It is the channel connecting the main channel and each cavity in the multi-groove mould. In order to make the melt fill each cavity at equal speed, the arrangement of the runner on the mould should be symmetrical and equidistant distribution. The shape and size of the cross section have an impact on the flow of plastic melts, the release of products and the difficulty of mold making. If the flow of equal amount of material, the flow path resistance of the circular section is minimized. But because of the smaller surface of the cylindrical runner, it is unfavorable to the cooling of the manifold, and the shunt channel must be opened in two halves, both Maki and difficult to be aligned. As a result, a trapezoidal or semicircular cross-sectional runner is often used and is opened on half the mold with a release lever. The surface of the runner must be polished to reduce the flow resistance to provide a faster mold filling speed. The size of the runner is determined by the size and thickness of the plastic variety, product. For most thermoplastics, the cross section width of the manifold is not more than 8mm, the extra large can reach 10-12mm, extra small 2-3mm.
To meet the needs of the premise should minimize the cross-sectional area, in order to increase the diversion and prolong the cooling time.