent local shrinkage of profiles.

    2、Imbalanced process      parameters: Mismatch between traction speed and extrusion speed, or uneven      pressure from the tractor.

    3、Raw material formula      issues: Excessive addition of fillers or improper proportion of      plasticizers and stabilizers.

    4、Mold design defects:      Uneven distribution of flow channels in the die head, resulting in      inconsistent material discharge speed.

Solutions

    1、Optimize the cooling      system: Adjust the temperature of each section of the calibration mold,      ensure uniform water temperature in the water tank, and extend the cooling      stroke.

    2、Calibrate traction      parameters: Set the traction speed slightly higher than the extrusion      speed, adjust the pressure of the upper/lower and left/right pressure      rollers of the tractor to ensure balanced force.

    3、Adjust raw material      formula: Reduce the filler dosage, add an appropriate amount of      plasticizer, and ensure sufficient stabilizer.

    4、Overhaul the mold:      Clean the accumulated material in the die head flow channels, check the      smoothness of the flow channel inner wall, and regrind or adjust the flow      channel design if necessary.

II. Defect 2: Bubbles (Hollow bubbles or pinholes on the surface or inside of products)

Root Cause Analysis

    1、Excessive moisture      content in raw materials: Plastic particles absorb moisture, and the water      evaporates when heated to form bubbles.

    2、Raw material impurity      issues: Air, dust, or volatile substances mixed into the raw materials.

    3、Abnormal extrusion      temperature: Excessively high temperature of the barrel or die head causes      raw material decomposition and gas generation; or excessively low      temperature results in insufficient plasticization of materials and air      entrapment.

    4、Vacuum calibration      system failure: Insufficient vacuum degree fails to timely discharge gas      from the materials.

Solutions

    1、Raw material      pretreatment: Dry the raw materials in a dryer and use immediately after      drying.

    2、Purify raw materials:      Screen raw materials to remove impurities and agglomerates; recycled      materials should be dried separately and the addition ratio controlled.

    3、Adjust extrusion      temperature: Lower the temperature at the rear end of the barrel, increase      the temperature at the front end and die head, and control the temperature      fluctuation within ±5℃.

    4、Overhaul the vacuum      system: Check the operation status of the vacuum pump, clean blockages in      the vacuum pipeline, and adjust the vacuum degree to 0.06-0.08MPa.

III. Defect 3: Color Difference (Uneven product color or deviation from the standard color sample)

Root Cause Analysis

    1、Masterbatch issues:      Poor dispersibility of masterbatch, uneven addition ratio, or unstable      quality of the masterbatch itself.

    2、Fluctuating extrusion      temperature: Excessively large temperature differences in each section of      the barrel lead to pigment decomposition or uneven dispersion.

    3、Uneven raw material      mixing: Insufficient stirring between masterbatch and base plastic, or      mixing of raw materials from different batches.

    4、Mold contamination:      Residual old material or coked material on the inner wall of the die head      mixes with new materials, causing local color abnormalities.

Solutions

    1、Optimize masterbatch      usage: Select masterbatch compatible with the base material, control the      addition ratio at 2-5%, and extend the stirring time to ensure uniform      mixing.

    2、Stabilize extrusion      temperature: Strictly control the temperature of each section of the      barrel, avoid frequent adjustments, and ensure the temperature deviation      does not exceed ±3℃.

    3、Unify raw material      batches: Use base plastic from the same batch; if batch replacement is      necessary, conduct small-batch trial production in advance to adjust the      masterbatch ratio for adaptation.

    4、Clean the mold:      Regularly disassemble the die head, clean residual coked material and old      material on the inner wall to avoid contamination of new materials.