Troubleshooting Focus: Flashing

Proper mold design provides a giant step toward reducing problems like flashing when injection molding with Eastman Tritan copolyester and other Eastman copolyesters. Collaborating with an Eastman technical service representative early in your project can help ensure you’re off on the right foot.

To help ensure continued molding success, this blog focuses on three different types of flashing problems, their possible causes, and corrective actions you can take for each.



General Flashing:


 
Possible cause Corrective action
 1. Poor mold spot  Spot mold to ensure fit and vent depths at ~0.025mm (0.001in).
 2. Injection Pressure too high  Reduce pressure. This may require higher melt temperature or lower injection speed.
 3. Coost time too long  Shorten boost time, lower boost pressure, or move transfer to an earlier position.
 4. Insufficient clamp tonnage  Increase clamp pressure or move to a machine with more tonnage.
 


Flash and Short Shot in Different Shots:
 

 
Possible Cause
Corrective action
 Check ring inconsistent; worn barrel Check and replace assembly ring. Replace/reline barrel as needed.



Flash and Short Shot in Same Shot:
 


 

Possible Cause Corrective action
 1. Core shift Check wall thickness for core shift. Investigate for source of core shift and repair mold.
 2. Inadequate clamp tonnage  Increase clamp pressure or move to a machine with more tonnage.
 3. Fill speed or pressure too high  Reduce speed or fill pressure.
 4. Melt temperature too low  Check and raise melt temperature if needed.
 5. Sprue too long too small, "O" dimension  Install correct-size sprue.

 


 

TMI TIP: Tritan can be successfully ultrasonic welded using energy director and shear-joint designs. The resulting device can exhibit outstanding impact strength, clarity, and durability—without weld joint flashing.
Watch video.

 


For more information about flashing, talk with your Eastman technical service representative. You can also download an Injection Molding Troubleshooting Guide (specify medical or durables).