A frequent blogger asked this question the other day...
MJ
I know, the rules for DII process as follows:
• A process that uses one injection speed to fill - whenever possible
• The mold fills 95 to 98 percent full during first stage
• All cavities are short shot during first stage
• First stage fill is velocity-controlled and not pressure limited
• Second stage pack is pressure-controller and not velocity limited
• Process uses only 20 to 80 percent of the machine’s available shot size
• The final cushion is approximately 10 percent of the overall shot size
Do you have something like this for DIII process?
My Response
As with above, the following items are also rules of thumb, and are not set in stone.
• A process that uses one injection speed to fill - whenever possible
• The mold fills 80-90 percent full during first stage
• All cavities are short shot during first stage
• First stage fill is velocity-controlled and not pressure limited
• Second stage pack is velocity-controlled and not pressure limited
• Second stage transfers at approximately 95-98 percent full
• Second stage transfer is controlled using post-gate cavity pressure
• Third stage hold is pressure-controller and not velocity limited
• Process uses only 20 to 80 percent of the machine’s available shot size
• The final cushion is approximately 10 percent of the overall shot size
Additional Thoughts
A DIII process requires cavity pressure transfer capabilities, and should only be used if you and your technicians have a high level of competence. Such a process gives you excellent control, but may be overkill for many applications with good processing windows.
-Andy
Thanks Andy for advice.
MJ