Line marks on the parison surface (die marks)

During the extrusion '2079851475616104457 production process, the product exhibits the quality defect of "Line marks on the parison surface (die marks)". Specifically manifested as longitudinal line marks appearing on the parison surface. This defect is relatively common when processing materials such as HDPE, PP, PVC, and PC, and its occurrence conditions are usually related to unreasonable settings of melt temperature, extrusion speed, blowing air pressure, and mold temperature. When the Line marks on the parison surface (die marks) situation is severe, it will cause a series of chain-reaction quality defects in the product in terms of appearance, dimensional accuracy, mechanical properties, etc., which not only reduces the usability and safety of the product, but also directly increases the scrap rate and production cost. Therefore, this problem requires systematic diagnosis and optimization from multiple dimensions, including material selection, the condition of the extruder, die head, die, mold clamping mechanism, and blowing system, as well as melt temperature, extrusion speed, blowing air pressure, and mold temperature.

1. Scratches on the die inner wall. This factor leading to the problem reflects that certain process conditions or material properties in extrusion blow '2079851475616104453ing have not met the optimal molding requirements. Such problems often have cumulative and hidden characteristics, and should be investigated and verified as key focus items during process debugging and finalization to ensure that hidden dangers are eliminated from the source. 2. Material buildup or foreign matter. The mixing in of external foreign matter will destroy the homogeneity of the melt, causing defects such as spots, voids, and stress concentration in the product. This foreign matter may come from the raw material itself, residues in the regrind, shedding of material accumulated in the equipment, or contaminants in the production environment. Strengthening raw material purification management and equipment cleaning is the key to preventing foreign matter from being mixed in. In addition, insufficient overall coordination between parison wall thickness control and parison temperature uniformity is also a factor that cannot be ignored; there are complex interactions and coupling relationships among the various process parameters, and the deviation of any single parameter may aggravate the degree of Line marks on the parison surface (die marks) through chain effects. In terms of equipment maintenance, inadequate regular overhaul and accuracy confirmation of the extruder, die head, die, mold clamping mechanism, and blowing system cause the actual operating parameters of the equipment to deviate from the process requirements, which can also become a potential inducement of the Line marks on the parison surface (die marks) problem.

1. Clean the die inner wall. Cleaning work should be incorporated into the equipment preventive maintenance plan, and the cleaning frequency should be reasonably determined according to the actual conditions of the processed material and the operating cycle. Use dedicated cleaning tools and cleaning materials to avoid scratching the cavity surface or electrolytic corrosion caused by improper operation. After cleaning, re-check and confirm that the key clearances are accurate. 2. Polish to repair the scratches. The polishing operation should proceed step by step from coarse to fine; each time a finer abrasive is used, the polishing direction should be changed to eliminate the texture marks of the previous step. The final surface roughness should be tested with a roughness meter to confirm that it meets the standard. After polishing is completed, it should be thoroughly cleaned to remove residues of abrasives and grinding agents to prevent them from entering the melt and contaminating the product. 3. Check the raw material cleanliness. Inspection work should establish a standardized inspection checklist, clarifying the inspection items, technical standards, inspection frequency, and responsible persons. Key equipment components should be regularly disassembled to inspect the condition of hidden parts, and judgment should not be based solely on operating appearance. Inspection results should be recorded in detail and a trend analysis mechanism established to predict potential failures. In terms of material management, incoming inspection of raw materials and in-process inspection of work-in-progress should be strengthened, and the key performance indicators of HDPE, PP, PVC, and PC should be strictly controlled to ensure the stability of molding quality from the source.

In summary, the causes of the "Line marks on the parison surface (die marks)" problem can be attributed to the combined action of multiple factors such as scratches on the die inner wall and material buildup or foreign matter. Solving this problem requires starting from aspects such as clean the die inner wall and polish to repair the scratches, and adopting systematic governance measures. In actual production, it is recommended to establish a prevention and rapid response mechanism for this problem, achieving stable production and continuous improvement through parison wall thickness control and parison temperature uniformity.