Common Extrusion Weld Defects

Like metal welding, plastic welding requires training and experience to become proficient. If the plastic welding procedure is not exactly right, defects can occur that will comprise the strength of the weld. Some of these defects are easily visible and others require sectioning or testing to tell if the weld is sound. Be careful not to assume a weld is strong based on how the surface looks; perform destructive tests on sample welds before you begin to ensure a good final weld. 

In this article we give some of the more common defects that might be seen when welding plastics.  To review proper welding technique please see our article: Using an Extrusion Welder.

Symptom	Possible Causes
Porosity	Plast temperature too high Moisture in welding rod High environmental humidity Wet welding area Accelerated cooling
Rough surface of the welding seam	Welding shoe too short Welding shoe too cold Rough welding shoe surface Dirty welding shoe Incorrect air temperature Moisture in welding rod, base materials, or environment
Weak weld	​Welding temperature too low Dirty materials Dissimilar plastic types
Discoloration, glossiness of welding seam	Temperatures too high

For more help with extrusion welding, contact your Technical Sales Representative.

STANMECH Technologies offers a one day welding course to get you started.  Contact us to find out when the next course is scheduled.