Molds & Tooling
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Improper PPO Runner Design
Problem Phenomenon
PPO products have filling difficulties and pressure loss due to excessively long and thin runners, cold slugs entering the cavity cause defects, and the sprue is difficult to demold.
Cause Analysis
The high viscosity of PPO requires short and thick runner design; the sprue should adopt a larger taper or a sprue puller structure; when hot runners are not used for long runners, cold slug problems are prominent; a straight-through nozzle with a bore of 3~6mm is preferable.
Solution
①Design runners according to the short and thick principle; ②large taper or sprue puller for the sprue; ③adopt hot runner structure for long runners; ④select a straight-through nozzle with a bore of 3~6mm.
Key Takeaway
PPO runner design has clear industry norms; short and thick runners reduce pressure loss; hot runners have significant value for long-flow parts.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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