Mold Venting Design: Solving Gas Traps and Burn Marks
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<p>Proper venting is often overlooked but accounts for many molding defects.</p>
<p><strong>Types of Vents:</strong></p>
<ul>
<li>Parting line vents: shallow grooves 0.02-0.05mm deep</li>
<li>Ejector pin vents: clearance 0.02-0.04mm</li>
<li>Insert vents at gas trap locations</li>
<li>Vacuum venting: active cavity evacuation</li>
</ul><p><strong>Vent Depth by Material:</strong></p>
<ul>
<li>Amorphous (ABS, PC): 0.03-0.04mm</li>
<li>Semi-crystalline (PE, PP): 0.02-0.03mm</li>
<li>High-flow (LCP): 0.02mm max</li>
<li>Rubber: 0.02-0.05mm</li>
</ul><p><strong>Land Length:</strong> 3-10mm before opening to atmosphere</p>
<p><strong>Diagnosing Issues:</strong></p>
<ol>
<li>Burn marks at last fill area → insufficient venting</li>
<li>Short shots with no other defects → trapped gas</li>
<li>Glossy marks at weld line → gas trapped at melt front</li>
</ol><p><strong>Advanced Solutions:</strong></p>
<ul>
<li>Porous steel inserts (25-30% porosity)</li>
<li>Stepped vent grooves</li>
<li>Automated vent cleaning for high-production molds</li>
</ul><hr>
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<p>新手建议收藏，老手欢迎指点。</p>