Conversely, excessive heat or prolonged exposure to high temperatures can lead to thermal degradation, where the polymer begins to break down. If the specific grade is not matched to the application requirements, the result is often incomplete filling or excessive internal stress.
Injection Molding Defects Material Guide: Identifying Material-Related Issues
Weld lines, as previously mentioned, occur when the flow front splits and merges around an obstruction, such as a hole or a post. This differential cooling leads to internal stress, warpage, and dimensional instability as the part shrinks unevenly upon ejection.
Material Degradation Signs Discoloration (yellowing or dark streaks) Brittle texture or lack of flexibility Burn marks or charred appearance Weak mechanical properties Mold Design and Mechanical Failures Even with optimal processing parameters, a poorly designed mold can guarantee the production of defective parts. Unlike the uniform flow of material, the meeting point of these fronts can create a visible line that compromises the part’s appearance and, in engineering terms, its load-bearing capacity.
Injection Molding Defects Material Guide: Identifying Material-Related Issues
An improperly placed gate can create jets, where the material shoots through the cavity in a thin stream, trapping air and creating surface defects known as "streaks" or "burns. This often manifests as a yellowish or burnt discoloration and is frequently accompanied by a brittle texture.
More About Injection molding defects
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