Cold Slug Well-This is designed to trap the cooler advancing front of the melt、thus permitting hotter melt to reach the cavities and gates. It usually has a snatch or pull pin or sucker pin underneath it to positively pull the sprue out of the sprue bush. Three basic designs are used for ejection pin systems and a slightly different system with an undercut pin for stripper plate ejection. The diameters of each design are based on the diameter of the sprue where it meets the runner. It is important to avoid any obstruction to the melt flow; therefore, the pins should always be designed to avoid its protruding into the runner area.
Each design should have an ejector pin beneath the cold slug well to eject it out of the tool when the tool opens.
In each case the pin .should be based on a standard diameter ejector pin size. The pin should also slide in a hardened bush to minimize wear from continued movement.
The Undercut ring design is the one normally preferred as the snatch and ejection is positive and not likely to hang up. The undercut ring need only be around 0.25 mm deep by 0*5 mm wide but this may vary with the material being used.
The tapered hole design is the least desirable as it usually has the largest mass and therefore the longest cooling time. However, this design does capture the colder advancing front of the material very well.
The Z snatch sometimes rends to fall away from the Z shape, although this design may be such as PS and SAN as the undercut ring and tapered on Ejection.‘hang up’ when it ‘refuses’ to p referred for brittle materials hole versions may break off.