Splay, or silver streaks in injection molded products, is a defect that affects both the visual appeal and potentially the functionality of the final piece. Tackling this issue involves an intricate understanding of the numerous factors that contribute to its occurrence. We're examining the various reasons that can cause splay through the lens of mold configuration, process settings, and material characteristics. This comprehensive review aims to equip practitioners with the necessary insights to identify and rectify the root causes of splay in the injection molding process.
Mold Causes:
- Water inlet too small, causing jetting.
- Poor venting, air traps causing splay.
- Sharp corners, residual material leading to splay.
- Nozzle gate or pin point too small.
- Dead angle in hot runner, residual material.
- Improper temperature sensing position in hot runner, abnormal lines.
- Half of the hot runner is blocked.
- Mold leakage.
- Hot runner temperature too high, material decomposition.
Process Causes:
- Incorrectly set back pressure.
- Injection speed too fast, causing splay.
- Incorrect front-end injection parameter settings, causing splay.
- Melting speed too fast, causing material decomposition.
- Injection not slowed down adequately at the end, causing trapped air splay.
- Nozzle blocked halfway.
- Mold temperature too low.
- Parting line vent blocked, needs cleaning every 4 hours.
- Pulling the material too long.
- Barrel temperature too high, causing material decomposition.
Design Causes:
- Sprue design not smooth, residual material causing splay.
- Improperly located venting, not enough vents.
- Improper method of water entrance (pin point, square, round, fan-shaped).
Equipment Causes:
- The three small parts, barrel damaged, poor pre-plastic quality.
- Nozzle and mold sprue not matching, air mixed in causing splay.
- Abnormal heating in material hopper, fan broken.
- Barrel temperature abnormal (one side not heating, influenced by the side).
Material Causes:
- Material not properly dried, incorrect baking temperature setting.
- Material has impurities.
- Material particles too large, uneven distribution.
- Material, sprue not mixed evenly.
- Abnormal dry granules, not properly dried.
As we reach the end of our comprehensive analysis, it's clear that splay in injection molded products is a multifactorial problem that requires a holistic approach to address effectively. By considering the detailed causes outlined, from mold design to material preparation, manufacturers and engineers can implement corrective measures to minimize the occurrence of splay. This focused attention to detail ensures the production of high-quality, visually flawless, and structurally sound injection molded products, maintaining the integrity and reputation of the molding industry.