𝐓𝐨𝐝𝐚𝐲'𝐬 𝐊𝐍𝐎𝐖𝐋𝐄𝐃𝐆𝐄 𝐒𝐡𝐚𝐫𝐞 : 𝐖𝐡𝐚𝐭 𝐫𝐨𝐥𝐞 𝐝𝐨𝐞𝐬 𝐠𝐥𝐚𝐬𝐬 𝐭𝐫𝐚𝐧𝐬𝐢𝐭𝐢𝐨𝐧 𝐩𝐥𝐚𝐲?

𝐓𝐨𝐝𝐚𝐲'𝐬 𝐊𝐍𝐎𝐖𝐋𝐄𝐃𝐆𝐄 𝐒𝐡𝐚𝐫𝐞

𝐌𝐨𝐥𝐝𝐞𝐝-𝐢𝐧 𝐬𝐭𝐫𝐞𝐬𝐬𝐞𝐬 𝐚𝐫𝐞 𝐨𝐟𝐭𝐞𝐧 𝐧𝐨𝐭 𝐯𝐢𝐬𝐢𝐛𝐥𝐞 𝐝𝐮𝐫𝐢𝐧𝐠 𝐢𝐧𝐬𝐩𝐞𝐜𝐭𝐢𝐨𝐧 𝐛𝐮𝐭 𝐜𝐚𝐧 𝐫𝐞𝐯𝐞𝐚𝐥 𝐭𝐡𝐞𝐦𝐬𝐞𝐥𝐯𝐞𝐬 𝐢𝐧 𝐭𝐡𝐞 𝐟𝐢𝐞𝐥𝐝. 𝐖𝐡𝐚𝐭 𝐫𝐨𝐥𝐞 𝐝𝐨𝐞𝐬 𝐠𝐥𝐚𝐬𝐬 𝐭𝐫𝐚𝐧𝐬𝐢𝐭𝐢𝐨𝐧 𝐩𝐥𝐚𝐲?


In injection molding, dimensional changes occur due to postmold shrinkage, influenced by the material's glass transition temperature. For materials with glass transition below room temperature, molecules continue shrinking after ejection, potentially taking days to stabilize, as seen in a thermoplastic elastomer overmold on a metal insert.


Lower mold temperatures freeze molecules prematurely, building in stress that releases later under heat, causing warpage—like a cassette exposed to 150°F or nylon parts with incomplete crystallization.


- Amorphous and crystalline resins both risk shrinkage if crystallization is incomplete.

- Annealing relieves stresses by allowing molecules to reach preferred positions.

- Ensure uniform postmold shrinkage before assembly to avoid failures.


Understanding these dynamics helps prevent field issues. Read the full article for details on optimizing processes. https://lnkd.in/e8Zzc2XT


source : Plastics Technology


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