Jetting / Jetting Mark

The melt is jetted into the cavity through the gate, forming snake-shaped marks. Jetting marks appear as snake-shaped or earthworm-like winding curves starting from the gate position, with darker color and gloss different from the surrounding area. This is because when the melt is jetted into the cavity at high speed through a small gate, the melt that enters first cools and solidifies quickly into snake-shaped strands, and the subsequent melt covers them but cannot fully fuse. The mechanical strength in the jetting mark area is extremely low, because a weak bonding interface is formed between the snake-shaped strands and the subsequent melt, similar to a collection of multiple cold weld lines.

1. Process parameter factors: gate size too small, injection speed too fast, melt temperature too low, no cold slug well provided. 2. Mold comprehensive factors: in addition to venting, mold design parameters such as cooling water channel layout, gate position and size, and demolding draft angle all have a systematic impact on part quality, and optimization is required from the source of mold design.

1. Process parameter optimization and adjustment: enlarge the gate cross-section, reduce injection speed, increase melt temperature, use overlap gates or tab gates. 2. Systematic troubleshooting method: troubleshoot item by item in the order of "parameters -> material -> mold -> equipment". First adjust the parameters that are easiest to change, such as injection pressure and temperature, and observe the effect; if there is no improvement, check the drying and fluidity of the raw material; further check mold venting and gate design; finally check the mechanical condition of the equipment (check ring, screw). Change only one variable at a time to determine the root cause. 3. Preventive management: establish standardized process parameter cards and quality control limits for each mold/product, and regularly conduct process capability index (CPK) evaluation. For recurring problems, use fishbone diagram or 5Why analysis to trace the root cause, and fix the countermeasures as PFMEA control points.

This problem is a typical manifestation of jetting/jetting marks in '2079851475616104452; the core of the solution lies in eliminating the root cause of the defect through systematic optimization of process parameters (temperature, pressure, speed) and rationality checks of mold design. It is recommended to start with process parameter adjustment and gradually go deeper into the equipment and mold levels.