I just got this quick question from one of our blog readers…
Larry
We have a small nozzle mold (0.2oz of Lexan PC) that traps air, but we can’t seem to find a way to vent it. The only success we have had is to reduce the clamp tonnage. Can you briefly state a procedure for identifying where to vent?
My Response
Since a clamp tonnage reduction helps your part quality, you have correctly determined that it is a venting issue. Additionally, it is most likely that you only need venting on the parting line to correct the issue.
The easiest way to determine the vent location is to mold a short shot which will allow you to see where the end of the flow front is located. In most cases, this is where the venting should take place.
Additional Thoughts
Since you are molding PC, your application may be optimized with a large vent encompassing most of the parting line.
In any case, your mold should have a deep channel behind the vents to ensure the venting can leave the mold easily and quickly.
-Andy
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