Page 449 - Injection Molding Advanced Troubleshooting Guide
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44.3 Stringers Troubleshooting 449
control zones. By maintaining multiple zones of control on nozzles and adapters
thermal control will be improved.
Figure 44.4 Extra-long nozzle assembly with multiple heater bands
Sometimes a nozzle tip must be isolated thermally from the mold to reduce string-
ers. The typical way to create this isolation is to add a piece of cardboard between
the nozzle tip and the sprue bushing. There are also molded insulators that can be
installed on the tip to help as well as Kevlar fabric insulators.
44.3.3.2 Machine: Machine Performance
See Chapter 8 on machine performance.
44.3.3.3 Machine: Nozzle Tip
Verify that the correct nozzle tip orifice and type are being used. The nozzle tip
information should always be clearly documented during process development to
ensure future repeatability. If the wrong nozzle tip is used the material may not
freeze off the same as it previously had. If the nozzle tip and sprue are extra thick
they may not cool well leading to stringing.
