Gas Porosity Defect

Gas trapped in the metal flow during die fill.

1. Eliminate trapped air:
• Use consistent pour rates.
• Delay after pouring to minimize splashing in the shot sleeve.
• Accelerate to slow shot speed correctly.
• Use critical slow shot speed.
• Accelerate to fast shot speed as late as possible.
2. Check the runner for smooth flow:
• No sharp corners.
• No blind ends or pockets.
• Ever decreasing areas properly used in runner path.
3. Check the vents:
• Right size (big enough).
• Vents kept open (not full of flash).
• Located at the last point to fill.
• Vents go to the edge of the die.
4. Check the vacuum system:
• Vacuum channels big enough.
• Vacuum channels located at last point to fill.
• Filters cleaned and open.
• Vacuum valves working.
• Vacuum level adequate.
5. Eliminate gas from lubricant:
• Use the minimum possible amount of plunger lubricant.
• Avoid putting lubricant in front of the tip.
• Use consistent application procedures.
• Avoid excessive die lubricant or anti-solder paste.
6. Eliminate steam:
• Make sure the die is dry when it closes.
• Use lots of air blow-off.
• Put drain holes in die where die lube (water) could accumulate.
• Check for water leaks after die is locked.
• Check for leaks from sprayer, hydraulic cylinders, etc.