I. Defects Associated with Direct Temperature
Local Overheating, Overflow, and Flash: The temperature shown in the temperature control channel is significantly lower than the actual temperature due to signal drift. The temperature in the nozzle area rises abruptly and the melt viscosity significantly decreases while the heating element keeps producing its full power. This causes flash at the parting line, nozzle dripping, and, in extreme situations, high-risk situations like splashing and melt jetting.
Inadequate Temperature, Short Shots, and Shortages: The temperature shown in the temperature control channel is higher than the actual temperature due to signal drift. The runner's viscosity increases and the melt temperature is insufficient because the heating element stops producing power too soon. This causes a significant rise in flow resistance, which prevents the cavity from filling completely and results in short shots and shortages.
Uneven Filling in Multiple Cavities: Significant temperature variations in the melt within each cavity are caused by inconsistent signal drift in various hot runner channels. While the melt flow rate in short runners is too rapid, the melt travelling through long runners cools too quickly, increasing viscosity. In the end, this causes substantial variations in the amount of filling in multi-cavity items, resulting in uneven filling in various regions and variations in product weight that surpass 10 grams. II. Defects in Product Performance and Appearance
Plastic Scorching and Decomposition: The melt stays in the hot runner for an extended period of time due to localised channel signal drift, which causes prolonged overheating and thermal degradation. This causes the product's surface to have burnt bubbles and streaks along with a faint smell of scorched plastic.
Weld Lines and Inadequate Strength: When the melt merges, some cavities' lower melt temperatures cause a notable drop in weld strength. In areas of crucial stress, obvious weld lines show up, leading to inadequate structural strength and possibly undetectable fissures.
Product Deformation and Dimensional Deviation: Significant variations in cooling shrinkage rates result from inconsistent melt temperatures throughout various cavities. After demolding, this causes uneven warping and crucial assembly dimensions that are larger than tolerances. The performance of electrical connections can be directly impacted by uneven pin length and thickness in connectors.
III. Defects in Production Stability
Uncontrolled Batch Product Consistency: Unpredictable variations in injection volume and holding pressure per mould cycle result from signal drift, which is constantly changing over time. The yield is significantly reduced when there are large weight variations within the same batch of items.
Hot runner hardware damage: Prolonged melt leakage brought on by overheating will directly corrode and harm the temperature control sensors and heating elements inside the hot runner, drastically reducing the system's lifespan and resulting in more equipment failures and downtime.
Precision injection molding's production stability is directly impacted by these flaws. In order to prevent generating batches of defective items, signal generator drift must be promptly checked and calibrated.
