Dictionary
EnglishShort definitionBurn marks are dark discolorations or streak-like markings on injection-molded parts caused by local overheating of the plastic melt or trapped air inside the mold cavity. They reduce visual quality and often point to poor venting, excessive injection speed, or overly high melt temperatures.
Dictionary
Burn marks (injection molding)Burn marks in injection molding appear as dark brown or black areas on molded parts when plastic or trapped air overheats during filling, often near the end of the flow path. They usually indicate poor venting, overly aggressive process settings, or problematic flow geometry and can affect both appearance and material integrity.
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Short shot (incomplete injection)Short shot, also called incomplete injection, occurs when the mold cavity is not fully filled with molten plastic, leaving missing sections or incomplete contours on the part. Common causes include insufficient shot volume, low injection pressure or speed, low mold or melt temperature, restricted flow paths, or poor venting.
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Injection molding parametersInjection molding parameters are the specific settings and conditions that are defined in the injection molding process to control the production of plastic parts. These include die and plastic temperatures, injection pressure, injection speed, dwell time and cooling times. The precise setting of these parameters is crucial for the quality and consistency of the parts produced, as they influence factors such as surface quality, dimensional accuracy and material properties. In practice, optimally tuned injection moulding parameters enable efficient production, reduce scrap rates and improve material utilization. They are therefore of great importance both from an academic perspective and in industry in order to produce competitive and high-quality plastic products.
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JettingJetting is an injection molding defect characterized by irregular, worm-like flow lines on the part surface when the plastic melt enters the cavity too quickly without immediately contacting the mold wall. It is often linked to gate design, melt temperature, or injection speed and can weaken appearance and surface consistency.
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Weld lines (knitting lines)Weld lines, also called knitting lines, are visible linear areas on injection-molded parts where two melt fronts meet but do not fuse completely. They can reduce local mechanical strength and visual quality, especially around holes or complex flow paths, and are influenced by melt temperature, tool design, venting, and flow balance.
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Sink marksSink marks are localized depressions on the surface of injection-molded parts, typically appearing above thick sections, ribs, or bosses when the material cools and shrinks unevenly. They affect appearance and dimensional stability and are often reduced by optimizing holding pressure, wall thickness, cooling, and gate design.
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