This defect typically appears in parts using point gates oriented perpendicular to the part's surface. It manifests as a radial pattern emanating from the gate, characterized by varying depths of color and gloss.<\/p>\n
If you are struggling with this issue, this guide will break down the symptoms, root causes, and professional solutions to eliminate it from your production line.<\/p>\n
![\"](\"https:\/\/ideal-pro.com\/wp-content\/uploads\/2026\/05\/injection-molding_-gate-halo-radiation-lines-guide.jpg\")
<\/p>\n
\n
What Does This Defect Look Like?<\/h2>\n
The \"radiation line\" defect usually presents itself in three distinct forms around the gate area:<\/p>\n
- \n
- Dark lines on a dark background:<\/strong> Subtle variations in gloss or texture creating a visible contrast.<\/li>\n
- Deep-colored lines on a light\/dull background.<\/strong><\/li>\n
- A dense, whitish haze:<\/strong> Darker lines clustered tightly around the gate, often appearing frosted or white.<\/li>\n<\/ol>\n
\n
\ucc38\uace0:<\/strong> This defect is most frequently observed when processing Polystyrene (PS) blends or modified Polystyrene compounds.<\/p>\n<\/blockquote>\n
\nRoot Cause Analysis<\/h2>\n
Why do these radiation lines occur? The phenomenon is primarily driven by inconsistencies in the melt flow and material composition. Key factors include:<\/p>\n
- \n
- Material Inconsistency:<\/strong> Differences in rheology (flow behavior) and colorant properties between base resins and additives.<\/li>\n
- Flow Dynamics:<\/strong> Variations in velocity and heat history between the laminar flow layer and the turbulent flow layer within the runner system.<\/li>\n
- Material Degradation:<\/strong> Thermal decomposition generating burnt streaks or \"slivers.\"<\/li>\n
- Gas Interference:<\/strong> Trapped air or volatiles interfering with the plastic as it enters the mold cavity.<\/li>\n<\/ul>\n
\nTroubleshooting & Solutions<\/h2>\n
To eliminate radiation lines, you need a systematic approach targeting materials, machine settings, and mold design.<\/p>\n
1. Optimize Material Preparation<\/strong><\/p>\n
- \n
- Uniform Mixing:<\/strong> When using polymer blends, ensure the pellets are uniform in size and thoroughly mixed. Inconsistent particle sizes can lead to uneven melting.<\/li>\n
- Masterbatch Dispersion:<\/strong> Ensure the colorant is perfectly blended with the resin. If necessary, use a mechanical mixer and add a suitable dispersing agent to prevent pigment clustering.<\/li>\n<\/ul>\n
2. Check Machine Plasticization<\/strong><\/p>\n
- \n
- Ensure the injection molding machine has good plasticizing performance. Incomplete melting will directly result in flow marks and visual defects.<\/li>\n<\/ul>\n
3. Adjust Process Parameters<\/strong>\nFine-tuning your injection parameters is often the quickest fix:<\/p>\n
- \n
- Reduce Injection Pressure & Speed:<\/strong> High shear rates can cause flow instability.<\/li>\n
- Shorten Injection & Holding Time:<\/strong> Minimize the stress on the gate area.<\/li>\n
- Temperature Management:<\/strong> Increase the \uae08\ud615 \uc628\ub3c4<\/strong> \uadf8\ub9ac\uace0 Nozzle Temperature<\/strong>, but consider reducing<\/em> the front barrel temperature to prevent overheating the melt before injection.<\/li>\n<\/ul>\n
4. Prevent Material Degradation<\/strong>\nDegraded material creates viscous slugs and burnt particles that ruin surface finish.<\/p>\n
- \n
- Inspect Hardware:<\/strong> Check if the screw or barrel is worn out, creating \"dead spots\" where plastic stagnates and burns.<\/li>\n
- Check Heating Systems:<\/strong> Ensure heating bands are functioning correctly to avoid uncontrolled temperature spikes.<\/li>\n
- Maintenance:<\/strong> Polish the internal surfaces of the screw and the front section of the barrel to prevent material hang-up.<\/li>\n<\/ul>\n
5. Improve Mold & Gate Design<\/strong>\nSometimes, the hardware design is the bottleneck. Consider these modifications:<\/p>\n
- \n
- Enlarge the Gate Diameter:<\/strong> Reduces shear stress.<\/li>\n
- Change Gate Location:<\/strong> Move the gate to a less visible area or an area with better flow dynamics.<\/li>\n
- Use a Radiused Gate:<\/strong> Transitioning to a rounded corner at the gate helps smooth the flow entry.<\/li>\n
- Local Gate Heating:<\/strong> Applying heat specifically to the gate area can improve flow front consistency.<\/li>\n
- Add a Cold Slug Well:<\/strong> Placing a cold slug well at the end of the runner traps the initial cooled material, preventing it from entering the cavity.<\/li>\n<\/ul>\n
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- Change Gate Location:<\/strong> Move the gate to a less visible area or an area with better flow dynamics.<\/li>\n
- Check Heating Systems:<\/strong> Ensure heating bands are functioning correctly to avoid uncontrolled temperature spikes.<\/li>\n
- Shorten Injection & Holding Time:<\/strong> Minimize the stress on the gate area.<\/li>\n
- Reduce Injection Pressure & Speed:<\/strong> High shear rates can cause flow instability.<\/li>\n
- Masterbatch Dispersion:<\/strong> Ensure the colorant is perfectly blended with the resin. If necessary, use a mechanical mixer and add a suitable dispersing agent to prevent pigment clustering.<\/li>\n<\/ul>\n
- Flow Dynamics:<\/strong> Variations in velocity and heat history between the laminar flow layer and the turbulent flow layer within the runner system.<\/li>\n
- Deep-colored lines on a light\/dull background.<\/strong><\/li>\n