Mold temperature too low

• Cause: The low mold temperature causes the molten plastic to cool too quickly in the runner, preventing full fusion.
• Solution: Increase the mold temperature to ensure the molten plastic flows smoothly and fuses completely.

Injection speed too slow

• Cause: Slow injection speed causes the plastic to flow slowly, extending cooling time and forming weld lines.
• Solution: Increase the injection speed so that the molten plastic quickly fills the mold cavity, reducing cooling time.

Melt temperature too low

• Cause: Low melt temperature results in poor flow, preventing full fusion in the weld area.
• Solution: Raise the melt temperature to improve the plastic's flowability and ensure better fusion.

Insufficient injection pressure

• Cause: Insufficient pressure prevents the molten plastic from fully filling the mold cavity, resulting in poor weld lines.
• Solution: Increase the injection pressure to ensure the molten plastic fully fills the cavity and fuses.

Poor venting

• Cause: Air in the mold cavity cannot be vented properly, obstructing the flow of the molten plastic and creating weld lines.
• Solution: Improve the mold's venting system to ensure smooth air evacuation.

Improper material ratio

• Cause: Incorrect material ratios, such as too much filler or inappropriate additives, affect the plastic's flow and fusion ability.
• Solution: Adjust the material ratio and select suitable fillers and additives to ensure material performance meets requirements.

Unreasonable mold design

• Cause: Poor runner design causes weld lines to form at the convergence points of the molten plastic.
• Solution: Improve mold design, optimize runner layout, and reduce the areas where the molten plastic converges.

Nozzle or runner blockage

• Cause: Partial blockage of the nozzle or runner obstructs the flow of the molten plastic, forming weld lines.
• Solution: Inspect and clean the nozzle and runner to ensure smooth plastic flow.

Improper cooling time

• Cause: Cooling time that is too long or too short results in uneven cooling of the plastic in the mold cavity, forming weld lines.
• Solution: Optimize cooling time to ensure even cooling and proper fusion of the plastic.

Insufficient material drying

• Cause: High moisture content in the plastic material causes bubbles during flow, leading to weld lines.
• Solution: Ensure sufficient material drying to reduce the moisture content in the material.

Improper machine settings

• Cause: Incorrect parameter settings on the injection molding machine lead to poor plastic flow and weld lines.
• Solution: Set the injection molding machine parameters—such as temperature, pressure, and speed—appropriately based on product requirements.

Uneven distribution of additives

• Cause: Uneven distribution of additives in the plastic results in poor local flow, creating weld lines.
• Solution: Improve the uniformity of material mixing to ensure even distribution of additives.