Mold-Masters Hot Runner, User Manual, Page: 288 / 319

20.1.2 Resin Drying Issues
During the drying stage of the resin (if applicable), ensure that:
• The resin pellets are not overpacked
• Adequate air circulation is present
• The drying system is properly sealed, according to manufacturers
instructions
20.1.3 Importance of Pre-Drying Resin
Thermoplastic resins can be hygroscopic, able to absorb moisture from the
air. Under normal processing conditions, this can lead to degradation of the
polymer during molding. Breakage of polymer chains changes the properties,
resulting in possible blisters, streaks, splay or other defects described in this
section.
Recycled resins can have higher hygroscopic properties due to greater
surface area and should be dried separately from fresh resins.
If moisture issues are ruled out, continue with the troubleshooting tables in
the following pages.
20.2 Pre-Molding Precautions
Prior to commencing production, ensure that the following conditions have
been met. This will greatly reduce any future need to troubleshoot defective
production.
20.2.1 History
• Review any documentation associated with your batch job regarding
the recipe using the mold, molding machine, thermoplastic resin,
environmental setting, etc.
• Review comments, notes, logbooks, blogs, and anything other resource
material that pertains to the batch job.
• Verify that all settings such as all time, temperature, pressure, material,
etc. are correct.
20.2.2 Material
• Ensure that the thermoplastic resin to be used is the right grade, and has
been stored and / or prepared/dried, etc, according to manufacturer’s
specifications.
• Verify that the pigment / dye to be used meets manufacturer’s
specifications, and is compatible with the resin / molding machine / mold.
• Verify the correct recycle ratio and adjust settings accordingly.
20-2
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TROUBLESHOOTING
Hot Runner User Manual