Profile dimensional fluctuation

Key dimensions of the profile cross-section (such as wall thickness, outer diameter, fitting dimensions) fluctuate beyond tolerance over time. When this defect appears in extrusion molded products, it is usually closely related to process links such as die design, screw plastication state, cooling and sizing system, or haul-off stability. Persistence of the defect will lead to out-of-tolerance product dimensions, unqualified appearance, or decreased mechanical properties, increasing scrap rate and rework costs. Timely diagnosis and troubleshooting from both extrusion process parameters and equipment status are basic requirements for ensuring stable continuous production.

1. Process parameter factors: Uneven feeding causes extrusion output changes. 2. Mold/tooling factors: Wear of vacuum sizing mold/dry sizing mold causes dimensional drift. 3. Cooling/environmental factors: Cooling water temperature fluctuation. 4. Mold/tooling factors: Melt temperature changes cause die swell effect changes.

1. Process parameter optimization and adjustment: Ensure feed system stability. 2. Mold/tooling improvement and maintenance: Regularly check key dimensions of sizing molds and replace worn parts. 3. Equipment inspection and system maintenance: Use a constant-temperature cooling water system. 4. Material/formulation optimization: Stabilize melt temperature control. 6. Preventive management: Establish standardized process parameter cards and quality control limits for each mold/product, and regularly conduct process capability index (CPK) evaluations. For recurring problems, use fishbone diagrams or 5Why analysis to trace the root cause, and solidify countermeasures as PFMEA control points. Establish a regular equipment maintenance system and implement life management for key tooling such as dies/spinnerets/calender rolls/coating heads.

This problem is a typical manifestation of profile dimensional fluctuation in extrusion molding. The core of the solution lies in eliminating the root cause of the defect through systematic optimization of process parameters (temperature, speed, pressure) and precision correction of the die/sizing system. It is recommended to start with parameter adjustment and gradually go deeper into the equipment and tooling levels.