a most-commonly-used ejector unit only play the role as ejecting tools. Sometimes, mandrils can also partake in the molding of plastic parts according to the needs thereof. Such mandrils can then be made into the same shape as certain part of the plastic parts or just as core. mandrils are usually made from T8A or T10A materials, with quenching hardness in head reaching over 50HRC and the surface roughness Ra less than 0.0008mm, forming a fitting of H8/f8 with the mandril hole. Mandrils are standard parts for molds and those of various diameters, lengths and sectional forms can be found in many cities’ marketplace for standard parts of molds.