Injection molding is a highly efficient and common method for producing plastic parts, but some common problems may arise during actual production, affecting the product's quality, appearance, and function. Here are some common problems encountered during injection molding and their possible causes:
Flow marks and burns: Flow marks are linear marks on the plastic surface, often caused by excessively fast material flow or uneven mold temperature; burns are black spots or blemishes caused by overheating or compression of gas within the mold cavity, resulting in scorching of the plastic.
Shrinkage marks: If shrinkage is not compensated during the cooling of the plastic part, depressions may form on the surface or inside.
Warpage or deformation: Inconsistent cooling rates or insufficient cooling time can lead to warping or deformation of the product.
Stress marks: Excessive internal stress can cause whitening, cracks, or brittle fracture on the surface of the plastic part.
Weld lines: Gaps formed when plastic flows converge in runners, right angles, or narrow holes affect the product's appearance and strength.
Incomplete or Short Injection: The plastic does not completely fill the mold, resulting in an incomplete product. This may be due to insufficient injection pressure or speed, excessively low plastic temperature, or unsuitable mold temperature.
Flash: Excess plastic material leaks out from the mold joint surface, forming thin flakes. This may be due to insufficient clamping force or mold quality issues.
Cold Slug at the Nozzle: The plastic begins to solidify before entering the cavity, forming hard spots in the product.
Insertion Displacement or Damage: During injection, the insertion part may shift or be damaged due to improper positioning, insecure fixing, or pressure during mold closing.
Surface Scratches or Wear: Improper mold surface treatment or excessive sticking of the plastic part to the mold can cause surface scratches or wear during demolding.
Solving these problems typically requires adjusting injection molding machine parameters (such as temperature, pressure, injection speed, and holding time), optimizing mold design (e.g., improving gate and runner design, increasing ventilation), improving plastic material handling, or adding or adjusting the cooling system. Each problem may require a comprehensive consideration of multiple factors to determine the best solution.
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