Flashing around Valve-Less Vacuum Blocks or Valve-Less Vent Blocks can buildup which holds the die open and compromises the efficacy of vacuum-assist or massive venting. This in turn can lead to continued porosity issues. It is critical to clean any flash from around Valve-Less Blocks.
|Gap Between Valve-Less Block and Cavity or Runner Insert|
Ensure that the Valve-Less Blocks are correctly installed and that there is no gap or height difference between the block and runner or cavity insert.
|Die Holding Open||If the die is not being held completely closed during the injection phase, this can lead to the stationary and ejector halves of the Valve-Less Vacuum or Vent Block also failing to close completely. The result can be flash as metal is not fully contained within the block runners and block flow pattern. In this case the die and/or press alignment is the issue and must be addressed accordingly.|
|Excessive Metal Velocity||If metal exits the runners from the cavity to the Valve-Less Block with excessive velocity, it can result in flash around the blocks as metal is not contained within the runners and flow pattern. Midland recommends a minimum of five 90 degree turns in the vacuum or vent runners before reaching the inlet of the Valve-Less Block(s)|