Page 437 - Injection Molding Advanced Troubleshooting Guide
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43.3 Sprue Sticking Troubleshooting 437
Figure 43.3 Z-style sprue puller
Figure 43.4 shows a back drafted style sprue puller with an added undercut ground
into the steel to help with sprue sticking. These extra undercuts can help with
sprue sticking but also may leading to flaking problems.
Figure 43.4 Back drafted sprue puller with ground in undercut; note that the cold slug well is
undersized for the sprue
Figure 43.5 shows an example of a sprue from a mold with a broken Z puller. This
can occur if the Z undercut is cut too deep resulting in a thin steel condition. Bro-
ken Z pullers will result in stuck sprues.
