Proper cooling saves time, improves quality
With any polymer, poor and uneven cooling can result in:
Considering the unique properties of Eastman Tritan™ copolyester, a few important guidelines will improve efficiency and part performance.
Because of the relatively low flex modulus of Tritan, uniform and efficient mold cooling—especially in the cores— is critical for the successful molding and ejection of parts.
When working with Tritan, you need to make sure you are cooling the resin enough to set up the outer skin of the part in order to get good release from the mold. This initial skin formation can take 10 to 20% longer than normal engineering resins, but cooling time throughout the rest of the part will be approximately the same.
Here are a few tips to improve cooling efficiency:
• Design ample mold-cooling channels with proper spacing and sizing.
• Use properly sized pumps and supply lines to deliver a good turbulent flow of water around the cavity. (The flow rate should be high enough to reach a minimum Reynolds number (Nr) of 6,000 in those areas where cooling is desired.)
• Use chillers, if practical, to ensure a proper supply of cool water to molds.
• Remove heat uniformly to avoid hot spots that can cause sticking and local deformation.
• Provide ample cooling near potential hot spots such as sprues and hot runners.
• Pay special attention to cooling heat sinks in pins and thin areas, and around slides.
• The mold should be cooled to 60°C (140°F) before ejection.
For more information, see May 29, 2014 Blog “Tooling design — keys to success”
For best results, involve an Eastman tech services engineer or design services engineer early in your planning. We’re prepared to discuss mold design, including line spacing and core cooling techniques such as baffles and bubblers, and much more.
|TMI TIP: For more information download the Eastman polymers Processing and mold design guidelines.|