Short shot (incomplete injection)

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Burn 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.

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Flash, also called burr, is a thin layer of excess material that forms along parting lines or ejector areas when molten material escapes from the mold cavity. It affects dimensional accuracy and surface quality and is usually caused by excessive injection pressure, insufficient clamping force, mold wear, or poor tool fit.

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Jetting 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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Injection 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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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.