Melt temperature too high

Extrusion melt temperature exceeds the upper limit of the process recommended range; the product shows yellowing, bubbles, and rough surface. 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: Excessive screw shear heating (compression ratio too large, rotation speed too high). 2. Equipment factors: Barrel temperature set too high. 3. Comprehensive factors: Excessive back pressure causes temperature rise. 4. Cooling/environmental factors: Insufficient cooling system capacity. 5. Die design factors: The geometry of the die flow channel, the land length, and the outlet dimensions directly affect melt flow stability and product dimensional accuracy. Unreasonable flow channel design (presence of dead corners, excessively large convergence angle) is an important root cause of melt fracture, material buildup, and flow marks, and must be addressed starting from optimization of the die structure.

1. Process parameter optimization and adjustment: Reduce screw rotation speed. 2. Mold/tooling improvement and maintenance: Appropriately reduce barrel set temperature. 3. Equipment inspection and system maintenance: Check and clean the screen to reduce back pressure. 4. Material/formulation optimization: Strengthen barrel cooling (fan or water cooling). 5. Operating specifications and preventive measures: If necessary, replace with a gentler screw (smaller compression ratio).

This problem is a typical manifestation of melt temperature too high 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.