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).
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Collaborate with a Tritan expert early in your project to help improve mold efficiency.  


 
TMI TIP: Metal coatings infused with PTFE usually can be chemically stripped with minimal damage to the substrate. However, be aware of special process tips for aluminum molds or when certain coatings penetrate the substrate. Order your free poster to see these tips and more.





 
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Tritan for medical-device applications
New medical-grade Eastman Tritan™ copolyester delivers peace of mind without sacrificing performance in medical-device applications. The unique combination of properties allows Tritan to satisfy a set of customer needs that previously have not been met by other polymers available to the medical-device industry.
Expect a balance of important advantages with Eastman Tritan™ copolyester MX711.  
 
  • Processability
  • Chemical resistance
  • Toughness
  • Hydrolytic stability
  • Compatibility with sterilization methods
  • Clarity
  • BPA-free
  • Secondary operations and assembly
  • Heat resistance
 
Eastman Tritan™ copolyester MX711 is well-suited for medical-device applications that demand superior chemical resistance, clarity and hydrolytic stability, including:
 
  • IV system components
  • Blood therapy devices
Find more information here about the advantages of Tritan for a wide range medical applications.

 
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Tooling design – keys to success
Proper Gating Selection
 
  •Select a compatible gating style for the selected resin. Most conventional cold gating styles work well with copolyesters. For hot runner systems, valve gates should be used.
 
Design Tooling with good Cooling/Thermal Control
 
  •Copolyesters require good thermal control throughout the cavity for optimal processing.
 
Design Tooling with a plan for venting
 
  •Poor venting can result in burn marks and incomplete fill.
 
Design Tooling with a plan for ejection
 
  •Parts should be adequately supported during ejection to avoid part deformation/breakage
 
Click here for more successful processing tips
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