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Injection molding defects and solutions

Injection molding is one of the best ways to mass produce plastic products. There are tons of different resins for specific purposes. Each resin has its own process tuning and mold design methods. Therefore, process control is not an easy task. We list several common injection molding defects and solutions for your reference below. Please feel free to contact BroadPlast fishing rod holder manufacturers if you have any other process control or mold design problems.

Injection molding defects and solutions
Defects Causes Solutions
Weld lines Two or more resin flow paths collide into each other. 1. Increase resin temperature.
2. Increase injection speed.
3. Increase hold pressure.
4. Add vent holes.
5. Add overflow well.
Short shots 1. Low material viscosity.
2. Narrow gate or runner.		 1. Increase resin temperature.
2. Increase injection speed.
3. Enlarge gate or runner.
4. Add vent holes.
Sink marks 1. Design issue.
2. Resin is not cool and cure properly.		 1. Optimize mold and product design.
2. Increase hold pressure and time.
Flow line Resin solidifies at different rates, often occurring near the gate. 1. Increase injection speed and pressure.
2. Enlarge gate size.
Surface delamination 1. Resin contamination(ex: mix with other resin).
2. Resin stick to the mold surface		 1. Replace resin.
2. Increase mold temperature.
3. Reduce injection speed and resin temperature.
Warping 1. Uneven thickness.
2. Design issue.(ex: undercut)		 1. Increase hold time and pressure.
2. Increase cooling time.
3. Modify mold.
Jetting Resin set cold before the cavity filled. 1. Change gate location.
2. Reduce the injection pressure and velocity.
3. Increase resin and mold temperature.
Burn marks 1. Near the gate or runner.
Resin temperature is too high.
2. End of filling part.
Injection speed too high or gas can not get out.		 1. Reduce resin temperature and process time.
2. Reduce injection speed at the end or improve vent.
Flash 1. Injection speed or pressure too high.
2. Mold damage.
3. Mold is not clamped properly.		 1. Reduce injection speed and pressure.
2. Modify mold.
3. Increase clamp pressure.
Void Gas trap inside the product. 1. Reduce injection speed.
2. Increase hold pressure and time.
3. Increase gate size.