Tunnel Gate Injection Molding

Pin gates are sometimes called post or tunnel gates and are commonly used on gears as shown here at left.

Tunnel gate injection molding.

Effectively it was a tunnel gate jumping into another tunnel gate. I mold tunnel gate inserts are recognized worldwide as innovative products with high cost reducing potential for moldmakers and molders. If the injection molding requirements meet the smaller the number of gates are the better it is it would reduce the weld marks. Tunnel gates also get a bad reputation for leaving a high gate vestige especially when the size of the gate is large.

These gates tunnel under the tool steel into a wall section. Tunnel gates can t be used with every material available for injection molding. Assuming you haven t. As the part ejects the tunnel gate is sheared off as the ejector pin pushes up on the runner causing the gate to rip at the opening of the gate orifice.

The tunnel gate submarine gate is used very frequently as a type of gate having a structure that automatically cuts the molded item and gate at the time of opening and closing the parting surface. Compatible materials for tunnel gates. If a material is too flexible a proper shearing action isn t achievable. Injection molding gate types edge gates.

While the size of the gate usually affects the size of the vestige the predominant controlling factor on how clean or how high a vestige you get is based on the angle of the wall it s gated into. Tunnel gate diameters vary from 0 5 0 8 mm for unreinforced plastics to larger diameters of 2 mm plus for reinforced materials. Time and cost reduction thanks to fast and easy application made of highly wear resistant hot work tool steel m2 1 3343 high degree of reliability in production process suitable for all plastics thanks to optimized feed channel geometry up to 60. The final part as seen at right shows the post from the pin or tunnel gate that was removed in a manual process.

From there the material would flow up the tunnel gate and into a short cold runner with an edge gate feeding the top inside edge of the gauge cutout. Clearly when designing for injection molding gate selection may require some deliberation.