Defects Are Introduced By Injection Mold Maker

• Posted by Jin hong April 15, 2021 - Filed in Arts & Culture - #Injection mold maker Plastic Compression Springs  - 714 views
  1. Flow lines
     Flow lines introoduced by Injection mold maker appear as a wavy pattern often of a slightly different color than the surrounding area and generally on narrower sections of the molded component. They may also appear as ring-shaped bands on a product’s surface near the entry points of the mold, or “gates”, which the molten material flows through. Flow marks won’t typically impact the integrity of the component. But they can be unsightly and may be unacceptable if found in certain consumer products, such as high-end sunglasses.

  Causes and remedies for flow lines
  Flow lines are most often the result of variations in the cooling speed of the material as it flows in different directions throughout the mold. Differences in wall thickness can also cause the material to cool at different rates, leaving behind flow lines.injection molding defects For example, molten plastic, cools very quickly during the injection process and flow marks are evident when the injection speed is too slow. The plastic becomes partially solid and gummy while still filling the mold, causing the wave pattern to appear.

  Here are some common remedies for flow lines in injection-molded products:

  Increase the injection speed, pressure and material temperature to ensure the material fills the mold before cooling
  Round the corners of the mold where wall thickness increases to help keep flow rate consistent and prevent flow lines
  Relocate mold gates to create more distance between them and the mold coolant to help prevent the material from cooling too early during flow
  Increase the nozzle diameter to raise flow speed and prevent early cooling
  2. Burn marks
  Burn marks typically appear as black or rust-colored discoloration on an edge or surface of a molded plastic part.injection molding defects Burn marks generally don’t affect part integrity, unless the plastic is burned to the extent of degradation.

  Causes and prevention of burn marks
  The usual cause for burn marks in injection-molded parts is trapped air, or the resin itself, overheating in the mold cavity during injection. Excessive injection speeds or heating of the material often lead to overheating that causes burns. Consider the following preventative measures to avoid burn marks in molded components:

  Lower the melt and mold temperature to prevent overheating
  Reduce the injection speed to limit the risk of trapping air inside the mold
  Enlarge gas vents and gates to allow trapped air to escape the mold
  Shorten the mold cycle time so that any trapped air and resin don’t have a chance to overheat
  3. Warping
  Warping is deformation that can occur in injection molded products when different parts of a component shrink unevenly. Just as wood can warp when it dries unevenly, plastic and other materials can warp during the cooling process when uneven shrinkage puts undue stress on different areas of the molded part. This undue stress results in bending or twisting of the finished part as it cools. This is evident in a part that’s meant to lie flat but leaves a gap when laid on a flat surface.

  Causes and prevention of warping in molded parts
  One of the main causes for warping in injection-molded plastic and similar materials is that cooling happens too quickly. injection molding defectsOften excessive temperature or low thermal conductivity of the molten material can worsen the problem. Other times mold design can contribute to warping when the walls of the mold are not of uniform thickness—shrinkage increases with wall thickness. Here are some common ways to prevent warping in your molded parts:

  Ensure the cooling process is gradual and long enough to prevent uneven stresses on the material
  Lower the temperature of the material or mold
  Try switching to a material that shrinks less during cooling (e.g. particle-filled thermoplastics shrink much less than semi-crystalline materials or unfilled grades)
  Redesign the mold with uniform wall thickness and part symmetry to ensure greater stability in the part during cooling

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