Extrusion & Post
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PTFE Dimensional Shrinkage Out of Tolerance
Fenómeno do problema
PTFE parts have large dimensional deviations after sintering, the 15~20% shrinkage rate is inaccurately estimated, and assembly and sealing fail.
Análise das causas
During PTFE sintering, powder particles fuse and densify with 15~20% shrinkage; thick-walled areas shrink more; uneven cooling and pressure aggravate the difference; improper compaction or extrusion rate causes uneven density.
Solução
①Apply uniform pressure in molding or extrusion; ②Include sintering shrinkage compensation in mold or die design; ③Use filled reinforced PTFE for critical applications to reduce shrinkage; ④Monitor the sintering cycle to avoid differential shrinkage.
Conclusão principal
PTFE's 15~20% shrinkage is an inherent characteristic of the powder metallurgy-type process; mold compensation design is the premise of dimensional accuracy; filled modification is a material means to reduce shrinkage.
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