The Gate Type And Selection Of Plastic Injection Mold
The gate of the plastic injection mold is a short and thin runner connecting the runner and the mold cavity. It is the entrance where the resin is injected into the mold cavity. The shape, quantity, size and position of the gate in the mold have great influence on the quality of plastic parts. So the choice of gate is one of the key points of mold design. Next , we will introduce the gate in the following aspects.
1. Sprue Gate or Dicrect Gate
It flows into the cavity directly, small pressure loss, fast feeding speed and easy molding. It is suitable for all kinds of plastics. It has the advantages of good pressure transfer, strong pressure maintaining and shrinkage, simple and compact mould structure and convenient manufacturing. However, it is difficult to remove the gate, and the gate marks are obvious. The heat concentration and slow condensation near the gate is easy to produce greater internal stress, and also easy to cause sink mark. It is suitable for large plastic parts or parts with thick wall.
2. Edge Gate
The side gate, also known as the edge gate, is generally opened on the parting surface and feeds from the outside side of the cavity. The side gate is a typical rectangular gate, which can conveniently adjust the shearing rate and gate closing time during mold filling, so it is also called the standard gate. The characteristics of edge gate are simple shape of gate section, convenient processing and precision machining of gate size; flexible selection of location of gate to improve the filling condition; correction without removing the moud from the injection molding machine; the convenience to remove the gate and the small mark . Edge gate is especially suitable for two - plate mold with multi - cavity. However, the plastic parts are easy to form weld marks, keyholes, sink mark and other defects. And it will cause big loss of injection pressure and bad venting for the shell plastic parts.
3. Pin Point Gate
The point gate can be applied to all kinds of products. The residual stress near the gate is small, and it can be pulled off by itself, so can realize automatic production. For larger products can be designed to feed from multi-point at the same time, which can shorten the flow process, and reduce the deformation caused by flow resistance. However, it will cause big loss of injection pressure.And the injection molding pressure is larger than the direct gate, so mostly will use three- plate mold.