Pin Hole in Gate

[The Rookie]

Hello all!

Just wondering if anyone has any advice or guidance on dealing with a pin hole in the gate.

Cavitation: 96
Material: PET
Hot Runner: Valve Gate

I was inspecting tubes for bubbles when I found this defect and began to wonder the possible causes. I am new to injection molding, hence the name, and I am just starting to learn processing (with the help of Robust Process Development and Scientific Molding: Theory and Practice).

This is my first project, and I would really like to hit a homerun! Thanks for any help.

[Joel JS]

Hello,

Try, (one at a time)

1. Slow the injection rate, as it enters the gate area
2. More pack time
3. Reduce Drop Temps

Joel

[chrisprocess]

Yea too hot drop temps or gate temps can cause voids like that. If the material is too hot near the gate, during mold opening the material will either stick to the gate side or stick to the part side. In the case it sticks to the gate side, it can tear a void like or pin-hole like feature through your gate into your part. And by lowering your gate temps you're allowing the material to cool in that area so when mold is opened that part stays whole. At least that's how I understand the defect shown above!
In terms of steel mods moving the drops or gate temps back away from the actual gate can help too

[The Rookie]

Joel and Chris,

Thanks for sharing! The mold is currently out for PMs, so I will give an update when we get it back in.

Rook

[rickbatey]

Is it always the same cavity in the mold? You could have a core cooling issue at the tip. Is there water in the entire core, a bubbler or cooling pin?
Rick