Silver Streaks:
Shiny, silvery lines appearing on the surface of the molded product or near the gate along the flow direction. These are caused by excessive moisture or volatile substances in the material, poor adhesion between the melt and the mold, or rapid cooling after the melt has been subjected to excessive shear stress—resulting in needle-like or mica-like streaks.
In addition, if the silver streaks appear irregularly in a comet-like pattern, they are caused by the resin overheating and decomposing into gases.
| 3.1 Causes | 3.2 Solutions |
|---|---|
| 3.1.1 High moisture content or excessive volatiles in the material. | 3.2.1 Dry the material thoroughly according to processing conditions. |
| 3.1.2 Low mold temperature and high melt temperature. | 3.2.2 Increase mold temperature and reduce melt temperature to prevent material decomposition. |
| 3.1.3 Low injection pressure. | 3.2.3 Increase injection pressure to allow complete exhaust of gas from the cavity. |
| 3.1.4 Poor air release or low back pressure during plasticizing. | 3.2.4 Increase back pressure to expel air and gas during plasticizing. |
| 3.1.5 Small gate causes high shear stress (especially when mold and melt temperatures are low and injection pressure/speed are high). | 3.2.5 Enlarge the runner and gate size to reduce shear stress. |
| 3.1.6 Moisture, lubricant, or excessive mold release agent on mold surface (results in white marks). | 3.2.6 Wipe off moisture or oil from mold cavity surface and use a suitable mold release agent. |
| 3.1.7 Low mold temperature, low injection pressure, and low speed cause slow filling and rapid cooling, forming white/silvery reflective layers (cold flow marks). | 3.2.7 Increase mold temperature, injection pressure, and injection speed to reduce cooling rate. |
| 3.1.8 Melt expands or volatile gases form when flowing from thin to thick sections, producing silver streaks. | 3.2.8 Adjust injection speed or modify wall thickness to minimize large thickness differences. |
| 3.1.9 Improper formulation or contamination with incompatible materials. | 3.2.9 Adjust material formulation or replace with compatible materials. |
| 3.1.10 High screw speed and low back pressure cause air entrapment in the melt. | 3.2.10 Reduce screw speed and increase back pressure to prevent air entrapment. |
| 3.1.11 Excessive clamping force hinders venting. | 3.2.11 Reduce clamping force to improve venting. |
| 3.1.12 Poor feeding or bridging allows air to enter the material. | 3.2.12 Ensure smooth feeding to prevent air intake. |
| 3.1.13 Poor alignment between nozzle and sprue bushing. | 3.2.13 Align nozzle and sprue properly (match the radii). |
| 3.1.14 Thermocouple detached or temperature control failure. | 3.2.14 Replace the thermocouple. |
| 3.1.15 Cold material chips at the shear gate. | 3.2.15 Increase mold temperature and adjust ejection speed to reduce chips. |
| 3.1.16 Material decomposition due to excessive temperature in the hot runner. | 3.2.16 Clean decomposed material and lower the hot runner temperature. |
follow us :
-- get updates with latest topics
e-mail
English
français
Deutsch
русский
italiano
español
português
العربية
日本語
한국의
中文