The best method for determining the

The best method for determining the true residence time within the melt delivery system is the use of tracer pellets of another color added at the feed throat. After adding the tracer pellets, continue to mold parts and time how long it takes before the new color shows up in the molded parts.There are less accurate ways to estimate residence time such as calculating the shot weight versus the barrel shot capacity. When doing this it is important to remember that barrel shot sizes on molding machine are based on polystyrene, which has a density of 1.04 g/cm³, but when using something other than poly-styrene it is important to account for the different density. It is also important to understand that solid density is different from melt density, making the calculation less accurate. Also, the plastic that is retained in the fights of the screw must be accounted for and this is usually done using a multiplier (normally 40%).